Sample Pages

Userrsquos Guide to Plastic

Ulf Bruder

ISBN (Book) 978-1-56990-734-4 ISBN (E-Book) 978-1-56990-735-1

For further information and order see

wwwhanserpublicationscom (in the Americas)

wwwhanser-fachbuchde (outside the Americas)

copy Carl Hanser Verlag Muumlnchen

V

Contents

Foreword XVII

Polymers and Plastics 111 Thermosets 312 Thermoplastics 413 Amorphous and Semi-crystalline Plastics 5

Commodities 721 Polyethylene (PE) 7

211 Classification 8212 Properties of Polyethylene 8213 Recycling 9214 Application Areas 9

22 Polypropylene (PP) 11221 Properties of Polypropylene 12222 Recycling 13

23 Polyvinylchloride (PVC) 13231 Properties of PVC 14232 Recycling 14

24 Polystyrene (PS) 15241 Classification 16242 Properties of Polystyrene 16243 Recycling 17244 Application Areas 17

25 Styrene-Acrylonitrile (SAN) 1726 Acrylonitrile-Butadiene-Styrene (ABS) 18

261 ABS Blends 19262 Properties of ABS 19263 Recycling 19264 Application Areas 20

27 Polymethyl Methacrylate (PMMA) 21271 Properties of PMMA 22272 Recycling 22273 Application Areas 22

Engineering Polymers 2331 Polyamide or Nylon 23

311 Classification 23312 Properties of Polyamide 24313 Recycling 25314 Application Areas 25

CHAPTER 1

CHAPTER 2

CHAPTER 3

VI

Contents

32 Acetal 26321 Properties of Acetal 27322 Recycling 28323 Application Areas 28

33 Polyester 29331 Properties of Polyester PBT and PET 31332 Recycling 31333 Application Areas 31

34 Polycarbonate 33341 Properties of Polycarbonate 34342 Recycling 34343 Application Areas 34

Thermoplastic Elastomers 3641 TPE-O 36

411 Properties of TPE-O 36412 Application Areas 37

42 TPE-S 38421 Properties of TPE-S 38422 Application Areas 39

43 TPE-V 39431 Properties of TPE-V 40432 Application Areas 40

44 TPE-U 41441 Properties of TPE-U 41442 Application Areas 42

45 TPE-E 42451 Properties of TPE-E 42452 Application Areas 43

46 TPE-A 44461 Properties of TPE-A 44462 Application Areas 45

High-Performance Polymers 4651 Advanced Thermoplastics 46

511 Recycling 4752 Fluoropolymers 47

521 Properties of PTFE 48522 Application Areas 48

53 ldquoHigh-Performancerdquo Nylon ndash PPA 48531 Properties of PPA 49532 Application Areas 50

54 ldquoLiquid Crystal Polymerrdquo ndash LCP 50541 Properties of LCP 50542 Application Areas 51

CHAPTER 4

CHAPTER 5

VII

Contents

55 Polyphenylene Sulfide ndash PPS 52551 Properties of PPS 52552 Application Areas 52

56 Polyether Ether Ketone ndash PEEK 53561 Properties of PEEK 53562 Application Areas 54

57 Polyetherimide ndash PEI 54571 Properties of PEI 55572 Application Areas 55

58 Polysulfone ndash PSU 56581 Properties of PSU 56582 Application Areas 57

59 Polyphenylsulfone ndash PPSU 57591 Properties of PPSU 57592 Application Areas 58

Bioplastics and Biocomposites 5961 Definition 59

611 What Do We Mean by Bioplastic 6062 The Market 6063 Bioplastics 6264 Biopolymers 6265 Biobased Polymers Biopolyester 6366 Biobased Polymers Biopolyamides 6567 Biobased Polymers from Microorganisms 6668 Bioethanol or Biomethanol 6769 Biocomposites 68610 More Information about Bioplastics 69

Plastic and the Environment 7071 Plastic is Climate-Friendly and Saves Energy 7072 Environmental Effects on Plastic 7273 Recycling Plastic 73

731 Plastic Recycling in the EU 74

Modification of Polymers 7681 Polymerization 7682 Additives 78

821 Stiffness and Tensile Strength 79822 Surface Hardness 79823 Wear Resistance 79824 Toughness 80

CHAPTER 6

CHAPTER 7

CHAPTER 8

VIII

Contents

83 Physical Properties 80831 Appearance 80832 Crystallinity 81833 Weather Resistance 81834 Friction 82835 Density 82

84 Chemical Properties 83841 Permeability 83842 Oxidation Resistance 83843 Hydrolysis Resistance 84

85 Electrical Properties 8486 Thermal Properties 85

861 Heat Stabilization 85862 Heat Deflection Temperature 86863 Flame Retardant Classification 86

87 Material Price 87

Material Data and Measurements 8891 Tensile Strength and Stiffness 8992 Impact Strength 9293 Maximum Service Temperature 93

931 UL Service Temperature 93932 Heat Deflection Temperature 93

94 Flammability Tests 95941 HB Rating 95942 V Rating 95

95 Electrical Properties 9696 Flow Properties Melt Index 9797 Shrinkage 97

Material Databases on the Internet 98101 CAMPUS 98

1011 Properties of CAMPUS 52 99102 Material Data Center 99

1021 Properties of Material Data Center 100103 Prospector Plastics Database 100

Test Methods for Plastic Raw Materials and Moldings 102111 Quality Control during Raw Material Production 102112 Visual Quality Control of Plastic Granules 103113 Visual Inspection of Plastic Parts 104114 Tests That Can Be Performed by the Molder 105115 Advanced Testing Methods 107

CHAPTER 9

CHAPTER 10

CHAPTER 11

IX

Contents

Injection-Molding Methods 110121 History 110122 Properties 111

1221 Limitations 111123 The Injection-Molding Machine 112

1231 The Injection Unit 1121232 Locking Unit 1131233 Injection-Molding Cycle 114

124 Alternative Injection-Molding Methods 1151241 Multi-component Injection Molding 1151242 Gas or Water Injection 116

Post-molding Operations 117131 Surface Treatment of Moldings 117

1311 Printing 1171312 ldquoHot Stamprdquo Printing 1181313 Tampon Printing 1191314 Screen Printing 1191315 IMD In-Mold Decoration 1201316 Laser Marking 1211317 Painting 1211318 MetalizingChroming 122

Different Types of Molds 123141 Two-Plate Molds 123142 Three-Plate Molds 124143 Molds with Slides 124144 Molds with Rotating Cores 125145 Stack Molds 125146 Molds with Ejection from the Fixed Half 126147 Family Molds 126148 Multi-component Molds 127149 Molds with Melt Cores 128

Structure of Molds 129151 The Function of the Mold 130152 Runner Systems ndash Cold Runners 130153 Runner Systems ndash Hot Runners 132154 Cold Slug PocketsPullers 133155 Tempering or Cooling Systems 134156 Venting Systems 136157 Ejector Systems 137158 Draft Angles 138

CHAPTER 12

CHAPTER 13

CHAPTER 14

CHAPTER 15

X

Contents

Mold Design and Product Quality 139161 Mold-Related Problems 139

1611 Too-Weak Mold Plates 1391612 Incorrect Sprue and Nozzle Design 1401613 Incorrect Runner Design 1411614 Incorrectly Designed Located

or Missing Cold Slug Pocket 1411615 Incorrect Gate Design 1421616 Incorrect Venting 1431617 Incorrect Mold Temperature Management 144

Prototype Molds and Mold Filling Analysis 145171 Prototype Molds 145172 Mold Filling Analysis 146173 Workflow 147

1731 Mesh Model 1471732 Material Selection 1481733 Process Parameters 1481734 Selection of Gate Location 1481735 Simulations 1491736 Results Generated by Simulations 1491737 Filling Sequence 1501738 Pressure Distribution 1501739 Clamping Force 15017310 Cooling Time 15117311 Temperature Control 15117312 Shrinkage and Warpage 15117313 Glass Fiber Orientation 15217314 Warpage Analysis 15217315 Gate Location 15217316 Material Replacement 15317317 Simulation Software 153

Rapid Prototyping and Additive Manufacturing 154181 Prototypes 154182 Rapid Prototyping (RP) 155

1821 SLA ndash Stereolithography 1561822 SLS ndash Selective Laser Sintering 1591823 The FDM Method 1611824 3DP Printing 1621825 3D Printing 1631826 PolyJet 164

183 Additive Manufacturing 166

CHAPTER 16

CHAPTER 17

CHAPTER 18

XI

Contents

Cost Calculations for Moldings 168191 Part Cost Calculator 169192 Part Cost Scenarios 173192 Replacement Cost 174

Extrusion 177201 The Extrusion Process 177

2011 Advantages (+) and Limitations (minus) 177202 Materials for Extrusion 179203 The Extruder Design 180

2031 The Cylinder 1802032 Single-Screws 1812033 Barrier Screws 1812034 Straight Twin-Screws 1822035 Conical Twin-Screws 1822036 Rotational Direction 1832037 Comparison of Single-Screws and Twin-Screws 1832038 ToolDie 1842039 Calibration 18420310 Corrugation 18520311 Cooling 18520312 Feeding 18620313 Marking 18620314 Further Processing 18620315 Cutting 18720316 Winding 188

204 Extrusion Processes 1882041 Straight Extrusion 1892042 Extrusion with Angle ToolCoating 1892043 Extrusion of Plates and Sheets 1902044 Co-extrusion 1912045 Film Blowing 191

20451 Advantages (+) and Limitations (minus) 1922046 Cable Production 1932047 Monofilament 1942048 Compounding 195

205 Design for Extrusion 1962051 Ribbing ndash Stiffening 1972052 Cavity 1972053 Sealing Lip 1972054 Hinge 1982055 Guide 1982056 Sliding Joint 1982057 Snap-Fit Joint 1992058 Bellow 1992059 InsertReinforcement 19920510 Friction Surface 200

CHAPTER 19

CHAPTER 20

XII

Contents

20511 PrintingStamping 20020512 Decoration Surface 20020513 Drilled Side Holes 20120514 Irregular Holes 20120515 Corrugation 20120516 Spiral Forming 20220517 Foaming 20220518 Extruded Screw Holes 20220519 Muffing and Hot Plate Welding 203

Alternative Processing Methods for Thermoplastics 204211 Blow Molding 204212 Rotational Molding 206213 Vacuum Forming 207

Material Selection Process 209221 How Do You Select the Right Material in

Your Development Project 209222 Development Cooperation 210223 Establishing the Requirement Specifications 210224 MUST Requirements 211225 WANT Requirements 212226 Specify and Sort the Material Candidates 213227 Make a Detailed Cost Analysis 214228 Establish a Meaningful Test Program 215

Requirements and Specification for Plastic Products 216231 Background Information 216232 Batch Size 217233 Part Size 218234 Tolerance Requirements 218235 Part Design 220236 Assembly Requirements 223237 Mechanical Load 223238 Chemical Resistance 224239 Electrical Properties 2252310 Environmental Impact 2262311 Color 2272312 Surface Properties 2282313 Other Properties 2302314 Regulatory Requirements 2312315 Recycling Requirements 2322316 Cost Requirements 233

CHAPTER 21

CHAPTER 22

CHAPTER 23

XIII

Contents

2317 Requirement Specification ndash Checklist 23423171 Background information 23423172 Batch Size 23423173 Part Size 23523174 Tolerance Requirements 23523175 Part Design 23523176 Assembly Requirements 23523177 Mechanical Load 23523178 Chemical Resistance 23523179 Electrical Properties 235231710 Environmental Impact 236231711 Color 236231712 Surface Properties 236231713 Other Properties 236231714 Regulatory Requirements 237231715 Recycling 237231716 Costs 237

Design Rules for Thermoplastic Moldings 238241 Rule 1 ndash Remember That Plastics Are Not Metals 239242 Rule 2 ndash Consider the Specific Characteristics of Plastics 240

2421 Anisotropic Behavior 2412422 Temperature-Dependent Behavior 2412423 Time-Dependent Stress-Strain Curve 242

24231 Creep 24224232 Relaxation 242

2424 Speed-Dependent Characteristics 2432425 Environmentally Dependent Characteristics 2442426 Easy to Design 2442427 Easy to Color 2442428 Easy to Assemble 2452429 Recycling 245

243 Rule 3 ndash Design with Regard to Future Recycling 2462431 Dismantling 2462432 Reused Materials 2482433 Coding 2482434 Cleaning 249

244 Rule 4 ndash Integrate Several Functions into One Component 249

245 Rule 5 ndash Maintain an Even Wall Thickness 251246 Rule 6 ndash Avoid Sharp Corners 252247 Rule 7 ndash Use Ribs to Increase Stiffness 254

2471 Limitations when Designing Ribs 2542472 Material-Saving Design 2552473 Avoid Sink Marks at Rib Joints 255

CHAPTER 24

XIV

Contents

248 Rule 8 ndash Be Careful with Gate Location and Dimensions 2562481 Weld Lines 257

249 Rule 9 ndash Avoid Tight Tolerances 2582410 Rule 10 ndash Choose an Appropriate Assembly Method 259

Assembly Methods for Thermoplastics 260251 Assembly Methods That Facilitate Disassembly 260252 Integrated Snap-Fits 261253 Permanent Assembly Methods 262

2531 Ultrasonic Welding 2622532 Vibration Welding 2632533 Rotational Welding 2642534 Hot Plate Welding 2652535 Infrared Welding 2662536 Laser Welding 2662537 Riveting 2682538 Gluing 269

The Injection-Molding Process 270261 Molding Processing Analysis 270262 Contact Information 272263 Information Pane 272264 Material Information 273265 Information about the Machine 274266 Information about the Mold 276267 Drying 278268 Processing Information 280269 Temperatures 2812610 Pressure Injection Speed and Screw Rotation Speed 2862611 Hold Pressure 2872612 Injection 2892613 Screw Rotation Speed 2902614 Time and Length Settings 292

Injection Molding Process Parameters 297

Problem Solving and Quality Management 301281 Increased Quality Demands 301282 Analytical Troubleshooting ndash ATS 301

2821 Definition of the Problem 3022822 Deviation Definition 302

283 Defining a Problem 3032831 Classification of Problems 3042832 Problem Analysis 306

CHAPTER 25

CHAPTER 26

CHAPTER 27

CHAPTER 28

XV

Contents

2833 Brainstorming 3082834 Verification of Causes 3082835 Planning of Actions to Take 309

284 Statistical Design of Experiments ndash DOE 3092841 Factorial Experiments 310

285 Failure Mode Effect Analysis ndash FMEA 3132851 General Concepts of FMEA 314

Troubleshooting ndash Causes and Effects 316291 Molding Problems 316292 Fill Ratio 318

2921 Short Shots ndash The Part Is Not Completely Filled 3182922 Flashes 3192923 Sink Marks 3192924 Voids or Pores 320

293 Surface Defects 3212931 Burn Marks 321

29311 Discoloration Dark Streaks or Degradation 32129312 Black Specks 32129313 Splays or Silver Streaks

(Partly over the Surface) 32229314 Diesel Effect ndash Entrapped Air 323

2932 Splays or Silver Streaks (All over the Surface) 3242933 Color Streaks ndash Bad Color Dispersion 3242934 Color Streaks ndash Unfavorable Pigment Orientation 3252935 Surface Gloss ndash MatteShiny Surface Variations 3252936 Surface Gloss ndash Corona Effect 3262937 Splays Stripes and Blisters 3262938 Glass Fiber Streaks 3272939 Weld-Lines (Knit-Lines) 32729310 Jetting 32829311 Delamination 32929312 Record Grooves (Orange Peel) 32929313 Cold Slug 33029314 Ejector Pin Marks 33029315 Oil Stain ndash Brown or Black Specks 33129316 Water Stain 331

294 Poor Mechanical Strength 3322941 Bubbles or Voids inside the Part 3322942 Cracks 3322943 Unmelts (Also Called Pitting) 3332944 Brittleness 3342945 Crazing 3342946 Problems with Regrind 335

CHAPTER 29

XVI

Contents

295 Dimensional Problems 3352951 Incorrect Shrinkage 3352952 Unrealistic Tolerances 3362953 Warpage 337

296 Production Problems 3382961 Part Sticks in the Cavity 3382962 Part Sticks on the Core 3382963 Part Sticks on the Ejector Pins 3392964 Sprue Sticks in the Mold 3402965 Stringing 341

Statistical Process Control (SPC) 342301enspWhy SPC 342302enspDefinitions in SPC 343

3021enspNormal Distribution (Gaussian Dispersion) 343303enspStandard Deviations 343

3031enspOne Standard Deviation 3433032enspSix Standard Deviations (Six Sigma) 3443033enspControl Limits 3443034enspTarget Value 3463035enspTarget Value Centering (TC) 3473036enspCapability Machine (Cm) 3473037enspCapability Machine Index (Cmk) 3483038enspCapability Process (Cp) 3483039enspCapability Process Index (Cpk) 34930310enspSix Important Factors 34930311enspMachine Capability 35030312enspProcess Capability 350

304enspHow SPC Works in Practice 3513041enspSoftware 3513042enspProcess Data Monitoring 352

Internet Links 354

Index 355

CHAPTER 30

CHAPTER 31

XVII

Foreword

For many years I had the idea of writing a book about injection molding as I have spent over 45 years of my working life on this subject

When I retired in 2009 I was given great support by my friends Katarina Elner- Haglund and Peter Schulz of the Swedish plastics magazine Plastforum who asked me to write a series of articles about thermoplastics and their processing for the magazine

I was also hired at this time to work with educational programs at the Lund Uni-versity of Technology the Royal University of Technology in Stockholm and a number of industrial companies in Sweden as a result of which this book was developed

My aim has been to write in such a way that this book can be understood by everyone regardless of prior knowledge about plastics The book has a practical approach with lots of pictures and is intended to be used in secondary schools universities industrial training and self-study In some of the chapters there are references to worksheets in Excel that can be downloaded free from my website wwwbruconse

In addition to the above-mentioned persons I would like to extend a warm thanks to my wife Ingeloumlv who has been very patient when Irsquove been totally absent in the ldquowonderful world of plasticsrdquo and then proofread the book my brother Hans-Peter who has spent countless hours on adjustments of all the images etc and my son-in-law Stefan Bruder who has checked the contents of the book and contributed with many valuable comments

I would also like to thank my previous employer DuPont Performance Polymers and especially my friends and former managers Bjoumlrn Hedlund and Stewart Day-kin who encouraged the development of my career as a trainer until I reached my ultimate goal and dream job of ldquoglobal technical training managerrdquo They have also contributed with a lot of information and many valuable images in this book

I also want said a big thank you to my friends and business partners in all educa-tional programs in recent years who have supported me and contributed with many valuable comments information and images for this book and a special thanks to those who have made this printing possible thanks to the ads in the beginning The whole list would be very long but you will find some of them in the list of internet links in Chapter 31

In this Second Edition

This edition contains greatly expanded coverage of extrusion collected into a new Chapter 20 There are also a number of new and updated figures with numerous small improvements and corrections throughout the text These are complemented by an all-new professional layout and structure which I hope will help readers to navigate the book comfortably

XVIII

Foreword

I would like to thank Mark Smith at Carl Hanser Verlag for all the support that I received during the last years with my book in various languages

Ulf Bruder

Karlskrona Sweden

10

Chapter 2 mdash Commodities

3) LDPE is used for film blowing and extrusion

A large part of all the polyethylene produced is used for film blowing If the film is soft and flexible it is either made of LDPE or LLDPE If it has the rustle of the free bags at the grocery store it is probably made of HDPE LLDPE is also used to improve the strength of LDPE film

Figure 27enspGarbage bags LDPE is excellent for film blowing and is the most common material used in bags plastic sacks and construction film

Figure 28enspCable jacketing LDPE is used in the extrusion of jacketing for high voltage cables

4) PEX

Cross-linked polyethylene is mainly used in the extrusion of tubes The cross-link-ing provides improved creep resistance and better high-temperature properties

You can even copolymerize ethylene with polar monomers and get everything from viscous products (ethinspg melting glue) to tough films and impact-resistant hard shells such as golf balls

A common copolymer is EVA (ethylene-vinyl-acetate) By varying the concentration of vinyl acetate (VA) from 25 to 95 you can control the properties and produce a range of different types of material Increased VA content leads to higher trans-parency and toughness

Adhesives carpet underlay cable insulation carriers of color masterbatches stretch film and coating film for cardboard and paper are typical uses of EVA

Figure 29enspTubes in PEX resist both high temperatures (120degC) and pres-sure and are used for the hot water supply of cleaning or washing machines

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

VI

Contents

32 Acetal 26321 Properties of Acetal 27322 Recycling 28323 Application Areas 28

33 Polyester 29331 Properties of Polyester PBT and PET 31332 Recycling 31333 Application Areas 31

34 Polycarbonate 33341 Properties of Polycarbonate 34342 Recycling 34343 Application Areas 34

Thermoplastic Elastomers 3641 TPE-O 36

411 Properties of TPE-O 36412 Application Areas 37

42 TPE-S 38421 Properties of TPE-S 38422 Application Areas 39

43 TPE-V 39431 Properties of TPE-V 40432 Application Areas 40

44 TPE-U 41441 Properties of TPE-U 41442 Application Areas 42

45 TPE-E 42451 Properties of TPE-E 42452 Application Areas 43

46 TPE-A 44461 Properties of TPE-A 44462 Application Areas 45

High-Performance Polymers 4651 Advanced Thermoplastics 46

511 Recycling 4752 Fluoropolymers 47

521 Properties of PTFE 48522 Application Areas 48

53 ldquoHigh-Performancerdquo Nylon ndash PPA 48531 Properties of PPA 49532 Application Areas 50

54 ldquoLiquid Crystal Polymerrdquo ndash LCP 50541 Properties of LCP 50542 Application Areas 51

CHAPTER 4

CHAPTER 5

VII

Contents

55 Polyphenylene Sulfide ndash PPS 52551 Properties of PPS 52552 Application Areas 52

56 Polyether Ether Ketone ndash PEEK 53561 Properties of PEEK 53562 Application Areas 54

57 Polyetherimide ndash PEI 54571 Properties of PEI 55572 Application Areas 55

58 Polysulfone ndash PSU 56581 Properties of PSU 56582 Application Areas 57

59 Polyphenylsulfone ndash PPSU 57591 Properties of PPSU 57592 Application Areas 58

Bioplastics and Biocomposites 5961 Definition 59

611 What Do We Mean by Bioplastic 6062 The Market 6063 Bioplastics 6264 Biopolymers 6265 Biobased Polymers Biopolyester 6366 Biobased Polymers Biopolyamides 6567 Biobased Polymers from Microorganisms 6668 Bioethanol or Biomethanol 6769 Biocomposites 68610 More Information about Bioplastics 69

Plastic and the Environment 7071 Plastic is Climate-Friendly and Saves Energy 7072 Environmental Effects on Plastic 7273 Recycling Plastic 73

731 Plastic Recycling in the EU 74

Modification of Polymers 7681 Polymerization 7682 Additives 78

821 Stiffness and Tensile Strength 79822 Surface Hardness 79823 Wear Resistance 79824 Toughness 80

CHAPTER 6

CHAPTER 7

CHAPTER 8

VIII

Contents

83 Physical Properties 80831 Appearance 80832 Crystallinity 81833 Weather Resistance 81834 Friction 82835 Density 82

84 Chemical Properties 83841 Permeability 83842 Oxidation Resistance 83843 Hydrolysis Resistance 84

85 Electrical Properties 8486 Thermal Properties 85

861 Heat Stabilization 85862 Heat Deflection Temperature 86863 Flame Retardant Classification 86

87 Material Price 87

Material Data and Measurements 8891 Tensile Strength and Stiffness 8992 Impact Strength 9293 Maximum Service Temperature 93

931 UL Service Temperature 93932 Heat Deflection Temperature 93

94 Flammability Tests 95941 HB Rating 95942 V Rating 95

95 Electrical Properties 9696 Flow Properties Melt Index 9797 Shrinkage 97

Material Databases on the Internet 98101 CAMPUS 98

1011 Properties of CAMPUS 52 99102 Material Data Center 99

1021 Properties of Material Data Center 100103 Prospector Plastics Database 100

Test Methods for Plastic Raw Materials and Moldings 102111 Quality Control during Raw Material Production 102112 Visual Quality Control of Plastic Granules 103113 Visual Inspection of Plastic Parts 104114 Tests That Can Be Performed by the Molder 105115 Advanced Testing Methods 107

CHAPTER 9

CHAPTER 10

CHAPTER 11

IX

Contents

Injection-Molding Methods 110121 History 110122 Properties 111

1221 Limitations 111123 The Injection-Molding Machine 112

1231 The Injection Unit 1121232 Locking Unit 1131233 Injection-Molding Cycle 114

124 Alternative Injection-Molding Methods 1151241 Multi-component Injection Molding 1151242 Gas or Water Injection 116

Post-molding Operations 117131 Surface Treatment of Moldings 117

1311 Printing 1171312 ldquoHot Stamprdquo Printing 1181313 Tampon Printing 1191314 Screen Printing 1191315 IMD In-Mold Decoration 1201316 Laser Marking 1211317 Painting 1211318 MetalizingChroming 122

Different Types of Molds 123141 Two-Plate Molds 123142 Three-Plate Molds 124143 Molds with Slides 124144 Molds with Rotating Cores 125145 Stack Molds 125146 Molds with Ejection from the Fixed Half 126147 Family Molds 126148 Multi-component Molds 127149 Molds with Melt Cores 128

Structure of Molds 129151 The Function of the Mold 130152 Runner Systems ndash Cold Runners 130153 Runner Systems ndash Hot Runners 132154 Cold Slug PocketsPullers 133155 Tempering or Cooling Systems 134156 Venting Systems 136157 Ejector Systems 137158 Draft Angles 138

CHAPTER 12

CHAPTER 13

CHAPTER 14

CHAPTER 15

X

Contents

Mold Design and Product Quality 139161 Mold-Related Problems 139

1611 Too-Weak Mold Plates 1391612 Incorrect Sprue and Nozzle Design 1401613 Incorrect Runner Design 1411614 Incorrectly Designed Located

or Missing Cold Slug Pocket 1411615 Incorrect Gate Design 1421616 Incorrect Venting 1431617 Incorrect Mold Temperature Management 144

Prototype Molds and Mold Filling Analysis 145171 Prototype Molds 145172 Mold Filling Analysis 146173 Workflow 147

1731 Mesh Model 1471732 Material Selection 1481733 Process Parameters 1481734 Selection of Gate Location 1481735 Simulations 1491736 Results Generated by Simulations 1491737 Filling Sequence 1501738 Pressure Distribution 1501739 Clamping Force 15017310 Cooling Time 15117311 Temperature Control 15117312 Shrinkage and Warpage 15117313 Glass Fiber Orientation 15217314 Warpage Analysis 15217315 Gate Location 15217316 Material Replacement 15317317 Simulation Software 153

Rapid Prototyping and Additive Manufacturing 154181 Prototypes 154182 Rapid Prototyping (RP) 155

1821 SLA ndash Stereolithography 1561822 SLS ndash Selective Laser Sintering 1591823 The FDM Method 1611824 3DP Printing 1621825 3D Printing 1631826 PolyJet 164

183 Additive Manufacturing 166

CHAPTER 16

CHAPTER 17

CHAPTER 18

XI

Contents

Cost Calculations for Moldings 168191 Part Cost Calculator 169192 Part Cost Scenarios 173192 Replacement Cost 174

Extrusion 177201 The Extrusion Process 177

2011 Advantages (+) and Limitations (minus) 177202 Materials for Extrusion 179203 The Extruder Design 180

2031 The Cylinder 1802032 Single-Screws 1812033 Barrier Screws 1812034 Straight Twin-Screws 1822035 Conical Twin-Screws 1822036 Rotational Direction 1832037 Comparison of Single-Screws and Twin-Screws 1832038 ToolDie 1842039 Calibration 18420310 Corrugation 18520311 Cooling 18520312 Feeding 18620313 Marking 18620314 Further Processing 18620315 Cutting 18720316 Winding 188

204 Extrusion Processes 1882041 Straight Extrusion 1892042 Extrusion with Angle ToolCoating 1892043 Extrusion of Plates and Sheets 1902044 Co-extrusion 1912045 Film Blowing 191

20451 Advantages (+) and Limitations (minus) 1922046 Cable Production 1932047 Monofilament 1942048 Compounding 195

205 Design for Extrusion 1962051 Ribbing ndash Stiffening 1972052 Cavity 1972053 Sealing Lip 1972054 Hinge 1982055 Guide 1982056 Sliding Joint 1982057 Snap-Fit Joint 1992058 Bellow 1992059 InsertReinforcement 19920510 Friction Surface 200

CHAPTER 19

CHAPTER 20

XII

Contents

20511 PrintingStamping 20020512 Decoration Surface 20020513 Drilled Side Holes 20120514 Irregular Holes 20120515 Corrugation 20120516 Spiral Forming 20220517 Foaming 20220518 Extruded Screw Holes 20220519 Muffing and Hot Plate Welding 203

Alternative Processing Methods for Thermoplastics 204211 Blow Molding 204212 Rotational Molding 206213 Vacuum Forming 207

Material Selection Process 209221 How Do You Select the Right Material in

Your Development Project 209222 Development Cooperation 210223 Establishing the Requirement Specifications 210224 MUST Requirements 211225 WANT Requirements 212226 Specify and Sort the Material Candidates 213227 Make a Detailed Cost Analysis 214228 Establish a Meaningful Test Program 215

Requirements and Specification for Plastic Products 216231 Background Information 216232 Batch Size 217233 Part Size 218234 Tolerance Requirements 218235 Part Design 220236 Assembly Requirements 223237 Mechanical Load 223238 Chemical Resistance 224239 Electrical Properties 2252310 Environmental Impact 2262311 Color 2272312 Surface Properties 2282313 Other Properties 2302314 Regulatory Requirements 2312315 Recycling Requirements 2322316 Cost Requirements 233

CHAPTER 21

CHAPTER 22

CHAPTER 23

XIII

Contents

2317 Requirement Specification ndash Checklist 23423171 Background information 23423172 Batch Size 23423173 Part Size 23523174 Tolerance Requirements 23523175 Part Design 23523176 Assembly Requirements 23523177 Mechanical Load 23523178 Chemical Resistance 23523179 Electrical Properties 235231710 Environmental Impact 236231711 Color 236231712 Surface Properties 236231713 Other Properties 236231714 Regulatory Requirements 237231715 Recycling 237231716 Costs 237

Design Rules for Thermoplastic Moldings 238241 Rule 1 ndash Remember That Plastics Are Not Metals 239242 Rule 2 ndash Consider the Specific Characteristics of Plastics 240

2421 Anisotropic Behavior 2412422 Temperature-Dependent Behavior 2412423 Time-Dependent Stress-Strain Curve 242

24231 Creep 24224232 Relaxation 242

2424 Speed-Dependent Characteristics 2432425 Environmentally Dependent Characteristics 2442426 Easy to Design 2442427 Easy to Color 2442428 Easy to Assemble 2452429 Recycling 245

243 Rule 3 ndash Design with Regard to Future Recycling 2462431 Dismantling 2462432 Reused Materials 2482433 Coding 2482434 Cleaning 249

244 Rule 4 ndash Integrate Several Functions into One Component 249

245 Rule 5 ndash Maintain an Even Wall Thickness 251246 Rule 6 ndash Avoid Sharp Corners 252247 Rule 7 ndash Use Ribs to Increase Stiffness 254

