PU-BAYER

A processing guide for

INJECTION MOLDING

T E X I N A N DD E S M O P A NT H E R M O P L A S T I C P O L Y U R E T H A N E S

Changing the world with great care.

1 of 60

TABLE OF CONTENTS

INTRODUCTION

5 Product Description

5 Product by Grade Type

6 Product by Market

6 Nomenclature

6 Grade Designation

7 Color Designation

7 Coloring the Resin

8 Coloring Molded Parts

8 Packaging and Labeling

MACHINE SELECTION

9 Machine Type and Design

9 Screws: Material, Configuration,

and Wear

10 Non-Return Valves

10 Nozzle Types and Tips

11 Nozzle Temperature Control

11 Process Controls

12 Temperature

13 Time and Pressure

13 Shot Size and Machine Capacity

13 Machine Ventilation

DRYING

14 Material Handling

14 Drying Equipment

14 Desiccant Hopper Drying

16 Hot Air Oven Drying

INJECTION MOLDING PROCESS

20 Typical Processing Temperatures

20 Barrel Heating Zones

20 Nozzle

21 Melt Temperature

22 Machine Conditions

22 Injection Pressures22 Hold Pressure

22 Injection Speed23 Injection Cushion23 Back Pressure

23 Screw Speed

24 Clamp Tonnage

24 Mold Temperature

25 Shot Weight

25 Cycle Time

25 Mold Release Agents

25 Part Ejection25 Using Regrind

26 Machine Preparation

26 Purging and Cleaning

27 Starup Procedure

27 Shutdown Procedure

27 Temporary Shutdown

27 Short-Term Shutdown

27 Long-Term Shutdown

27 Changing from Texin or Desmopan

Resins to Another Material

27 Post-Mold Conditioning

3 of 60

TABLE OF CONTENTS, continued

TOOLING

29 Mold Shrinkage

29 Mold Design

29 Material Selection

29 Surface Finish

29 Venting

30 Part Draft

30 Texturing

30 Weld Lines

30 Undercuts

30 Tolerances

32 Mold Cooling

32 Mold Types

32 2- or 3-Plate Molds

32 Single- and Multiple Cavity Molds

32 Sprue Bushings

33 Sprue Pullers

33 Runners and Runner Systems

33 Hot Runner Molds

34 Gating

34 Sprue Gate

35 Edge Gates

35 Disc and Ring Gates

35 Pinpoint Gates

35 Insert Molding

35 Metal Inserts

36 Nonmetal Inserts /Over-Molding

TROUBLESHOOTING GUIDE

38 Blisters and Splay Marks

39 Burn Marks

40 Flash

41 Short Shots

42 Sinks

43 Sticking Parts

44 Voids

45 Warpage

SAFETY CONSIDERATIONS

46 General

46 Health and Safety Precautions

GENERAL INFORMATION

47 Developmental Product Information

47 Regulatory Compliance

47 Medical Grade Information

47 Sterilization Information

48 Biocompatibility Information

48 Technical Support

APPENDIX A

49 List of Tables

APPENDIX B

50 List of Figures

INDEX

51 Index

PRODUCT DESCRIPTION

Texin and Desmopan resins are thermo-plastic polyurethane elastomers (TPUs)based on polyesters, polyethers, specialcopolymers, and blends of polyurethaneand polycarbonate, which exhibit a widerange of properties suitable for manydifferent applications. Finished partsmade from Texin and Desmopan resinspossess all the excellent propertieswhich are normally associated withpolyurethane elastomers. Theseproperties include:

l High tensile and tear strength.

l Excellent abrasion resistance.

l Excellent resistance to fuels, oils, ozone, and oxygen.

l High elasticity and resilience com-bined with high load-bearing capacity and hardness.

l Hydrolysis and microbe resistance.

Product by Grade Type

Texin and Desmopan resins are availablein unreinforced general-purpose gradesof various hardness. Desmopan KU2-8651 resin, the softest grade available, is used in applications wherehigh flexibility is required. Desmopan453 resin, a harder and more rigidgrade, is used for low-deflection, load-bearing applications. Texin 390 resinhas intermediate hardness and modulus.

Several modifications of the general Texin and Desmopan resin gradeswhich have been designed to meet

5 of 60

INTRODUCTION

Resin Type Shore Resin Type ShoreOld Name New Name Hardness Old Name New Name Hardness

Table 1 Texin and Desmopan TPU Injection Molding Resins

Polyesters Specialty Polyethers, continued

Texin 345D Desmopan 445 45D Texin DP7-1047 Texin 950U 50D

Texin 355D Desmopan 453 53D Texin DP7-1051 Texin 985U 86A

Texin 360D Desmopan 459 60D Texin DP7-1052 Texin 945U 45D

Polyesters General-Purpose Texin DP-7-1078 Texin 990R 90A

Texin 445D Texin 245 45D Polyurethane/Polycarbonate Blends

Texin 455D Texin 255 55D Texin 3203 Texin 3203 60D



Texin 480A Texin 285 87A Texin 4206 Texin 4206 65D



Polyethers Special Market Grades

Texin 970D Texin 970U 70D Texin 5265 Texin 5265 65D

Texin 985A Texin 985 86A Texin 5286 Texin 5286 86A


Texin DP7-1018 Texin 950 50D

specific requirements are available.Properties intermediate to those of thestandard grades of Texin and DesmopanTPU resin can also be obtained by blend-ing any combination of Texin andDesmopan resins, provided they arethoroughly mixed. For some applica-tions, it is necessary to mix differentformulations in a melted state toachieve the required blend uniformity.

Table 1 lists various grades of Texinand Desmopan resins suitable for injec-tion molding. Further details about thesuitability of injection molding Texinand Desmopan resins or blending theseresins for your application are availableby contacting a Bayer CorporationTechnical Group representative forTexin and Desmopan resins at 412-777-2000.

Product by Market

Texin and Desmopan TPU resins are used to mold a variety of automotivecomponents such as cams, gears, andmechanical parts, as well as for exteriorapplications. In-line skate boots, skigoggle frames, and shoe componentsare among the consumer applicationsfor Texin and Desmopan resins.Industrial-mechanical applicationsinclude mine screens, caster wheels,cable connectors, and hydraulic seals.Medical applications include a varietyof diagnostic devices, tubing andcatheters, and connectors. Additionalinformation regarding medical gradesand their usage can be found in theGeneral Information section on page 47 of this brochure.