2471 Limitations when Designing Ribs 2542472 Material-Saving Design 2552473 Avoid Sink Marks at Rib Joints 255

CHAPTER 24

XIV

Contents

248 Rule 8 ndash Be Careful with Gate Location and Dimensions 2562481 Weld Lines 257

249 Rule 9 ndash Avoid Tight Tolerances 2582410 Rule 10 ndash Choose an Appropriate Assembly Method 259

Assembly Methods for Thermoplastics 260251 Assembly Methods That Facilitate Disassembly 260252 Integrated Snap-Fits 261253 Permanent Assembly Methods 262

2531 Ultrasonic Welding 2622532 Vibration Welding 2632533 Rotational Welding 2642534 Hot Plate Welding 2652535 Infrared Welding 2662536 Laser Welding 2662537 Riveting 2682538 Gluing 269

The Injection-Molding Process 270261 Molding Processing Analysis 270262 Contact Information 272263 Information Pane 272264 Material Information 273265 Information about the Machine 274266 Information about the Mold 276267 Drying 278268 Processing Information 280269 Temperatures 2812610 Pressure Injection Speed and Screw Rotation Speed 2862611 Hold Pressure 2872612 Injection 2892613 Screw Rotation Speed 2902614 Time and Length Settings 292

Injection Molding Process Parameters 297

Problem Solving and Quality Management 301281 Increased Quality Demands 301282 Analytical Troubleshooting ndash ATS 301

2821 Definition of the Problem 3022822 Deviation Definition 302

283 Defining a Problem 3032831 Classification of Problems 3042832 Problem Analysis 306

CHAPTER 25

CHAPTER 26

CHAPTER 27

CHAPTER 28

XV

Contents

2833 Brainstorming 3082834 Verification of Causes 3082835 Planning of Actions to Take 309

284 Statistical Design of Experiments ndash DOE 3092841 Factorial Experiments 310

285 Failure Mode Effect Analysis ndash FMEA 3132851 General Concepts of FMEA 314

Troubleshooting ndash Causes and Effects 316291 Molding Problems 316292 Fill Ratio 318

2921 Short Shots ndash The Part Is Not Completely Filled 3182922 Flashes 3192923 Sink Marks 3192924 Voids or Pores 320

293 Surface Defects 3212931 Burn Marks 321

29311 Discoloration Dark Streaks or Degradation 32129312 Black Specks 32129313 Splays or Silver Streaks

(Partly over the Surface) 32229314 Diesel Effect ndash Entrapped Air 323

2932 Splays or Silver Streaks (All over the Surface) 3242933 Color Streaks ndash Bad Color Dispersion 3242934 Color Streaks ndash Unfavorable Pigment Orientation 3252935 Surface Gloss ndash MatteShiny Surface Variations 3252936 Surface Gloss ndash Corona Effect 3262937 Splays Stripes and Blisters 3262938 Glass Fiber Streaks 3272939 Weld-Lines (Knit-Lines) 32729310 Jetting 32829311 Delamination 32929312 Record Grooves (Orange Peel) 32929313 Cold Slug 33029314 Ejector Pin Marks 33029315 Oil Stain ndash Brown or Black Specks 33129316 Water Stain 331

294 Poor Mechanical Strength 3322941 Bubbles or Voids inside the Part 3322942 Cracks 3322943 Unmelts (Also Called Pitting) 3332944 Brittleness 3342945 Crazing 3342946 Problems with Regrind 335

CHAPTER 29

XVI

Contents

295 Dimensional Problems 3352951 Incorrect Shrinkage 3352952 Unrealistic Tolerances 3362953 Warpage 337

296 Production Problems 3382961 Part Sticks in the Cavity 3382962 Part Sticks on the Core 3382963 Part Sticks on the Ejector Pins 3392964 Sprue Sticks in the Mold 3402965 Stringing 341

Statistical Process Control (SPC) 342301enspWhy SPC 342302enspDefinitions in SPC 343

3021enspNormal Distribution (Gaussian Dispersion) 343303enspStandard Deviations 343

3031enspOne Standard Deviation 3433032enspSix Standard Deviations (Six Sigma) 3443033enspControl Limits 3443034enspTarget Value 3463035enspTarget Value Centering (TC) 3473036enspCapability Machine (Cm) 3473037enspCapability Machine Index (Cmk) 3483038enspCapability Process (Cp) 3483039enspCapability Process Index (Cpk) 34930310enspSix Important Factors 34930311enspMachine Capability 35030312enspProcess Capability 350

304enspHow SPC Works in Practice 3513041enspSoftware 3513042enspProcess Data Monitoring 352

Internet Links 354

Index 355

CHAPTER 30

CHAPTER 31

XVII

Foreword

For many years I had the idea of writing a book about injection molding as I have spent over 45 years of my working life on this subject

When I retired in 2009 I was given great support by my friends Katarina Elner- Haglund and Peter Schulz of the Swedish plastics magazine Plastforum who asked me to write a series of articles about thermoplastics and their processing for the magazine

I was also hired at this time to work with educational programs at the Lund Uni-versity of Technology the Royal University of Technology in Stockholm and a number of industrial companies in Sweden as a result of which this book was developed

My aim has been to write in such a way that this book can be understood by everyone regardless of prior knowledge about plastics The book has a practical approach with lots of pictures and is intended to be used in secondary schools universities industrial training and self-study In some of the chapters there are references to worksheets in Excel that can be downloaded free from my website wwwbruconse

In addition to the above-mentioned persons I would like to extend a warm thanks to my wife Ingeloumlv who has been very patient when Irsquove been totally absent in the ldquowonderful world of plasticsrdquo and then proofread the book my brother Hans-Peter who has spent countless hours on adjustments of all the images etc and my son-in-law Stefan Bruder who has checked the contents of the book and contributed with many valuable comments

I would also like to thank my previous employer DuPont Performance Polymers and especially my friends and former managers Bjoumlrn Hedlund and Stewart Day-kin who encouraged the development of my career as a trainer until I reached my ultimate goal and dream job of ldquoglobal technical training managerrdquo They have also contributed with a lot of information and many valuable images in this book

I also want said a big thank you to my friends and business partners in all educa-tional programs in recent years who have supported me and contributed with many valuable comments information and images for this book and a special thanks to those who have made this printing possible thanks to the ads in the beginning The whole list would be very long but you will find some of them in the list of internet links in Chapter 31

In this Second Edition

This edition contains greatly expanded coverage of extrusion collected into a new Chapter 20 There are also a number of new and updated figures with numerous small improvements and corrections throughout the text These are complemented by an all-new professional layout and structure which I hope will help readers to navigate the book comfortably

XVIII

Foreword

I would like to thank Mark Smith at Carl Hanser Verlag for all the support that I received during the last years with my book in various languages

Ulf Bruder

Karlskrona Sweden

10

Chapter 2 mdash Commodities

3) LDPE is used for film blowing and extrusion

A large part of all the polyethylene produced is used for film blowing If the film is soft and flexible it is either made of LDPE or LLDPE If it has the rustle of the free bags at the grocery store it is probably made of HDPE LLDPE is also used to improve the strength of LDPE film

Figure 27enspGarbage bags LDPE is excellent for film blowing and is the most common material used in bags plastic sacks and construction film

Figure 28enspCable jacketing LDPE is used in the extrusion of jacketing for high voltage cables

4) PEX

Cross-linked polyethylene is mainly used in the extrusion of tubes The cross-link-ing provides improved creep resistance and better high-temperature properties

You can even copolymerize ethylene with polar monomers and get everything from viscous products (ethinspg melting glue) to tough films and impact-resistant hard shells such as golf balls

A common copolymer is EVA (ethylene-vinyl-acetate) By varying the concentration of vinyl acetate (VA) from 25 to 95 you can control the properties and produce a range of different types of material Increased VA content leads to higher trans-parency and toughness

Adhesives carpet underlay cable insulation carriers of color masterbatches stretch film and coating film for cardboard and paper are typical uses of EVA

Figure 29enspTubes in PEX resist both high temperatures (120degC) and pres-sure and are used for the hot water supply of cleaning or washing machines

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

VII

Contents

55 Polyphenylene Sulfide ndash PPS 52551 Properties of PPS 52552 Application Areas 52

56 Polyether Ether Ketone ndash PEEK 53561 Properties of PEEK 53562 Application Areas 54

57 Polyetherimide ndash PEI 54571 Properties of PEI 55572 Application Areas 55

58 Polysulfone ndash PSU 56581 Properties of PSU 56582 Application Areas 57

59 Polyphenylsulfone ndash PPSU 57591 Properties of PPSU 57592 Application Areas 58

Bioplastics and Biocomposites 5961 Definition 59

611 What Do We Mean by Bioplastic 6062 The Market 6063 Bioplastics 6264 Biopolymers 6265 Biobased Polymers Biopolyester 6366 Biobased Polymers Biopolyamides 6567 Biobased Polymers from Microorganisms 6668 Bioethanol or Biomethanol 6769 Biocomposites 68610 More Information about Bioplastics 69

Plastic and the Environment 7071 Plastic is Climate-Friendly and Saves Energy 7072 Environmental Effects on Plastic 7273 Recycling Plastic 73

731 Plastic Recycling in the EU 74

Modification of Polymers 7681 Polymerization 7682 Additives 78

821 Stiffness and Tensile Strength 79822 Surface Hardness 79823 Wear Resistance 79824 Toughness 80

CHAPTER 6

CHAPTER 7

CHAPTER 8

VIII

Contents

83 Physical Properties 80831 Appearance 80832 Crystallinity 81833 Weather Resistance 81834 Friction 82835 Density 82

84 Chemical Properties 83841 Permeability 83842 Oxidation Resistance 83843 Hydrolysis Resistance 84

85 Electrical Properties 8486 Thermal Properties 85

861 Heat Stabilization 85862 Heat Deflection Temperature 86863 Flame Retardant Classification 86

87 Material Price 87

Material Data and Measurements 8891 Tensile Strength and Stiffness 8992 Impact Strength 9293 Maximum Service Temperature 93

931 UL Service Temperature 93932 Heat Deflection Temperature 93

94 Flammability Tests 95941 HB Rating 95942 V Rating 95

95 Electrical Properties 9696 Flow Properties Melt Index 9797 Shrinkage 97

Material Databases on the Internet 98101 CAMPUS 98

1011 Properties of CAMPUS 52 99102 Material Data Center 99

1021 Properties of Material Data Center 100103 Prospector Plastics Database 100

Test Methods for Plastic Raw Materials and Moldings 102111 Quality Control during Raw Material Production 102112 Visual Quality Control of Plastic Granules 103113 Visual Inspection of Plastic Parts 104114 Tests That Can Be Performed by the Molder 105115 Advanced Testing Methods 107

CHAPTER 9

CHAPTER 10

CHAPTER 11

IX

Contents

Injection-Molding Methods 110121 History 110122 Properties 111

1221 Limitations 111123 The Injection-Molding Machine 112

1231 The Injection Unit 1121232 Locking Unit 1131233 Injection-Molding Cycle 114

124 Alternative Injection-Molding Methods 1151241 Multi-component Injection Molding 1151242 Gas or Water Injection 116

Post-molding Operations 117131 Surface Treatment of Moldings 117

1311 Printing 1171312 ldquoHot Stamprdquo Printing 1181313 Tampon Printing 1191314 Screen Printing 1191315 IMD In-Mold Decoration 1201316 Laser Marking 1211317 Painting 1211318 MetalizingChroming 122

Different Types of Molds 123141 Two-Plate Molds 123142 Three-Plate Molds 124143 Molds with Slides 124144 Molds with Rotating Cores 125145 Stack Molds 125146 Molds with Ejection from the Fixed Half 126147 Family Molds 126148 Multi-component Molds 127149 Molds with Melt Cores 128

Structure of Molds 129151 The Function of the Mold 130152 Runner Systems ndash Cold Runners 130153 Runner Systems ndash Hot Runners 132154 Cold Slug PocketsPullers 133155 Tempering or Cooling Systems 134156 Venting Systems 136157 Ejector Systems 137158 Draft Angles 138

CHAPTER 12

CHAPTER 13

CHAPTER 14

CHAPTER 15

X

Contents

Mold Design and Product Quality 139161 Mold-Related Problems 139

1611 Too-Weak Mold Plates 1391612 Incorrect Sprue and Nozzle Design 1401613 Incorrect Runner Design 1411614 Incorrectly Designed Located

or Missing Cold Slug Pocket 1411615 Incorrect Gate Design 1421616 Incorrect Venting 1431617 Incorrect Mold Temperature Management 144

Prototype Molds and Mold Filling Analysis 145171 Prototype Molds 145172 Mold Filling Analysis 146173 Workflow 147

1731 Mesh Model 1471732 Material Selection 1481733 Process Parameters 1481734 Selection of Gate Location 1481735 Simulations 1491736 Results Generated by Simulations 1491737 Filling Sequence 1501738 Pressure Distribution 1501739 Clamping Force 15017310 Cooling Time 15117311 Temperature Control 15117312 Shrinkage and Warpage 15117313 Glass Fiber Orientation 15217314 Warpage Analysis 15217315 Gate Location 15217316 Material Replacement 15317317 Simulation Software 153

Rapid Prototyping and Additive Manufacturing 154181 Prototypes 154182 Rapid Prototyping (RP) 155

1821 SLA ndash Stereolithography 1561822 SLS ndash Selective Laser Sintering 1591823 The FDM Method 1611824 3DP Printing 1621825 3D Printing 1631826 PolyJet 164

183 Additive Manufacturing 166

CHAPTER 16

CHAPTER 17

CHAPTER 18

XI

Contents

Cost Calculations for Moldings 168191 Part Cost Calculator 169192 Part Cost Scenarios 173192 Replacement Cost 174

Extrusion 177201 The Extrusion Process 177

2011 Advantages (+) and Limitations (minus) 177202 Materials for Extrusion 179203 The Extruder Design 180

2031 The Cylinder 1802032 Single-Screws 1812033 Barrier Screws 1812034 Straight Twin-Screws 1822035 Conical Twin-Screws 1822036 Rotational Direction 1832037 Comparison of Single-Screws and Twin-Screws 1832038 ToolDie 1842039 Calibration 18420310 Corrugation 18520311 Cooling 18520312 Feeding 18620313 Marking 18620314 Further Processing 18620315 Cutting 18720316 Winding 188

204 Extrusion Processes 1882041 Straight Extrusion 1892042 Extrusion with Angle ToolCoating 1892043 Extrusion of Plates and Sheets 1902044 Co-extrusion 1912045 Film Blowing 191

20451 Advantages (+) and Limitations (minus) 1922046 Cable Production 1932047 Monofilament 1942048 Compounding 195

205 Design for Extrusion 1962051 Ribbing ndash Stiffening 1972052 Cavity 1972053 Sealing Lip 1972054 Hinge 1982055 Guide 1982056 Sliding Joint 1982057 Snap-Fit Joint 1992058 Bellow 1992059 InsertReinforcement 19920510 Friction Surface 200

CHAPTER 19

CHAPTER 20

XII

Contents

20511 PrintingStamping 20020512 Decoration Surface 20020513 Drilled Side Holes 20120514 Irregular Holes 20120515 Corrugation 20120516 Spiral Forming 20220517 Foaming 20220518 Extruded Screw Holes 20220519 Muffing and Hot Plate Welding 203

Alternative Processing Methods for Thermoplastics 204211 Blow Molding 204212 Rotational Molding 206213 Vacuum Forming 207

Material Selection Process 209221 How Do You Select the Right Material in

Your Development Project 209222 Development Cooperation 210223 Establishing the Requirement Specifications 210224 MUST Requirements 211225 WANT Requirements 212226 Specify and Sort the Material Candidates 213227 Make a Detailed Cost Analysis 214228 Establish a Meaningful Test Program 215

Requirements and Specification for Plastic Products 216231 Background Information 216232 Batch Size 217233 Part Size 218234 Tolerance Requirements 218235 Part Design 220236 Assembly Requirements 223237 Mechanical Load 223238 Chemical Resistance 224239 Electrical Properties 2252310 Environmental Impact 2262311 Color 2272312 Surface Properties 2282313 Other Properties 2302314 Regulatory Requirements 2312315 Recycling Requirements 2322316 Cost Requirements 233

CHAPTER 21

CHAPTER 22

CHAPTER 23

XIII

Contents

2317 Requirement Specification ndash Checklist 23423171 Background information 23423172 Batch Size 23423173 Part Size 23523174 Tolerance Requirements 23523175 Part Design 23523176 Assembly Requirements 23523177 Mechanical Load 23523178 Chemical Resistance 23523179 Electrical Properties 235231710 Environmental Impact 236231711 Color 236231712 Surface Properties 236231713 Other Properties 236231714 Regulatory Requirements 237231715 Recycling 237231716 Costs 237

Design Rules for Thermoplastic Moldings 238241 Rule 1 ndash Remember That Plastics Are Not Metals 239242 Rule 2 ndash Consider the Specific Characteristics of Plastics 240

2421 Anisotropic Behavior 2412422 Temperature-Dependent Behavior 2412423 Time-Dependent Stress-Strain Curve 242

24231 Creep 24224232 Relaxation 242

2424 Speed-Dependent Characteristics 2432425 Environmentally Dependent Characteristics 2442426 Easy to Design 2442427 Easy to Color 2442428 Easy to Assemble 2452429 Recycling 245

243 Rule 3 ndash Design with Regard to Future Recycling 2462431 Dismantling 2462432 Reused Materials 2482433 Coding 2482434 Cleaning 249

244 Rule 4 ndash Integrate Several Functions into One Component 249

245 Rule 5 ndash Maintain an Even Wall Thickness 251246 Rule 6 ndash Avoid Sharp Corners 252247 Rule 7 ndash Use Ribs to Increase Stiffness 254

2471 Limitations when Designing Ribs 2542472 Material-Saving Design 2552473 Avoid Sink Marks at Rib Joints 255

CHAPTER 24

XIV

Contents

248 Rule 8 ndash Be Careful with Gate Location and Dimensions 2562481 Weld Lines 257

249 Rule 9 ndash Avoid Tight Tolerances 2582410 Rule 10 ndash Choose an Appropriate Assembly Method 259

Assembly Methods for Thermoplastics 260251 Assembly Methods That Facilitate Disassembly 260252 Integrated Snap-Fits 261253 Permanent Assembly Methods 262

2531 Ultrasonic Welding 2622532 Vibration Welding 2632533 Rotational Welding 2642534 Hot Plate Welding 2652535 Infrared Welding 2662536 Laser Welding 2662537 Riveting 2682538 Gluing 269

The Injection-Molding Process 270261 Molding Processing Analysis 270262 Contact Information 272263 Information Pane 272264 Material Information 273265 Information about the Machine 274266 Information about the Mold 276267 Drying 278268 Processing Information 280269 Temperatures 2812610 Pressure Injection Speed and Screw Rotation Speed 2862611 Hold Pressure 2872612 Injection 2892613 Screw Rotation Speed 2902614 Time and Length Settings 292

Injection Molding Process Parameters 297

Problem Solving and Quality Management 301281 Increased Quality Demands 301282 Analytical Troubleshooting ndash ATS 301

2821 Definition of the Problem 3022822 Deviation Definition 302

283 Defining a Problem 3032831 Classification of Problems 3042832 Problem Analysis 306

CHAPTER 25

CHAPTER 26

CHAPTER 27

CHAPTER 28

XV

Contents

2833 Brainstorming 3082834 Verification of Causes 3082835 Planning of Actions to Take 309

284 Statistical Design of Experiments ndash DOE 3092841 Factorial Experiments 310

285 Failure Mode Effect Analysis ndash FMEA 3132851 General Concepts of FMEA 314

Troubleshooting ndash Causes and Effects 316291 Molding Problems 316292 Fill Ratio 318

2921 Short Shots ndash The Part Is Not Completely Filled 3182922 Flashes 3192923 Sink Marks 3192924 Voids or Pores 320

293 Surface Defects 3212931 Burn Marks 321

29311 Discoloration Dark Streaks or Degradation 32129312 Black Specks 32129313 Splays or Silver Streaks

(Partly over the Surface) 32229314 Diesel Effect ndash Entrapped Air 323

2932 Splays or Silver Streaks (All over the Surface) 3242933 Color Streaks ndash Bad Color Dispersion 3242934 Color Streaks ndash Unfavorable Pigment Orientation 3252935 Surface Gloss ndash MatteShiny Surface Variations 3252936 Surface Gloss ndash Corona Effect 3262937 Splays Stripes and Blisters 3262938 Glass Fiber Streaks 3272939 Weld-Lines (Knit-Lines) 32729310 Jetting 32829311 Delamination 32929312 Record Grooves (Orange Peel) 32929313 Cold Slug 33029314 Ejector Pin Marks 33029315 Oil Stain ndash Brown or Black Specks 33129316 Water Stain 331

294 Poor Mechanical Strength 3322941 Bubbles or Voids inside the Part 3322942 Cracks 3322943 Unmelts (Also Called Pitting) 3332944 Brittleness 3342945 Crazing 3342946 Problems with Regrind 335

CHAPTER 29

XVI

Contents

295 Dimensional Problems 3352951 Incorrect Shrinkage 3352952 Unrealistic Tolerances 3362953 Warpage 337

296 Production Problems 3382961 Part Sticks in the Cavity 3382962 Part Sticks on the Core 3382963 Part Sticks on the Ejector Pins 3392964 Sprue Sticks in the Mold 3402965 Stringing 341

Statistical Process Control (SPC) 342301enspWhy SPC 342302enspDefinitions in SPC 343

3021enspNormal Distribution (Gaussian Dispersion) 343303enspStandard Deviations 343

3031enspOne Standard Deviation 3433032enspSix Standard Deviations (Six Sigma) 3443033enspControl Limits 3443034enspTarget Value 3463035enspTarget Value Centering (TC) 3473036enspCapability Machine (Cm) 3473037enspCapability Machine Index (Cmk) 3483038enspCapability Process (Cp) 3483039enspCapability Process Index (Cpk) 34930310enspSix Important Factors 34930311enspMachine Capability 35030312enspProcess Capability 350

304enspHow SPC Works in Practice 3513041enspSoftware 3513042enspProcess Data Monitoring 352

Internet Links 354

Index 355

CHAPTER 30

CHAPTER 31

XVII

Foreword

For many years I had the idea of writing a book about injection molding as I have spent over 45 years of my working life on this subject

When I retired in 2009 I was given great support by my friends Katarina Elner- Haglund and Peter Schulz of the Swedish plastics magazine Plastforum who asked me to write a series of articles about thermoplastics and their processing for the magazine

I was also hired at this time to work with educational programs at the Lund Uni-versity of Technology the Royal University of Technology in Stockholm and a number of industrial companies in Sweden as a result of which this book was developed

My aim has been to write in such a way that this book can be understood by everyone regardless of prior knowledge about plastics The book has a practical approach with lots of pictures and is intended to be used in secondary schools universities industrial training and self-study In some of the chapters there are references to worksheets in Excel that can be downloaded free from my website wwwbruconse

In addition to the above-mentioned persons I would like to extend a warm thanks to my wife Ingeloumlv who has been very patient when Irsquove been totally absent in the ldquowonderful world of plasticsrdquo and then proofread the book my brother Hans-Peter who has spent countless hours on adjustments of all the images etc and my son-in-law Stefan Bruder who has checked the contents of the book and contributed with many valuable comments

I would also like to thank my previous employer DuPont Performance Polymers and especially my friends and former managers Bjoumlrn Hedlund and Stewart Day-kin who encouraged the development of my career as a trainer until I reached my ultimate goal and dream job of ldquoglobal technical training managerrdquo They have also contributed with a lot of information and many valuable images in this book

I also want said a big thank you to my friends and business partners in all educa-tional programs in recent years who have supported me and contributed with many valuable comments information and images for this book and a special thanks to those who have made this printing possible thanks to the ads in the beginning The whole list would be very long but you will find some of them in the list of internet links in Chapter 31

In this Second Edition

This edition contains greatly expanded coverage of extrusion collected into a new Chapter 20 There are also a number of new and updated figures with numerous small improvements and corrections throughout the text These are complemented by an all-new professional layout and structure which I hope will help readers to navigate the book comfortably

XVIII

Foreword

I would like to thank Mark Smith at Carl Hanser Verlag for all the support that I received during the last years with my book in various languages

Ulf Bruder

Karlskrona Sweden

10

Chapter 2 mdash Commodities

3) LDPE is used for film blowing and extrusion

A large part of all the polyethylene produced is used for film blowing If the film is soft and flexible it is either made of LDPE or LLDPE If it has the rustle of the free bags at the grocery store it is probably made of HDPE LLDPE is also used to improve the strength of LDPE film

Figure 27enspGarbage bags LDPE is excellent for film blowing and is the most common material used in bags plastic sacks and construction film

Figure 28enspCable jacketing LDPE is used in the extrusion of jacketing for high voltage cables

4) PEX

Cross-linked polyethylene is mainly used in the extrusion of tubes The cross-link-ing provides improved creep resistance and better high-temperature properties

You can even copolymerize ethylene with polar monomers and get everything from viscous products (ethinspg melting glue) to tough films and impact-resistant hard shells such as golf balls

A common copolymer is EVA (ethylene-vinyl-acetate) By varying the concentration of vinyl acetate (VA) from 25 to 95 you can control the properties and produce a range of different types of material Increased VA content leads to higher trans-parency and toughness

Adhesives carpet underlay cable insulation carriers of color masterbatches stretch film and coating film for cardboard and paper are typical uses of EVA

Figure 29enspTubes in PEX resist both high temperatures (120degC) and pres-sure and are used for the hot water supply of cleaning or washing machines

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

VIII

Contents

83 Physical Properties 80831 Appearance 80832 Crystallinity 81833 Weather Resistance 81834 Friction 82835 Density 82

84 Chemical Properties 83841 Permeability 83842 Oxidation Resistance 83843 Hydrolysis Resistance 84

85 Electrical Properties 8486 Thermal Properties 85

861 Heat Stabilization 85862 Heat Deflection Temperature 86863 Flame Retardant Classification 86

87 Material Price 87

Material Data and Measurements 8891 Tensile Strength and Stiffness 8992 Impact Strength 9293 Maximum Service Temperature 93

931 UL Service Temperature 93932 Heat Deflection Temperature 93

94 Flammability Tests 95941 HB Rating 95942 V Rating 95

95 Electrical Properties 9696 Flow Properties Melt Index 9797 Shrinkage 97

Material Databases on the Internet 98101 CAMPUS 98

1011 Properties of CAMPUS 52 99102 Material Data Center 99

1021 Properties of Material Data Center 100103 Prospector Plastics Database 100

Test Methods for Plastic Raw Materials and Moldings 102111 Quality Control during Raw Material Production 102112 Visual Quality Control of Plastic Granules 103113 Visual Inspection of Plastic Parts 104114 Tests That Can Be Performed by the Molder 105115 Advanced Testing Methods 107

CHAPTER 9

CHAPTER 10

CHAPTER 11

IX

Contents

Injection-Molding Methods 110121 History 110122 Properties 111

1221 Limitations 111123 The Injection-Molding Machine 112

1231 The Injection Unit 1121232 Locking Unit 1131233 Injection-Molding Cycle 114

124 Alternative Injection-Molding Methods 1151241 Multi-component Injection Molding 1151242 Gas or Water Injection 116

Post-molding Operations 117131 Surface Treatment of Moldings 117

1311 Printing 1171312 ldquoHot Stamprdquo Printing 1181313 Tampon Printing 1191314 Screen Printing 1191315 IMD In-Mold Decoration 1201316 Laser Marking 1211317 Painting 1211318 MetalizingChroming 122

Different Types of Molds 123141 Two-Plate Molds 123142 Three-Plate Molds 124143 Molds with Slides 124144 Molds with Rotating Cores 125145 Stack Molds 125146 Molds with Ejection from the Fixed Half 126147 Family Molds 126148 Multi-component Molds 127149 Molds with Melt Cores 128

Structure of Molds 129151 The Function of the Mold 130152 Runner Systems ndash Cold Runners 130153 Runner Systems ndash Hot Runners 132154 Cold Slug PocketsPullers 133155 Tempering or Cooling Systems 134156 Venting Systems 136157 Ejector Systems 137158 Draft Angles 138

CHAPTER 12

CHAPTER 13

CHAPTER 14

CHAPTER 15

X

Contents

Mold Design and Product Quality 139161 Mold-Related Problems 139

1611 Too-Weak Mold Plates 1391612 Incorrect Sprue and Nozzle Design 1401613 Incorrect Runner Design 1411614 Incorrectly Designed Located

or Missing Cold Slug Pocket 1411615 Incorrect Gate Design 1421616 Incorrect Venting 1431617 Incorrect Mold Temperature Management 144

Prototype Molds and Mold Filling Analysis 145171 Prototype Molds 145172 Mold Filling Analysis 146173 Workflow 147

1731 Mesh Model 1471732 Material Selection 1481733 Process Parameters 1481734 Selection of Gate Location 1481735 Simulations 1491736 Results Generated by Simulations 1491737 Filling Sequence 1501738 Pressure Distribution 1501739 Clamping Force 15017310 Cooling Time 15117311 Temperature Control 15117312 Shrinkage and Warpage 15117313 Glass Fiber Orientation 15217314 Warpage Analysis 15217315 Gate Location 15217316 Material Replacement 15317317 Simulation Software 153

Rapid Prototyping and Additive Manufacturing 154181 Prototypes 154182 Rapid Prototyping (RP) 155

1821 SLA ndash Stereolithography 1561822 SLS ndash Selective Laser Sintering 1591823 The FDM Method 1611824 3DP Printing 1621825 3D Printing 1631826 PolyJet 164

183 Additive Manufacturing 166

CHAPTER 16

CHAPTER 17

CHAPTER 18

XI

Contents

Cost Calculations for Moldings 168191 Part Cost Calculator 169192 Part Cost Scenarios 173192 Replacement Cost 174

Extrusion 177201 The Extrusion Process 177

2011 Advantages (+) and Limitations (minus) 177202 Materials for Extrusion 179203 The Extruder Design 180

2031 The Cylinder 1802032 Single-Screws 1812033 Barrier Screws 1812034 Straight Twin-Screws 1822035 Conical Twin-Screws 1822036 Rotational Direction 1832037 Comparison of Single-Screws and Twin-Screws 1832038 ToolDie 1842039 Calibration 18420310 Corrugation 18520311 Cooling 18520312 Feeding 18620313 Marking 18620314 Further Processing 18620315 Cutting 18720316 Winding 188

204 Extrusion Processes 1882041 Straight Extrusion 1892042 Extrusion with Angle ToolCoating 1892043 Extrusion of Plates and Sheets 1902044 Co-extrusion 1912045 Film Blowing 191

20451 Advantages (+) and Limitations (minus) 1922046 Cable Production 1932047 Monofilament 1942048 Compounding 195

205 Design for Extrusion 1962051 Ribbing ndash Stiffening 1972052 Cavity 1972053 Sealing Lip 1972054 Hinge 1982055 Guide 1982056 Sliding Joint 1982057 Snap-Fit Joint 1992058 Bellow 1992059 InsertReinforcement 19920510 Friction Surface 200

CHAPTER 19

CHAPTER 20

XII

Contents

20511 PrintingStamping 20020512 Decoration Surface 20020513 Drilled Side Holes 20120514 Irregular Holes 20120515 Corrugation 20120516 Spiral Forming 20220517 Foaming 20220518 Extruded Screw Holes 20220519 Muffing and Hot Plate Welding 203

Alternative Processing Methods for Thermoplastics 204211 Blow Molding 204212 Rotational Molding 206213 Vacuum Forming 207

Material Selection Process 209221 How Do You Select the Right Material in

Your Development Project 209222 Development Cooperation 210223 Establishing the Requirement Specifications 210224 MUST Requirements 211225 WANT Requirements 212226 Specify and Sort the Material Candidates 213227 Make a Detailed Cost Analysis 214228 Establish a Meaningful Test Program 215

Requirements and Specification for Plastic Products 216231 Background Information 216232 Batch Size 217233 Part Size 218234 Tolerance Requirements 218235 Part Design 220236 Assembly Requirements 223237 Mechanical Load 223238 Chemical Resistance 224239 Electrical Properties 2252310 Environmental Impact 2262311 Color 2272312 Surface Properties 2282313 Other Properties 2302314 Regulatory Requirements 2312315 Recycling Requirements 2322316 Cost Requirements 233

CHAPTER 21

CHAPTER 22

CHAPTER 23

XIII

Contents

2317 Requirement Specification ndash Checklist 23423171 Background information 23423172 Batch Size 23423173 Part Size 23523174 Tolerance Requirements 23523175 Part Design 23523176 Assembly Requirements 23523177 Mechanical Load 23523178 Chemical Resistance 23523179 Electrical Properties 235231710 Environmental Impact 236231711 Color 236231712 Surface Properties 236231713 Other Properties 236231714 Regulatory Requirements 237231715 Recycling 237231716 Costs 237

Design Rules for Thermoplastic Moldings 238241 Rule 1 ndash Remember That Plastics Are Not Metals 239242 Rule 2 ndash Consider the Specific Characteristics of Plastics 240

2421 Anisotropic Behavior 2412422 Temperature-Dependent Behavior 2412423 Time-Dependent Stress-Strain Curve 242

24231 Creep 24224232 Relaxation 242

2424 Speed-Dependent Characteristics 2432425 Environmentally Dependent Characteristics 2442426 Easy to Design 2442427 Easy to Color 2442428 Easy to Assemble 2452429 Recycling 245

243 Rule 3 ndash Design with Regard to Future Recycling 2462431 Dismantling 2462432 Reused Materials 2482433 Coding 2482434 Cleaning 249

244 Rule 4 ndash Integrate Several Functions into One Component 249

245 Rule 5 ndash Maintain an Even Wall Thickness 251246 Rule 6 ndash Avoid Sharp Corners 252247 Rule 7 ndash Use Ribs to Increase Stiffness 254

2471 Limitations when Designing Ribs 2542472 Material-Saving Design 2552473 Avoid Sink Marks at Rib Joints 255

CHAPTER 24

XIV

Contents

248 Rule 8 ndash Be Careful with Gate Location and Dimensions 2562481 Weld Lines 257

249 Rule 9 ndash Avoid Tight Tolerances 2582410 Rule 10 ndash Choose an Appropriate Assembly Method 259

Assembly Methods for Thermoplastics 260251 Assembly Methods That Facilitate Disassembly 260252 Integrated Snap-Fits 261253 Permanent Assembly Methods 262

2531 Ultrasonic Welding 2622532 Vibration Welding 2632533 Rotational Welding 2642534 Hot Plate Welding 2652535 Infrared Welding 2662536 Laser Welding 2662537 Riveting 2682538 Gluing 269

The Injection-Molding Process 270261 Molding Processing Analysis 270262 Contact Information 272263 Information Pane 272264 Material Information 273265 Information about the Machine 274266 Information about the Mold 276267 Drying 278268 Processing Information 280269 Temperatures 2812610 Pressure Injection Speed and Screw Rotation Speed 2862611 Hold Pressure 2872612 Injection 2892613 Screw Rotation Speed 2902614 Time and Length Settings 292

Injection Molding Process Parameters 297

Problem Solving and Quality Management 301281 Increased Quality Demands 301282 Analytical Troubleshooting ndash ATS 301

2821 Definition of the Problem 3022822 Deviation Definition 302

283 Defining a Problem 3032831 Classification of Problems 3042832 Problem Analysis 306

CHAPTER 25

CHAPTER 26

CHAPTER 27

CHAPTER 28

XV

Contents

2833 Brainstorming 3082834 Verification of Causes 3082835 Planning of Actions to Take 309

284 Statistical Design of Experiments ndash DOE 3092841 Factorial Experiments 310

285 Failure Mode Effect Analysis ndash FMEA 3132851 General Concepts of FMEA 314

Troubleshooting ndash Causes and Effects 316291 Molding Problems 316292 Fill Ratio 318

2921 Short Shots ndash The Part Is Not Completely Filled 3182922 Flashes 3192923 Sink Marks 3192924 Voids or Pores 320

293 Surface Defects 3212931 Burn Marks 321

29311 Discoloration Dark Streaks or Degradation 32129312 Black Specks 32129313 Splays or Silver Streaks

(Partly over the Surface) 32229314 Diesel Effect ndash Entrapped Air 323

2932 Splays or Silver Streaks (All over the Surface) 3242933 Color Streaks ndash Bad Color Dispersion 3242934 Color Streaks ndash Unfavorable Pigment Orientation 3252935 Surface Gloss ndash MatteShiny Surface Variations 3252936 Surface Gloss ndash Corona Effect 3262937 Splays Stripes and Blisters 3262938 Glass Fiber Streaks 3272939 Weld-Lines (Knit-Lines) 32729310 Jetting 32829311 Delamination 32929312 Record Grooves (Orange Peel) 32929313 Cold Slug 33029314 Ejector Pin Marks 33029315 Oil Stain ndash Brown or Black Specks 33129316 Water Stain 331

294 Poor Mechanical Strength 3322941 Bubbles or Voids inside the Part 3322942 Cracks 3322943 Unmelts (Also Called Pitting) 3332944 Brittleness 3342945 Crazing 3342946 Problems with Regrind 335

CHAPTER 29

XVI

Contents

295 Dimensional Problems 3352951 Incorrect Shrinkage 3352952 Unrealistic Tolerances 3362953 Warpage 337

296 Production Problems 3382961 Part Sticks in the Cavity 3382962 Part Sticks on the Core 3382963 Part Sticks on the Ejector Pins 3392964 Sprue Sticks in the Mold 3402965 Stringing 341

Statistical Process Control (SPC) 342301enspWhy SPC 342302enspDefinitions in SPC 343

3021enspNormal Distribution (Gaussian Dispersion) 343303enspStandard Deviations 343

3031enspOne Standard Deviation 3433032enspSix Standard Deviations (Six Sigma) 3443033enspControl Limits 3443034enspTarget Value 3463035enspTarget Value Centering (TC) 3473036enspCapability Machine (Cm) 3473037enspCapability Machine Index (Cmk) 3483038enspCapability Process (Cp) 3483039enspCapability Process Index (Cpk) 34930310enspSix Important Factors 34930311enspMachine Capability 35030312enspProcess Capability 350

304enspHow SPC Works in Practice 3513041enspSoftware 3513042enspProcess Data Monitoring 352

Internet Links 354

Index 355

CHAPTER 30

CHAPTER 31

XVII

Foreword

For many years I had the idea of writing a book about injection molding as I have spent over 45 years of my working life on this subject

When I retired in 2009 I was given great support by my friends Katarina Elner- Haglund and Peter Schulz of the Swedish plastics magazine Plastforum who asked me to write a series of articles about thermoplastics and their processing for the magazine

I was also hired at this time to work with educational programs at the Lund Uni-versity of Technology the Royal University of Technology in Stockholm and a number of industrial companies in Sweden as a result of which this book was developed

My aim has been to write in such a way that this book can be understood by everyone regardless of prior knowledge about plastics The book has a practical approach with lots of pictures and is intended to be used in secondary schools universities industrial training and self-study In some of the chapters there are references to worksheets in Excel that can be downloaded free from my website wwwbruconse

In addition to the above-mentioned persons I would like to extend a warm thanks to my wife Ingeloumlv who has been very patient when Irsquove been totally absent in the ldquowonderful world of plasticsrdquo and then proofread the book my brother Hans-Peter who has spent countless hours on adjustments of all the images etc and my son-in-law Stefan Bruder who has checked the contents of the book and contributed with many valuable comments

I would also like to thank my previous employer DuPont Performance Polymers and especially my friends and former managers Bjoumlrn Hedlund and Stewart Day-kin who encouraged the development of my career as a trainer until I reached my ultimate goal and dream job of ldquoglobal technical training managerrdquo They have also contributed with a lot of information and many valuable images in this book

I also want said a big thank you to my friends and business partners in all educa-tional programs in recent years who have supported me and contributed with many valuable comments information and images for this book and a special thanks to those who have made this printing possible thanks to the ads in the beginning The whole list would be very long but you will find some of them in the list of internet links in Chapter 31

In this Second Edition

This edition contains greatly expanded coverage of extrusion collected into a new Chapter 20 There are also a number of new and updated figures with numerous small improvements and corrections throughout the text These are complemented by an all-new professional layout and structure which I hope will help readers to navigate the book comfortably

XVIII

Foreword

I would like to thank Mark Smith at Carl Hanser Verlag for all the support that I received during the last years with my book in various languages

Ulf Bruder

Karlskrona Sweden

10

Chapter 2 mdash Commodities

3) LDPE is used for film blowing and extrusion

A large part of all the polyethylene produced is used for film blowing If the film is soft and flexible it is either made of LDPE or LLDPE If it has the rustle of the free bags at the grocery store it is probably made of HDPE LLDPE is also used to improve the strength of LDPE film

Figure 27enspGarbage bags LDPE is excellent for film blowing and is the most common material used in bags plastic sacks and construction film

Figure 28enspCable jacketing LDPE is used in the extrusion of jacketing for high voltage cables

4) PEX

Cross-linked polyethylene is mainly used in the extrusion of tubes The cross-link-ing provides improved creep resistance and better high-temperature properties

You can even copolymerize ethylene with polar monomers and get everything from viscous products (ethinspg melting glue) to tough films and impact-resistant hard shells such as golf balls

A common copolymer is EVA (ethylene-vinyl-acetate) By varying the concentration of vinyl acetate (VA) from 25 to 95 you can control the properties and produce a range of different types of material Increased VA content leads to higher trans-parency and toughness

Adhesives carpet underlay cable insulation carriers of color masterbatches stretch film and coating film for cardboard and paper are typical uses of EVA

Figure 29enspTubes in PEX resist both high temperatures (120degC) and pres-sure and are used for the hot water supply of cleaning or washing machines

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

IX

Contents

Injection-Molding Methods 110121 History 110122 Properties 111

1221 Limitations 111123 The Injection-Molding Machine 112

1231 The Injection Unit 1121232 Locking Unit 1131233 Injection-Molding Cycle 114

124 Alternative Injection-Molding Methods 1151241 Multi-component Injection Molding 1151242 Gas or Water Injection 116

Post-molding Operations 117131 Surface Treatment of Moldings 117

1311 Printing 1171312 ldquoHot Stamprdquo Printing 1181313 Tampon Printing 1191314 Screen Printing 1191315 IMD In-Mold Decoration 1201316 Laser Marking 1211317 Painting 1211318 MetalizingChroming 122

Different Types of Molds 123141 Two-Plate Molds 123142 Three-Plate Molds 124143 Molds with Slides 124144 Molds with Rotating Cores 125145 Stack Molds 125146 Molds with Ejection from the Fixed Half 126147 Family Molds 126148 Multi-component Molds 127149 Molds with Melt Cores 128

Structure of Molds 129151 The Function of the Mold 130152 Runner Systems ndash Cold Runners 130153 Runner Systems ndash Hot Runners 132154 Cold Slug PocketsPullers 133155 Tempering or Cooling Systems 134156 Venting Systems 136157 Ejector Systems 137158 Draft Angles 138

CHAPTER 12

CHAPTER 13

CHAPTER 14

CHAPTER 15

X

Contents

Mold Design and Product Quality 139161 Mold-Related Problems 139

1611 Too-Weak Mold Plates 1391612 Incorrect Sprue and Nozzle Design 1401613 Incorrect Runner Design 1411614 Incorrectly Designed Located

or Missing Cold Slug Pocket 1411615 Incorrect Gate Design 1421616 Incorrect Venting 1431617 Incorrect Mold Temperature Management 144

Prototype Molds and Mold Filling Analysis 145171 Prototype Molds 145172 Mold Filling Analysis 146173 Workflow 147

1731 Mesh Model 1471732 Material Selection 1481733 Process Parameters 1481734 Selection of Gate Location 1481735 Simulations 1491736 Results Generated by Simulations 1491737 Filling Sequence 1501738 Pressure Distribution 1501739 Clamping Force 15017310 Cooling Time 15117311 Temperature Control 15117312 Shrinkage and Warpage 15117313 Glass Fiber Orientation 15217314 Warpage Analysis 15217315 Gate Location 15217316 Material Replacement 15317317 Simulation Software 153

Rapid Prototyping and Additive Manufacturing 154181 Prototypes 154182 Rapid Prototyping (RP) 155

1821 SLA ndash Stereolithography 1561822 SLS ndash Selective Laser Sintering 1591823 The FDM Method 1611824 3DP Printing 1621825 3D Printing 1631826 PolyJet 164

183 Additive Manufacturing 166

CHAPTER 16

CHAPTER 17

CHAPTER 18

XI

Contents

Cost Calculations for Moldings 168191 Part Cost Calculator 169192 Part Cost Scenarios 173192 Replacement Cost 174

Extrusion 177201 The Extrusion Process 177

2011 Advantages (+) and Limitations (minus) 177202 Materials for Extrusion 179203 The Extruder Design 180

2031 The Cylinder 1802032 Single-Screws 1812033 Barrier Screws 1812034 Straight Twin-Screws 1822035 Conical Twin-Screws 1822036 Rotational Direction 1832037 Comparison of Single-Screws and Twin-Screws 1832038 ToolDie 1842039 Calibration 18420310 Corrugation 18520311 Cooling 18520312 Feeding 18620313 Marking 18620314 Further Processing 18620315 Cutting 18720316 Winding 188

204 Extrusion Processes 1882041 Straight Extrusion 1892042 Extrusion with Angle ToolCoating 1892043 Extrusion of Plates and Sheets 1902044 Co-extrusion 1912045 Film Blowing 191

20451 Advantages (+) and Limitations (minus) 1922046 Cable Production 1932047 Monofilament 1942048 Compounding 195

205 Design for Extrusion 1962051 Ribbing ndash Stiffening 1972052 Cavity 1972053 Sealing Lip 1972054 Hinge 1982055 Guide 1982056 Sliding Joint 1982057 Snap-Fit Joint 1992058 Bellow 1992059 InsertReinforcement 19920510 Friction Surface 200

CHAPTER 19

CHAPTER 20

XII

Contents

20511 PrintingStamping 20020512 Decoration Surface 20020513 Drilled Side Holes 20120514 Irregular Holes 20120515 Corrugation 20120516 Spiral Forming 20220517 Foaming 20220518 Extruded Screw Holes 20220519 Muffing and Hot Plate Welding 203

Alternative Processing Methods for Thermoplastics 204211 Blow Molding 204212 Rotational Molding 206213 Vacuum Forming 207

Material Selection Process 209221 How Do You Select the Right Material in

Your Development Project 209222 Development Cooperation 210223 Establishing the Requirement Specifications 210224 MUST Requirements 211225 WANT Requirements 212226 Specify and Sort the Material Candidates 213227 Make a Detailed Cost Analysis 214228 Establish a Meaningful Test Program 215

Requirements and Specification for Plastic Products 216231 Background Information 216232 Batch Size 217233 Part Size 218234 Tolerance Requirements 218235 Part Design 220236 Assembly Requirements 223237 Mechanical Load 223238 Chemical Resistance 224239 Electrical Properties 2252310 Environmental Impact 2262311 Color 2272312 Surface Properties 2282313 Other Properties 2302314 Regulatory Requirements 2312315 Recycling Requirements 2322316 Cost Requirements 233

CHAPTER 21

CHAPTER 22

CHAPTER 23

XIII

Contents

2317 Requirement Specification ndash Checklist 23423171 Background information 23423172 Batch Size 23423173 Part Size 23523174 Tolerance Requirements 23523175 Part Design 23523176 Assembly Requirements 23523177 Mechanical Load 23523178 Chemical Resistance 23523179 Electrical Properties 235231710 Environmental Impact 236231711 Color 236231712 Surface Properties 236231713 Other Properties 236231714 Regulatory Requirements 237231715 Recycling 237231716 Costs 237

Design Rules for Thermoplastic Moldings 238241 Rule 1 ndash Remember That Plastics Are Not Metals 239242 Rule 2 ndash Consider the Specific Characteristics of Plastics 240

2421 Anisotropic Behavior 2412422 Temperature-Dependent Behavior 2412423 Time-Dependent Stress-Strain Curve 242

24231 Creep 24224232 Relaxation 242

2424 Speed-Dependent Characteristics 2432425 Environmentally Dependent Characteristics 2442426 Easy to Design 2442427 Easy to Color 2442428 Easy to Assemble 2452429 Recycling 245

243 Rule 3 ndash Design with Regard to Future Recycling 2462431 Dismantling 2462432 Reused Materials 2482433 Coding 2482434 Cleaning 249

244 Rule 4 ndash Integrate Several Functions into One Component 249

245 Rule 5 ndash Maintain an Even Wall Thickness 251246 Rule 6 ndash Avoid Sharp Corners 252247 Rule 7 ndash Use Ribs to Increase Stiffness 254

2471 Limitations when Designing Ribs 2542472 Material-Saving Design 2552473 Avoid Sink Marks at Rib Joints 255

CHAPTER 24

XIV

Contents

248 Rule 8 ndash Be Careful with Gate Location and Dimensions 2562481 Weld Lines 257

249 Rule 9 ndash Avoid Tight Tolerances 2582410 Rule 10 ndash Choose an Appropriate Assembly Method 259

Assembly Methods for Thermoplastics 260251 Assembly Methods That Facilitate Disassembly 260252 Integrated Snap-Fits 261253 Permanent Assembly Methods 262

2531 Ultrasonic Welding 2622532 Vibration Welding 2632533 Rotational Welding 2642534 Hot Plate Welding 2652535 Infrared Welding 2662536 Laser Welding 2662537 Riveting 2682538 Gluing 269

The Injection-Molding Process 270261 Molding Processing Analysis 270262 Contact Information 272263 Information Pane 272264 Material Information 273265 Information about the Machine 274266 Information about the Mold 276267 Drying 278268 Processing Information 280269 Temperatures 2812610 Pressure Injection Speed and Screw Rotation Speed 2862611 Hold Pressure 2872612 Injection 2892613 Screw Rotation Speed 2902614 Time and Length Settings 292

Injection Molding Process Parameters 297

Problem Solving and Quality Management 301281 Increased Quality Demands 301282 Analytical Troubleshooting ndash ATS 301

2821 Definition of the Problem 3022822 Deviation Definition 302

283 Defining a Problem 3032831 Classification of Problems 3042832 Problem Analysis 306

CHAPTER 25

CHAPTER 26

CHAPTER 27

CHAPTER 28

XV

Contents

2833 Brainstorming 3082834 Verification of Causes 3082835 Planning of Actions to Take 309

284 Statistical Design of Experiments ndash DOE 3092841 Factorial Experiments 310

285 Failure Mode Effect Analysis ndash FMEA 3132851 General Concepts of FMEA 314

Troubleshooting ndash Causes and Effects 316291 Molding Problems 316292 Fill Ratio 318

2921 Short Shots ndash The Part Is Not Completely Filled 3182922 Flashes 3192923 Sink Marks 3192924 Voids or Pores 320

293 Surface Defects 3212931 Burn Marks 321

29311 Discoloration Dark Streaks or Degradation 32129312 Black Specks 32129313 Splays or Silver Streaks

(Partly over the Surface) 32229314 Diesel Effect ndash Entrapped Air 323

2932 Splays or Silver Streaks (All over the Surface) 3242933 Color Streaks ndash Bad Color Dispersion 3242934 Color Streaks ndash Unfavorable Pigment Orientation 3252935 Surface Gloss ndash MatteShiny Surface Variations 3252936 Surface Gloss ndash Corona Effect 3262937 Splays Stripes and Blisters 3262938 Glass Fiber Streaks 3272939 Weld-Lines (Knit-Lines) 32729310 Jetting 32829311 Delamination 32929312 Record Grooves (Orange Peel) 32929313 Cold Slug 33029314 Ejector Pin Marks 33029315 Oil Stain ndash Brown or Black Specks 33129316 Water Stain 331

294 Poor Mechanical Strength 3322941 Bubbles or Voids inside the Part 3322942 Cracks 3322943 Unmelts (Also Called Pitting) 3332944 Brittleness 3342945 Crazing 3342946 Problems with Regrind 335

CHAPTER 29

XVI

Contents

295 Dimensional Problems 3352951 Incorrect Shrinkage 3352952 Unrealistic Tolerances 3362953 Warpage 337

296 Production Problems 3382961 Part Sticks in the Cavity 3382962 Part Sticks on the Core 3382963 Part Sticks on the Ejector Pins 3392964 Sprue Sticks in the Mold 3402965 Stringing 341

Statistical Process Control (SPC) 342301enspWhy SPC 342302enspDefinitions in SPC 343

3021enspNormal Distribution (Gaussian Dispersion) 343303enspStandard Deviations 343

3031enspOne Standard Deviation 3433032enspSix Standard Deviations (Six Sigma) 3443033enspControl Limits 3443034enspTarget Value 3463035enspTarget Value Centering (TC) 3473036enspCapability Machine (Cm) 3473037enspCapability Machine Index (Cmk) 3483038enspCapability Process (Cp) 3483039enspCapability Process Index (Cpk) 34930310enspSix Important Factors 34930311enspMachine Capability 35030312enspProcess Capability 350

304enspHow SPC Works in Practice 3513041enspSoftware 3513042enspProcess Data Monitoring 352

Internet Links 354

Index 355

CHAPTER 30

CHAPTER 31

XVII

Foreword

For many years I had the idea of writing a book about injection molding as I have spent over 45 years of my working life on this subject

When I retired in 2009 I was given great support by my friends Katarina Elner- Haglund and Peter Schulz of the Swedish plastics magazine Plastforum who asked me to write a series of articles about thermoplastics and their processing for the magazine

I was also hired at this time to work with educational programs at the Lund Uni-versity of Technology the Royal University of Technology in Stockholm and a number of industrial companies in Sweden as a result of which this book was developed

My aim has been to write in such a way that this book can be understood by everyone regardless of prior knowledge about plastics The book has a practical approach with lots of pictures and is intended to be used in secondary schools universities industrial training and self-study In some of the chapters there are references to worksheets in Excel that can be downloaded free from my website wwwbruconse

In addition to the above-mentioned persons I would like to extend a warm thanks to my wife Ingeloumlv who has been very patient when Irsquove been totally absent in the ldquowonderful world of plasticsrdquo and then proofread the book my brother Hans-Peter who has spent countless hours on adjustments of all the images etc and my son-in-law Stefan Bruder who has checked the contents of the book and contributed with many valuable comments

I would also like to thank my previous employer DuPont Performance Polymers and especially my friends and former managers Bjoumlrn Hedlund and Stewart Day-kin who encouraged the development of my career as a trainer until I reached my ultimate goal and dream job of ldquoglobal technical training managerrdquo They have also contributed with a lot of information and many valuable images in this book

I also want said a big thank you to my friends and business partners in all educa-tional programs in recent years who have supported me and contributed with many valuable comments information and images for this book and a special thanks to those who have made this printing possible thanks to the ads in the beginning The whole list would be very long but you will find some of them in the list of internet links in Chapter 31

In this Second Edition

This edition contains greatly expanded coverage of extrusion collected into a new Chapter 20 There are also a number of new and updated figures with numerous small improvements and corrections throughout the text These are complemented by an all-new professional layout and structure which I hope will help readers to navigate the book comfortably

XVIII

Foreword

I would like to thank Mark Smith at Carl Hanser Verlag for all the support that I received during the last years with my book in various languages

Ulf Bruder

Karlskrona Sweden

10

Chapter 2 mdash Commodities

3) LDPE is used for film blowing and extrusion

A large part of all the polyethylene produced is used for film blowing If the film is soft and flexible it is either made of LDPE or LLDPE If it has the rustle of the free bags at the grocery store it is probably made of HDPE LLDPE is also used to improve the strength of LDPE film

Figure 27enspGarbage bags LDPE is excellent for film blowing and is the most common material used in bags plastic sacks and construction film

Figure 28enspCable jacketing LDPE is used in the extrusion of jacketing for high voltage cables

4) PEX

Cross-linked polyethylene is mainly used in the extrusion of tubes The cross-link-ing provides improved creep resistance and better high-temperature properties

You can even copolymerize ethylene with polar monomers and get everything from viscous products (ethinspg melting glue) to tough films and impact-resistant hard shells such as golf balls

A common copolymer is EVA (ethylene-vinyl-acetate) By varying the concentration of vinyl acetate (VA) from 25 to 95 you can control the properties and produce a range of different types of material Increased VA content leads to higher trans-parency and toughness

Adhesives carpet underlay cable insulation carriers of color masterbatches stretch film and coating film for cardboard and paper are typical uses of EVA

Figure 29enspTubes in PEX resist both high temperatures (120degC) and pres-sure and are used for the hot water supply of cleaning or washing machines

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

X

Contents

Mold Design and Product Quality 139161 Mold-Related Problems 139

1611 Too-Weak Mold Plates 1391612 Incorrect Sprue and Nozzle Design 1401613 Incorrect Runner Design 1411614 Incorrectly Designed Located

or Missing Cold Slug Pocket 1411615 Incorrect Gate Design 1421616 Incorrect Venting 1431617 Incorrect Mold Temperature Management 144

Prototype Molds and Mold Filling Analysis 145171 Prototype Molds 145172 Mold Filling Analysis 146173 Workflow 147

1731 Mesh Model 1471732 Material Selection 1481733 Process Parameters 1481734 Selection of Gate Location 1481735 Simulations 1491736 Results Generated by Simulations 1491737 Filling Sequence 1501738 Pressure Distribution 1501739 Clamping Force 15017310 Cooling Time 15117311 Temperature Control 15117312 Shrinkage and Warpage 15117313 Glass Fiber Orientation 15217314 Warpage Analysis 15217315 Gate Location 15217316 Material Replacement 15317317 Simulation Software 153

Rapid Prototyping and Additive Manufacturing 154181 Prototypes 154182 Rapid Prototyping (RP) 155

1821 SLA ndash Stereolithography 1561822 SLS ndash Selective Laser Sintering 1591823 The FDM Method 1611824 3DP Printing 1621825 3D Printing 1631826 PolyJet 164

183 Additive Manufacturing 166

CHAPTER 16

CHAPTER 17

CHAPTER 18

XI

Contents

Cost Calculations for Moldings 168191 Part Cost Calculator 169192 Part Cost Scenarios 173192 Replacement Cost 174

Extrusion 177201 The Extrusion Process 177

2011 Advantages (+) and Limitations (minus) 177202 Materials for Extrusion 179203 The Extruder Design 180

2031 The Cylinder 1802032 Single-Screws 1812033 Barrier Screws 1812034 Straight Twin-Screws 1822035 Conical Twin-Screws 1822036 Rotational Direction 1832037 Comparison of Single-Screws and Twin-Screws 1832038 ToolDie 1842039 Calibration 18420310 Corrugation 18520311 Cooling 18520312 Feeding 18620313 Marking 18620314 Further Processing 18620315 Cutting 18720316 Winding 188

204 Extrusion Processes 1882041 Straight Extrusion 1892042 Extrusion with Angle ToolCoating 1892043 Extrusion of Plates and Sheets 1902044 Co-extrusion 1912045 Film Blowing 191

20451 Advantages (+) and Limitations (minus) 1922046 Cable Production 1932047 Monofilament 1942048 Compounding 195

205 Design for Extrusion 1962051 Ribbing ndash Stiffening 1972052 Cavity 1972053 Sealing Lip 1972054 Hinge 1982055 Guide 1982056 Sliding Joint 1982057 Snap-Fit Joint 1992058 Bellow 1992059 InsertReinforcement 19920510 Friction Surface 200

CHAPTER 19

CHAPTER 20

XII

Contents

20511 PrintingStamping 20020512 Decoration Surface 20020513 Drilled Side Holes 20120514 Irregular Holes 20120515 Corrugation 20120516 Spiral Forming 20220517 Foaming 20220518 Extruded Screw Holes 20220519 Muffing and Hot Plate Welding 203

Alternative Processing Methods for Thermoplastics 204211 Blow Molding 204212 Rotational Molding 206213 Vacuum Forming 207

Material Selection Process 209221 How Do You Select the Right Material in

Your Development Project 209222 Development Cooperation 210223 Establishing the Requirement Specifications 210224 MUST Requirements 211225 WANT Requirements 212226 Specify and Sort the Material Candidates 213227 Make a Detailed Cost Analysis 214228 Establish a Meaningful Test Program 215

Requirements and Specification for Plastic Products 216231 Background Information 216232 Batch Size 217233 Part Size 218234 Tolerance Requirements 218235 Part Design 220236 Assembly Requirements 223237 Mechanical Load 223238 Chemical Resistance 224239 Electrical Properties 2252310 Environmental Impact 2262311 Color 2272312 Surface Properties 2282313 Other Properties 2302314 Regulatory Requirements 2312315 Recycling Requirements 2322316 Cost Requirements 233

CHAPTER 21

CHAPTER 22

CHAPTER 23

XIII

Contents

2317 Requirement Specification ndash Checklist 23423171 Background information 23423172 Batch Size 23423173 Part Size 23523174 Tolerance Requirements 23523175 Part Design 23523176 Assembly Requirements 23523177 Mechanical Load 23523178 Chemical Resistance 23523179 Electrical Properties 235231710 Environmental Impact 236231711 Color 236231712 Surface Properties 236231713 Other Properties 236231714 Regulatory Requirements 237231715 Recycling 237231716 Costs 237

Design Rules for Thermoplastic Moldings 238241 Rule 1 ndash Remember That Plastics Are Not Metals 239242 Rule 2 ndash Consider the Specific Characteristics of Plastics 240

2421 Anisotropic Behavior 2412422 Temperature-Dependent Behavior 2412423 Time-Dependent Stress-Strain Curve 242

24231 Creep 24224232 Relaxation 242

2424 Speed-Dependent Characteristics 2432425 Environmentally Dependent Characteristics 2442426 Easy to Design 2442427 Easy to Color 2442428 Easy to Assemble 2452429 Recycling 245

243 Rule 3 ndash Design with Regard to Future Recycling 2462431 Dismantling 2462432 Reused Materials 2482433 Coding 2482434 Cleaning 249

244 Rule 4 ndash Integrate Several Functions into One Component 249

245 Rule 5 ndash Maintain an Even Wall Thickness 251246 Rule 6 ndash Avoid Sharp Corners 252247 Rule 7 ndash Use Ribs to Increase Stiffness 254

2471 Limitations when Designing Ribs 2542472 Material-Saving Design 2552473 Avoid Sink Marks at Rib Joints 255

CHAPTER 24

XIV

Contents

248 Rule 8 ndash Be Careful with Gate Location and Dimensions 2562481 Weld Lines 257

249 Rule 9 ndash Avoid Tight Tolerances 2582410 Rule 10 ndash Choose an Appropriate Assembly Method 259

Assembly Methods for Thermoplastics 260251 Assembly Methods That Facilitate Disassembly 260252 Integrated Snap-Fits 261253 Permanent Assembly Methods 262

2531 Ultrasonic Welding 2622532 Vibration Welding 2632533 Rotational Welding 2642534 Hot Plate Welding 2652535 Infrared Welding 2662536 Laser Welding 2662537 Riveting 2682538 Gluing 269