NOMENCLATUREGrade Designation

The grade designation for Texin and Desmopan resins consists of two parts:

1. Product Information Number.The first digit represents the basic composition of the resin grade, asshown in Table 2. The last two digits represent hardness.* If the lasttwo digits are equal to or greater than 75, the hardness value is Shore A. If the last two digits are less than 75, the value is Shore D. For exam-ple, Texin 985 resin is a polyether-based TPU with a Shore hardness of 85A.

*These values are provided as general infor-mation only. They are approximate values and are not part of the product specification.

6 of 60

Composition Designation

Grade Composition and Designations forTexin and Desmopan Resins

Basic Polyester 1Polyester, Good Hydrolytic Stability 2Polyester, Better Hydrolytic Stability 3Polyester, Good Low and High Temperature Performance 4

Special Polyester /Polyether Mixture 5Future Grades 6Special Copolymers 7Future Aliphatics 8Polyether 9

Performance Additive Designation

Performance Additives and Designations forTexin and Desmopan Resins

UV and Heat Stabilizers UBetter Mold Release RSpecial Additive SLow Viscosity L

Table 2 Table 3

2. Suffix.A capital letter following the three-digit product information numberrepresents the type of performance additive in the grade, as listed inTable 3.

Color Designation

Texin and Desmopan TPU are supplied as natural resins in pellet form. (SeeFigure 1.) The molded part color canvary from nearly transparent to translu-cent to opaque, depending on the wallthickness of the article. Some grades of Texin and Desmopan resins are alsooffered in black or gray color as a salt-and-pepper resin blend.

COLORING THE RESIN

Texin and Desmopan resins can be colored by blending in color concen-trates or by dry blending the pigmentsdirectly onto the pellets. A list of colorconcentrates, pigments, and dyes suit-able for Texin or Desmopan resins isavailable from your Bayer CorporationTechnical Group representative forTexin and Desmopan resins at 412-777-2000.

7 of 60

INTRODUCTION, continued

Before blending any colorants into the Texin or Desmopan resins, be sure theresin is dry. (See Drying on page 14.)If a color concentrate is used, dry it in the same manner as the Texin orDesmopan resin. Dry the pigments or dyes at a temperature as high as ispractical. Many inorganic pigmentscontain water which must be removedbefore the pigment is incorporated intoTexin or Desmopan TPU resins. Theseinorganic pigments may be adequatelydried by heating them to 450F (233C)for 30 45 minutes.

After the pigment has been properly dried, tumbler-blend it or the colorconcentrate into the Texin or Desmopanresins pellets in the desired concentra-tion for 5 10 minutes. This blend canthen be injection-molded with a colordispersion nozzle. If more than 10

Texin and Desmopan Resin PelletsFigure 1

8 of 60

minutes will elapse before the colorblend is processed, protect the colorblend from exposure to moisture or dryit prior to introducing it to the injectionmolding machine.

COLORING MOLDED PARTS

When a given part must be produced in a wide range of colors and it is uneco-nomical to mold each color separately,dip dying may be employed. Partsmolded of Texin or Desmopan TPUcan be successfully dyed with colorants

known as disperse dyes. However,some regulatory organizations (e.g.,FDA) limit the choice of color that maybe used. A list of suggested dyes maybe obtained from a Bayer CorporationTechnical Group representative forTexin and Desmopan resins.

PACKAGING AND LABELING

Texin and Desmopan resins are avail-able in 25-lb (10-kg) boxes, 50-lb (20-kg) bags, 300-lb (135-kg) drums, 1,000-lb (450-kg) cartons, and bulk trucks.

The boxes, bags, and cartons have poly-ethylene liners in which the resin issealed to help prevent contaminationfrom dust, dirt, and moisture.

When opening and resealing the bags and cartons, be careful to avoid theintroduction of dust or dirt. Any partic-ulate contamination in the feedstockwill show up in the finished part.

Texin and Desmopan TPU resins are hygroscopic. In fact, moisture absorp-tion begins as soon as the resin isexposed to the air. Resin exposed to theair for as little as 15 minutes can absorbenough moisture to cause injectionmolding problems. Resin exposed to theair for a few days or processed wet willsuffer a permanent reduction in propertyperformance. Therefore, keep eachpackage of Texin or Desmopan resinssealed until it is to be used.

Avoid storing Texin and Desmopan TPU resins where the temperatureexceeds 95F (35C). Also avoidstorage areas that are subject to highhumidity or in close proximity to steam pipes or other hot lines.

An example of a label for Texin andDesmopan resins is shown in Figure 2.

Label Information for Texin and Desmopan Thermoplastic Polyurethane ResinsFigure 2

TEXIN 270

Bayer CorporationBayer RoadPittsburgh, PA15205-9741

9 of 60

MACHINE SELECTION

MACHINE TYPE AND DESIGN

Texin and Desmopan resins can be molded on both in-line reciprocatingscrew-type and plunger or ram-typeinjection molding machines. An in-linereciprocating screw machine like theone shown in Figure 3 is preferredbecause it produces a more homogen-eous material and a more uniform melttemperature. It also permits processingat lower temperatures, which is general-ly an advantage.

Use a machine that can provide temper-ature control up to 475F (246C) andinjection pressure of up to 15,000 psi (103 MPa). The mold clamp forceneeded for Texin and Desmopan resins is 3 5 t / in.2 (40-70 kPa) of a partsprojected area.

SCREWS: MATERIAL, CONFIGURATION, AND WEAR

Following are important considerations in choosing a screw for injection mold-ing Texin and Desmopan resins:

l A general-purpose screw with alength-to-diameter ratio (L/D) of at least 20:1 is satisfactory (see Figure 4).

l A compression ratio of 2:0-1 to 3.0:1 is preferred. A 2.5:1 compression ratio is applicable for most situations. Rapid-transition (nylon-type) screws are not recommended because of the excessive melt temperature and consequent degradation of the resins that can occur with them.

l Chrome-plated screws are recommended for ease of cleaning.

l An abrasion-resistant, bimetallic barrel liner, such as Xaloy,* is preferred.

*Xaloy is the registered trademark of Xaloy, Inc.

Typical Injection Molding MachineFigure 3

10 of 60

NON-RETURN VALVES

Non-return valves prevent the moltenpolymer in the holding space in front of the screw from flowing back into the screw during the injection cycle.

When processing Texin or Desmopan TPU resins, use a free-flowing, slidingcheck-ring style non-return valve madeof fully hardened H-13 steel, preferablynitrided to retard wear (see Figure 5).

Good flow characteristics, as shown in Figure 6, are essential in a non-returnvalve. A fully channeled tip will mini-mize flow restrictions because Texinand Desmopan TPUs, like most thermo-plastics, will degrade when subjected to excess shear at flow restrictions.

NOZZLE TYPES AND TIPS

Most standard steel nozzle types used with other thermoplastics are satis-factory for molding Texin or Desmopanresins. A straight-through nozzle or areplaceable-tip nozzle with a reversetaper at the nozzle exit are recom-mended. (See Figure 7.)

Reverse-taper nozzles are desirable when drool is a problem. Their flowpath narrows to a small diameter, then

Figure 4

Screw Profile

MeteringZoneDepth

FeedZoneDepth

20D

DDiameter (D)

Metering Transition Feed ZoneZone Zone 60%20% 20%

Feed Depth ZoneMetering Zone Depth

Compression Ration =

The injection molding screw feeds the resin from the throat of the resin hopper through the barrel of the injection molding machine to the nozzle. The screw should be chrome-plated and highly polished.

11 of 60

MACHINE SELECTION, continued

This type of valve checks the return of material during the injectioncycle. Ball-check valves are not recommended.

Free-Flowing, Sliding Check-Ring Style Non-Return ValveFigure 5 Figure 6

Resin Flow

Note:Cross-sectional area in valve should equal cross-sectional areaof the screw metering section.

Flow Characteristics of the Non-Return Valve

widens where the nozzle meets thesprue bushing. This causes the melt totear off inside the nozzle, allowing theportion of the material forming a coldslug for the succeeding shot to beremoved with the sprue. (See Figure 9.)

The nozzle should be as short as possible. If a long nozzle is necessary, it should have a large internal diameterproportional to its length. It is essentialthat the nozzle and sprue bushing mateproperly. The nozzle orifice should beslightly smaller (about 20%) than thesprue bushing orifice.

Nozzle Temperature Control

A separate temperature control for the nozzle is preferred. Heater bands on thenozzle with separate temperature con-trols will help to prevent cooling orsolidification of the melt in the nozzle.A rapid-cycling, variable temperaturecontroller is preferred to a slow-cyclingcontroller.

It is important that all heater bandswork properly. Burned-out bands canresult in material hang-ups or causeother bands to overwork, both of whichcan overheat or burn the material.

PROCESS CONTROLS

Texin and Desmopan TPU resins are melted in the barrel by a combination of heat transferred from external heatersthrough the barrel wall and frictionalheat generated by screw rotation. Theratio of external heat to frictional heatdepends upon the power of the heaters,the resin throughput rate and residencetime, and the length and geometry of the screw.

12 of 60

Proper temperature control on an in-jection molding machine involvesmaintaining a specified melt tempera-ture at as constant a level as possibleover a long period of operation. Withproper temperature control, injectionmolding machinery can run automati-cally. Proper temperature control canalso lead to improved part quality andeconomies.

Increasing the temperature of the external heaters might seem to be asolution when a less-than-optimumscrew is used. However, because thethermal conductivity of plastics is low,

a large temperature gradient acrossthe melt could occur, causing inconsis-tencies in processing or, in extremecases, degradation of the melt itself.

Increasing the back pressure can provide additional frictional and externalheat to the melt. However, an increase in back pressure results in only a slightincrease in frictional heating with deep-flighted screws. Increased back pressurecan also increase the cycle time due toprolonged screw retraction. Therefore,adjustment of back pressure is not al-ways a solution to a less-than-optimumscrew design.

Temperature

An obvious solution to regulating melt temperature would be to locate temper-ature sensors directly in the plasticatingmelt. This has not been satisfactorilyaccomplished, however, because thesensor would interfere with and bedestroyed by the flow of the materialand movement of the screw. Nor can asensor easily be sealed against leakageat the high injection pressures.

The solution, then, has been to locate temperature sensors in wells drilled in-to the cylinder walls and regulate melttemperature by measuring and control-ling the cylinder wall temperature.However, the depth of the well affects

Figure 7 Removable and Non-Removable Nozzle Tips

Either standard straight-through or reverse-taper nozzles arerecommended for molding Texin and Desmopan resins.

Figure 8 Internal Flow Channel of a Standard Nozzle Tip

13 of 60

MACHINE SELECTION, continued

The reverse-taper type is preferred, however, because it causesthe melt to tear off inside the nozzle. This allows the portion of thematerial forming a cold slug to be removed with the sprue.

Figure 9Internal Flow Channel of a Reverse-Taper Nozzle Tip

the temperature measured by the sensor,since a temperature gradient exists inthe cylinder wall. To minimize thiseffect, the thickness of the steel at thebottom of the well is usually equal to its diameter.

In order to further minimize error, periodically check to make sure thatthe sensors are clean and fit firmly inthe wells. Impurities, such as charredpellets, or a cushion of air between thecylinder wall and the sensor have led to readings that are inaccurate by asmuch as 54F (30C).

The temperature measured by the sensoris seldom exactly equal to the tempera-

ture of the plastic melt. Therefore,adjust cylinder and nozzle temperatureset-points to get an actual measuredmelt temperature that is within therecommended range for the grade ofthe Texin or Desmopan resins beingprocessed.

Time and Pressure

Uniform molding cycles are essential to maintaining optimum processingconditions and producing the highest-quality parts. State-of-the-art closed-loop control systems can ensure boththe precise injection stroke and switch-over point that are critical for molding

quality parts. This control equipmentcan adjust hold pressure in incrementsto minimize sinks and voids. In addi-tion, it can maintain melt pressure inthe mold cavity uniformly from shot toshot despite variations in the operatingconditions of the machine.

Some advanced controls adjust the holding pressure and cooling time toensure that each part is ejected from the mold at the same temperature andweight. This improves part-to-partweight and dimensional uniformity.