The Injection-Molding Process 270261 Molding Processing Analysis 270262 Contact Information 272263 Information Pane 272264 Material Information 273265 Information about the Machine 274266 Information about the Mold 276267 Drying 278268 Processing Information 280269 Temperatures 2812610 Pressure Injection Speed and Screw Rotation Speed 2862611 Hold Pressure 2872612 Injection 2892613 Screw Rotation Speed 2902614 Time and Length Settings 292

Injection Molding Process Parameters 297

Problem Solving and Quality Management 301281 Increased Quality Demands 301282 Analytical Troubleshooting ndash ATS 301

2821 Definition of the Problem 3022822 Deviation Definition 302

283 Defining a Problem 3032831 Classification of Problems 3042832 Problem Analysis 306

CHAPTER 25

CHAPTER 26

CHAPTER 27

CHAPTER 28

XV

Contents

2833 Brainstorming 3082834 Verification of Causes 3082835 Planning of Actions to Take 309

284 Statistical Design of Experiments ndash DOE 3092841 Factorial Experiments 310

285 Failure Mode Effect Analysis ndash FMEA 3132851 General Concepts of FMEA 314

Troubleshooting ndash Causes and Effects 316291 Molding Problems 316292 Fill Ratio 318

2921 Short Shots ndash The Part Is Not Completely Filled 3182922 Flashes 3192923 Sink Marks 3192924 Voids or Pores 320

293 Surface Defects 3212931 Burn Marks 321

29311 Discoloration Dark Streaks or Degradation 32129312 Black Specks 32129313 Splays or Silver Streaks

(Partly over the Surface) 32229314 Diesel Effect ndash Entrapped Air 323

2932 Splays or Silver Streaks (All over the Surface) 3242933 Color Streaks ndash Bad Color Dispersion 3242934 Color Streaks ndash Unfavorable Pigment Orientation 3252935 Surface Gloss ndash MatteShiny Surface Variations 3252936 Surface Gloss ndash Corona Effect 3262937 Splays Stripes and Blisters 3262938 Glass Fiber Streaks 3272939 Weld-Lines (Knit-Lines) 32729310 Jetting 32829311 Delamination 32929312 Record Grooves (Orange Peel) 32929313 Cold Slug 33029314 Ejector Pin Marks 33029315 Oil Stain ndash Brown or Black Specks 33129316 Water Stain 331

294 Poor Mechanical Strength 3322941 Bubbles or Voids inside the Part 3322942 Cracks 3322943 Unmelts (Also Called Pitting) 3332944 Brittleness 3342945 Crazing 3342946 Problems with Regrind 335

CHAPTER 29

XVI

Contents

295 Dimensional Problems 3352951 Incorrect Shrinkage 3352952 Unrealistic Tolerances 3362953 Warpage 337

296 Production Problems 3382961 Part Sticks in the Cavity 3382962 Part Sticks on the Core 3382963 Part Sticks on the Ejector Pins 3392964 Sprue Sticks in the Mold 3402965 Stringing 341

Statistical Process Control (SPC) 342301enspWhy SPC 342302enspDefinitions in SPC 343

3021enspNormal Distribution (Gaussian Dispersion) 343303enspStandard Deviations 343

3031enspOne Standard Deviation 3433032enspSix Standard Deviations (Six Sigma) 3443033enspControl Limits 3443034enspTarget Value 3463035enspTarget Value Centering (TC) 3473036enspCapability Machine (Cm) 3473037enspCapability Machine Index (Cmk) 3483038enspCapability Process (Cp) 3483039enspCapability Process Index (Cpk) 34930310enspSix Important Factors 34930311enspMachine Capability 35030312enspProcess Capability 350

304enspHow SPC Works in Practice 3513041enspSoftware 3513042enspProcess Data Monitoring 352

Internet Links 354

Index 355

CHAPTER 30

CHAPTER 31

XVII

Foreword

For many years I had the idea of writing a book about injection molding as I have spent over 45 years of my working life on this subject

When I retired in 2009 I was given great support by my friends Katarina Elner- Haglund and Peter Schulz of the Swedish plastics magazine Plastforum who asked me to write a series of articles about thermoplastics and their processing for the magazine

I was also hired at this time to work with educational programs at the Lund Uni-versity of Technology the Royal University of Technology in Stockholm and a number of industrial companies in Sweden as a result of which this book was developed

My aim has been to write in such a way that this book can be understood by everyone regardless of prior knowledge about plastics The book has a practical approach with lots of pictures and is intended to be used in secondary schools universities industrial training and self-study In some of the chapters there are references to worksheets in Excel that can be downloaded free from my website wwwbruconse

In addition to the above-mentioned persons I would like to extend a warm thanks to my wife Ingeloumlv who has been very patient when Irsquove been totally absent in the ldquowonderful world of plasticsrdquo and then proofread the book my brother Hans-Peter who has spent countless hours on adjustments of all the images etc and my son-in-law Stefan Bruder who has checked the contents of the book and contributed with many valuable comments

I would also like to thank my previous employer DuPont Performance Polymers and especially my friends and former managers Bjoumlrn Hedlund and Stewart Day-kin who encouraged the development of my career as a trainer until I reached my ultimate goal and dream job of ldquoglobal technical training managerrdquo They have also contributed with a lot of information and many valuable images in this book

I also want said a big thank you to my friends and business partners in all educa-tional programs in recent years who have supported me and contributed with many valuable comments information and images for this book and a special thanks to those who have made this printing possible thanks to the ads in the beginning The whole list would be very long but you will find some of them in the list of internet links in Chapter 31

In this Second Edition

This edition contains greatly expanded coverage of extrusion collected into a new Chapter 20 There are also a number of new and updated figures with numerous small improvements and corrections throughout the text These are complemented by an all-new professional layout and structure which I hope will help readers to navigate the book comfortably

XVIII

Foreword

I would like to thank Mark Smith at Carl Hanser Verlag for all the support that I received during the last years with my book in various languages

Ulf Bruder

Karlskrona Sweden

10

Chapter 2 mdash Commodities

3) LDPE is used for film blowing and extrusion

A large part of all the polyethylene produced is used for film blowing If the film is soft and flexible it is either made of LDPE or LLDPE If it has the rustle of the free bags at the grocery store it is probably made of HDPE LLDPE is also used to improve the strength of LDPE film

Figure 27enspGarbage bags LDPE is excellent for film blowing and is the most common material used in bags plastic sacks and construction film

Figure 28enspCable jacketing LDPE is used in the extrusion of jacketing for high voltage cables

4) PEX

Cross-linked polyethylene is mainly used in the extrusion of tubes The cross-link-ing provides improved creep resistance and better high-temperature properties

You can even copolymerize ethylene with polar monomers and get everything from viscous products (ethinspg melting glue) to tough films and impact-resistant hard shells such as golf balls

A common copolymer is EVA (ethylene-vinyl-acetate) By varying the concentration of vinyl acetate (VA) from 25 to 95 you can control the properties and produce a range of different types of material Increased VA content leads to higher trans-parency and toughness

Adhesives carpet underlay cable insulation carriers of color masterbatches stretch film and coating film for cardboard and paper are typical uses of EVA

Figure 29enspTubes in PEX resist both high temperatures (120degC) and pres-sure and are used for the hot water supply of cleaning or washing machines

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

XI

Contents

Cost Calculations for Moldings 168191 Part Cost Calculator 169192 Part Cost Scenarios 173192 Replacement Cost 174

Extrusion 177201 The Extrusion Process 177

2011 Advantages (+) and Limitations (minus) 177202 Materials for Extrusion 179203 The Extruder Design 180

2031 The Cylinder 1802032 Single-Screws 1812033 Barrier Screws 1812034 Straight Twin-Screws 1822035 Conical Twin-Screws 1822036 Rotational Direction 1832037 Comparison of Single-Screws and Twin-Screws 1832038 ToolDie 1842039 Calibration 18420310 Corrugation 18520311 Cooling 18520312 Feeding 18620313 Marking 18620314 Further Processing 18620315 Cutting 18720316 Winding 188

204 Extrusion Processes 1882041 Straight Extrusion 1892042 Extrusion with Angle ToolCoating 1892043 Extrusion of Plates and Sheets 1902044 Co-extrusion 1912045 Film Blowing 191

20451 Advantages (+) and Limitations (minus) 1922046 Cable Production 1932047 Monofilament 1942048 Compounding 195

205 Design for Extrusion 1962051 Ribbing ndash Stiffening 1972052 Cavity 1972053 Sealing Lip 1972054 Hinge 1982055 Guide 1982056 Sliding Joint 1982057 Snap-Fit Joint 1992058 Bellow 1992059 InsertReinforcement 19920510 Friction Surface 200

CHAPTER 19

CHAPTER 20

XII

Contents

20511 PrintingStamping 20020512 Decoration Surface 20020513 Drilled Side Holes 20120514 Irregular Holes 20120515 Corrugation 20120516 Spiral Forming 20220517 Foaming 20220518 Extruded Screw Holes 20220519 Muffing and Hot Plate Welding 203

Alternative Processing Methods for Thermoplastics 204211 Blow Molding 204212 Rotational Molding 206213 Vacuum Forming 207

Material Selection Process 209221 How Do You Select the Right Material in

Your Development Project 209222 Development Cooperation 210223 Establishing the Requirement Specifications 210224 MUST Requirements 211225 WANT Requirements 212226 Specify and Sort the Material Candidates 213227 Make a Detailed Cost Analysis 214228 Establish a Meaningful Test Program 215

Requirements and Specification for Plastic Products 216231 Background Information 216232 Batch Size 217233 Part Size 218234 Tolerance Requirements 218235 Part Design 220236 Assembly Requirements 223237 Mechanical Load 223238 Chemical Resistance 224239 Electrical Properties 2252310 Environmental Impact 2262311 Color 2272312 Surface Properties 2282313 Other Properties 2302314 Regulatory Requirements 2312315 Recycling Requirements 2322316 Cost Requirements 233

CHAPTER 21

CHAPTER 22

CHAPTER 23

XIII

Contents

2317 Requirement Specification ndash Checklist 23423171 Background information 23423172 Batch Size 23423173 Part Size 23523174 Tolerance Requirements 23523175 Part Design 23523176 Assembly Requirements 23523177 Mechanical Load 23523178 Chemical Resistance 23523179 Electrical Properties 235231710 Environmental Impact 236231711 Color 236231712 Surface Properties 236231713 Other Properties 236231714 Regulatory Requirements 237231715 Recycling 237231716 Costs 237

Design Rules for Thermoplastic Moldings 238241 Rule 1 ndash Remember That Plastics Are Not Metals 239242 Rule 2 ndash Consider the Specific Characteristics of Plastics 240

2421 Anisotropic Behavior 2412422 Temperature-Dependent Behavior 2412423 Time-Dependent Stress-Strain Curve 242

24231 Creep 24224232 Relaxation 242

2424 Speed-Dependent Characteristics 2432425 Environmentally Dependent Characteristics 2442426 Easy to Design 2442427 Easy to Color 2442428 Easy to Assemble 2452429 Recycling 245

243 Rule 3 ndash Design with Regard to Future Recycling 2462431 Dismantling 2462432 Reused Materials 2482433 Coding 2482434 Cleaning 249

244 Rule 4 ndash Integrate Several Functions into One Component 249

245 Rule 5 ndash Maintain an Even Wall Thickness 251246 Rule 6 ndash Avoid Sharp Corners 252247 Rule 7 ndash Use Ribs to Increase Stiffness 254

2471 Limitations when Designing Ribs 2542472 Material-Saving Design 2552473 Avoid Sink Marks at Rib Joints 255

CHAPTER 24

XIV

Contents

248 Rule 8 ndash Be Careful with Gate Location and Dimensions 2562481 Weld Lines 257

249 Rule 9 ndash Avoid Tight Tolerances 2582410 Rule 10 ndash Choose an Appropriate Assembly Method 259

Assembly Methods for Thermoplastics 260251 Assembly Methods That Facilitate Disassembly 260252 Integrated Snap-Fits 261253 Permanent Assembly Methods 262

2531 Ultrasonic Welding 2622532 Vibration Welding 2632533 Rotational Welding 2642534 Hot Plate Welding 2652535 Infrared Welding 2662536 Laser Welding 2662537 Riveting 2682538 Gluing 269

The Injection-Molding Process 270261 Molding Processing Analysis 270262 Contact Information 272263 Information Pane 272264 Material Information 273265 Information about the Machine 274266 Information about the Mold 276267 Drying 278268 Processing Information 280269 Temperatures 2812610 Pressure Injection Speed and Screw Rotation Speed 2862611 Hold Pressure 2872612 Injection 2892613 Screw Rotation Speed 2902614 Time and Length Settings 292

Injection Molding Process Parameters 297

Problem Solving and Quality Management 301281 Increased Quality Demands 301282 Analytical Troubleshooting ndash ATS 301

2821 Definition of the Problem 3022822 Deviation Definition 302

283 Defining a Problem 3032831 Classification of Problems 3042832 Problem Analysis 306

CHAPTER 25

CHAPTER 26

CHAPTER 27

CHAPTER 28

XV

Contents

2833 Brainstorming 3082834 Verification of Causes 3082835 Planning of Actions to Take 309

284 Statistical Design of Experiments ndash DOE 3092841 Factorial Experiments 310

285 Failure Mode Effect Analysis ndash FMEA 3132851 General Concepts of FMEA 314

Troubleshooting ndash Causes and Effects 316291 Molding Problems 316292 Fill Ratio 318

2921 Short Shots ndash The Part Is Not Completely Filled 3182922 Flashes 3192923 Sink Marks 3192924 Voids or Pores 320

293 Surface Defects 3212931 Burn Marks 321

29311 Discoloration Dark Streaks or Degradation 32129312 Black Specks 32129313 Splays or Silver Streaks

(Partly over the Surface) 32229314 Diesel Effect ndash Entrapped Air 323

2932 Splays or Silver Streaks (All over the Surface) 3242933 Color Streaks ndash Bad Color Dispersion 3242934 Color Streaks ndash Unfavorable Pigment Orientation 3252935 Surface Gloss ndash MatteShiny Surface Variations 3252936 Surface Gloss ndash Corona Effect 3262937 Splays Stripes and Blisters 3262938 Glass Fiber Streaks 3272939 Weld-Lines (Knit-Lines) 32729310 Jetting 32829311 Delamination 32929312 Record Grooves (Orange Peel) 32929313 Cold Slug 33029314 Ejector Pin Marks 33029315 Oil Stain ndash Brown or Black Specks 33129316 Water Stain 331

294 Poor Mechanical Strength 3322941 Bubbles or Voids inside the Part 3322942 Cracks 3322943 Unmelts (Also Called Pitting) 3332944 Brittleness 3342945 Crazing 3342946 Problems with Regrind 335

CHAPTER 29

XVI

Contents

295 Dimensional Problems 3352951 Incorrect Shrinkage 3352952 Unrealistic Tolerances 3362953 Warpage 337

296 Production Problems 3382961 Part Sticks in the Cavity 3382962 Part Sticks on the Core 3382963 Part Sticks on the Ejector Pins 3392964 Sprue Sticks in the Mold 3402965 Stringing 341

Statistical Process Control (SPC) 342301enspWhy SPC 342302enspDefinitions in SPC 343

3021enspNormal Distribution (Gaussian Dispersion) 343303enspStandard Deviations 343

3031enspOne Standard Deviation 3433032enspSix Standard Deviations (Six Sigma) 3443033enspControl Limits 3443034enspTarget Value 3463035enspTarget Value Centering (TC) 3473036enspCapability Machine (Cm) 3473037enspCapability Machine Index (Cmk) 3483038enspCapability Process (Cp) 3483039enspCapability Process Index (Cpk) 34930310enspSix Important Factors 34930311enspMachine Capability 35030312enspProcess Capability 350

304enspHow SPC Works in Practice 3513041enspSoftware 3513042enspProcess Data Monitoring 352

Internet Links 354

Index 355

CHAPTER 30

CHAPTER 31

XVII

Foreword

For many years I had the idea of writing a book about injection molding as I have spent over 45 years of my working life on this subject

When I retired in 2009 I was given great support by my friends Katarina Elner- Haglund and Peter Schulz of the Swedish plastics magazine Plastforum who asked me to write a series of articles about thermoplastics and their processing for the magazine

I was also hired at this time to work with educational programs at the Lund Uni-versity of Technology the Royal University of Technology in Stockholm and a number of industrial companies in Sweden as a result of which this book was developed

My aim has been to write in such a way that this book can be understood by everyone regardless of prior knowledge about plastics The book has a practical approach with lots of pictures and is intended to be used in secondary schools universities industrial training and self-study In some of the chapters there are references to worksheets in Excel that can be downloaded free from my website wwwbruconse

In addition to the above-mentioned persons I would like to extend a warm thanks to my wife Ingeloumlv who has been very patient when Irsquove been totally absent in the ldquowonderful world of plasticsrdquo and then proofread the book my brother Hans-Peter who has spent countless hours on adjustments of all the images etc and my son-in-law Stefan Bruder who has checked the contents of the book and contributed with many valuable comments

I would also like to thank my previous employer DuPont Performance Polymers and especially my friends and former managers Bjoumlrn Hedlund and Stewart Day-kin who encouraged the development of my career as a trainer until I reached my ultimate goal and dream job of ldquoglobal technical training managerrdquo They have also contributed with a lot of information and many valuable images in this book

I also want said a big thank you to my friends and business partners in all educa-tional programs in recent years who have supported me and contributed with many valuable comments information and images for this book and a special thanks to those who have made this printing possible thanks to the ads in the beginning The whole list would be very long but you will find some of them in the list of internet links in Chapter 31

In this Second Edition

This edition contains greatly expanded coverage of extrusion collected into a new Chapter 20 There are also a number of new and updated figures with numerous small improvements and corrections throughout the text These are complemented by an all-new professional layout and structure which I hope will help readers to navigate the book comfortably

XVIII

Foreword

I would like to thank Mark Smith at Carl Hanser Verlag for all the support that I received during the last years with my book in various languages

Ulf Bruder

Karlskrona Sweden

10

Chapter 2 mdash Commodities

3) LDPE is used for film blowing and extrusion

A large part of all the polyethylene produced is used for film blowing If the film is soft and flexible it is either made of LDPE or LLDPE If it has the rustle of the free bags at the grocery store it is probably made of HDPE LLDPE is also used to improve the strength of LDPE film

Figure 27enspGarbage bags LDPE is excellent for film blowing and is the most common material used in bags plastic sacks and construction film

Figure 28enspCable jacketing LDPE is used in the extrusion of jacketing for high voltage cables

4) PEX

Cross-linked polyethylene is mainly used in the extrusion of tubes The cross-link-ing provides improved creep resistance and better high-temperature properties

You can even copolymerize ethylene with polar monomers and get everything from viscous products (ethinspg melting glue) to tough films and impact-resistant hard shells such as golf balls

A common copolymer is EVA (ethylene-vinyl-acetate) By varying the concentration of vinyl acetate (VA) from 25 to 95 you can control the properties and produce a range of different types of material Increased VA content leads to higher trans-parency and toughness

Adhesives carpet underlay cable insulation carriers of color masterbatches stretch film and coating film for cardboard and paper are typical uses of EVA

Figure 29enspTubes in PEX resist both high temperatures (120degC) and pres-sure and are used for the hot water supply of cleaning or washing machines

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

XII

Contents

20511 PrintingStamping 20020512 Decoration Surface 20020513 Drilled Side Holes 20120514 Irregular Holes 20120515 Corrugation 20120516 Spiral Forming 20220517 Foaming 20220518 Extruded Screw Holes 20220519 Muffing and Hot Plate Welding 203

Alternative Processing Methods for Thermoplastics 204211 Blow Molding 204212 Rotational Molding 206213 Vacuum Forming 207

Material Selection Process 209221 How Do You Select the Right Material in

Your Development Project 209222 Development Cooperation 210223 Establishing the Requirement Specifications 210224 MUST Requirements 211225 WANT Requirements 212226 Specify and Sort the Material Candidates 213227 Make a Detailed Cost Analysis 214228 Establish a Meaningful Test Program 215

Requirements and Specification for Plastic Products 216231 Background Information 216232 Batch Size 217233 Part Size 218234 Tolerance Requirements 218235 Part Design 220236 Assembly Requirements 223237 Mechanical Load 223238 Chemical Resistance 224239 Electrical Properties 2252310 Environmental Impact 2262311 Color 2272312 Surface Properties 2282313 Other Properties 2302314 Regulatory Requirements 2312315 Recycling Requirements 2322316 Cost Requirements 233

CHAPTER 21

CHAPTER 22

CHAPTER 23

XIII

Contents

2317 Requirement Specification ndash Checklist 23423171 Background information 23423172 Batch Size 23423173 Part Size 23523174 Tolerance Requirements 23523175 Part Design 23523176 Assembly Requirements 23523177 Mechanical Load 23523178 Chemical Resistance 23523179 Electrical Properties 235231710 Environmental Impact 236231711 Color 236231712 Surface Properties 236231713 Other Properties 236231714 Regulatory Requirements 237231715 Recycling 237231716 Costs 237

Design Rules for Thermoplastic Moldings 238241 Rule 1 ndash Remember That Plastics Are Not Metals 239242 Rule 2 ndash Consider the Specific Characteristics of Plastics 240

2421 Anisotropic Behavior 2412422 Temperature-Dependent Behavior 2412423 Time-Dependent Stress-Strain Curve 242

24231 Creep 24224232 Relaxation 242

2424 Speed-Dependent Characteristics 2432425 Environmentally Dependent Characteristics 2442426 Easy to Design 2442427 Easy to Color 2442428 Easy to Assemble 2452429 Recycling 245

243 Rule 3 ndash Design with Regard to Future Recycling 2462431 Dismantling 2462432 Reused Materials 2482433 Coding 2482434 Cleaning 249

244 Rule 4 ndash Integrate Several Functions into One Component 249

245 Rule 5 ndash Maintain an Even Wall Thickness 251246 Rule 6 ndash Avoid Sharp Corners 252247 Rule 7 ndash Use Ribs to Increase Stiffness 254

2471 Limitations when Designing Ribs 2542472 Material-Saving Design 2552473 Avoid Sink Marks at Rib Joints 255

CHAPTER 24

XIV

Contents

248 Rule 8 ndash Be Careful with Gate Location and Dimensions 2562481 Weld Lines 257

249 Rule 9 ndash Avoid Tight Tolerances 2582410 Rule 10 ndash Choose an Appropriate Assembly Method 259

Assembly Methods for Thermoplastics 260251 Assembly Methods That Facilitate Disassembly 260252 Integrated Snap-Fits 261253 Permanent Assembly Methods 262

2531 Ultrasonic Welding 2622532 Vibration Welding 2632533 Rotational Welding 2642534 Hot Plate Welding 2652535 Infrared Welding 2662536 Laser Welding 2662537 Riveting 2682538 Gluing 269

The Injection-Molding Process 270261 Molding Processing Analysis 270262 Contact Information 272263 Information Pane 272264 Material Information 273265 Information about the Machine 274266 Information about the Mold 276267 Drying 278268 Processing Information 280269 Temperatures 2812610 Pressure Injection Speed and Screw Rotation Speed 2862611 Hold Pressure 2872612 Injection 2892613 Screw Rotation Speed 2902614 Time and Length Settings 292

Injection Molding Process Parameters 297

Problem Solving and Quality Management 301281 Increased Quality Demands 301282 Analytical Troubleshooting ndash ATS 301

2821 Definition of the Problem 3022822 Deviation Definition 302

283 Defining a Problem 3032831 Classification of Problems 3042832 Problem Analysis 306

CHAPTER 25

CHAPTER 26

CHAPTER 27

CHAPTER 28

XV

Contents

2833 Brainstorming 3082834 Verification of Causes 3082835 Planning of Actions to Take 309

284 Statistical Design of Experiments ndash DOE 3092841 Factorial Experiments 310

285 Failure Mode Effect Analysis ndash FMEA 3132851 General Concepts of FMEA 314

Troubleshooting ndash Causes and Effects 316291 Molding Problems 316292 Fill Ratio 318

2921 Short Shots ndash The Part Is Not Completely Filled 3182922 Flashes 3192923 Sink Marks 3192924 Voids or Pores 320

293 Surface Defects 3212931 Burn Marks 321

29311 Discoloration Dark Streaks or Degradation 32129312 Black Specks 32129313 Splays or Silver Streaks

(Partly over the Surface) 32229314 Diesel Effect ndash Entrapped Air 323

2932 Splays or Silver Streaks (All over the Surface) 3242933 Color Streaks ndash Bad Color Dispersion 3242934 Color Streaks ndash Unfavorable Pigment Orientation 3252935 Surface Gloss ndash MatteShiny Surface Variations 3252936 Surface Gloss ndash Corona Effect 3262937 Splays Stripes and Blisters 3262938 Glass Fiber Streaks 3272939 Weld-Lines (Knit-Lines) 32729310 Jetting 32829311 Delamination 32929312 Record Grooves (Orange Peel) 32929313 Cold Slug 33029314 Ejector Pin Marks 33029315 Oil Stain ndash Brown or Black Specks 33129316 Water Stain 331

294 Poor Mechanical Strength 3322941 Bubbles or Voids inside the Part 3322942 Cracks 3322943 Unmelts (Also Called Pitting) 3332944 Brittleness 3342945 Crazing 3342946 Problems with Regrind 335

CHAPTER 29

XVI

Contents

295 Dimensional Problems 3352951 Incorrect Shrinkage 3352952 Unrealistic Tolerances 3362953 Warpage 337

296 Production Problems 3382961 Part Sticks in the Cavity 3382962 Part Sticks on the Core 3382963 Part Sticks on the Ejector Pins 3392964 Sprue Sticks in the Mold 3402965 Stringing 341

Statistical Process Control (SPC) 342301enspWhy SPC 342302enspDefinitions in SPC 343

3021enspNormal Distribution (Gaussian Dispersion) 343303enspStandard Deviations 343

3031enspOne Standard Deviation 3433032enspSix Standard Deviations (Six Sigma) 3443033enspControl Limits 3443034enspTarget Value 3463035enspTarget Value Centering (TC) 3473036enspCapability Machine (Cm) 3473037enspCapability Machine Index (Cmk) 3483038enspCapability Process (Cp) 3483039enspCapability Process Index (Cpk) 34930310enspSix Important Factors 34930311enspMachine Capability 35030312enspProcess Capability 350

304enspHow SPC Works in Practice 3513041enspSoftware 3513042enspProcess Data Monitoring 352

Internet Links 354

Index 355

CHAPTER 30

CHAPTER 31

XVII

Foreword

For many years I had the idea of writing a book about injection molding as I have spent over 45 years of my working life on this subject

When I retired in 2009 I was given great support by my friends Katarina Elner- Haglund and Peter Schulz of the Swedish plastics magazine Plastforum who asked me to write a series of articles about thermoplastics and their processing for the magazine

I was also hired at this time to work with educational programs at the Lund Uni-versity of Technology the Royal University of Technology in Stockholm and a number of industrial companies in Sweden as a result of which this book was developed

My aim has been to write in such a way that this book can be understood by everyone regardless of prior knowledge about plastics The book has a practical approach with lots of pictures and is intended to be used in secondary schools universities industrial training and self-study In some of the chapters there are references to worksheets in Excel that can be downloaded free from my website wwwbruconse

In addition to the above-mentioned persons I would like to extend a warm thanks to my wife Ingeloumlv who has been very patient when Irsquove been totally absent in the ldquowonderful world of plasticsrdquo and then proofread the book my brother Hans-Peter who has spent countless hours on adjustments of all the images etc and my son-in-law Stefan Bruder who has checked the contents of the book and contributed with many valuable comments

I would also like to thank my previous employer DuPont Performance Polymers and especially my friends and former managers Bjoumlrn Hedlund and Stewart Day-kin who encouraged the development of my career as a trainer until I reached my ultimate goal and dream job of ldquoglobal technical training managerrdquo They have also contributed with a lot of information and many valuable images in this book

I also want said a big thank you to my friends and business partners in all educa-tional programs in recent years who have supported me and contributed with many valuable comments information and images for this book and a special thanks to those who have made this printing possible thanks to the ads in the beginning The whole list would be very long but you will find some of them in the list of internet links in Chapter 31

In this Second Edition

This edition contains greatly expanded coverage of extrusion collected into a new Chapter 20 There are also a number of new and updated figures with numerous small improvements and corrections throughout the text These are complemented by an all-new professional layout and structure which I hope will help readers to navigate the book comfortably

XVIII

Foreword

I would like to thank Mark Smith at Carl Hanser Verlag for all the support that I received during the last years with my book in various languages

Ulf Bruder

Karlskrona Sweden

10

Chapter 2 mdash Commodities

3) LDPE is used for film blowing and extrusion

A large part of all the polyethylene produced is used for film blowing If the film is soft and flexible it is either made of LDPE or LLDPE If it has the rustle of the free bags at the grocery store it is probably made of HDPE LLDPE is also used to improve the strength of LDPE film

Figure 27enspGarbage bags LDPE is excellent for film blowing and is the most common material used in bags plastic sacks and construction film

Figure 28enspCable jacketing LDPE is used in the extrusion of jacketing for high voltage cables

4) PEX

Cross-linked polyethylene is mainly used in the extrusion of tubes The cross-link-ing provides improved creep resistance and better high-temperature properties

You can even copolymerize ethylene with polar monomers and get everything from viscous products (ethinspg melting glue) to tough films and impact-resistant hard shells such as golf balls

A common copolymer is EVA (ethylene-vinyl-acetate) By varying the concentration of vinyl acetate (VA) from 25 to 95 you can control the properties and produce a range of different types of material Increased VA content leads to higher trans-parency and toughness

Adhesives carpet underlay cable insulation carriers of color masterbatches stretch film and coating film for cardboard and paper are typical uses of EVA

Figure 29enspTubes in PEX resist both high temperatures (120degC) and pres-sure and are used for the hot water supply of cleaning or washing machines

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

XIII

Contents

2317 Requirement Specification ndash Checklist 23423171 Background information 23423172 Batch Size 23423173 Part Size 23523174 Tolerance Requirements 23523175 Part Design 23523176 Assembly Requirements 23523177 Mechanical Load 23523178 Chemical Resistance 23523179 Electrical Properties 235231710 Environmental Impact 236231711 Color 236231712 Surface Properties 236231713 Other Properties 236231714 Regulatory Requirements 237231715 Recycling 237231716 Costs 237

Design Rules for Thermoplastic Moldings 238241 Rule 1 ndash Remember That Plastics Are Not Metals 239242 Rule 2 ndash Consider the Specific Characteristics of Plastics 240

2421 Anisotropic Behavior 2412422 Temperature-Dependent Behavior 2412423 Time-Dependent Stress-Strain Curve 242

24231 Creep 24224232 Relaxation 242

2424 Speed-Dependent Characteristics 2432425 Environmentally Dependent Characteristics 2442426 Easy to Design 2442427 Easy to Color 2442428 Easy to Assemble 2452429 Recycling 245

243 Rule 3 ndash Design with Regard to Future Recycling 2462431 Dismantling 2462432 Reused Materials 2482433 Coding 2482434 Cleaning 249

244 Rule 4 ndash Integrate Several Functions into One Component 249

245 Rule 5 ndash Maintain an Even Wall Thickness 251246 Rule 6 ndash Avoid Sharp Corners 252247 Rule 7 ndash Use Ribs to Increase Stiffness 254