Shot Size and Machine Capacity

When running on screw-type machines, utilization of 40% 80% of the barrelcapacity is desirable. Although shotweights smaller than 40% have beenmolded successfully, the material candegrade when the shot weight is toosmall and excessive heat builds up inthe melt.

Machine Ventilation

A ventilation hood should be located at the front or nozzle end of the moldingmachine to remove any fumes generatedduring injection molding or purging.

MATERIAL HANDLING

Texin and Desmopan TPU resins are hygroscopic, meaning that they willabsorb and react with moisture in theatmosphere. As Figure 10 shows, Texinand Desmopan TPU resins exposed tothe atmosphere begin absorbing mois-ture immediately. Moisture in the resinadversely affects processing and thequality of the molded part. So eventhough Texin and Desmopan resins aresupplied in sealed containers, it isessential to use a desiccant dehumidi-fying hopper dryer to keep the resin dryduring processing.

Warm to room temperature any sealedcontainers which have been stored inunheated warehouses before openingthem. This will help prevent rapidcondensation of ambient moisture oncool pellets.

Single drums or cartons can take 24 hours or more to warm. Stackedcontainers can take a week or longer.

DRYING EQUIPMENT

Desiccant Hopper Drying

Use a desiccant dehumidifying hopper dryer to remove moisture from Texin orDesmopan resin and to maintain properresin moisture content of less than0.03% during processing. The dryermust meet the following requirementsto properly remove moisture from Texinor Desmopan TPU resins:

l Hopper dryer should be sufficient to ensure that the resin remains in the

DRYING

Figure 11Typical Desiccant Dehumidifying Hopper Dryer System

14 of 60

Figure 10

0 5 10 15 20

MO

ISTU

RE C

ONT

ENT

(% H

2 O)

TIME (min.)

Moisture Absorption Rate ofTexin and Desmopan Resins

0.050

0.040

0.030

0.020

0.010

0.000

15 of 60

l Dew point of the inlet air to the hopper at 0F (-18C) or less.

Some recent dryer designs perform to less demanding requirements. However,use caution when deviating from theseguidelines since the quality of partsmolded of Texin and Desmopan resinsdepends on low moisture content.

A typical desiccant dehumidifying hopper dryer system and airflow areshown in Figures 11 and 12. Note thatthe hopper is tall and cylindrical andhas a diverter cone to diffuse the airuniformly and reduce channeling of

drying hopper at least 2 hours prior tobeing injection molded.

l Hopper inlet air temperature of 180 230F (82 110C). For softer materials, use lower tempera-tures in this range. Temperatures in excess of 230F (110C) may cause the pellets to block in the hopper.

l Airflow to the hopper of 1.0 cubic foot per minute (CFM) for every pound of resin per hour of throughput.

the pellets. It should be sized to accom-modate the throughput rate of the mold-ing machine and allow for a dryingtime of 2 3 hours prior to and duringprocessing.

If the hopper dryer has not been used for 24 hours, dry-cycle it before intro-ducing the Texin or Desmopan resins.This will help to ensure the desiccant is dry prior to processing (refer to themanufacturers recommendations forthe procedure). Then load the resin anddry it for at least 2 hours prior to beingintroduced into the molding machine.

Desiccant Dehumidifying Hopper Dryer System AirflowFigure 12

Resin Inlet175F

110F

Air Outlet

Inlet Air180 230F

andDew Point of

< 0F

HeaterOff

550F HeaterOff

Air Intake

Heater Heater

Heater Heater

Desiccant Desiccant

Filter

After Cooler

Diverter Cone

Air Path forResin Drying

Air Path forDesiccant Drying

180 220F

16 of 60

Hot Air Oven Drying

The use of a conventional hot air drying oven is not recommended as a substitutefor a dehumidifying hopper dryer. How-ever, if it is the only method available,then the recommended oven tempera-ture is 200 220F (93 104C) for 2 4 hours. Place the resin pellets in the drying trays at a depth of 1 in. (25.4 mm) or less. Dry no other types of resin in an oven containing Texin or

Desmopan resins. Once oven-dried resinhas been put in the hopper, close andheat it during processing. Otherwise, theresin should remain in that hopper forno longer than 30 minutes.

Another way to avoid unwanted mois-ture absorption by oven-dried resin is totransfer small amounts of dried resinfrom the oven tray to the hopper duringinjection molding.

If regrind is used, dry it to the same moisture content level as required forvirgin pellets. In fact, it may be neces-sary to dry regrind longer than virginpellets due to the irregular shape andsize of the regrind pellets. Beware ofexcessive fines (very small particlescause by grinding). Fines melt morerapidly and may cause black specks to form.

Figure 13 Bubble Formation During Purging

17 of 60

DRYING, continued

Dehumidifying Hopper Dryer Troubleshooting Guide

Improper Drying Condition Drying Equipment Defect Possible Corrective Action

Poor Dew Point l Dirty filter(s). l Clean or replace filter(s).l Saturated desiccant. l Dry-cycle machine for several complete

cycles. Saturated desiccant is a commonproblem with machines that are not incontinuous use.

l Excessive return air temperature. l Add after-cooler on return air line.l Burned-out heater(s). l Repair or replace heater(s).l Contaminated or worn-out desiccant. l Replace desiccant.l Bad heater thermostat or thermocouple. l Repair or replace thermostat or

thermocouple.l Malfunctioning regeneration cycle timer. l Adjust or replace timer.l Air control butterfly valves not seating. l Adjust valve seating.l Moist room air leaking into the dry l Check all hose connections and tighten

process air. as required.l Check all hoses for leaks and replace

as needed.l Check filter covers for secure fit and

tighten as required.l Desiccant beds not switching. l Check electrical connections.

l Check switching mechanism.

Material Residence Time in l Dryer hopper too small for the amount of l Use a larger dryer hopper.Hopper Too Short material being processed per hour.

l Not keeping hopper at least 2/3 filled. l Keep drying hopper full.

Incorrect Process Air Temperature l Incorrect drying air temperature. l Dial in correct temperature of 180 230F (85 110C).

l Dryer temperature controller malfunction. l Repair or replace controller.l Thermocouple malfunction. l Repair or replace thermocouple.l Faulty process air heating elements. l Repair or replace heating elements.l Supply voltage different than required l Check supply voltage against name-

heater voltage. plate voltage.l Non-insulated inlet-air hose. l Repair or replace inlet-air hose.l Excessive changeover temperature. l Increase reactivation airflow.

Insufficient Inlet Airflow l Dirty or clogged filter. l Clean or replace filters.(Good dew point but resin still wet.)

l Incorrect blower rotation. l Change blower rotation. (Consult equipment manufacturers electrical instructions.)

l Obstruction in air ducts. l Remove air duct obstruction.

Table 4

Figure 14 Temperature Zones/Machine Cross Section

l

Optimizing the injection moldingprocess involves several variables:

l Ratio of heat transferred by externalheaters to frictional heat.

l Injection speed and pressure.

l Holding pressure and time.

l Cooling time.

l Mold temperature.

The following processing data repre-sent the range for initial processingsettings to be used during start-up andmay need adjustment to meet therequirements of individual parts.

Processing parameters that optimize the appearance of a molded part can be

easily determined. However, thesesame settings may not give the part itsoptimum dimensions or shape. Whenmolding parts which must hold to crit-ical dimensional tolerances, conduct a statistical study to optimize bothdimensions and appearance. Thenadjust certain processing parameters to change part dimensions as required.

Nozzle

Front Zone

Melt

Middle Zone Rear Zone

INJECTION MOLDING PROCESS

18 of 60

19 of 60

Suggested Starting Conditions for Processing Texin and Desmopan TPU Resins

Texin 185 Texin 245 Texin 245 Texin 270 Texin 3215Texin 985 Texin 285 Texin 260 Texin 970U Texin 4210

Texin 390 Texin 3203 Texin 4215Desmopan Texin 990 Desmopan 453 Texin 4203KU2-8651 Desmopan 459 Texin 4206

Conditions KU2-8655 Desmopan 445

Table 5

Processing Temperatures

Zones

Rear 350 380F 360 390F 380 410F 410 455F 430 450F (177 193C) (183199C) (193 210C) (210 235C) (221 232C)Middle

360 390F 360 400F 380 420F 415 460F 440 460F (183 199C) (183 204C) (193 216C) (213 238C) (227 238C)

Front360 400F 360 410F 390 430F 420 460F 440 460F (183 204C) (183 210C) (199 221C) (216 238C) (227 238C)

Nozzle365 405F 370 415F 400 440F 425 465F 450 475F(185 207C) (188 213C) (204 227C) (218 241C) (232 246C)

Melt*385 465F 385 465F 385 465F 385 465F 385 465F(196241C) (196241C) (196241C) (196241C) (196241C)

Mold ** 60110F 60110F 60110F 80110F 80110F(16 43C) (16 43C) (16 43C) (2743C) (2743C)

Machine ConditionsInjection 6,000 15,000 psi 6,000 15,000 psi 6,000 15,000 psi 6,000 15,000 psi 6,000 15,000 psiPressure (41 103 MPa) (41 103 MPa) (41 103 MPa) (41 103 MPa) (41 103 MPa)Injection Speed Slow Slow Medium Medium Medium

Hold 5,000 10,000 psi 5,000 10,000 psi 5,000 10,000 psi 5,000 10,000 psi 5,000 10,000 psiPressure (33 69 MPa) (33 69 MPa) (33 69 MPa) (33 69 MPa) (33 69 MPa)Injection 0.125 in. max 0.125 in. max 0.125 in. max 0.125 in. max 0.125 in. maxCushion (3.175 mm max) (3.175 mm max) (3.175 mm max) (3.175 mm max) (3.175 mm max)Back 200 psi max 200 psi max 200 psi max 200 psi max 200 psi maxPressure (1.4 MPa max) (1.4 MPa max) (1.4 MPa max) (1.4 MPa max) (1.4 MPa max)Screw 40 80 rpm 40 80 rpm 40 80 rpm 40 80 rpm 60 80 rpmSpeedClamp 3 5 t / in.2 3 5 t / in.2 3 5 t / in.2 3 5 t / in.2 3 5 t / in.2Tonnage (0.5 0.8 mt /cm2) (0.5 0.8 mt /cm2) (0.5 0.8 mt /cm2) (0.5 0.8 mt /cm2) (0.5 0.8 mt /cm2)Cycle 20 60 sec. 20 60 sec. 20 60 sec. 20 60 sec. 20 60 sec.TimeInjection 5 10 sec. 5 10 sec. 5 10 sec. 5 10 sec. 5 10 sec.Time

* To obtain proper melt temperature, take an air shot and measure the melt with a heated pyrometer probe. ** Check mold temperature on the part cavity and core surface.

20 of 60

Barrel Heating Zones

The initial barrel temperature ranges areapproximate and can vary, depending onscrew geometry, frictional heating, cycletime, and material flow length. Takecare to maintain a consistent melt tem-perature and inspect the heater bandsperiodically.

Nozzle

It is important that the nozzle be equipped with an independent heatingsystem to maintain a constant melttemperature. The optimum nozzle tem-perature is slightly higher than the frontbarrel zone. The normal processingrange for the nozzle temperature settingis 365 475F (188 246C).

TYPICAL PROCESSING TEMPERATURES

Table 6a Barrel Heating Temperatures

Texin 185 Texin 245 Texin 245 Texin 270 Texin 3215Texin 985 Texin 285 Texin 260 Texin 970-U Texin 4210

Desmopan Texin 390 Desmopan 453 Texin 3203 Texin 4215KU2-8651 Texin 990 Desmopan 459 Texin 4203

Zones KU2-8655 Desmopan 445 Texin 4206

Rear 350 380F 360 390F 380 410F 410 455F 430 450F (177 193C) (183 199C) (193 210C) (210 235C) (221 232C)

Middle 360 390F 360 400F 380 420F 415 460F 440 460F (183 199C) (183 204C) (193 216C) (213 238C) (227 238C)

Front 360 400F 360 410F 390 430F 420 460F 440 460F (183 204C) (183 210C) (199 221C) (216 238C) (227 238C)

Table 6b Nozzle Temperatures


Desmopan Texin 390 Desmopan 453 Texin 3203 Texin 4215Processing KU2-8651 Texin 990 Desmopan 459 Texin 4203Temp. KU2-8655 Desmopan 445 Texin 4206

Nozzle 365 405F 370 415F 400 440F 425 465F 450 475F (185 207C) (188 213C) (204 227C) (218 241C) (232 246C)

Melt Temperature

When Texin and Desmopan TPU resins are processed properly, the melt shouldappear homogeneous and be slightlyoff-white or beige in color. Excessivetransparency usually indicates too high a melt temperature. If the melt appearsbubbly, moisture is probably present andfurther drying is necessary.