2471 Limitations when Designing Ribs 2542472 Material-Saving Design 2552473 Avoid Sink Marks at Rib Joints 255

CHAPTER 24

XIV

Contents

248 Rule 8 ndash Be Careful with Gate Location and Dimensions 2562481 Weld Lines 257

249 Rule 9 ndash Avoid Tight Tolerances 2582410 Rule 10 ndash Choose an Appropriate Assembly Method 259

Assembly Methods for Thermoplastics 260251 Assembly Methods That Facilitate Disassembly 260252 Integrated Snap-Fits 261253 Permanent Assembly Methods 262

2531 Ultrasonic Welding 2622532 Vibration Welding 2632533 Rotational Welding 2642534 Hot Plate Welding 2652535 Infrared Welding 2662536 Laser Welding 2662537 Riveting 2682538 Gluing 269

The Injection-Molding Process 270261 Molding Processing Analysis 270262 Contact Information 272263 Information Pane 272264 Material Information 273265 Information about the Machine 274266 Information about the Mold 276267 Drying 278268 Processing Information 280269 Temperatures 2812610 Pressure Injection Speed and Screw Rotation Speed 2862611 Hold Pressure 2872612 Injection 2892613 Screw Rotation Speed 2902614 Time and Length Settings 292

Injection Molding Process Parameters 297

Problem Solving and Quality Management 301281 Increased Quality Demands 301282 Analytical Troubleshooting ndash ATS 301

2821 Definition of the Problem 3022822 Deviation Definition 302

283 Defining a Problem 3032831 Classification of Problems 3042832 Problem Analysis 306

CHAPTER 25

CHAPTER 26

CHAPTER 27

CHAPTER 28

XV

Contents

2833 Brainstorming 3082834 Verification of Causes 3082835 Planning of Actions to Take 309

284 Statistical Design of Experiments ndash DOE 3092841 Factorial Experiments 310

285 Failure Mode Effect Analysis ndash FMEA 3132851 General Concepts of FMEA 314

Troubleshooting ndash Causes and Effects 316291 Molding Problems 316292 Fill Ratio 318

2921 Short Shots ndash The Part Is Not Completely Filled 3182922 Flashes 3192923 Sink Marks 3192924 Voids or Pores 320

293 Surface Defects 3212931 Burn Marks 321

29311 Discoloration Dark Streaks or Degradation 32129312 Black Specks 32129313 Splays or Silver Streaks

(Partly over the Surface) 32229314 Diesel Effect ndash Entrapped Air 323

2932 Splays or Silver Streaks (All over the Surface) 3242933 Color Streaks ndash Bad Color Dispersion 3242934 Color Streaks ndash Unfavorable Pigment Orientation 3252935 Surface Gloss ndash MatteShiny Surface Variations 3252936 Surface Gloss ndash Corona Effect 3262937 Splays Stripes and Blisters 3262938 Glass Fiber Streaks 3272939 Weld-Lines (Knit-Lines) 32729310 Jetting 32829311 Delamination 32929312 Record Grooves (Orange Peel) 32929313 Cold Slug 33029314 Ejector Pin Marks 33029315 Oil Stain ndash Brown or Black Specks 33129316 Water Stain 331

294 Poor Mechanical Strength 3322941 Bubbles or Voids inside the Part 3322942 Cracks 3322943 Unmelts (Also Called Pitting) 3332944 Brittleness 3342945 Crazing 3342946 Problems with Regrind 335

CHAPTER 29

XVI

Contents

295 Dimensional Problems 3352951 Incorrect Shrinkage 3352952 Unrealistic Tolerances 3362953 Warpage 337

296 Production Problems 3382961 Part Sticks in the Cavity 3382962 Part Sticks on the Core 3382963 Part Sticks on the Ejector Pins 3392964 Sprue Sticks in the Mold 3402965 Stringing 341

Statistical Process Control (SPC) 342301enspWhy SPC 342302enspDefinitions in SPC 343

3021enspNormal Distribution (Gaussian Dispersion) 343303enspStandard Deviations 343

3031enspOne Standard Deviation 3433032enspSix Standard Deviations (Six Sigma) 3443033enspControl Limits 3443034enspTarget Value 3463035enspTarget Value Centering (TC) 3473036enspCapability Machine (Cm) 3473037enspCapability Machine Index (Cmk) 3483038enspCapability Process (Cp) 3483039enspCapability Process Index (Cpk) 34930310enspSix Important Factors 34930311enspMachine Capability 35030312enspProcess Capability 350

304enspHow SPC Works in Practice 3513041enspSoftware 3513042enspProcess Data Monitoring 352

Internet Links 354

Index 355

CHAPTER 30

CHAPTER 31

XVII

Foreword

For many years I had the idea of writing a book about injection molding as I have spent over 45 years of my working life on this subject

When I retired in 2009 I was given great support by my friends Katarina Elner- Haglund and Peter Schulz of the Swedish plastics magazine Plastforum who asked me to write a series of articles about thermoplastics and their processing for the magazine

I was also hired at this time to work with educational programs at the Lund Uni-versity of Technology the Royal University of Technology in Stockholm and a number of industrial companies in Sweden as a result of which this book was developed

My aim has been to write in such a way that this book can be understood by everyone regardless of prior knowledge about plastics The book has a practical approach with lots of pictures and is intended to be used in secondary schools universities industrial training and self-study In some of the chapters there are references to worksheets in Excel that can be downloaded free from my website wwwbruconse

In addition to the above-mentioned persons I would like to extend a warm thanks to my wife Ingeloumlv who has been very patient when Irsquove been totally absent in the ldquowonderful world of plasticsrdquo and then proofread the book my brother Hans-Peter who has spent countless hours on adjustments of all the images etc and my son-in-law Stefan Bruder who has checked the contents of the book and contributed with many valuable comments

I would also like to thank my previous employer DuPont Performance Polymers and especially my friends and former managers Bjoumlrn Hedlund and Stewart Day-kin who encouraged the development of my career as a trainer until I reached my ultimate goal and dream job of ldquoglobal technical training managerrdquo They have also contributed with a lot of information and many valuable images in this book

I also want said a big thank you to my friends and business partners in all educa-tional programs in recent years who have supported me and contributed with many valuable comments information and images for this book and a special thanks to those who have made this printing possible thanks to the ads in the beginning The whole list would be very long but you will find some of them in the list of internet links in Chapter 31

In this Second Edition

This edition contains greatly expanded coverage of extrusion collected into a new Chapter 20 There are also a number of new and updated figures with numerous small improvements and corrections throughout the text These are complemented by an all-new professional layout and structure which I hope will help readers to navigate the book comfortably

XVIII

Foreword

I would like to thank Mark Smith at Carl Hanser Verlag for all the support that I received during the last years with my book in various languages

Ulf Bruder

Karlskrona Sweden

10

Chapter 2 mdash Commodities

3) LDPE is used for film blowing and extrusion

A large part of all the polyethylene produced is used for film blowing If the film is soft and flexible it is either made of LDPE or LLDPE If it has the rustle of the free bags at the grocery store it is probably made of HDPE LLDPE is also used to improve the strength of LDPE film

Figure 27enspGarbage bags LDPE is excellent for film blowing and is the most common material used in bags plastic sacks and construction film

Figure 28enspCable jacketing LDPE is used in the extrusion of jacketing for high voltage cables

4) PEX

Cross-linked polyethylene is mainly used in the extrusion of tubes The cross-link-ing provides improved creep resistance and better high-temperature properties

You can even copolymerize ethylene with polar monomers and get everything from viscous products (ethinspg melting glue) to tough films and impact-resistant hard shells such as golf balls

A common copolymer is EVA (ethylene-vinyl-acetate) By varying the concentration of vinyl acetate (VA) from 25 to 95 you can control the properties and produce a range of different types of material Increased VA content leads to higher trans-parency and toughness

Adhesives carpet underlay cable insulation carriers of color masterbatches stretch film and coating film for cardboard and paper are typical uses of EVA

Figure 29enspTubes in PEX resist both high temperatures (120degC) and pres-sure and are used for the hot water supply of cleaning or washing machines

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

XIV

Contents

248 Rule 8 ndash Be Careful with Gate Location and Dimensions 2562481 Weld Lines 257

249 Rule 9 ndash Avoid Tight Tolerances 2582410 Rule 10 ndash Choose an Appropriate Assembly Method 259

Assembly Methods for Thermoplastics 260251 Assembly Methods That Facilitate Disassembly 260252 Integrated Snap-Fits 261253 Permanent Assembly Methods 262

2531 Ultrasonic Welding 2622532 Vibration Welding 2632533 Rotational Welding 2642534 Hot Plate Welding 2652535 Infrared Welding 2662536 Laser Welding 2662537 Riveting 2682538 Gluing 269

The Injection-Molding Process 270261 Molding Processing Analysis 270262 Contact Information 272263 Information Pane 272264 Material Information 273265 Information about the Machine 274266 Information about the Mold 276267 Drying 278268 Processing Information 280269 Temperatures 2812610 Pressure Injection Speed and Screw Rotation Speed 2862611 Hold Pressure 2872612 Injection 2892613 Screw Rotation Speed 2902614 Time and Length Settings 292

Injection Molding Process Parameters 297

Problem Solving and Quality Management 301281 Increased Quality Demands 301282 Analytical Troubleshooting ndash ATS 301

2821 Definition of the Problem 3022822 Deviation Definition 302

283 Defining a Problem 3032831 Classification of Problems 3042832 Problem Analysis 306

CHAPTER 25

CHAPTER 26

CHAPTER 27

CHAPTER 28

XV

Contents

2833 Brainstorming 3082834 Verification of Causes 3082835 Planning of Actions to Take 309

284 Statistical Design of Experiments ndash DOE 3092841 Factorial Experiments 310

285 Failure Mode Effect Analysis ndash FMEA 3132851 General Concepts of FMEA 314

Troubleshooting ndash Causes and Effects 316291 Molding Problems 316292 Fill Ratio 318

2921 Short Shots ndash The Part Is Not Completely Filled 3182922 Flashes 3192923 Sink Marks 3192924 Voids or Pores 320

293 Surface Defects 3212931 Burn Marks 321

29311 Discoloration Dark Streaks or Degradation 32129312 Black Specks 32129313 Splays or Silver Streaks

(Partly over the Surface) 32229314 Diesel Effect ndash Entrapped Air 323

2932 Splays or Silver Streaks (All over the Surface) 3242933 Color Streaks ndash Bad Color Dispersion 3242934 Color Streaks ndash Unfavorable Pigment Orientation 3252935 Surface Gloss ndash MatteShiny Surface Variations 3252936 Surface Gloss ndash Corona Effect 3262937 Splays Stripes and Blisters 3262938 Glass Fiber Streaks 3272939 Weld-Lines (Knit-Lines) 32729310 Jetting 32829311 Delamination 32929312 Record Grooves (Orange Peel) 32929313 Cold Slug 33029314 Ejector Pin Marks 33029315 Oil Stain ndash Brown or Black Specks 33129316 Water Stain 331

294 Poor Mechanical Strength 3322941 Bubbles or Voids inside the Part 3322942 Cracks 3322943 Unmelts (Also Called Pitting) 3332944 Brittleness 3342945 Crazing 3342946 Problems with Regrind 335

CHAPTER 29

XVI

Contents

295 Dimensional Problems 3352951 Incorrect Shrinkage 3352952 Unrealistic Tolerances 3362953 Warpage 337

296 Production Problems 3382961 Part Sticks in the Cavity 3382962 Part Sticks on the Core 3382963 Part Sticks on the Ejector Pins 3392964 Sprue Sticks in the Mold 3402965 Stringing 341

Statistical Process Control (SPC) 342301enspWhy SPC 342302enspDefinitions in SPC 343

3021enspNormal Distribution (Gaussian Dispersion) 343303enspStandard Deviations 343

3031enspOne Standard Deviation 3433032enspSix Standard Deviations (Six Sigma) 3443033enspControl Limits 3443034enspTarget Value 3463035enspTarget Value Centering (TC) 3473036enspCapability Machine (Cm) 3473037enspCapability Machine Index (Cmk) 3483038enspCapability Process (Cp) 3483039enspCapability Process Index (Cpk) 34930310enspSix Important Factors 34930311enspMachine Capability 35030312enspProcess Capability 350

304enspHow SPC Works in Practice 3513041enspSoftware 3513042enspProcess Data Monitoring 352

Internet Links 354

Index 355

CHAPTER 30

CHAPTER 31

XVII

Foreword

For many years I had the idea of writing a book about injection molding as I have spent over 45 years of my working life on this subject

When I retired in 2009 I was given great support by my friends Katarina Elner- Haglund and Peter Schulz of the Swedish plastics magazine Plastforum who asked me to write a series of articles about thermoplastics and their processing for the magazine

I was also hired at this time to work with educational programs at the Lund Uni-versity of Technology the Royal University of Technology in Stockholm and a number of industrial companies in Sweden as a result of which this book was developed

My aim has been to write in such a way that this book can be understood by everyone regardless of prior knowledge about plastics The book has a practical approach with lots of pictures and is intended to be used in secondary schools universities industrial training and self-study In some of the chapters there are references to worksheets in Excel that can be downloaded free from my website wwwbruconse

In addition to the above-mentioned persons I would like to extend a warm thanks to my wife Ingeloumlv who has been very patient when Irsquove been totally absent in the ldquowonderful world of plasticsrdquo and then proofread the book my brother Hans-Peter who has spent countless hours on adjustments of all the images etc and my son-in-law Stefan Bruder who has checked the contents of the book and contributed with many valuable comments

I would also like to thank my previous employer DuPont Performance Polymers and especially my friends and former managers Bjoumlrn Hedlund and Stewart Day-kin who encouraged the development of my career as a trainer until I reached my ultimate goal and dream job of ldquoglobal technical training managerrdquo They have also contributed with a lot of information and many valuable images in this book

I also want said a big thank you to my friends and business partners in all educa-tional programs in recent years who have supported me and contributed with many valuable comments information and images for this book and a special thanks to those who have made this printing possible thanks to the ads in the beginning The whole list would be very long but you will find some of them in the list of internet links in Chapter 31

In this Second Edition

This edition contains greatly expanded coverage of extrusion collected into a new Chapter 20 There are also a number of new and updated figures with numerous small improvements and corrections throughout the text These are complemented by an all-new professional layout and structure which I hope will help readers to navigate the book comfortably

XVIII

Foreword

I would like to thank Mark Smith at Carl Hanser Verlag for all the support that I received during the last years with my book in various languages

Ulf Bruder

Karlskrona Sweden

10

Chapter 2 mdash Commodities

3) LDPE is used for film blowing and extrusion

A large part of all the polyethylene produced is used for film blowing If the film is soft and flexible it is either made of LDPE or LLDPE If it has the rustle of the free bags at the grocery store it is probably made of HDPE LLDPE is also used to improve the strength of LDPE film

Figure 27enspGarbage bags LDPE is excellent for film blowing and is the most common material used in bags plastic sacks and construction film

Figure 28enspCable jacketing LDPE is used in the extrusion of jacketing for high voltage cables

4) PEX

Cross-linked polyethylene is mainly used in the extrusion of tubes The cross-link-ing provides improved creep resistance and better high-temperature properties

You can even copolymerize ethylene with polar monomers and get everything from viscous products (ethinspg melting glue) to tough films and impact-resistant hard shells such as golf balls

A common copolymer is EVA (ethylene-vinyl-acetate) By varying the concentration of vinyl acetate (VA) from 25 to 95 you can control the properties and produce a range of different types of material Increased VA content leads to higher trans-parency and toughness

Adhesives carpet underlay cable insulation carriers of color masterbatches stretch film and coating film for cardboard and paper are typical uses of EVA

Figure 29enspTubes in PEX resist both high temperatures (120degC) and pres-sure and are used for the hot water supply of cleaning or washing machines

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

XV

Contents

2833 Brainstorming 3082834 Verification of Causes 3082835 Planning of Actions to Take 309

284 Statistical Design of Experiments ndash DOE 3092841 Factorial Experiments 310

285 Failure Mode Effect Analysis ndash FMEA 3132851 General Concepts of FMEA 314

Troubleshooting ndash Causes and Effects 316291 Molding Problems 316292 Fill Ratio 318

2921 Short Shots ndash The Part Is Not Completely Filled 3182922 Flashes 3192923 Sink Marks 3192924 Voids or Pores 320

293 Surface Defects 3212931 Burn Marks 321

29311 Discoloration Dark Streaks or Degradation 32129312 Black Specks 32129313 Splays or Silver Streaks

(Partly over the Surface) 32229314 Diesel Effect ndash Entrapped Air 323

2932 Splays or Silver Streaks (All over the Surface) 3242933 Color Streaks ndash Bad Color Dispersion 3242934 Color Streaks ndash Unfavorable Pigment Orientation 3252935 Surface Gloss ndash MatteShiny Surface Variations 3252936 Surface Gloss ndash Corona Effect 3262937 Splays Stripes and Blisters 3262938 Glass Fiber Streaks 3272939 Weld-Lines (Knit-Lines) 32729310 Jetting 32829311 Delamination 32929312 Record Grooves (Orange Peel) 32929313 Cold Slug 33029314 Ejector Pin Marks 33029315 Oil Stain ndash Brown or Black Specks 33129316 Water Stain 331

294 Poor Mechanical Strength 3322941 Bubbles or Voids inside the Part 3322942 Cracks 3322943 Unmelts (Also Called Pitting) 3332944 Brittleness 3342945 Crazing 3342946 Problems with Regrind 335

CHAPTER 29

XVI

Contents

295 Dimensional Problems 3352951 Incorrect Shrinkage 3352952 Unrealistic Tolerances 3362953 Warpage 337

296 Production Problems 3382961 Part Sticks in the Cavity 3382962 Part Sticks on the Core 3382963 Part Sticks on the Ejector Pins 3392964 Sprue Sticks in the Mold 3402965 Stringing 341

Statistical Process Control (SPC) 342301enspWhy SPC 342302enspDefinitions in SPC 343

3021enspNormal Distribution (Gaussian Dispersion) 343303enspStandard Deviations 343

3031enspOne Standard Deviation 3433032enspSix Standard Deviations (Six Sigma) 3443033enspControl Limits 3443034enspTarget Value 3463035enspTarget Value Centering (TC) 3473036enspCapability Machine (Cm) 3473037enspCapability Machine Index (Cmk) 3483038enspCapability Process (Cp) 3483039enspCapability Process Index (Cpk) 34930310enspSix Important Factors 34930311enspMachine Capability 35030312enspProcess Capability 350

304enspHow SPC Works in Practice 3513041enspSoftware 3513042enspProcess Data Monitoring 352

Internet Links 354

Index 355

CHAPTER 30

CHAPTER 31

XVII

Foreword

For many years I had the idea of writing a book about injection molding as I have spent over 45 years of my working life on this subject

When I retired in 2009 I was given great support by my friends Katarina Elner- Haglund and Peter Schulz of the Swedish plastics magazine Plastforum who asked me to write a series of articles about thermoplastics and their processing for the magazine

I was also hired at this time to work with educational programs at the Lund Uni-versity of Technology the Royal University of Technology in Stockholm and a number of industrial companies in Sweden as a result of which this book was developed

My aim has been to write in such a way that this book can be understood by everyone regardless of prior knowledge about plastics The book has a practical approach with lots of pictures and is intended to be used in secondary schools universities industrial training and self-study In some of the chapters there are references to worksheets in Excel that can be downloaded free from my website wwwbruconse

In addition to the above-mentioned persons I would like to extend a warm thanks to my wife Ingeloumlv who has been very patient when Irsquove been totally absent in the ldquowonderful world of plasticsrdquo and then proofread the book my brother Hans-Peter who has spent countless hours on adjustments of all the images etc and my son-in-law Stefan Bruder who has checked the contents of the book and contributed with many valuable comments

I would also like to thank my previous employer DuPont Performance Polymers and especially my friends and former managers Bjoumlrn Hedlund and Stewart Day-kin who encouraged the development of my career as a trainer until I reached my ultimate goal and dream job of ldquoglobal technical training managerrdquo They have also contributed with a lot of information and many valuable images in this book

I also want said a big thank you to my friends and business partners in all educa-tional programs in recent years who have supported me and contributed with many valuable comments information and images for this book and a special thanks to those who have made this printing possible thanks to the ads in the beginning The whole list would be very long but you will find some of them in the list of internet links in Chapter 31

In this Second Edition

This edition contains greatly expanded coverage of extrusion collected into a new Chapter 20 There are also a number of new and updated figures with numerous small improvements and corrections throughout the text These are complemented by an all-new professional layout and structure which I hope will help readers to navigate the book comfortably

XVIII

Foreword

I would like to thank Mark Smith at Carl Hanser Verlag for all the support that I received during the last years with my book in various languages

Ulf Bruder

Karlskrona Sweden

10

Chapter 2 mdash Commodities

3) LDPE is used for film blowing and extrusion

A large part of all the polyethylene produced is used for film blowing If the film is soft and flexible it is either made of LDPE or LLDPE If it has the rustle of the free bags at the grocery store it is probably made of HDPE LLDPE is also used to improve the strength of LDPE film

Figure 27enspGarbage bags LDPE is excellent for film blowing and is the most common material used in bags plastic sacks and construction film

Figure 28enspCable jacketing LDPE is used in the extrusion of jacketing for high voltage cables

4) PEX

Cross-linked polyethylene is mainly used in the extrusion of tubes The cross-link-ing provides improved creep resistance and better high-temperature properties

You can even copolymerize ethylene with polar monomers and get everything from viscous products (ethinspg melting glue) to tough films and impact-resistant hard shells such as golf balls

A common copolymer is EVA (ethylene-vinyl-acetate) By varying the concentration of vinyl acetate (VA) from 25 to 95 you can control the properties and produce a range of different types of material Increased VA content leads to higher trans-parency and toughness

Adhesives carpet underlay cable insulation carriers of color masterbatches stretch film and coating film for cardboard and paper are typical uses of EVA

Figure 29enspTubes in PEX resist both high temperatures (120degC) and pres-sure and are used for the hot water supply of cleaning or washing machines

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

XVI

Contents

295 Dimensional Problems 3352951 Incorrect Shrinkage 3352952 Unrealistic Tolerances 3362953 Warpage 337

296 Production Problems 3382961 Part Sticks in the Cavity 3382962 Part Sticks on the Core 3382963 Part Sticks on the Ejector Pins 3392964 Sprue Sticks in the Mold 3402965 Stringing 341

Statistical Process Control (SPC) 342301enspWhy SPC 342302enspDefinitions in SPC 343

3021enspNormal Distribution (Gaussian Dispersion) 343303enspStandard Deviations 343

3031enspOne Standard Deviation 3433032enspSix Standard Deviations (Six Sigma) 3443033enspControl Limits 3443034enspTarget Value 3463035enspTarget Value Centering (TC) 3473036enspCapability Machine (Cm) 3473037enspCapability Machine Index (Cmk) 3483038enspCapability Process (Cp) 3483039enspCapability Process Index (Cpk) 34930310enspSix Important Factors 34930311enspMachine Capability 35030312enspProcess Capability 350

304enspHow SPC Works in Practice 3513041enspSoftware 3513042enspProcess Data Monitoring 352

Internet Links 354

Index 355

CHAPTER 30

CHAPTER 31

XVII

Foreword

For many years I had the idea of writing a book about injection molding as I have spent over 45 years of my working life on this subject

When I retired in 2009 I was given great support by my friends Katarina Elner- Haglund and Peter Schulz of the Swedish plastics magazine Plastforum who asked me to write a series of articles about thermoplastics and their processing for the magazine

I was also hired at this time to work with educational programs at the Lund Uni-versity of Technology the Royal University of Technology in Stockholm and a number of industrial companies in Sweden as a result of which this book was developed

My aim has been to write in such a way that this book can be understood by everyone regardless of prior knowledge about plastics The book has a practical approach with lots of pictures and is intended to be used in secondary schools universities industrial training and self-study In some of the chapters there are references to worksheets in Excel that can be downloaded free from my website wwwbruconse

In addition to the above-mentioned persons I would like to extend a warm thanks to my wife Ingeloumlv who has been very patient when Irsquove been totally absent in the ldquowonderful world of plasticsrdquo and then proofread the book my brother Hans-Peter who has spent countless hours on adjustments of all the images etc and my son-in-law Stefan Bruder who has checked the contents of the book and contributed with many valuable comments

I would also like to thank my previous employer DuPont Performance Polymers and especially my friends and former managers Bjoumlrn Hedlund and Stewart Day-kin who encouraged the development of my career as a trainer until I reached my ultimate goal and dream job of ldquoglobal technical training managerrdquo They have also contributed with a lot of information and many valuable images in this book

I also want said a big thank you to my friends and business partners in all educa-tional programs in recent years who have supported me and contributed with many valuable comments information and images for this book and a special thanks to those who have made this printing possible thanks to the ads in the beginning The whole list would be very long but you will find some of them in the list of internet links in Chapter 31

In this Second Edition

This edition contains greatly expanded coverage of extrusion collected into a new Chapter 20 There are also a number of new and updated figures with numerous small improvements and corrections throughout the text These are complemented by an all-new professional layout and structure which I hope will help readers to navigate the book comfortably

XVIII

Foreword

I would like to thank Mark Smith at Carl Hanser Verlag for all the support that I received during the last years with my book in various languages

Ulf Bruder

Karlskrona Sweden

10

Chapter 2 mdash Commodities

3) LDPE is used for film blowing and extrusion

A large part of all the polyethylene produced is used for film blowing If the film is soft and flexible it is either made of LDPE or LLDPE If it has the rustle of the free bags at the grocery store it is probably made of HDPE LLDPE is also used to improve the strength of LDPE film

Figure 27enspGarbage bags LDPE is excellent for film blowing and is the most common material used in bags plastic sacks and construction film

Figure 28enspCable jacketing LDPE is used in the extrusion of jacketing for high voltage cables

4) PEX

Cross-linked polyethylene is mainly used in the extrusion of tubes The cross-link-ing provides improved creep resistance and better high-temperature properties

You can even copolymerize ethylene with polar monomers and get everything from viscous products (ethinspg melting glue) to tough films and impact-resistant hard shells such as golf balls

A common copolymer is EVA (ethylene-vinyl-acetate) By varying the concentration of vinyl acetate (VA) from 25 to 95 you can control the properties and produce a range of different types of material Increased VA content leads to higher trans-parency and toughness

Adhesives carpet underlay cable insulation carriers of color masterbatches stretch film and coating film for cardboard and paper are typical uses of EVA

Figure 29enspTubes in PEX resist both high temperatures (120degC) and pres-sure and are used for the hot water supply of cleaning or washing machines

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

XVII

Foreword

For many years I had the idea of writing a book about injection molding as I have spent over 45 years of my working life on this subject

When I retired in 2009 I was given great support by my friends Katarina Elner- Haglund and Peter Schulz of the Swedish plastics magazine Plastforum who asked me to write a series of articles about thermoplastics and their processing for the magazine

I was also hired at this time to work with educational programs at the Lund Uni-versity of Technology the Royal University of Technology in Stockholm and a number of industrial companies in Sweden as a result of which this book was developed

My aim has been to write in such a way that this book can be understood by everyone regardless of prior knowledge about plastics The book has a practical approach with lots of pictures and is intended to be used in secondary schools universities industrial training and self-study In some of the chapters there are references to worksheets in Excel that can be downloaded free from my website wwwbruconse

In addition to the above-mentioned persons I would like to extend a warm thanks to my wife Ingeloumlv who has been very patient when Irsquove been totally absent in the ldquowonderful world of plasticsrdquo and then proofread the book my brother Hans-Peter who has spent countless hours on adjustments of all the images etc and my son-in-law Stefan Bruder who has checked the contents of the book and contributed with many valuable comments

I would also like to thank my previous employer DuPont Performance Polymers and especially my friends and former managers Bjoumlrn Hedlund and Stewart Day-kin who encouraged the development of my career as a trainer until I reached my ultimate goal and dream job of ldquoglobal technical training managerrdquo They have also contributed with a lot of information and many valuable images in this book

I also want said a big thank you to my friends and business partners in all educa-tional programs in recent years who have supported me and contributed with many valuable comments information and images for this book and a special thanks to those who have made this printing possible thanks to the ads in the beginning The whole list would be very long but you will find some of them in the list of internet links in Chapter 31

In this Second Edition

This edition contains greatly expanded coverage of extrusion collected into a new Chapter 20 There are also a number of new and updated figures with numerous small improvements and corrections throughout the text These are complemented by an all-new professional layout and structure which I hope will help readers to navigate the book comfortably

XVIII

Foreword

I would like to thank Mark Smith at Carl Hanser Verlag for all the support that I received during the last years with my book in various languages

Ulf Bruder

Karlskrona Sweden

10

Chapter 2 mdash Commodities

3) LDPE is used for film blowing and extrusion

A large part of all the polyethylene produced is used for film blowing If the film is soft and flexible it is either made of LDPE or LLDPE If it has the rustle of the free bags at the grocery store it is probably made of HDPE LLDPE is also used to improve the strength of LDPE film

Figure 27enspGarbage bags LDPE is excellent for film blowing and is the most common material used in bags plastic sacks and construction film

Figure 28enspCable jacketing LDPE is used in the extrusion of jacketing for high voltage cables

4) PEX

Cross-linked polyethylene is mainly used in the extrusion of tubes The cross-link-ing provides improved creep resistance and better high-temperature properties

You can even copolymerize ethylene with polar monomers and get everything from viscous products (ethinspg melting glue) to tough films and impact-resistant hard shells such as golf balls

A common copolymer is EVA (ethylene-vinyl-acetate) By varying the concentration of vinyl acetate (VA) from 25 to 95 you can control the properties and produce a range of different types of material Increased VA content leads to higher trans-parency and toughness

Adhesives carpet underlay cable insulation carriers of color masterbatches stretch film and coating film for cardboard and paper are typical uses of EVA

Figure 29enspTubes in PEX resist both high temperatures (120degC) and pres-sure and are used for the hot water supply of cleaning or washing machines

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

XVIII

Foreword

I would like to thank Mark Smith at Carl Hanser Verlag for all the support that I received during the last years with my book in various languages

Ulf Bruder

Karlskrona Sweden

10

Chapter 2 mdash Commodities

3) LDPE is used for film blowing and extrusion

A large part of all the polyethylene produced is used for film blowing If the film is soft and flexible it is either made of LDPE or LLDPE If it has the rustle of the free bags at the grocery store it is probably made of HDPE LLDPE is also used to improve the strength of LDPE film

Figure 27enspGarbage bags LDPE is excellent for film blowing and is the most common material used in bags plastic sacks and construction film

Figure 28enspCable jacketing LDPE is used in the extrusion of jacketing for high voltage cables

4) PEX

Cross-linked polyethylene is mainly used in the extrusion of tubes The cross-link-ing provides improved creep resistance and better high-temperature properties

You can even copolymerize ethylene with polar monomers and get everything from viscous products (ethinspg melting glue) to tough films and impact-resistant hard shells such as golf balls

A common copolymer is EVA (ethylene-vinyl-acetate) By varying the concentration of vinyl acetate (VA) from 25 to 95 you can control the properties and produce a range of different types of material Increased VA content leads to higher trans-parency and toughness

Adhesives carpet underlay cable insulation carriers of color masterbatches stretch film and coating film for cardboard and paper are typical uses of EVA

Figure 29enspTubes in PEX resist both high temperatures (120degC) and pres-sure and are used for the hot water supply of cleaning or washing machines

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

10

Chapter 2 mdash Commodities

3) LDPE is used for film blowing and extrusion

A large part of all the polyethylene produced is used for film blowing If the film is soft and flexible it is either made of LDPE or LLDPE If it has the rustle of the free bags at the grocery store it is probably made of HDPE LLDPE is also used to improve the strength of LDPE film