Check the actual temperature of the meltat the nozzle from an air shot and cor-rect the temperature control settingsaccordingly. To obtain an accurate melttemperature measurement, make an airshot from a normal processing cycle andimmediately insert a pre-heated thermo-couple probe into the center of the melt.Keep it in the melt until the maximumtemperature is reached (see Figure 15).

To obtain an accurate melt temperature for adjusting the controller settings, make an airshot from a normal processing cycle. Immediately insert the temperature probe into thecenter of the melt until the maximum temperature is reached.

Making an Accurate Melt Temperature ReadingFigure 15

21 of 60

INJECTION MOLDING PROCESS, continued

* To obtain the proper melt temperature, take an air shot and measure the melt with a heated pyrometer probe.

Table 6c Melt Temperatures


Desmopan Texin 390 Desmopan 453 Texin 3203 Texin 4215Processing KU2-8651 Texin 990 Desmopan 459 Texin 4203Temp. KU2-8655 Desmopan 445 Texin 4206

MELT* 385 465F (196 241C)

22 of 60

Injection Pressures

Injection pressures of 6,000 15,000 psi (41 103 MPa) are adequate for moldingmost parts from Texin or Desmopan TPUresins. Low injection pressure may notfill the mold completely with resin. Toomuch pressure may cause the material tooverpack and flash the part.

Hold Pressure

Holding pressures of about 60% 80% of the injection pressure are the generalrule.

Injection Speed

In general, fill the mold as rapidly as possible to minimize the appearance ofweld lines, improve weld-line strength,improve surface finish, and lower therequired injection pressure. Overallinjection time depends on the machineand part geometry. Fast injection speed isnecessary for thin-walled parts to fill themold cavity before the material cools.Slow injection speeds may be necessaryto minimize jetting or weld lines.

MACHINE CONDITIONS

Table7a Injection Pressures


Desmopan Texin 390 Desmopan 453 Texin 3203 Texin 4215Machine KU2-8651 Texin 990 Desmopan 459 Texin 4203Conditions KU2-8655 Desmopan 445 Texin 4206

Injection 6,000 15,000 psi (41 103 MPa)Pressure

Table 7b Hold Pressures



Hold 5,000 10,000 psi (33 69 MPa)Pressure

Table 7c Injection Speed



Injection Slow Slow Medium Medium MediumSpeed

Injection Cushion

Avoid excessive injection cushion. Best results can be obtained when the cushiondoes not exceed 0.125 in. (3.175 mm).Too much cushion may lead to over-packing the part. No cushion may lead to the screw bottoming out, preventingcomplete packing of the part.

Back Pressure

Keep back pressure 200 psi (1.4 MPa) if possible.

Screw Speed

A rotational screw speed of 40 80 rpm can be used with Texin and Desmopanresins. However, screw speeds in the lowrange, 20 40 rpm, are preferred. Lowscrew speed results in a more homo-geneous temperature distribution in themelt than high screw speed.

23 of 60


Table 7d Injection Cushion



Injection 0.125 in. (3.175 mm) max.Cushion

Table 7e Back Pressure



Back 200 psi (1.4 MPa) max.Pressure

Table 7f Screw Speed



Screw 40 80 rpm 40 80 rpm 40 80 rpm 40 80 rpm 60 80 rpmSpeed

24 of 60

Clamp Tonnage

Properly matching the size of the injec-tion molding machine and the part to bemolded is very important. Due to theflow characteristics of Texin andDesmopan resins, a minimum clampingpressure of 3 5 t /in.2 (0.5 0.8 mt/cm2)of projected part surface area is required.

Mold Temperature

Optimal mold temperature varies according to part thickness and the particulargrade of Texin or Desmopan TPU resinbeing processed. Thicker parts require alower temperature to effectively cool theresin within a reasonable cycle time.Softer resin grades should be moldedusing a lower mold temperature than theharder grades. The range may be fromabout 60F (16C) for Texin 285 resin to 110F (43C) for Texin 453 resin.

Check mold temperature on the steel cavity and core surfaces rather than rely-ing on the mold temperature controlsettings (see Figure 16).

To help ensure proper mold tempera-ture, temperature controllers on the moldare necessary for molding Texin orDesmopan resins. Ordinary water-circulating heat exchanger units aresatisfactory. They should be capable ofmaintaining mold temperatures in therange of 50 150F (10 66C). A

Measuring Mold TemperatureFigure 16

Table 7g Clamp Tonnage



Clamp 3 5 t / in.2 (0.5 0.8 mt /cm2)Tonnage

Table 7h Mold Temperature



Mold* 60 110F (16 43C) 80 110 F (27 43C)* Check mold temperature on the part cavity and core surfaces.

separate controller for each half of themold is desirable because of the need tooperate two halves at different tempera-tures to effect the proper release ofsome parts.

Shot Weight

Utilization of 40% 80% of the barrel capacity is preferred when processingTexin and Desmopan resins on screw-type machines. Although shot weightssmaller than 40% can be moldedsuccessfully, the material can degradewhen the shot weight is too small andexcessive heat builds up in the melt.

Cycle Time

The optimum cycle to produce qualityparts includes a fast fill, a hold time justlong enough for the gates to freeze, anda cooling time long enough so that thepart ejectors do not penetrate the part.Cooling time is the major portion of the total molding cycle. The coolingrequirements of a part are stronglydependent on its wall thickness, run-ner size, and sprue size.

MOLD RELEASE AGENTS

Should they be necessary, non-silicone-type mold releases, such as a dry fluoro-carbon, are recommended. Siliconelubricants work well but generally leavea film on the parts for several shots afterapplication and may cause performanceproblems in electronic products. Con-sult a Bayer Corporation TechnicalGroup representative for Texin andDesmopan resins to help determine thebest solution to a part release problem.

PART EJECTION

Pin ejection can be used provided that the pin areas are as large as practical for the part. Use air or plate ejectioninstead of pin ejection whenever pos-sible, particularly on parts with thicksections. Pins can occasionally indent or pierce thick parts which take time tosolidify. There is less tendency tostretch or distort parts with air or plateejection.

USING REGRIND

For all grades of Texin and Desmopan TPU resins, up to 20% regrind may beused with virgin material, dependingupon the end-use requirements of themolded part and provided that the mate-rial is kept free of contamination and isproperly dried at 180 230F (82110C) for 1 3 hours. (See Drying

on page 14 for details.) Any regrindused must be generated from properlymolded parts, sprues, and/or runners.All regrind must be clean, uncontami-nated, and thoroughly blended withvirgin resin prior to drying and process-ing. Under no circumstances shoulddegraded, discolored, or contaminatedmaterial be used for regrind. Materialsof this type should be discarded.

Improperly mixed and/or dried resin may diminish the desired properties of Texin and Desmopan resins. Youmust conduct testing on finished partsproduced with any amount of regrind to ensure that your end-use perfor-mance requirements are fully met.Regulatory organizations, e.g., Under-writers Laboratories (UL), may havespecific requirements limiting theallowable amount of regrind. Because third-party regrind generallydoes not have a traceable heat history,nor offer any assurance that propertemperatures, conditions, and/ormaterials were used in processing,extreme caution must be exercised inbuying and using regrind from thirdparties.

The use of regrind material should beavoided entirely in those applicationswhere resin properties equivalent tovirgin material are required, includ-ing, but not limited to, color quality,impact strength, resin purity, and/orload-bearing performance.

25 of 60


26 of 60

MACHINE PREPARATIONPurging and Cleaning

Before molding Texin or Desmopanresins, thoroughly purge or mechani-cally clean (Figure 18) any residualmaterial from the machine. Commercialpurging compounds are the best mate-rials for cleaning the internal parts ofthe molding machine prior to introduc-ing Texin or Desmopan TPU resin.High-density polyethylene or poly-propylene are an effective substitute.After purging, introduce Texin orDesmopan resins and rapidly make airshots of the melt until it is free of anycontamination.

4. Once the nozzle has been removed,turn off the heat on the main cylinder and push the screw forward until a few flights are exposed.

5. Remove the hot melt from the screw with a brass brush and a brass knife. Push the screw forward and clean it in this manner until all of the flights are clean.

6. Remove the screw and clean the barrel with a rotary-type brush on an extension rod attached to an electric drill.

Mechanical cleaning is more thorough than purging and is preferred by manymolders. The same procedure can beused either before molding Texin andDesmopan resins or after a molding run.

Follow these steps:

1. Flush the cylinder rapidly with the purging compound.

2. Remove the nozzle while keeping theheat on in the main cylinder.

3. Clean the nozzle either by heating it in a muffle furnace or by soaking it indimethyl acetamide (follow the manu-facturers MSDS recommendations)after it has cooled.

Figure 17 Regrind Pellets

Recommended grinder screen size is0.31 in. (8mm).

Figure 18 Mechanical Cleaning of the Screw

Changing from Texin or Desmopan

Resins to Another Material

Follow the same procedure as for a long-term shutdown.

POST-MOLD CONDITIONING

Most parts molded of Texin or Desmopan resins are placed in servicewithout annealing because they attainessentially all of their ultimate proper-ties shortly after normal fabrication.Thus, post-mold conditioning is gener-ally unnecessary.

However, when lower compression set or better creep and tensile decay are required for the application, post-curing/annealing the parts willenhance these properties. Desmopan400 series of ester-based TPU have thebest compression set properties.

To achieve ultimate physical propertiesimmediately after fabrication, annealthe molded parts at 230F (110C) for14 18 hours. A circulating air ovenwith a temperature control accuracy of9F (5C) is satisfactory for post-mold annealing.

If the parts are stored for a period of 2 3 weeks after molding, then thecuring effect achieved from exposureto ambient air can approach that ofelevated temperature curing.

Short-Term Shutdown

For shutdowns limited to a period of4 6 hours:

l Shut off the hopper feed.

l Purge the machine empty, or makeshots until no material remains in themachine.

l Move the screw forward.

l Lower all heat zones on the cylinderand nozzle to 300F (150C).

Long-Term Shutdown

For a shutdown exceeding 6 hours or extending to several days:

l Shut off the hopper feed.

l Flush the machine with a commercialpurging compound, high-densitypolyethylene or polypropylene andpurge it empty.

l Leave the screw forward in thecylinder.

l Turn off all heat zones.

When molding with Texin or Desmopan resins is completed, clean the machinethoroughly by mechanical cleaning.(See Machine Preparation, Purging and Cleaning, page 26.)

Startup Procedure

Suggested starting process conditions for Texin and Desmopan TPU resin arelisted in Table 8. Use these parametersas guidelines for setting initial machineconditions. However, many factors suchas part design, machine type, and molddesign affect the determination of thefinal molding conditions. Therefore, the final conditions used may varyconsiderably from those listed here.

Start with a short-shot that contacts theejector pins, then increase the shot sizeand injection pressure until the mold isfilled. Make initial shots with less thanmaximum injection pressure.

Shutdown Procedure

Shut down the molding machine at theend of a production run according to theprocedure for either a short- or long-term shutdown. Observing the propershutdown procedure is important toprepare the machine to restart produc-tion and to avoid problems that may becaused by the material or machine dur-ing future startups.

Temporary Shutdown

When brief interruptions in the molding cycle occur, make air shots periodicallyto prevent degrading of the material inthe barrel.