Figure 27enspGarbage bags LDPE is excellent for film blowing and is the most common material used in bags plastic sacks and construction film

Figure 28enspCable jacketing LDPE is used in the extrusion of jacketing for high voltage cables

4) PEX

Cross-linked polyethylene is mainly used in the extrusion of tubes The cross-link-ing provides improved creep resistance and better high-temperature properties

You can even copolymerize ethylene with polar monomers and get everything from viscous products (ethinspg melting glue) to tough films and impact-resistant hard shells such as golf balls

A common copolymer is EVA (ethylene-vinyl-acetate) By varying the concentration of vinyl acetate (VA) from 25 to 95 you can control the properties and produce a range of different types of material Increased VA content leads to higher trans-parency and toughness

Adhesives carpet underlay cable insulation carriers of color masterbatches stretch film and coating film for cardboard and paper are typical uses of EVA

Figure 29enspTubes in PEX resist both high temperatures (120degC) and pres-sure and are used for the hot water supply of cleaning or washing machines

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

11

22enspPolypropylene (PP)

22enspPolypropylene (PP)

Chemical facts

PP has a simple structure and is made up like PE only of carbon and hydrogen It also belongs to the category of plastics called olefins Polypropylene is made up of a chain of carbon atoms where eve-ry other carbon atom is bonded to two hydrogen atoms and every other to a hydrogen atom and a methyl group The monomer for-mula is

Graphically you describe polypropylene

Polypropylene is a semi-crystalline commodity denoted bymdashand commonly referred to asmdashPP It is also known as ldquopolypropylenerdquo It is the second-largest plastic on the market after LDPE

Polypropylene was discovered in 1954 almost simultaneously by two independent researchers Ziegler and Natta who went on to share the Nobel Prize in 1963

The Italian chemical company Montecatini launched the material on the market in 1957

The polymerization of polypropylene can control both crystallinity and molecule size One can also copolymerize polypropylene with other monomers (ethinspg ethy-lene)

Polypropylene can occur as a homopolymer random or block copolymer depend-ing on the polymerization method Polypropylene can also be mixed with elasto-mers (ethinspg EPDM) filled with talc (chalk) or reinforced with glass fiber In this way it is possible to obtain more grades with widely differing characteristics than can be achieved for any other plastic Certain grades of polypropylene can handle a continuous temperature of 100thinspdegC plus peaks of up to 140thinspdegC and can therefore be classified as engineering plastics

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

22

Chapter 2 mdash Commodities

271enspProperties of PMMA+ Very high transparency (98)+ High rigidity and surface hardness+ Very good UV resistance+ Good optical properties+ Can be used in implants

minus High thermal expansion coefficientminus Scratch resistanceminus Low resistance to stress-crackingminus Solvent resistanceminus High melt viscosity (difficult to fill thin

walls)

272enspRecyclingPMMA can be easily recycled and is denoted by the recycling code gt PMMA lt

273enspApplication AreasPMMA can be injection molded and extruded Semi-finished products in PMMA can be processed with conventional machining PMMA is superior to polycarbon-ate and polystyrene for laser marking

Figure 227enspPMMA works really well in reflective items Figure 228enspPMMA is much used by the lighting industry ethinspg as a screen for fluorescent tubes

Figure 229enspOphthalmic lenses PMMA is highly compatible with the human body and is therefore used in implants Due to its extremely good optical properties PMMA is used in artificial lenses that are surgically inserted into the eye

Figure 230enspSafety glass at sports arenas The protective glass shields around hockey rinks are usually made of PMMA as the material has high transparency and sufficient tough-ness

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

23

Chapter 3

Engineering Polymers

31enspPolyamide or Nylon

Polyamide is a semi-crystalline engineering plastic denoted by PA There are several different types of polyamide of which PA6 and PA66 are the most common Polyamide was the first engineering polymer launched on the market It is also the largest in volume since it is widely used in the automotive industry

Polyamide was invented by DuPont in the United States in 1934 and was first launched as a fiber in parachutes and womenrsquos stockings under the trade name Nylon

A few years later the injection-molding grades were launched Nylon became a general term DuPont lost the trademark and currently markets its polyamides under the trade name Zytel Ultramid from BASF Durethan from Lanxess and Akulon from DSM are some of the other famous trade names on the market

311enspClassificationThe development of polyamide has focused on improving the high-temperature properties and reducing water absorption This has led to a number of variants where in addition to PA6 and PA66 the following types should be mentioned PA666 PA46 PA11 PA12 and PA612

About a decade ago aromatic ldquohigh performancerdquo polyamides were introduced usually known as PPA which stands for polyphthalamide The latest trend is ldquobio-polyamidesrdquo made from long-chain monomers ethinspg PA410 PA610 PA1010 PA10 PA11 and PA612

Chemical facts

Polyamide is available in a number of variations labeled alpha-numerically ethinspg PA66 indicating the number of carbon atoms in the molecules that make up the monomer PA6 is the most com-mon type of polyamide and has the simplest structure

PA66 has a monomer that consists of two different molecules wherein each molecule has six carbon atoms as illustrated below

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

34

Chapter 3 mdash Engineering Polymers

341enspProperties of Polycarbonate+ Crystal clear (light permeability 89)+ Very high impact strength (at low

temperatures down to minus40thinspdegC)+ High operating temperature (120thinspdegC

constant and 145thinspdegC short-term peak load)

+ Negligible moisture absorption and good dimensional stability

+ Lower mold shrinkage than most other plastics

+ Good electrical properties

+ Self-extinguishing V-2 and can be V-0 with additives

+ Food-approved grades availableminus High tendency to stress-crack under

constant loadminus Solvent triggers crackingminus Degrades in water hotter than 60thinspdegC but

can be machine washed

342enspRecyclingMaterial recycling is preferable for PC although incineration for energy extraction is also an option The recycling code is gt PC lt

343enspApplication AreasPolycarbonate can be processed by injection molding and extrusion both with and without glass fiber PC sheets can be vacuum formed

Figure 326enspPolycarbonate has a poor chemical resistance as can be seen from the cracks caused by vinegar in the salad bowl here

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

35

34enspPolycarbonate

Figure 327enspExtruded tubes of glass fiber reinforced polycarbonate are both stiff and strong and can withstand tough impact as the paddle in this picture shows

Figure 328enspThe glass for car head-lamps is made of polycarbonate and coated with a thin layer of siloxane to improve scratch resistance UV protec-tion and protection against solvents

Figure 329enspPolycarbonate is both incredibly impact resistant and suitable for painting making it an excellent material for motorcycle helmets The visor is also produced in polycarbonate

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

66

Chapter 6 mdash Bioplastics and Biocomposites

Figure 69ensp Castor bean plant

Figure 610enspGas pipes and fittings for gas pipes can be made of PA11 This material is the first high-performance polyamide that has been approved to be used for pipes up to 100 mm (4 inches) in diame-ter at operating pressures up to 14 bars This material may be biobased and contain 100 renewably sourced ingredients by weight

Figure 611enspAutomotive radiator end tanks can be produced from PA610 bio-polyamide and resist the hot chemically aggressive underhood environment PA610 also has low water absorption Some PA610 contains more than 40 renewably sourced ingre-dients by weight

67enspBiobased Polymers from Microorganisms

PHA (polyhydroxyalkanoate) is a linear semi-crystalline polyester produced by the bacterial fermentation of sugar glucose or lipids ithinspe a group of substances consisting of fats and fat-like substances The material was developed by ICI in the 1980s and there are very few producers in the market The material has good weathering properties and low water permeability Overall it has properties sim-ilar to PP

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

67

68enspBioethanol or Biomethanol

68enspBioethanol or Biomethanol

PE is a commodity that has begun to be produced again of renewable biobased raw materials

In the 1970s a substantial proportion of Indiarsquos ethanol was used for the manu-facture of PE PVC and PS In the 1980s companies in Brazil began to manufacture biobased PE and PVC However when oil prices dropped in the early 1990s pro-duction stopped Twenty years later production is beginning to build up again

Today the Brazilian company Braskem is a world leader in biobased PE Commer-cial production started in September 2010 using sugar cane as a raw material to prepare bioethanol which is then converted into ethylene used in the production of PE Total production is currently around 200000 tons and represents 17 of the market for bioplastics

Bio-PE is nonbiodegradable

Other commodities that can come from renewable resources are PP and PVC

Figure 612enspPHA has many medical applications PHA fibers can be used to suture wounds

Figure 613enspA plastic shopping bag produced in green Bio-PE

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

76

Chapter 8

Modification of Polymers

This chapter describes the polymerization of thermoplastics and how to control their properties by using various additives

81enspPolymerization

The polymerization of monomers obtained by cracking of oil or natural gas creates polymers (synthetic materials) that can be either plastic or rubber The type of monomer determines which type of material you get while the polymerization process itself can create different variations of the molecular chains such as linear or branched as shown below

Linear polymer

Side branched polymer

Crosslinked polymer

Figure 81 ensp95 of all the plastics produced are based on natural gas and oil The remaining 5 comes from renewable sources ithinspe plants In 2010 plastics accounted for about 4 of the total oil consumption as follows Heating 35 Transport 29 Energy 22 Plastic materials 4 Rubber materials 2 Chemicals and medicine 1 Other 7

Figure 82enspPolymerization of ethylene can produce different variants of poly-ethylene LLDPE is made up of linear chains like the one at the top of the figure LDPE has a branched chain structure as shown in the middle And PEX has cross-linked chains ithinspe where there are molecular bonds between the chains as shown at the bottom

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

77

81enspPolymerization

If a polymer is made up of a single monomer it is called a homopolymer If there are more monomers in the chain it is called a copolymer Acetal and polypropylene are resins that can occur in both these variations The copolymer group (the sec-ond monomer) is mainly located after the main monomer in the chain In the case of acetal there are about 40 main monomers between every copolymer group The copolymer may also occur as a side branch in the main chain in which case it is known as a graft copolymer

Homopolymer

Alloy or blend

Copolymer

Graft copolymer

An additional way to modify the polymer is to control where the different molecules end up in the chain (see next)

Isotactic chain

Syndiotactic chain

Atactic chain

Figure 83enspAt the top we can see the linear chain of a pure polymer such as polypropylene By adding ethylene you get a polypropylene copolymer with a block structure according to the sec-ond chain from the top This material has much better impact resistance than normal polypropylene By adding EPDM (rubber monomer) you get a graft polymer with a chain struc-ture and a material with extremely high impact strength You can also create a copolymer by mixing the granules from different polymers In this case the material is known as an alloy or blend ABS + PC is an example of this type of copolymer

Figure 84enspTo a certain extent we can control the properties of a polymer by influencing how a particular molecule in the chain is oriented The red circles in the top two chains symbolize the ndashCH3 group in polypropylene If all the ndashCH3 groups are oriented in the same direction it is called isotactic In polypropylene with the help of a so-called metallocene catalyst you can orient the groups so that they are evenly distributed in different direc-tions In this case the chain is called syndiotactic In a material such as polystyrene there is an aromatic molecule with 6 carbon atoms in a ring (symbolized by the red circle in the lower chain) This molecule ends up completely random both in orientation and distribution in the chain Such a chain is called atactic

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

94

Chapter 9 mdash Material Data and Measurements

In the tables below with values from the CAMPUS materials database (see next chapter) you will find HDT for a number of thermoplastics NOTE Some deviation from the values below may occur depending on the viscosity and additives of the materials

Table 91enspTable with common plastics heat deflection temperatures

Type of polymer HDT at 045 MPa HDT at 18 MPa Melting pointABS 100  90 ndashAcetal copolymer 160 104 166Acetal homopolymer 160  95 178HDPE polyethylene  75  44 130PA 6 160  55 221PA 6 + 30 glass fiber 220 205 220PA 66 200  70 262PA 66 + 30 glass fiber 250 260 263Polyester PBT 180  60 225PBT + 30 glass fiber 220 205 225Polyester PET  75  70 255PET + 30 glass fiber 245 224 252PMMA (acrylic plastic) 120 110 ndashPolycarbonate 138 125 ndashPolystyrene  90  80 ndashPP polypropylene 100  55 163PP + 30 glass fiber 160 145 163

Note The amorphous materials have no melting point

Figure 913enspWhen measuring HDT you have to fix a test bar horizontally at both ends Then you put it into an oven and load it in the middle with either 045 or 18 MPa You let the oven temperature rise by 2thinspdegC per minute and record the tem-perature at which the sample bar has bent down 025 mm as the HDT

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

95

94enspFlammability Tests

94enspFlammability Tests

The international testing institute Underwriters Laboratories has developed var-ious tests to specify a materialrsquos fire resistance You select test bars with different thickness and ignite them either horizontally or vertically We specify this as HB (= horizontal burning) or V-2 V-1 or V-0 (V = vertical burning) For a material to be classified as fire resistant it must be extinguished by itself within a certain distance (HB) and at a certain time When testing a material for V-0 to V-2 you will also give attention to possible drops that ignite cotton (see below)

941enspHB Rating

942enspV Rating

Figure 914enspThe flame is applied for 30 seconds before the ignition speed is measured HB classification is obtained if the ignition speed measured between two points does not exceed 1 40 mmmin for 3ndash13 mm test bars 2 75 mmmin for test bars ltthinsp3 mm 3 If the flame goes out before the first

mark

Figure 915enspWhen testing a test bar in a vertical position you will apply the flame twice during each 10 seconds The contact time of the second ignition begins immediately after extinguishing the test bar of the first flame

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

168

Chapter 19

Cost Calculations for Moldings

Most molders are using advanced computer-based software to calculate costs or post-costs of injection-molded parts Unfortunately it is very seldom that injection machine setters have insight into or get the opportunity to use such software even though they have great potential to affect the costs by adjusting the injection-mold-ing parameters

How often does it happen that setters add a few seconds of extra cooling time when they have a temporary disturbance of the injection-molding cycle And then forget to change back to the original settings before the parameters are saved for the next time the mold will be set up Those extra seconds can mean thousands of Euros or Dollars in unnecessary production costs per year and may also reduce the companyrsquos competitiveness

The purpose of this chapter is to show how a fairly detailed cost calculation for injection-molded parts can be made The setter also gets a tool that enables himher to see how changes that are made in the process can influence the cost of the molded part This tool is based on Microsoft Excel and is available for downloading at wwwbruconse The user does not need any extensive knowledge of Excel in order to fill in the input values required to immediately obtain the final cost picture at the bottom of the page

The rest of this chapter will explain how to use the Excel file and what the differ-ent input values mean

When you open the file called Costcalculatorxls you must first make a copy of this file to your computerrsquos hard drive otherwise the macro functions will not work Depending on how the default values are set for your own Excel program it may be necessary to make modifications of the security settings Detailed information of how this is to be done can also be found on the authorrsquos homepage The Excel file is also in ldquoread-onlyrdquo mode so it should be saved under a different name once you have completed it

Figure 191enspThe start menu once the Excel file has been opened

169

191enspPart Cost Calculator

There are three different functions to choose between

1 Read about the functions of this software

2 Compare the costs between two different materials

3 Make a full part cost calculation

Before you click on the key ldquoI accept the conditionsrdquo you are only able to ldquoRead about the functions of the softwarerdquo The two other keys will only display blank pages

Figure 192enspOnce you have clicked on ldquoI accept the conditionsrdquo you will see ldquoThe file is activerdquo and all the different functions can now be used

191enspPart Cost Calculator

We will start with the ldquoPart cost calculatorrdquo This is the most advanced function and we will go through all input values before we end the chapter with the ldquoMate-rial comparison calculatorrdquo

In ldquoPart cost calculatorrdquo you can make a relatively complete cost calculation for a single part total delivery volume or annual volume When filling in the white input fields with blue text a quick way to get to the next field is to use the ldquoTabrdquo key on your computer keyboard

The final result is obtained at a given sales price but it is also possible to get the sales price using a predetermined profit that you wish to achieve

Figure 193enspIf you wish to practice with the same values that are shown above just click on the key ldquoFill in an examplerdquo and the spreadsheet will automatically be filled with the values

270

Chapter 26

The Injection-Molding Process

261enspMolding Processing Analysis

In this chapter we will go through the main injection-molding parameters that affect the quality of the moldings We will also emphasize the value of working systematically and having good documentation

Figure 261 shows a document called ldquoInjection Moulding Process Analysisrdquo There is an Excel file that can be downloaded at wwwbruconse On this sheet we can record most of the parameters that need to be documented to describe the injec-tion-molding process for a molded part

This document was designed by the author of this book when he was responsible for the technical service at one of the leading plastic suppliers in the Nordic region

You may think Why should I spend time to fill it in when I can get all the para-meters printed out directly from the computer system in my molding machine

The answer is that you would probably drown in all the figures and only with difficulty find the cause of the problem You would also have difficulties in finding the key parameters as the printouts from different machines are completely dif-ferent

This document is perfect for use both in problem solving and as a basis for process and cost optimization as well as for documenting a test drive or a start-up of a new job If you fill in the document when the process is at its best you will have good benchmarks for comparison when there is a disturbance in the process Therefore we will closely examine the structure of this document and explain the meaning of the information in each input field On the last page of this chapter the document is presented in full-page format (Figure 2648)

270

Chapter 26

The Injection-Molding Process

261enspMolding Processing Analysis

In this chapter we will go through the main injection-molding parameters that affect the quality of the moldings We will also emphasize the value of working systematically and having good documentation

Figure 261 shows a document called ldquoInjection Moulding Process Analysisrdquo There is an Excel file that can be downloaded at wwwbruconse On this sheet we can record most of the parameters that need to be documented to describe the injec-tion-molding process for a molded part

This document was designed by the author of this book when he was responsible for the technical service at one of the leading plastic suppliers in the Nordic region

You may think Why should I spend time to fill it in when I can get all the para-meters printed out directly from the computer system in my molding machine

The answer is that you would probably drown in all the figures and only with difficulty find the cause of the problem You would also have difficulties in finding the key parameters as the printouts from different machines are completely dif-ferent

This document is perfect for use both in problem solving and as a basis for process and cost optimization as well as for documenting a test drive or a start-up of a new job If you fill in the document when the process is at its best you will have good benchmarks for comparison when there is a disturbance in the process Therefore we will closely examine the structure of this document and explain the meaning of the information in each input field On the last page of this chapter the document is presented in full-page format (Figure 2648)

271

261enspMolding Processing Analysis

jk

INJECTION MOULDING PROCESS ANALYSIS

Date LocationCustomer

Email Phone noContact person

Problem Desire

Alternative usable material Material

MB content Masterbatch Lot no

NkClamping force Hold pressure profile possible Machine

Screw diameterVented barrelShut-off nozzleScrew type mm

No of cavitiesHot-runner systemMould part name

mm Min wall thicknmm Max wall thickness Wall thickness at gate

Nozzle diameter g Full shot weightg Parts weight (sum)mm

Processing

degC

secHold press timeMPaHold pressureMPa Injection pressure

Injection speed

Peripheral screw speedRPMScrew rotationMPaBack pressure msec

Cushion stablemm Cushionmm Hold pressure switch

Comments

Calculated

wwwbruconse 2016

gtgtgt Profile ltltlt

Calculated

gtgtgt Profile ltltlt

Regrind

Sprue dimension mm

mm

Runner dimension Gate dimensionmm mm

Drying Hot air dryer Dehumidified dryer Direct transport of dried resin to hopper

Drying temp Drying time hoursdegC

Cylinder temp Nozzle (front) degC Zone 4 Zone 3 Zone 2 Zone 1degC degC degC

Melt temperature degC Mould temp moving Mould temp fixed Temp checked by pyrometerdegC degC

mmsec Fill time sec

Dosing time

Dosing length

Cooling time Total cycle time Hold-up time minsecsec sec

mm cm3 Max dosing length mm cm3 Suck-back mm cm3

Please use tab button when filling in this sheet

Figure 261enspThe working tool ldquoInjection moulding process analysisrdquo which is described in this chapter

298

Chapter 27 mdash Injection Molding Process Parameters

rotation speed compared to a less viscous standard grade For example impact-mod-ified acetal with a melt index of 1ndash2 g10 min has a recommended maximum peripheral speed of 02 ms compared to 03 ms for a standard grade with melt index of 5ndash10 g10 min For glass fiber reinforced grades you will usually find the recommended maximum peripheral speed to be 30ndash50 of the speed for the unreinforced grade Also impact modified flame retardant grades used to be more sensitive to shear than standard grades

Having sufficiently high Hold pressure is especially important for semi-crystalline plastics Usually it is recommended to have as high a pressure as possible without getting flashes in the parting line or having ejection problems We provide hold pressures because many molders sometimes in good faith set far too low a hold pressure resulting in poorer quality

Other important parameters such as hold pressure time hold pressure switch back pressure injection speed and decompression are more dependent on the part design and machine conditions We therefore cannot give any general values of these parameters but refer you instead to Chapter 26

Table 271enspTypical processing data for unmodified standard grades of common thermoplastics

Semi-crystalline commoditiesMaterial Type Melt temperature Mold

tempDrying Hold

pressureMax peripheral speed

Nominal Range Temp Time Max moisture

Dew point

Unit degC degC degC degC Hours degC MPa msPolyethylene PEHD 200 200ndash280 25ndash60 Does not normally need to be dried 25ndash35 13Polyethylene PELD 200 180ndash240 20ndash60 Does not normally need to be dried 25ndash35 09Polyethylene PELLD 200 180ndash240 20ndash60 Does not normally need to be dried 25ndash35 09Polyethylene PEMD 200 200ndash260 25ndash60 Does not normally need to be dried 25ndash35 11Polypropylene PP 240 220ndash280 20ndash60 Does not normally need to be dried 35ndash45 11

Amorphous commoditiesMaterial Type Melt temperature Mold

tempDrying Hold

pressureMax peripheral speed

Nominal Range Temp Time Max moisture

Dew point

Unit degC degC degC degC Hours degC MPa msPolystyrene PS 230 210ndash280 10ndash70 Does not normally need to be dried 45ndash50 09HIPS PSSB 230 220ndash270 30ndash70 Does not normally need to be dried 45ndash50 06SAN 240 220ndash290 40ndash80 Does not normally need to be dried 45ndash50 06ABS 240 220ndash280 40ndash80 80 3 01 minusthinsp18 45ndash50 05ASA 250 220ndash280 40ndash80 90 3ndash4 01 minusthinsp18 40ndash45 05PVC Soft 170 160ndash220 30ndash50 Does not normally need to be dried 40ndash45 05PVC Hard 190 180ndash215 30ndash60 Does not normally need to be dried 50ndash55 02PMMA 230 190ndash260 30ndash80 8 4 005 minus18 60ndash80 06

299

27enspInjection Molding Process Parameters

Semi-crystalline engineering polymersMaterial Type Melt temperature Mold

tempDrying Hold

pressureMax peripheral speed

Nominal Range Temp Time Max moisture

Dew point

Unit degC degC degC degC Hours degC MPa msAcetal POM

Homo215 210ndash220 90ndash120 Does not normally need to be

dried60ndash80 03

Acetal POM Copo

205 200ndash220 60ndash120 Does not normally need to be dried

60ndash80 04

Polyamide 6 PA6 270 260ndash280 50ndash90 80 2ndash4 02 minusthinsp18 55ndash60 08Polyamide 66 PA66 290 280ndash300 50ndash90 80 2ndash4 02 minusthinsp18 55ndash60 08Polyester PBT 250 240ndash260 30ndash130 120 2ndash4 004 minusthinsp29 50ndash55 04Polyester PET+ GF 285 280ndash300 80ndash120 120 4 002 minusthinsp40 50ndash55 02

Amorphous engineering polymersMaterial Type Melt temperature Mold

tempDrying Hold

pressureMax peripheral speed

Nominal Range Temp Time Max moisture

Dew point

Unit degC degC degC degC Hours degC MPa msPolycarbonate PC 290 280ndash330 80ndash120 120 2ndash4 002 minusthinsp29 60ndash80 04Polycarbonate PCABS 250 230ndash280 70ndash100 110 2ndash4 002 minusthinsp29 40ndash45 03Polycarbonate PCPBT 260 255ndash270 40ndash80 120 2ndash4 002 minusthinsp29 60ndash80 04Polycarbonate PCASA 250 240ndash280 40ndash80 110 4 01 minusthinsp18 40ndash45 03Mod PPO 290 280ndash310 80ndash120 110 3ndash4 001 minusthinsp29 35ndash70 03

Semi-crystalline advanced thermoplasticsMaterial Type Melt temperature Mold

tempDrying Hold

pressureMax peripheral speed

Nominal Range Temp Time Max moisture

Dew point

Unit degC degC degC degC Hours degC MPa msFluoroplastic FEP

PFA350 300ndash380 150 Does not normally need to be

driedLow

Aromatic polyamide

PA6T66 325 320ndash330  85ndash105 100 6ndash8 01 minusthinsp18 35ndash140 02PA6TXT 325 320ndash330 140ndash160 100 6ndash8 01 minusthinsp18 35ndash140 02

LCP 355 350ndash360  60ndash120 150 3 001 minusthinsp29 20ndash60 MaxPPS 330 300ndash345  70ndash180 150 3ndash6 004 minusthinsp29 45ndash50 02PEEK 370 360ndash430 160ndash200 160 2ndash3 01 minusthinsp18 50ndash65 02

330

Chapter 29 mdash Troubleshooting ndash Causes and Effects

29313enspCold SlugPossible causes (listed in the most likely order)1 The material freezes in the nozzle

2 None or incorrectly located cold slug pocket in the runner

3 The melt flows into the fixed half during the opening or closing phase of the injection-molding cycle

Suggested remedies (according to the causes above)1 Increase the nozzle temperature

2 Locate the cold slug pocket opposite the sprue in the mold

3 Reduce the risk of melt leakage into the mold

Increase the decompression (suck-back)

Reverse the injection unit during the opening and closing phase

Increase the injection speed

29314enspEjector Pin MarksPossible causes (listed in the most likely order)1 The part sticks too tightly in the cavity

2 The part is not cold enough (stiff) at the ejection

3 Mold problems or a faulty design

Suggested remedies (according to the causes above)1 Reduce the mold shrinkage

Reduce the hold pressure

Reduce the hold pressure time

Increase the release agent (surface lubrication) in the resin

Use a release spray (initially)

2 Eject or cool the part more efficiently

Increase or decrease the ejection speed

Reduce the mold temperature

Increase the hold pressure time or the cooling time

3 Workshop action required (see also Chapter 16) Increase the draft angles in the cavity

Change the size or design of the ejector pins

Cold slugSprue

Figure 2921enspThe picture shows the center of a hubcap The gate is located on the opposite side During the opening and closing phase melt material has flowed into the cavity due to the injection unit abutting the mold

Figure 2922enspHere there are visible ejector pin marks looking like white crescent moons You can also see a clear sink mark

331

293enspSurface Defects

29315enspOil Stain ndash Brown or Black SpecksPossible causes (listed in the most likely order)1 Leaking cooling fluid when an oil temperature control unit is used

2 Leaking hydraulic oil hoses (cores)

3 Lubrication drops from the mold

4 Contamination from the gripper of the robot

5 Micro-cracks in the walls or plates of the mold

Suggested remedies (according to the causes above)1 Check hoses

2 Check hose connections

3 Clean the mold

4 Clean the gripper of the robot

5 Workshop action required (see also Chapter 16) Repair the mold

29316enspWater StainPossible causes (listed in the most likely order)1 Leaking temperature-control hoses in the mold

2 Leaking gaskets in the mold

3 Cracks in the plates of the mold

Suggested remedies (according to the causes above)1 Check hose connections and hoses

2 Check O-rings and gaskets in the mold

3 Workshop action required (see also Chapter 16) Repair the mold

Figure 2923enspHere there are brown greasy oil stains on a white plastic cap

Stain due towater leakage

Figure 2924enspHere there is a diagonal mark on the surface that was formed when plastic melt came in contact with water in the cavity

355

Index

A

ABSensp 18acetalensp 26acrylonitrile-butadiene-styreneensp 18actual valueensp 302additive manufacturingensp 154additivesensp 78amorphousensp 5analytical troubleshootingensp 301angle toolensp 189anisotropic behaviorensp 241assembly methodsensp 260atacticensp 77

B

back pressureensp 289barrier screwsensp 181biocompositesensp 59 68biodegradableensp 59bioplasticsensp 59 62biopolyamideensp 65biopolyesterensp 63blistersensp 326blow moldingensp 204brainstormingensp 308brittlenessensp 334bubblesensp 332burn marksensp 321

C

cable productionensp 193CAMPUSensp 98capability machineensp 347capability processensp 348celluloseensp 63chemical propertiesensp 83chromingensp 122co-extrusionensp 191cold slugensp 330cold slug pocketsensp 133color streaksensp 324compoundingensp 195control limitsensp 344

cooling systemsensp 134cooling timeensp 292corner radiusensp 252corrugationensp 185cost calculationsensp 168cracksensp 332crazingensp 334creepensp 242cushionensp 295cylinderensp 180

D

dark streaksensp 321decompressionensp 294degradationensp 321delaminationensp 329design of experimentsensp 309design rulesensp 238deviationensp 302diesel effectensp 323dimensional problemsensp 335discolorationensp 321dosing lengthensp 294dosing timeensp 292draft anglesensp 138dry air dryerensp 279dryingensp 278

E

ejector pin marksensp 330ejector systemsensp 137electrical propertiesensp 84 96environmental factorsensp 70EPSensp 15extrusionensp 177

F

factorial experimentsensp 310family moldsensp 126feedingensp 186fill ratioensp 318film blowingensp 191

flame retardancyensp 86flammabilityensp 95 107flashesensp 319flexural modulusensp 91fluoropolymersensp 47

G

gas injectionensp 116gateensp 131gate locationensp 256glass fiber streaksensp 327glass transition temperatureensp 5granulation methodsensp 78

H

HB ratingensp 95HDPEensp 8heat deflection temperatureensp 86 93heat stabilizationensp 85high-performance thermoplasticsensp

46hingeensp 198hold pressureensp 287hold pressure switchensp 294hold pressure timeensp 287hot air dryerensp 279hot plate weldingensp 265hot runner systemsensp 132rdquohot stamprdquo printingensp 118hygroscopicensp 278

I

impact strengthensp 92infrared spectrophotometerensp 108infrared weldingensp 266injection-molding cycleensp 114injection-molding machineensp 110injection-molding methodsensp 110injection-molding processensp 270injection pressureensp 286injection speedensp 286 289injection unitensp 112

356

Index

in-mold decorationensp 120isotacticensp 77

J

jettingensp 328

L

laser markingensp 121laser weldingensp 266LCPensp 50LCPAensp 65LDPEensp 8liquid crystal polymerensp 50LLDPEensp 8locking unitensp 113

M

machine capabilityensp 350masterbatchensp 80material dataensp 88Material Data Centerensp 98material selectionensp 209MDPEensp 8mechanical propertiesensp 79melt indexensp 97melting pointensp 5melt temperatureensp 282metalizingensp 122microtome analysisensp 109moldensp 123mold designensp 139mold filling analysisensp 146mold shrinkageensp 97 284molds with melt coresensp 128monofilamentensp 194monomerensp 76muffingensp 203multi-component injection moldingensp

115multi-component moldsensp 127

N

nonlinearensp 240nozzle diameterensp 278nylonensp 23

O

oil stainensp 331orange peelensp 329

P

PAensp 23paintingensp 121PBTensp 29PCensp 33PEensp 7PEEKensp 53PEIensp 54peripheral speedensp 280 291PETensp 29PEXensp 8PHAensp 66physical propertiesensp 80PLAensp 64plasticensp 1PMMAensp 21polyamideensp 23polybutylene terephthalateensp 29polycarbonateensp 33polyesterensp 29polyether ether ketoneensp 53polyetherimideensp 54polyethyleneensp 7polyethylene terephthalateensp 30polylactideensp 64polymerensp 1polymerizationensp 76polymethyl methacrylateensp 21polyoxymethyleneensp 26polyphenylene sulfideensp 52polyphenylsulfoneensp 57polypropyleneensp 11polystyreneensp 15polysulfoneensp 56polytetrafluoroethyleneensp 47polyvinylchlorideensp 13POMensp 26poresensp 320post-shrinkageensp 284PPensp 11PPAensp 48PPSensp 52PPSUensp 57

printingensp 117problem analysisensp 306process capabilityensp 350processing dataensp 298process parametersensp 297production problemsensp 338profileensp 196prototype moldsensp 145PSensp 15PSUensp 56PTFEensp 47PTTensp 65PVCensp 13pyrometerensp 282

Q

quality controlensp 102

R

record groovesensp 329recyclingensp 73regrindensp 335rejectensp 170relaxationensp 242replacement cost calculationensp 175requirement specificationsensp 210ribsensp 254rivetingensp 268rotating coresensp 125rotational moldingensp 206rotational weldingensp 264runner systemsensp 130

S

SANensp 17SBSensp 38scanning electron microscopeensp 108screen printingensp 119screw diameterensp 292screw rotationensp 292screw rotation speedensp 290sealing lipensp 197SEBSensp 38semi-crystallineensp 5service temperatureensp 93setpointensp 302

357

Index

shrinkageensp 284 335silver streaksensp 322 324single-screw extruderensp 181sink marksensp 319Six Sigmaensp 344sliding jointensp 198snap-fit jointensp 199specific heatensp 6specific volumeensp 6spiral formingensp 202splaysensp 322 324 326stack moldsensp 125standard deviationsensp 343starchensp 63statistical design of experimentsensp

309statistical process controlensp 342stiffnessensp 89stress concentrationensp 252stress-strain curveensp 90stringingensp 341stripesensp 326styrene-acrylonitrileensp 17suck-backensp 294surface treatmentensp 117syndiotacticensp 77

T

tampon printingensp 119target valueensp 346target value centeringensp 347temperature profileensp 281tensile modulusensp 91tensile strengthensp 88testing methodsensp 105thermal propertiesensp 85thermoplastic elastomersensp 36thermosetsensp 3three-plate moldsensp 124tolerancesensp 258 336total shrinkageensp 284toughnessensp 89TPC-ETensp 42TPE-Aensp 44TPE-Eensp 42TPE-Oensp 36TPE-Sensp 38TPE-Uensp 41TPE-Vensp 39TPOensp 36TPUensp 41TPVensp 39troubleshootingensp 316twin-screw extruderensp 182two-component moldingensp 115two-plate moldsensp 123

U

UHMWPEensp 8UL service temperatureensp 93ultrasonic weldingensp 262unmeltsensp 333

V

vacuum formingensp 207venting systemsensp 136venting zoneensp 180vibration weldingensp 263visual inspectionensp 104voidsensp 320 332V ratingensp 95

W

wall thicknessensp 251warpageensp 337water injection moldingensp 116water stainensp 331weather resistanceensp 81weld linesensp 257weld-linesensp 327windingensp 188

Y

yield stressensp 90

• Deckblatt_Sample_pages
• contents
• foreword
• 10-11
• 22-23
• 34-35
• 66-67
• 76-77
• 94-95
• 168-169
• 270-271
• 298-299
• 330-331
• Index

298

Chapter 27 mdash Injection Molding Process Parameters

rotation speed compared to a less viscous standard grade For example impact-mod-ified acetal with a melt index of 1ndash2 g10 min has a recommended maximum peripheral speed of 02 ms compared to 03 ms for a standard grade with melt index of 5ndash10 g10 min For glass fiber reinforced grades you will usually find the recommended maximum peripheral speed to be 30ndash50 of the speed for the unreinforced grade Also impact modified flame retardant grades used to be more sensitive to shear than standard grades

Having sufficiently high Hold pressure is especially important for semi-crystalline plastics Usually it is recommended to have as high a pressure as possible without getting flashes in the parting line or having ejection problems We provide hold pressures because many molders sometimes in good faith set far too low a hold pressure resulting in poorer quality

Other important parameters such as hold pressure time hold pressure switch back pressure injection speed and decompression are more dependent on the part design and machine conditions We therefore cannot give any general values of these parameters but refer you instead to Chapter 26

Table 271enspTypical processing data for unmodified standard grades of common thermoplastics

Semi-crystalline commoditiesMaterial Type Melt temperature Mold

tempDrying Hold

pressureMax peripheral speed

Nominal Range Temp Time Max moisture

Dew point

Unit degC degC degC degC Hours degC MPa msPolyethylene PEHD 200 200ndash280 25ndash60 Does not normally need to be dried 25ndash35 13Polyethylene PELD 200 180ndash240 20ndash60 Does not normally need to be dried 25ndash35 09Polyethylene PELLD 200 180ndash240 20ndash60 Does not normally need to be dried 25ndash35 09Polyethylene PEMD 200 200ndash260 25ndash60 Does not normally need to be dried 25ndash35 11Polypropylene PP 240 220ndash280 20ndash60 Does not normally need to be dried 35ndash45 11

Amorphous commoditiesMaterial Type Melt temperature Mold

tempDrying Hold

pressureMax peripheral speed

Nominal Range Temp Time Max moisture

Dew point

Unit degC degC degC degC Hours degC MPa msPolystyrene PS 230 210ndash280 10ndash70 Does not normally need to be dried 45ndash50 09HIPS PSSB 230 220ndash270 30ndash70 Does not normally need to be dried 45ndash50 06SAN 240 220ndash290 40ndash80 Does not normally need to be dried 45ndash50 06ABS 240 220ndash280 40ndash80 80 3 01 minusthinsp18 45ndash50 05ASA 250 220ndash280 40ndash80 90 3ndash4 01 minusthinsp18 40ndash45 05PVC Soft 170 160ndash220 30ndash50 Does not normally need to be dried 40ndash45 05PVC Hard 190 180ndash215 30ndash60 Does not normally need to be dried 50ndash55 02PMMA 230 190ndash260 30ndash80 8 4 005 minus18 60ndash80 06

299

27enspInjection Molding Process Parameters

Semi-crystalline engineering polymersMaterial Type Melt temperature Mold

tempDrying Hold

pressureMax peripheral speed

Nominal Range Temp Time Max moisture

Dew point

Unit degC degC degC degC Hours degC MPa msAcetal POM

Homo215 210ndash220 90ndash120 Does not normally need to be

dried60ndash80 03

Acetal POM Copo

205 200ndash220 60ndash120 Does not normally need to be dried

60ndash80 04

Polyamide 6 PA6 270 260ndash280 50ndash90 80 2ndash4 02 minusthinsp18 55ndash60 08Polyamide 66 PA66 290 280ndash300 50ndash90 80 2ndash4 02 minusthinsp18 55ndash60 08Polyester PBT 250 240ndash260 30ndash130 120 2ndash4 004 minusthinsp29 50ndash55 04Polyester PET+ GF 285 280ndash300 80ndash120 120 4 002 minusthinsp40 50ndash55 02

Amorphous engineering polymersMaterial Type Melt temperature Mold

tempDrying Hold

pressureMax peripheral speed

Nominal Range Temp Time Max moisture

Dew point

Unit degC degC degC degC Hours degC MPa msPolycarbonate PC 290 280ndash330 80ndash120 120 2ndash4 002 minusthinsp29 60ndash80 04Polycarbonate PCABS 250 230ndash280 70ndash100 110 2ndash4 002 minusthinsp29 40ndash45 03Polycarbonate PCPBT 260 255ndash270 40ndash80 120 2ndash4 002 minusthinsp29 60ndash80 04Polycarbonate PCASA 250 240ndash280 40ndash80 110 4 01 minusthinsp18 40ndash45 03Mod PPO 290 280ndash310 80ndash120 110 3ndash4 001 minusthinsp29 35ndash70 03

Semi-crystalline advanced thermoplasticsMaterial Type Melt temperature Mold

tempDrying Hold

pressureMax peripheral speed

Nominal Range Temp Time Max moisture

Dew point

Unit degC degC degC degC Hours degC MPa msFluoroplastic FEP

PFA350 300ndash380 150 Does not normally need to be

driedLow

Aromatic polyamide

PA6T66 325 320ndash330  85ndash105 100 6ndash8 01 minusthinsp18 35ndash140 02PA6TXT 325 320ndash330 140ndash160 100 6ndash8 01 minusthinsp18 35ndash140 02

LCP 355 350ndash360  60ndash120 150 3 001 minusthinsp29 20ndash60 MaxPPS 330 300ndash345  70ndash180 150 3ndash6 004 minusthinsp29 45ndash50 02PEEK 370 360ndash430 160ndash200 160 2ndash3 01 minusthinsp18 50ndash65 02

330

Chapter 29 mdash Troubleshooting ndash Causes and Effects

29313enspCold SlugPossible causes (listed in the most likely order)1 The material freezes in the nozzle

2 None or incorrectly located cold slug pocket in the runner

3 The melt flows into the fixed half during the opening or closing phase of the injection-molding cycle

Suggested remedies (according to the causes above)1 Increase the nozzle temperature

2 Locate the cold slug pocket opposite the sprue in the mold

3 Reduce the risk of melt leakage into the mold

Increase the decompression (suck-back)

Reverse the injection unit during the opening and closing phase

Increase the injection speed

29314enspEjector Pin MarksPossible causes (listed in the most likely order)1 The part sticks too tightly in the cavity

2 The part is not cold enough (stiff) at the ejection

3 Mold problems or a faulty design

Suggested remedies (according to the causes above)1 Reduce the mold shrinkage

Reduce the hold pressure

Reduce the hold pressure time

Increase the release agent (surface lubrication) in the resin

Use a release spray (initially)

2 Eject or cool the part more efficiently

Increase or decrease the ejection speed

Reduce the mold temperature

Increase the hold pressure time or the cooling time

3 Workshop action required (see also Chapter 16) Increase the draft angles in the cavity

Change the size or design of the ejector pins

Cold slugSprue

Figure 2921enspThe picture shows the center of a hubcap The gate is located on the opposite side During the opening and closing phase melt material has flowed into the cavity due to the injection unit abutting the mold

Figure 2922enspHere there are visible ejector pin marks looking like white crescent moons You can also see a clear sink mark

331

293enspSurface Defects

29315enspOil Stain ndash Brown or Black SpecksPossible causes (listed in the most likely order)1 Leaking cooling fluid when an oil temperature control unit is used

2 Leaking hydraulic oil hoses (cores)

3 Lubrication drops from the mold

4 Contamination from the gripper of the robot

5 Micro-cracks in the walls or plates of the mold

Suggested remedies (according to the causes above)1 Check hoses

2 Check hose connections

3 Clean the mold

4 Clean the gripper of the robot

5 Workshop action required (see also Chapter 16) Repair the mold

29316enspWater StainPossible causes (listed in the most likely order)1 Leaking temperature-control hoses in the mold

2 Leaking gaskets in the mold

3 Cracks in the plates of the mold

Suggested remedies (according to the causes above)1 Check hose connections and hoses

2 Check O-rings and gaskets in the mold

3 Workshop action required (see also Chapter 16) Repair the mold

Figure 2923enspHere there are brown greasy oil stains on a white plastic cap

Stain due towater leakage

Figure 2924enspHere there is a diagonal mark on the surface that was formed when plastic melt came in contact with water in the cavity

355

Index

A

ABSensp 18acetalensp 26acrylonitrile-butadiene-styreneensp 18actual valueensp 302additive manufacturingensp 154additivesensp 78amorphousensp 5analytical troubleshootingensp 301angle toolensp 189anisotropic behaviorensp 241assembly methodsensp 260atacticensp 77

B

back pressureensp 289barrier screwsensp 181biocompositesensp 59 68biodegradableensp 59bioplasticsensp 59 62biopolyamideensp 65biopolyesterensp 63blistersensp 326blow moldingensp 204brainstormingensp 308brittlenessensp 334bubblesensp 332burn marksensp 321

C

cable productionensp 193CAMPUSensp 98capability machineensp 347capability processensp 348celluloseensp 63chemical propertiesensp 83chromingensp 122co-extrusionensp 191cold slugensp 330cold slug pocketsensp 133color streaksensp 324compoundingensp 195control limitsensp 344

cooling systemsensp 134cooling timeensp 292corner radiusensp 252corrugationensp 185cost calculationsensp 168cracksensp 332crazingensp 334creepensp 242cushionensp 295cylinderensp 180

D

dark streaksensp 321decompressionensp 294degradationensp 321delaminationensp 329design of experimentsensp 309design rulesensp 238deviationensp 302diesel effectensp 323dimensional problemsensp 335discolorationensp 321dosing lengthensp 294dosing timeensp 292draft anglesensp 138dry air dryerensp 279dryingensp 278

E

ejector pin marksensp 330ejector systemsensp 137electrical propertiesensp 84 96environmental factorsensp 70EPSensp 15extrusionensp 177

F

factorial experimentsensp 310family moldsensp 126feedingensp 186fill ratioensp 318film blowingensp 191

flame retardancyensp 86flammabilityensp 95 107flashesensp 319flexural modulusensp 91fluoropolymersensp 47

G

gas injectionensp 116gateensp 131gate locationensp 256glass fiber streaksensp 327glass transition temperatureensp 5granulation methodsensp 78

H

HB ratingensp 95HDPEensp 8heat deflection temperatureensp 86 93heat stabilizationensp 85high-performance thermoplasticsensp

46hingeensp 198hold pressureensp 287hold pressure switchensp 294hold pressure timeensp 287hot air dryerensp 279hot plate weldingensp 265hot runner systemsensp 132rdquohot stamprdquo printingensp 118hygroscopicensp 278

I

impact strengthensp 92infrared spectrophotometerensp 108infrared weldingensp 266injection-molding cycleensp 114injection-molding machineensp 110injection-molding methodsensp 110injection-molding processensp 270injection pressureensp 286injection speedensp 286 289injection unitensp 112

356

Index

in-mold decorationensp 120isotacticensp 77

J

jettingensp 328

L

laser markingensp 121laser weldingensp 266LCPensp 50LCPAensp 65LDPEensp 8liquid crystal polymerensp 50LLDPEensp 8locking unitensp 113

M

machine capabilityensp 350masterbatchensp 80material dataensp 88Material Data Centerensp 98material selectionensp 209MDPEensp 8mechanical propertiesensp 79melt indexensp 97melting pointensp 5melt temperatureensp 282metalizingensp 122microtome analysisensp 109moldensp 123mold designensp 139mold filling analysisensp 146mold shrinkageensp 97 284molds with melt coresensp 128monofilamentensp 194monomerensp 76muffingensp 203multi-component injection moldingensp

115multi-component moldsensp 127

N

nonlinearensp 240nozzle diameterensp 278nylonensp 23

O

oil stainensp 331orange peelensp 329

P

PAensp 23paintingensp 121PBTensp 29PCensp 33PEensp 7PEEKensp 53PEIensp 54peripheral speedensp 280 291PETensp 29PEXensp 8PHAensp 66physical propertiesensp 80PLAensp 64plasticensp 1PMMAensp 21polyamideensp 23polybutylene terephthalateensp 29polycarbonateensp 33polyesterensp 29polyether ether ketoneensp 53polyetherimideensp 54polyethyleneensp 7polyethylene terephthalateensp 30polylactideensp 64polymerensp 1polymerizationensp 76polymethyl methacrylateensp 21polyoxymethyleneensp 26polyphenylene sulfideensp 52polyphenylsulfoneensp 57polypropyleneensp 11polystyreneensp 15polysulfoneensp 56polytetrafluoroethyleneensp 47polyvinylchlorideensp 13POMensp 26poresensp 320post-shrinkageensp 284PPensp 11PPAensp 48PPSensp 52PPSUensp 57

printingensp 117problem analysisensp 306process capabilityensp 350processing dataensp 298process parametersensp 297production problemsensp 338profileensp 196prototype moldsensp 145PSensp 15PSUensp 56PTFEensp 47PTTensp 65PVCensp 13pyrometerensp 282

Q

quality controlensp 102

R

record groovesensp 329recyclingensp 73regrindensp 335rejectensp 170relaxationensp 242replacement cost calculationensp 175requirement specificationsensp 210ribsensp 254rivetingensp 268rotating coresensp 125rotational moldingensp 206rotational weldingensp 264runner systemsensp 130

S

SANensp 17SBSensp 38scanning electron microscopeensp 108screen printingensp 119screw diameterensp 292screw rotationensp 292screw rotation speedensp 290sealing lipensp 197SEBSensp 38semi-crystallineensp 5service temperatureensp 93setpointensp 302

357

Index

shrinkageensp 284 335silver streaksensp 322 324single-screw extruderensp 181sink marksensp 319Six Sigmaensp 344sliding jointensp 198snap-fit jointensp 199specific heatensp 6specific volumeensp 6spiral formingensp 202splaysensp 322 324 326stack moldsensp 125standard deviationsensp 343starchensp 63statistical design of experimentsensp

309statistical process controlensp 342stiffnessensp 89stress concentrationensp 252stress-strain curveensp 90stringingensp 341stripesensp 326styrene-acrylonitrileensp 17suck-backensp 294surface treatmentensp 117syndiotacticensp 77

T

tampon printingensp 119target valueensp 346target value centeringensp 347temperature profileensp 281tensile modulusensp 91tensile strengthensp 88testing methodsensp 105thermal propertiesensp 85thermoplastic elastomersensp 36thermosetsensp 3three-plate moldsensp 124tolerancesensp 258 336total shrinkageensp 284toughnessensp 89TPC-ETensp 42TPE-Aensp 44TPE-Eensp 42TPE-Oensp 36TPE-Sensp 38TPE-Uensp 41TPE-Vensp 39TPOensp 36TPUensp 41TPVensp 39troubleshootingensp 316twin-screw extruderensp 182two-component moldingensp 115two-plate moldsensp 123

U

UHMWPEensp 8UL service temperatureensp 93ultrasonic weldingensp 262unmeltsensp 333

V

vacuum formingensp 207venting systemsensp 136venting zoneensp 180vibration weldingensp 263visual inspectionensp 104voidsensp 320 332V ratingensp 95

W

wall thicknessensp 251warpageensp 337water injection moldingensp 116water stainensp 331weather resistanceensp 81weld linesensp 257weld-linesensp 327windingensp 188

Y

yield stressensp 90

• Deckblatt_Sample_pages
• contents
• foreword
• 10-11
• 22-23
• 34-35
• 66-67
• 76-77
• 94-95
• 168-169
• 270-271
• 298-299
• 330-331
• Index

299

27enspInjection Molding Process Parameters

Semi-crystalline engineering polymersMaterial Type Melt temperature Mold

tempDrying Hold

pressureMax peripheral speed

Nominal Range Temp Time Max moisture

Dew point

Unit degC degC degC degC Hours degC MPa msAcetal POM

Homo215 210ndash220 90ndash120 Does not normally need to be

dried60ndash80 03

Acetal POM Copo

205 200ndash220 60ndash120 Does not normally need to be dried

60ndash80 04

Polyamide 6 PA6 270 260ndash280 50ndash90 80 2ndash4 02 minusthinsp18 55ndash60 08Polyamide 66 PA66 290 280ndash300 50ndash90 80 2ndash4 02 minusthinsp18 55ndash60 08Polyester PBT 250 240ndash260 30ndash130 120 2ndash4 004 minusthinsp29 50ndash55 04Polyester PET+ GF 285 280ndash300 80ndash120 120 4 002 minusthinsp40 50ndash55 02

Amorphous engineering polymersMaterial Type Melt temperature Mold

tempDrying Hold

pressureMax peripheral speed

Nominal Range Temp Time Max moisture

Dew point

Unit degC degC degC degC Hours degC MPa msPolycarbonate PC 290 280ndash330 80ndash120 120 2ndash4 002 minusthinsp29 60ndash80 04Polycarbonate PCABS 250 230ndash280 70ndash100 110 2ndash4 002 minusthinsp29 40ndash45 03Polycarbonate PCPBT 260 255ndash270 40ndash80 120 2ndash4 002 minusthinsp29 60ndash80 04Polycarbonate PCASA 250 240ndash280 40ndash80 110 4 01 minusthinsp18 40ndash45 03Mod PPO 290 280ndash310 80ndash120 110 3ndash4 001 minusthinsp29 35ndash70 03

Semi-crystalline advanced thermoplasticsMaterial Type Melt temperature Mold

tempDrying Hold

pressureMax peripheral speed

Nominal Range Temp Time Max moisture

Dew point

Unit degC degC degC degC Hours degC MPa msFluoroplastic FEP

PFA350 300ndash380 150 Does not normally need to be

driedLow

Aromatic polyamide

PA6T66 325 320ndash330  85ndash105 100 6ndash8 01 minusthinsp18 35ndash140 02PA6TXT 325 320ndash330 140ndash160 100 6ndash8 01 minusthinsp18 35ndash140 02

LCP 355 350ndash360  60ndash120 150 3 001 minusthinsp29 20ndash60 MaxPPS 330 300ndash345  70ndash180 150 3ndash6 004 minusthinsp29 45ndash50 02PEEK 370 360ndash430 160ndash200 160 2ndash3 01 minusthinsp18 50ndash65 02

330

Chapter 29 mdash Troubleshooting ndash Causes and Effects

29313enspCold SlugPossible causes (listed in the most likely order)1 The material freezes in the nozzle

2 None or incorrectly located cold slug pocket in the runner

3 The melt flows into the fixed half during the opening or closing phase of the injection-molding cycle

Suggested remedies (according to the causes above)1 Increase the nozzle temperature

2 Locate the cold slug pocket opposite the sprue in the mold

3 Reduce the risk of melt leakage into the mold

Increase the decompression (suck-back)

Reverse the injection unit during the opening and closing phase

Increase the injection speed

29314enspEjector Pin MarksPossible causes (listed in the most likely order)1 The part sticks too tightly in the cavity

2 The part is not cold enough (stiff) at the ejection

3 Mold problems or a faulty design

Suggested remedies (according to the causes above)1 Reduce the mold shrinkage

Reduce the hold pressure

Reduce the hold pressure time

Increase the release agent (surface lubrication) in the resin

Use a release spray (initially)

2 Eject or cool the part more efficiently

Increase or decrease the ejection speed

Reduce the mold temperature

Increase the hold pressure time or the cooling time

3 Workshop action required (see also Chapter 16) Increase the draft angles in the cavity

Change the size or design of the ejector pins

Cold slugSprue

Figure 2921enspThe picture shows the center of a hubcap The gate is located on the opposite side During the opening and closing phase melt material has flowed into the cavity due to the injection unit abutting the mold

Figure 2922enspHere there are visible ejector pin marks looking like white crescent moons You can also see a clear sink mark

331

293enspSurface Defects

29315enspOil Stain ndash Brown or Black SpecksPossible causes (listed in the most likely order)1 Leaking cooling fluid when an oil temperature control unit is used

2 Leaking hydraulic oil hoses (cores)

3 Lubrication drops from the mold

4 Contamination from the gripper of the robot

5 Micro-cracks in the walls or plates of the mold

Suggested remedies (according to the causes above)1 Check hoses

2 Check hose connections

3 Clean the mold

4 Clean the gripper of the robot

5 Workshop action required (see also Chapter 16) Repair the mold

29316enspWater StainPossible causes (listed in the most likely order)1 Leaking temperature-control hoses in the mold

2 Leaking gaskets in the mold

3 Cracks in the plates of the mold

Suggested remedies (according to the causes above)1 Check hose connections and hoses

2 Check O-rings and gaskets in the mold

3 Workshop action required (see also Chapter 16) Repair the mold

Figure 2923enspHere there are brown greasy oil stains on a white plastic cap

Stain due towater leakage

Figure 2924enspHere there is a diagonal mark on the surface that was formed when plastic melt came in contact with water in the cavity

355

Index

A

ABSensp 18acetalensp 26acrylonitrile-butadiene-styreneensp 18actual valueensp 302additive manufacturingensp 154additivesensp 78amorphousensp 5analytical troubleshootingensp 301angle toolensp 189anisotropic behaviorensp 241assembly methodsensp 260atacticensp 77

B

back pressureensp 289barrier screwsensp 181biocompositesensp 59 68biodegradableensp 59bioplasticsensp 59 62biopolyamideensp 65biopolyesterensp 63blistersensp 326blow moldingensp 204brainstormingensp 308brittlenessensp 334bubblesensp 332burn marksensp 321

C

cable productionensp 193CAMPUSensp 98capability machineensp 347capability processensp 348celluloseensp 63chemical propertiesensp 83chromingensp 122co-extrusionensp 191cold slugensp 330cold slug pocketsensp 133color streaksensp 324compoundingensp 195control limitsensp 344

cooling systemsensp 134cooling timeensp 292corner radiusensp 252corrugationensp 185cost calculationsensp 168cracksensp 332crazingensp 334creepensp 242cushionensp 295cylinderensp 180

D

dark streaksensp 321decompressionensp 294degradationensp 321delaminationensp 329design of experimentsensp 309design rulesensp 238deviationensp 302diesel effectensp 323dimensional problemsensp 335discolorationensp 321dosing lengthensp 294dosing timeensp 292draft anglesensp 138dry air dryerensp 279dryingensp 278

E

ejector pin marksensp 330ejector systemsensp 137electrical propertiesensp 84 96environmental factorsensp 70EPSensp 15extrusionensp 177

F

factorial experimentsensp 310family moldsensp 126feedingensp 186fill ratioensp 318film blowingensp 191

flame retardancyensp 86flammabilityensp 95 107flashesensp 319flexural modulusensp 91fluoropolymersensp 47

G

gas injectionensp 116gateensp 131gate locationensp 256glass fiber streaksensp 327glass transition temperatureensp 5granulation methodsensp 78

H

HB ratingensp 95HDPEensp 8heat deflection temperatureensp 86 93heat stabilizationensp 85high-performance thermoplasticsensp

46hingeensp 198hold pressureensp 287hold pressure switchensp 294hold pressure timeensp 287hot air dryerensp 279hot plate weldingensp 265hot runner systemsensp 132rdquohot stamprdquo printingensp 118hygroscopicensp 278

I

impact strengthensp 92infrared spectrophotometerensp 108infrared weldingensp 266injection-molding cycleensp 114injection-molding machineensp 110injection-molding methodsensp 110injection-molding processensp 270injection pressureensp 286injection speedensp 286 289injection unitensp 112

356

Index

in-mold decorationensp 120isotacticensp 77

J

jettingensp 328

L

laser markingensp 121laser weldingensp 266LCPensp 50LCPAensp 65LDPEensp 8liquid crystal polymerensp 50LLDPEensp 8locking unitensp 113

M

machine capabilityensp 350masterbatchensp 80material dataensp 88Material Data Centerensp 98material selectionensp 209MDPEensp 8mechanical propertiesensp 79melt indexensp 97melting pointensp 5melt temperatureensp 282metalizingensp 122microtome analysisensp 109moldensp 123mold designensp 139mold filling analysisensp 146mold shrinkageensp 97 284molds with melt coresensp 128monofilamentensp 194monomerensp 76muffingensp 203multi-component injection moldingensp

115multi-component moldsensp 127

N

nonlinearensp 240nozzle diameterensp 278nylonensp 23

O

oil stainensp 331orange peelensp 329

P

PAensp 23paintingensp 121PBTensp 29PCensp 33PEensp 7PEEKensp 53PEIensp 54peripheral speedensp 280 291PETensp 29PEXensp 8PHAensp 66physical propertiesensp 80PLAensp 64plasticensp 1PMMAensp 21polyamideensp 23polybutylene terephthalateensp 29polycarbonateensp 33polyesterensp 29polyether ether ketoneensp 53polyetherimideensp 54polyethyleneensp 7polyethylene terephthalateensp 30polylactideensp 64polymerensp 1polymerizationensp 76polymethyl methacrylateensp 21polyoxymethyleneensp 26polyphenylene sulfideensp 52polyphenylsulfoneensp 57polypropyleneensp 11polystyreneensp 15polysulfoneensp 56polytetrafluoroethyleneensp 47polyvinylchlorideensp 13POMensp 26poresensp 320post-shrinkageensp 284PPensp 11PPAensp 48PPSensp 52PPSUensp 57

printingensp 117problem analysisensp 306process capabilityensp 350processing dataensp 298process parametersensp 297production problemsensp 338profileensp 196prototype moldsensp 145PSensp 15PSUensp 56PTFEensp 47PTTensp 65PVCensp 13pyrometerensp 282

Q

quality controlensp 102

R

record groovesensp 329recyclingensp 73regrindensp 335rejectensp 170relaxationensp 242replacement cost calculationensp 175requirement specificationsensp 210ribsensp 254rivetingensp 268rotating coresensp 125rotational moldingensp 206rotational weldingensp 264runner systemsensp 130

S

SANensp 17SBSensp 38scanning electron microscopeensp 108screen printingensp 119screw diameterensp 292screw rotationensp 292screw rotation speedensp 290sealing lipensp 197SEBSensp 38semi-crystallineensp 5service temperatureensp 93setpointensp 302

357

Index

shrinkageensp 284 335silver streaksensp 322 324single-screw extruderensp 181sink marksensp 319Six Sigmaensp 344sliding jointensp 198snap-fit jointensp 199specific heatensp 6specific volumeensp 6spiral formingensp 202splaysensp 322 324 326stack moldsensp 125standard deviationsensp 343starchensp 63statistical design of experimentsensp

309statistical process controlensp 342stiffnessensp 89stress concentrationensp 252stress-strain curveensp 90stringingensp 341stripesensp 326styrene-acrylonitrileensp 17suck-backensp 294surface treatmentensp 117syndiotacticensp 77

T

tampon printingensp 119target valueensp 346target value centeringensp 347temperature profileensp 281tensile modulusensp 91tensile strengthensp 88testing methodsensp 105thermal propertiesensp 85thermoplastic elastomersensp 36thermosetsensp 3three-plate moldsensp 124tolerancesensp 258 336total shrinkageensp 284toughnessensp 89TPC-ETensp 42TPE-Aensp 44TPE-Eensp 42TPE-Oensp 36TPE-Sensp 38TPE-Uensp 41TPE-Vensp 39TPOensp 36TPUensp 41TPVensp 39troubleshootingensp 316twin-screw extruderensp 182two-component moldingensp 115two-plate moldsensp 123

U

UHMWPEensp 8UL service temperatureensp 93ultrasonic weldingensp 262unmeltsensp 333

V

vacuum formingensp 207venting systemsensp 136venting zoneensp 180vibration weldingensp 263visual inspectionensp 104voidsensp 320 332V ratingensp 95

W

wall thicknessensp 251warpageensp 337water injection moldingensp 116water stainensp 331weather resistanceensp 81weld linesensp 257weld-linesensp 327windingensp 188

Y

yield stressensp 90

• Deckblatt_Sample_pages
• contents
• foreword
• 10-11
• 22-23
• 34-35
• 66-67
• 76-77
• 94-95
• 168-169
• 270-271
• 298-299
• 330-331
• Index

330

Chapter 29 mdash Troubleshooting ndash Causes and Effects

29313enspCold SlugPossible causes (listed in the most likely order)1 The material freezes in the nozzle

2 None or incorrectly located cold slug pocket in the runner

3 The melt flows into the fixed half during the opening or closing phase of the injection-molding cycle

Suggested remedies (according to the causes above)1 Increase the nozzle temperature

2 Locate the cold slug pocket opposite the sprue in the mold

3 Reduce the risk of melt leakage into the mold

Increase the decompression (suck-back)

Reverse the injection unit during the opening and closing phase

Increase the injection speed

29314enspEjector Pin MarksPossible causes (listed in the most likely order)1 The part sticks too tightly in the cavity

2 The part is not cold enough (stiff) at the ejection

3 Mold problems or a faulty design

Suggested remedies (according to the causes above)1 Reduce the mold shrinkage

Reduce the hold pressure

Reduce the hold pressure time

Increase the release agent (surface lubrication) in the resin

Use a release spray (initially)

2 Eject or cool the part more efficiently

Increase or decrease the ejection speed

Reduce the mold temperature

Increase the hold pressure time or the cooling time

3 Workshop action required (see also Chapter 16) Increase the draft angles in the cavity

Change the size or design of the ejector pins

Cold slugSprue

Figure 2921enspThe picture shows the center of a hubcap The gate is located on the opposite side During the opening and closing phase melt material has flowed into the cavity due to the injection unit abutting the mold

Figure 2922enspHere there are visible ejector pin marks looking like white crescent moons You can also see a clear sink mark

331

293enspSurface Defects

29315enspOil Stain ndash Brown or Black SpecksPossible causes (listed in the most likely order)1 Leaking cooling fluid when an oil temperature control unit is used

2 Leaking hydraulic oil hoses (cores)

3 Lubrication drops from the mold

4 Contamination from the gripper of the robot

5 Micro-cracks in the walls or plates of the mold

Suggested remedies (according to the causes above)1 Check hoses

2 Check hose connections

3 Clean the mold

4 Clean the gripper of the robot

5 Workshop action required (see also Chapter 16) Repair the mold

29316enspWater StainPossible causes (listed in the most likely order)1 Leaking temperature-control hoses in the mold

2 Leaking gaskets in the mold

3 Cracks in the plates of the mold

Suggested remedies (according to the causes above)1 Check hose connections and hoses

2 Check O-rings and gaskets in the mold

3 Workshop action required (see also Chapter 16) Repair the mold

Figure 2923enspHere there are brown greasy oil stains on a white plastic cap

Stain due towater leakage

Figure 2924enspHere there is a diagonal mark on the surface that was formed when plastic melt came in contact with water in the cavity

355

Index

A

ABSensp 18acetalensp 26acrylonitrile-butadiene-styreneensp 18actual valueensp 302additive manufacturingensp 154additivesensp 78amorphousensp 5analytical troubleshootingensp 301angle toolensp 189anisotropic behaviorensp 241assembly methodsensp 260atacticensp 77

B

back pressureensp 289barrier screwsensp 181biocompositesensp 59 68biodegradableensp 59bioplasticsensp 59 62biopolyamideensp 65biopolyesterensp 63blistersensp 326blow moldingensp 204brainstormingensp 308brittlenessensp 334bubblesensp 332burn marksensp 321

C

cable productionensp 193CAMPUSensp 98capability machineensp 347capability processensp 348celluloseensp 63chemical propertiesensp 83chromingensp 122co-extrusionensp 191cold slugensp 330cold slug pocketsensp 133color streaksensp 324compoundingensp 195control limitsensp 344

cooling systemsensp 134cooling timeensp 292corner radiusensp 252corrugationensp 185cost calculationsensp 168cracksensp 332crazingensp 334creepensp 242cushionensp 295cylinderensp 180

D

dark streaksensp 321decompressionensp 294degradationensp 321delaminationensp 329design of experimentsensp 309design rulesensp 238deviationensp 302diesel effectensp 323dimensional problemsensp 335discolorationensp 321dosing lengthensp 294dosing timeensp 292draft anglesensp 138dry air dryerensp 279dryingensp 278

E

ejector pin marksensp 330ejector systemsensp 137electrical propertiesensp 84 96environmental factorsensp 70EPSensp 15extrusionensp 177

F

factorial experimentsensp 310family moldsensp 126feedingensp 186fill ratioensp 318film blowingensp 191

flame retardancyensp 86flammabilityensp 95 107flashesensp 319flexural modulusensp 91fluoropolymersensp 47

G

gas injectionensp 116gateensp 131gate locationensp 256glass fiber streaksensp 327glass transition temperatureensp 5granulation methodsensp 78

H

HB ratingensp 95HDPEensp 8heat deflection temperatureensp 86 93heat stabilizationensp 85high-performance thermoplasticsensp

46hingeensp 198hold pressureensp 287hold pressure switchensp 294hold pressure timeensp 287hot air dryerensp 279hot plate weldingensp 265hot runner systemsensp 132rdquohot stamprdquo printingensp 118hygroscopicensp 278

I

impact strengthensp 92infrared spectrophotometerensp 108infrared weldingensp 266injection-molding cycleensp 114injection-molding machineensp 110injection-molding methodsensp 110injection-molding processensp 270injection pressureensp 286injection speedensp 286 289injection unitensp 112

356

Index

in-mold decorationensp 120isotacticensp 77

J

jettingensp 328

L

laser markingensp 121laser weldingensp 266LCPensp 50LCPAensp 65LDPEensp 8liquid crystal polymerensp 50LLDPEensp 8locking unitensp 113

M

machine capabilityensp 350masterbatchensp 80material dataensp 88Material Data Centerensp 98material selectionensp 209MDPEensp 8mechanical propertiesensp 79melt indexensp 97melting pointensp 5melt temperatureensp 282metalizingensp 122microtome analysisensp 109moldensp 123mold designensp 139mold filling analysisensp 146mold shrinkageensp 97 284molds with melt coresensp 128monofilamentensp 194monomerensp 76muffingensp 203multi-component injection moldingensp

115multi-component moldsensp 127

N

nonlinearensp 240nozzle diameterensp 278nylonensp 23

O

oil stainensp 331orange peelensp 329

P

PAensp 23paintingensp 121PBTensp 29PCensp 33PEensp 7PEEKensp 53PEIensp 54peripheral speedensp 280 291PETensp 29PEXensp 8PHAensp 66physical propertiesensp 80PLAensp 64plasticensp 1PMMAensp 21polyamideensp 23polybutylene terephthalateensp 29polycarbonateensp 33polyesterensp 29polyether ether ketoneensp 53polyetherimideensp 54polyethyleneensp 7polyethylene terephthalateensp 30polylactideensp 64polymerensp 1polymerizationensp 76polymethyl methacrylateensp 21polyoxymethyleneensp 26polyphenylene sulfideensp 52polyphenylsulfoneensp 57polypropyleneensp 11polystyreneensp 15polysulfoneensp 56polytetrafluoroethyleneensp 47polyvinylchlorideensp 13POMensp 26poresensp 320post-shrinkageensp 284PPensp 11PPAensp 48PPSensp 52PPSUensp 57

printingensp 117problem analysisensp 306process capabilityensp 350processing dataensp 298process parametersensp 297production problemsensp 338profileensp 196prototype moldsensp 145PSensp 15PSUensp 56PTFEensp 47PTTensp 65PVCensp 13pyrometerensp 282

Q

quality controlensp 102

R

record groovesensp 329recyclingensp 73regrindensp 335rejectensp 170relaxationensp 242replacement cost calculationensp 175requirement specificationsensp 210ribsensp 254rivetingensp 268rotating coresensp 125rotational moldingensp 206rotational weldingensp 264runner systemsensp 130

S

SANensp 17SBSensp 38scanning electron microscopeensp 108screen printingensp 119screw diameterensp 292screw rotationensp 292screw rotation speedensp 290sealing lipensp 197SEBSensp 38semi-crystallineensp 5service temperatureensp 93setpointensp 302

357

Index

shrinkageensp 284 335silver streaksensp 322 324single-screw extruderensp 181sink marksensp 319Six Sigmaensp 344sliding jointensp 198snap-fit jointensp 199specific heatensp 6specific volumeensp 6spiral formingensp 202splaysensp 322 324 326stack moldsensp 125standard deviationsensp 343starchensp 63statistical design of experimentsensp

309statistical process controlensp 342stiffnessensp 89stress concentrationensp 252stress-strain curveensp 90stringingensp 341stripesensp 326styrene-acrylonitrileensp 17suck-backensp 294surface treatmentensp 117syndiotacticensp 77

T

tampon printingensp 119target valueensp 346target value centeringensp 347temperature profileensp 281tensile modulusensp 91tensile strengthensp 88testing methodsensp 105thermal propertiesensp 85thermoplastic elastomersensp 36thermosetsensp 3three-plate moldsensp 124tolerancesensp 258 336total shrinkageensp 284toughnessensp 89TPC-ETensp 42TPE-Aensp 44TPE-Eensp 42TPE-Oensp 36TPE-Sensp 38TPE-Uensp 41TPE-Vensp 39TPOensp 36TPUensp 41TPVensp 39troubleshootingensp 316twin-screw extruderensp 182two-component moldingensp 115two-plate moldsensp 123

U

UHMWPEensp 8UL service temperatureensp 93ultrasonic weldingensp 262unmeltsensp 333

V

vacuum formingensp 207venting systemsensp 136venting zoneensp 180vibration weldingensp 263visual inspectionensp 104voidsensp 320 332V ratingensp 95

W

wall thicknessensp 251warpageensp 337water injection moldingensp 116water stainensp 331weather resistanceensp 81weld linesensp 257weld-linesensp 327windingensp 188

Y

yield stressensp 90

• Deckblatt_Sample_pages
• contents
• foreword
• 10-11
• 22-23
• 34-35
• 66-67
• 76-77
• 94-95
• 168-169
• 270-271
• 298-299
• 330-331
• Index

331

293enspSurface Defects

29315enspOil Stain ndash Brown or Black SpecksPossible causes (listed in the most likely order)1 Leaking cooling fluid when an oil temperature control unit is used

2 Leaking hydraulic oil hoses (cores)

3 Lubrication drops from the mold

4 Contamination from the gripper of the robot

5 Micro-cracks in the walls or plates of the mold

Suggested remedies (according to the causes above)1 Check hoses

2 Check hose connections

3 Clean the mold

4 Clean the gripper of the robot

5 Workshop action required (see also Chapter 16) Repair the mold

29316enspWater StainPossible causes (listed in the most likely order)1 Leaking temperature-control hoses in the mold

2 Leaking gaskets in the mold

3 Cracks in the plates of the mold

Suggested remedies (according to the causes above)1 Check hose connections and hoses

2 Check O-rings and gaskets in the mold

3 Workshop action required (see also Chapter 16) Repair the mold

Figure 2923enspHere there are brown greasy oil stains on a white plastic cap

Stain due towater leakage

Figure 2924enspHere there is a diagonal mark on the surface that was formed when plastic melt came in contact with water in the cavity

355

Index

A

ABSensp 18acetalensp 26acrylonitrile-butadiene-styreneensp 18actual valueensp 302additive manufacturingensp 154additivesensp 78amorphousensp 5analytical troubleshootingensp 301angle toolensp 189anisotropic behaviorensp 241assembly methodsensp 260atacticensp 77

B

back pressureensp 289barrier screwsensp 181biocompositesensp 59 68biodegradableensp 59bioplasticsensp 59 62biopolyamideensp 65biopolyesterensp 63blistersensp 326blow moldingensp 204brainstormingensp 308brittlenessensp 334bubblesensp 332burn marksensp 321

C

cable productionensp 193CAMPUSensp 98capability machineensp 347capability processensp 348celluloseensp 63chemical propertiesensp 83chromingensp 122co-extrusionensp 191cold slugensp 330cold slug pocketsensp 133color streaksensp 324compoundingensp 195control limitsensp 344

cooling systemsensp 134cooling timeensp 292corner radiusensp 252corrugationensp 185cost calculationsensp 168cracksensp 332crazingensp 334creepensp 242cushionensp 295cylinderensp 180

D

dark streaksensp 321decompressionensp 294degradationensp 321delaminationensp 329design of experimentsensp 309design rulesensp 238deviationensp 302diesel effectensp 323dimensional problemsensp 335discolorationensp 321dosing lengthensp 294dosing timeensp 292draft anglesensp 138dry air dryerensp 279dryingensp 278

E

ejector pin marksensp 330ejector systemsensp 137electrical propertiesensp 84 96environmental factorsensp 70EPSensp 15extrusionensp 177

F

factorial experimentsensp 310family moldsensp 126feedingensp 186fill ratioensp 318film blowingensp 191

flame retardancyensp 86flammabilityensp 95 107flashesensp 319flexural modulusensp 91fluoropolymersensp 47

G

gas injectionensp 116gateensp 131gate locationensp 256glass fiber streaksensp 327glass transition temperatureensp 5granulation methodsensp 78

H

HB ratingensp 95HDPEensp 8heat deflection temperatureensp 86 93heat stabilizationensp 85high-performance thermoplasticsensp

46hingeensp 198hold pressureensp 287hold pressure switchensp 294hold pressure timeensp 287hot air dryerensp 279hot plate weldingensp 265hot runner systemsensp 132rdquohot stamprdquo printingensp 118hygroscopicensp 278

I

impact strengthensp 92infrared spectrophotometerensp 108infrared weldingensp 266injection-molding cycleensp 114injection-molding machineensp 110injection-molding methodsensp 110injection-molding processensp 270injection pressureensp 286injection speedensp 286 289injection unitensp 112

356

Index

in-mold decorationensp 120isotacticensp 77

J

jettingensp 328

L

laser markingensp 121laser weldingensp 266LCPensp 50LCPAensp 65LDPEensp 8liquid crystal polymerensp 50LLDPEensp 8locking unitensp 113

M

machine capabilityensp 350masterbatchensp 80material dataensp 88Material Data Centerensp 98material selectionensp 209MDPEensp 8mechanical propertiesensp 79melt indexensp 97melting pointensp 5melt temperatureensp 282metalizingensp 122microtome analysisensp 109moldensp 123mold designensp 139mold filling analysisensp 146mold shrinkageensp 97 284molds with melt coresensp 128monofilamentensp 194monomerensp 76muffingensp 203multi-component injection moldingensp

115multi-component moldsensp 127

N

nonlinearensp 240nozzle diameterensp 278nylonensp 23

O

oil stainensp 331orange peelensp 329

P

PAensp 23paintingensp 121PBTensp 29PCensp 33PEensp 7PEEKensp 53PEIensp 54peripheral speedensp 280 291PETensp 29PEXensp 8PHAensp 66physical propertiesensp 80PLAensp 64plasticensp 1PMMAensp 21polyamideensp 23polybutylene terephthalateensp 29polycarbonateensp 33polyesterensp 29polyether ether ketoneensp 53polyetherimideensp 54polyethyleneensp 7polyethylene terephthalateensp 30polylactideensp 64polymerensp 1polymerizationensp 76polymethyl methacrylateensp 21polyoxymethyleneensp 26polyphenylene sulfideensp 52polyphenylsulfoneensp 57polypropyleneensp 11polystyreneensp 15polysulfoneensp 56polytetrafluoroethyleneensp 47polyvinylchlorideensp 13POMensp 26poresensp 320post-shrinkageensp 284PPensp 11PPAensp 48PPSensp 52PPSUensp 57

printingensp 117problem analysisensp 306process capabilityensp 350processing dataensp 298process parametersensp 297production problemsensp 338profileensp 196prototype moldsensp 145PSensp 15PSUensp 56PTFEensp 47PTTensp 65PVCensp 13pyrometerensp 282

Q

quality controlensp 102

R

record groovesensp 329recyclingensp 73regrindensp 335rejectensp 170relaxationensp 242replacement cost calculationensp 175requirement specificationsensp 210ribsensp 254rivetingensp 268rotating coresensp 125rotational moldingensp 206rotational weldingensp 264runner systemsensp 130

S

SANensp 17SBSensp 38scanning electron microscopeensp 108screen printingensp 119screw diameterensp 292screw rotationensp 292screw rotation speedensp 290sealing lipensp 197SEBSensp 38semi-crystallineensp 5service temperatureensp 93setpointensp 302

357

Index

shrinkageensp 284 335silver streaksensp 322 324single-screw extruderensp 181sink marksensp 319Six Sigmaensp 344sliding jointensp 198snap-fit jointensp 199specific heatensp 6specific volumeensp 6spiral formingensp 202splaysensp 322 324 326stack moldsensp 125standard deviationsensp 343starchensp 63statistical design of experimentsensp

309statistical process controlensp 342stiffnessensp 89stress concentrationensp 252stress-strain curveensp 90stringingensp 341stripesensp 326styrene-acrylonitrileensp 17suck-backensp 294surface treatmentensp 117syndiotacticensp 77

T

tampon printingensp 119target valueensp 346target value centeringensp 347temperature profileensp 281tensile modulusensp 91tensile strengthensp 88testing methodsensp 105thermal propertiesensp 85thermoplastic elastomersensp 36thermosetsensp 3three-plate moldsensp 124tolerancesensp 258 336total shrinkageensp 284toughnessensp 89TPC-ETensp 42TPE-Aensp 44TPE-Eensp 42TPE-Oensp 36TPE-Sensp 38TPE-Uensp 41TPE-Vensp 39TPOensp 36TPUensp 41TPVensp 39troubleshootingensp 316twin-screw extruderensp 182two-component moldingensp 115two-plate moldsensp 123

U

UHMWPEensp 8UL service temperatureensp 93ultrasonic weldingensp 262unmeltsensp 333

V

vacuum formingensp 207venting systemsensp 136venting zoneensp 180vibration weldingensp 263visual inspectionensp 104voidsensp 320 332V ratingensp 95

W

wall thicknessensp 251warpageensp 337water injection moldingensp 116water stainensp 331weather resistanceensp 81weld linesensp 257weld-linesensp 327windingensp 188

Y

yield stressensp 90

• Deckblatt_Sample_pages
• contents
• foreword
• 10-11
• 22-23
• 34-35
• 66-67
• 76-77
• 94-95
• 168-169
• 270-271
• 298-299
• 330-331
• Index

355

Index

A

ABSensp 18acetalensp 26acrylonitrile-butadiene-styreneensp 18actual valueensp 302additive manufacturingensp 154additivesensp 78amorphousensp 5analytical troubleshootingensp 301angle toolensp 189anisotropic behaviorensp 241assembly methodsensp 260atacticensp 77

B

back pressureensp 289barrier screwsensp 181biocompositesensp 59 68biodegradableensp 59bioplasticsensp 59 62biopolyamideensp 65biopolyesterensp 63blistersensp 326blow moldingensp 204brainstormingensp 308brittlenessensp 334bubblesensp 332burn marksensp 321

C

cable productionensp 193CAMPUSensp 98capability machineensp 347capability processensp 348celluloseensp 63chemical propertiesensp 83chromingensp 122co-extrusionensp 191cold slugensp 330cold slug pocketsensp 133color streaksensp 324compoundingensp 195control limitsensp 344

cooling systemsensp 134cooling timeensp 292corner radiusensp 252corrugationensp 185cost calculationsensp 168cracksensp 332crazingensp 334creepensp 242cushionensp 295cylinderensp 180

D

dark streaksensp 321decompressionensp 294degradationensp 321delaminationensp 329design of experimentsensp 309design rulesensp 238deviationensp 302diesel effectensp 323dimensional problemsensp 335discolorationensp 321dosing lengthensp 294dosing timeensp 292draft anglesensp 138dry air dryerensp 279dryingensp 278

E

ejector pin marksensp 330ejector systemsensp 137electrical propertiesensp 84 96environmental factorsensp 70EPSensp 15extrusionensp 177

F

factorial experimentsensp 310family moldsensp 126feedingensp 186fill ratioensp 318film blowingensp 191

flame retardancyensp 86flammabilityensp 95 107flashesensp 319flexural modulusensp 91fluoropolymersensp 47

G

gas injectionensp 116gateensp 131gate locationensp 256glass fiber streaksensp 327glass transition temperatureensp 5granulation methodsensp 78

H

HB ratingensp 95HDPEensp 8heat deflection temperatureensp 86 93heat stabilizationensp 85high-performance thermoplasticsensp

46hingeensp 198hold pressureensp 287hold pressure switchensp 294hold pressure timeensp 287hot air dryerensp 279hot plate weldingensp 265hot runner systemsensp 132rdquohot stamprdquo printingensp 118hygroscopicensp 278

I

impact strengthensp 92infrared spectrophotometerensp 108infrared weldingensp 266injection-molding cycleensp 114injection-molding machineensp 110injection-molding methodsensp 110injection-molding processensp 270injection pressureensp 286injection speedensp 286 289injection unitensp 112

356

Index

in-mold decorationensp 120isotacticensp 77

J

jettingensp 328

L

laser markingensp 121laser weldingensp 266LCPensp 50LCPAensp 65LDPEensp 8liquid crystal polymerensp 50LLDPEensp 8locking unitensp 113

M

machine capabilityensp 350masterbatchensp 80material dataensp 88Material Data Centerensp 98material selectionensp 209MDPEensp 8mechanical propertiesensp 79melt indexensp 97melting pointensp 5melt temperatureensp 282metalizingensp 122microtome analysisensp 109moldensp 123mold designensp 139mold filling analysisensp 146mold shrinkageensp 97 284molds with melt coresensp 128monofilamentensp 194monomerensp 76muffingensp 203multi-component injection moldingensp

115multi-component moldsensp 127

N

nonlinearensp 240nozzle diameterensp 278nylonensp 23

O

oil stainensp 331orange peelensp 329

P

PAensp 23paintingensp 121PBTensp 29PCensp 33PEensp 7PEEKensp 53PEIensp 54peripheral speedensp 280 291PETensp 29PEXensp 8PHAensp 66physical propertiesensp 80PLAensp 64plasticensp 1PMMAensp 21polyamideensp 23polybutylene terephthalateensp 29polycarbonateensp 33polyesterensp 29polyether ether ketoneensp 53polyetherimideensp 54polyethyleneensp 7polyethylene terephthalateensp 30polylactideensp 64polymerensp 1polymerizationensp 76polymethyl methacrylateensp 21polyoxymethyleneensp 26polyphenylene sulfideensp 52polyphenylsulfoneensp 57polypropyleneensp 11polystyreneensp 15polysulfoneensp 56polytetrafluoroethyleneensp 47polyvinylchlorideensp 13POMensp 26poresensp 320post-shrinkageensp 284PPensp 11PPAensp 48PPSensp 52PPSUensp 57

printingensp 117problem analysisensp 306process capabilityensp 350processing dataensp 298process parametersensp 297production problemsensp 338profileensp 196prototype moldsensp 145PSensp 15PSUensp 56PTFEensp 47PTTensp 65PVCensp 13pyrometerensp 282

Q

quality controlensp 102

R

record groovesensp 329recyclingensp 73regrindensp 335rejectensp 170relaxationensp 242replacement cost calculationensp 175requirement specificationsensp 210ribsensp 254rivetingensp 268rotating coresensp 125rotational moldingensp 206rotational weldingensp 264runner systemsensp 130

S

SANensp 17SBSensp 38scanning electron microscopeensp 108screen printingensp 119screw diameterensp 292screw rotationensp 292screw rotation speedensp 290sealing lipensp 197SEBSensp 38semi-crystallineensp 5service temperatureensp 93setpointensp 302

357

Index

shrinkageensp 284 335silver streaksensp 322 324single-screw extruderensp 181sink marksensp 319Six Sigmaensp 344sliding jointensp 198snap-fit jointensp 199specific heatensp 6specific volumeensp 6spiral formingensp 202splaysensp 322 324 326stack moldsensp 125standard deviationsensp 343starchensp 63statistical design of experimentsensp

309statistical process controlensp 342stiffnessensp 89stress concentrationensp 252stress-strain curveensp 90stringingensp 341stripesensp 326styrene-acrylonitrileensp 17suck-backensp 294surface treatmentensp 117syndiotacticensp 77

T

tampon printingensp 119target valueensp 346target value centeringensp 347temperature profileensp 281tensile modulusensp 91tensile strengthensp 88testing methodsensp 105thermal propertiesensp 85thermoplastic elastomersensp 36thermosetsensp 3three-plate moldsensp 124tolerancesensp 258 336total shrinkageensp 284toughnessensp 89TPC-ETensp 42TPE-Aensp 44TPE-Eensp 42TPE-Oensp 36TPE-Sensp 38TPE-Uensp 41TPE-Vensp 39TPOensp 36TPUensp 41TPVensp 39troubleshootingensp 316twin-screw extruderensp 182two-component moldingensp 115two-plate moldsensp 123

U

UHMWPEensp 8UL service temperatureensp 93ultrasonic weldingensp 262unmeltsensp 333

V

vacuum formingensp 207venting systemsensp 136venting zoneensp 180vibration weldingensp 263visual inspectionensp 104voidsensp 320 332V ratingensp 95

W

wall thicknessensp 251warpageensp 337water injection moldingensp 116water stainensp 331weather resistanceensp 81weld linesensp 257weld-linesensp 327windingensp 188

Y

yield stressensp 90

• Deckblatt_Sample_pages
• contents
• foreword
• 10-11
• 22-23
• 34-35
• 66-67
• 76-77
• 94-95
• 168-169
• 270-271
• 298-299
• 330-331
• Index

356

Index

in-mold decorationensp 120isotacticensp 77

J

jettingensp 328

L

laser markingensp 121laser weldingensp 266LCPensp 50LCPAensp 65LDPEensp 8liquid crystal polymerensp 50LLDPEensp 8locking unitensp 113

M

machine capabilityensp 350masterbatchensp 80material dataensp 88Material Data Centerensp 98material selectionensp 209MDPEensp 8mechanical propertiesensp 79melt indexensp 97melting pointensp 5melt temperatureensp 282metalizingensp 122microtome analysisensp 109moldensp 123mold designensp 139mold filling analysisensp 146mold shrinkageensp 97 284molds with melt coresensp 128monofilamentensp 194monomerensp 76muffingensp 203multi-component injection moldingensp

115multi-component moldsensp 127

N

nonlinearensp 240nozzle diameterensp 278nylonensp 23

O

oil stainensp 331orange peelensp 329

P

PAensp 23paintingensp 121PBTensp 29PCensp 33PEensp 7PEEKensp 53PEIensp 54peripheral speedensp 280 291PETensp 29PEXensp 8PHAensp 66physical propertiesensp 80PLAensp 64plasticensp 1PMMAensp 21polyamideensp 23polybutylene terephthalateensp 29polycarbonateensp 33polyesterensp 29polyether ether ketoneensp 53polyetherimideensp 54polyethyleneensp 7polyethylene terephthalateensp 30polylactideensp 64polymerensp 1polymerizationensp 76polymethyl methacrylateensp 21polyoxymethyleneensp 26polyphenylene sulfideensp 52polyphenylsulfoneensp 57polypropyleneensp 11polystyreneensp 15polysulfoneensp 56polytetrafluoroethyleneensp 47polyvinylchlorideensp 13POMensp 26poresensp 320post-shrinkageensp 284PPensp 11PPAensp 48PPSensp 52PPSUensp 57

printingensp 117problem analysisensp 306process capabilityensp 350processing dataensp 298process parametersensp 297production problemsensp 338profileensp 196prototype moldsensp 145PSensp 15PSUensp 56PTFEensp 47PTTensp 65PVCensp 13pyrometerensp 282

Q

quality controlensp 102

R

record groovesensp 329recyclingensp 73regrindensp 335rejectensp 170relaxationensp 242replacement cost calculationensp 175requirement specificationsensp 210ribsensp 254rivetingensp 268rotating coresensp 125rotational moldingensp 206rotational weldingensp 264runner systemsensp 130

S

SANensp 17SBSensp 38scanning electron microscopeensp 108screen printingensp 119screw diameterensp 292screw rotationensp 292screw rotation speedensp 290sealing lipensp 197SEBSensp 38semi-crystallineensp 5service temperatureensp 93setpointensp 302

357

Index

shrinkageensp 284 335silver streaksensp 322 324single-screw extruderensp 181sink marksensp 319Six Sigmaensp 344sliding jointensp 198snap-fit jointensp 199specific heatensp 6specific volumeensp 6spiral formingensp 202splaysensp 322 324 326stack moldsensp 125standard deviationsensp 343starchensp 63statistical design of experimentsensp

309statistical process controlensp 342stiffnessensp 89stress concentrationensp 252stress-strain curveensp 90stringingensp 341stripesensp 326styrene-acrylonitrileensp 17suck-backensp 294surface treatmentensp 117syndiotacticensp 77

T

tampon printingensp 119target valueensp 346target value centeringensp 347temperature profileensp 281tensile modulusensp 91tensile strengthensp 88testing methodsensp 105thermal propertiesensp 85thermoplastic elastomersensp 36thermosetsensp 3three-plate moldsensp 124tolerancesensp 258 336total shrinkageensp 284toughnessensp 89TPC-ETensp 42TPE-Aensp 44TPE-Eensp 42TPE-Oensp 36TPE-Sensp 38TPE-Uensp 41TPE-Vensp 39TPOensp 36TPUensp 41TPVensp 39troubleshootingensp 316twin-screw extruderensp 182two-component moldingensp 115two-plate moldsensp 123

U

UHMWPEensp 8UL service temperatureensp 93ultrasonic weldingensp 262unmeltsensp 333

V

vacuum formingensp 207venting systemsensp 136venting zoneensp 180vibration weldingensp 263visual inspectionensp 104voidsensp 320 332V ratingensp 95

W

wall thicknessensp 251warpageensp 337water injection moldingensp 116water stainensp 331weather resistanceensp 81weld linesensp 257weld-linesensp 327windingensp 188

Y

yield stressensp 90

• Deckblatt_Sample_pages
• contents
• foreword
• 10-11
• 22-23
• 34-35
• 66-67
• 76-77
• 94-95
• 168-169
• 270-271
• 298-299
• 330-331
• Index

357

Index

shrinkageensp 284 335silver streaksensp 322 324single-screw extruderensp 181sink marksensp 319Six Sigmaensp 344sliding jointensp 198snap-fit jointensp 199specific heatensp 6specific volumeensp 6spiral formingensp 202splaysensp 322 324 326stack moldsensp 125standard deviationsensp 343starchensp 63statistical design of experimentsensp

309statistical process controlensp 342stiffnessensp 89stress concentrationensp 252stress-strain curveensp 90stringingensp 341stripesensp 326styrene-acrylonitrileensp 17suck-backensp 294surface treatmentensp 117syndiotacticensp 77

T

tampon printingensp 119target valueensp 346target value centeringensp 347temperature profileensp 281tensile modulusensp 91tensile strengthensp 88testing methodsensp 105thermal propertiesensp 85thermoplastic elastomersensp 36thermosetsensp 3three-plate moldsensp 124tolerancesensp 258 336total shrinkageensp 284toughnessensp 89TPC-ETensp 42TPE-Aensp 44TPE-Eensp 42TPE-Oensp 36TPE-Sensp 38TPE-Uensp 41TPE-Vensp 39TPOensp 36TPUensp 41TPVensp 39troubleshootingensp 316twin-screw extruderensp 182two-component moldingensp 115two-plate moldsensp 123

U

UHMWPEensp 8UL service temperatureensp 93ultrasonic weldingensp 262unmeltsensp 333

V

vacuum formingensp 207venting systemsensp 136venting zoneensp 180vibration weldingensp 263visual inspectionensp 104voidsensp 320 332V ratingensp 95

W

wall thicknessensp 251warpageensp 337water injection moldingensp 116water stainensp 331weather resistanceensp 81weld linesensp 257weld-linesensp 327windingensp 188

Y

yield stressensp 90

• Deckblatt_Sample_pages
• contents
• foreword
• 10-11
• 22-23
• 34-35
• 66-67
• 76-77
• 94-95
• 168-169
• 270-271
• 298-299
• 330-331
• Index