27 of 60


28 of 60

Suggested Starting Conditions for Processing Texin and Desmopan TPU Resins

Texin 185 Texin 245 Texin 245 Texin 270 Texin 3215Texin 985 Texin 285 Texin 260 Texin 970U Texin 4210

Texin 390 Texin 3203 Texin 4215Desmopan Texin 990 Desmopan 453 Texin 4203KU2-8651 Desmopan 459 Texin 4206

Conditions KU2-8655 Desmopan 445

Table 8

Processing Temperatures

Zones

Rear 350 380F 360 390F 380 410F 410 455F 430 450F (177 193C) (183199C) (193 210C) (210 235C) (221 232C)Middle

360 390F 360 400F 380 420F 415 460F 440 460F (183 199C) (183 204C) (193 216C) (213 238C) (227 238C)

Front360 400F 360 410F 390 430F 420 460F 440 460F (183 204C) (183 210C) (199 221C) (216 238C) (227 238C)

Nozzle365 405F 370 415F 400 440F 425 465F 450 475F(185 207C) (188 213C) (204 227C) (218 241C) (232 246C)

Melt*385 465F 385 465F 385 465F 385 465F 385 465F(196241C) (196241C) (196241C) (196241C) (196241C)

Mold ** 60110F 60110F 60110F 80110F 80110F(16 43C) (16 43C) (16 43C) (2743C) (2743C)

Machine ConditionsInjection 6,000 15,000 psi 6,000 15,000 psi 6,000 15,000 psi 6,000 15,000 psi 6,000 15,000 psiPressure (41 103 MPa) (41 103 MPa) (41 103 MPa) (41 103 MPa) (41 103 MPa)Injection Speed Slow Slow Medium Medium Medium

Hold 5,000 10,000 psi 5,000 10,000 psi 5,000 10,000 psi 5,000 10,000 psi 5,000 10,000 psiPressure (33 69 MPa) (33 69 MPa) (33 69 MPa) (33 69 MPa) (33 69 MPa)Injection 0.125 in. max 0.125 in. max 0.125 in. max 0.125 in. max 0.125 in. maxCushion (3.175 mm max) (3.175 mm max) (3.175 mm max) (3.175 mm max) (3.175 mm max)Back 200 psi max 200 psi max 200 psi max 200 psi max 200 psi maxPressure (1.4 MPa max) (1.4 MPa max) (1.4 MPa max) (1.4 MPa max) (1.4 MPa max)Screw 40 80 rpm 40 80 rpm 40 80 rpm 40 80 rpm 60 80 rpmSpeedClamp 3 5 t / in.2 3 5 t / in.2 3 5 t / in.2 3 5 t / in.2 3 5 t / in.2Tonnage (0.5 0.8 mt /cm2) (0.5 0.8 mt /cm2) (0.5 0.8 mt /cm2) (0.5 0.8 mt /cm2) (0.5 0.8 mt /cm2)Cycle 20 60 sec. 20 60 sec. 20 60 sec. 20 60 sec. 20 60 sec.TimeInjection 5 10 sec. 5 10 sec. 5 10 sec. 5 10 sec. 5 10 sec.Time

* To obtain proper melt temperature, take an air shot and measure the melt with a heated pyrometer probe. ** Check mold temperature on the part cavity and core surface.

29 of 60

Venting

Trapped gas will produce a marred surface, usually a white color. In moreserious cases, it will prevent the moldfrom completely filling.

Venting enables trapped gas or air to easily escape from the mold. But sinceTexin and Desmopan resins are quitefree-flowing at their melt temperature,even very shallow venting can lead topart flash. Therefore, attempt correctivemeasures before venting the mold.Design the part and tool so that the flowis uniform and inject the melt slowly toallow a gradual escape of any trappedgas or air.

If venting is necessary, it should be as shallow as possible. Start at a depth of1/2 mil and increase the depth asneeded.

The following information is presentedas an overview. Detailed information is available in the Design Manual forEngineering Resins, which can beobtained by contacting a BayerCorporation Technical Group repre-sentative for Texin and Desmopanresins at 412-777-2000.

MOLD SHRINKAGE

The mold shrinkage values for parts molded of Texin and Desmopan TPUresin are provided in Table 9. For mostparts, a value of 0.010 in. per in. (mm/mm) can be used with reliable results.Complicated part designs and flow pat-terns can make shrinkage complex.Parts with undercuts that are pushedfrom the mold with no side action willnot hold tight tolerances.

MOLD DESIGNMaterial Selection

Mold steels, such as AISI P-20, S-7, and H-13, are commonly used forTexin and Desmopan resins. Aluminum(Type 6061 T-6) can be used for short-run or prototype molds.

Surface Finish

Because Texin and Desmopan TPUresins can stick to highly polishedsurfaces, a rougher mold surface finishcan be used. An SPI D-2 finish(formerly SPE/SPI #5 or vapor hone)is an excellent choice for our TPU resin.Where possible, the surface treatmentshould extend to sprue bushings, run-ners, etc., to help ensure easy ejectionof the entire shot.

TOOLING

Sample Thickness Shrinkage

Table 9Shrinkage Values for Parts Molded of Texin and Desmopan TPU Resins

< 0.125 in. (< 3.175 mm) 0.007 0.010 in. / in. (mm/mm)0.125 0.250 in. (3.175 6.35 mm) 0.010 0.015 in. / in. (mm/mm)> 0.25 in. (> 6.35 mm) 0.015 0.020 in. / in. (mm/mm)

30 of 60

Part Draft

A generous draft and taper help to avoid problems removing the part fromthe mold. Incorporate a 2 or greatertaper on all part walls in the direction ofthe draw (see Figure 19). A lesser tapermay require frequent use of a moldrelease agent to aid part removal fromthe tool.

Texturing

Typically, the surface texture of the mold depends upon the end-use require-ments of the finished part. Texturedsurfaces require an additional 1 ofdraft for every 0.001 in. (0.025 mm)depth of texturing.

Weld Lines

Weld lines are created whenever two flow fronts come together in the cavityduring injection of the melt. This gen-erally occurs on the side of a molded-in hole opposite the gate or where theflows from multiple gates meet. Ingeneral, Texin and Desmopan resinsexhibit good weld-line strength. Ventsat the weld line can help eliminatetrapped gasses.

Undercuts

Parts with undercuts up to 375 mils have been successfully molded withTexin and Desmopan TPU resin. Partswith small undercuts can be removedfrom a mold using normal pin or plateejection. However, with pin or plate

ejection there is the danger of tearingthe part or stretching it out of shape.This can be avoided by using an airejection system to blow the parts off the core. Air ejection works particular-ly well with low-durometer materials.

Tolerances

It is difficult and expensive to mold to close tolerances. Thus, keep the num-ber of close tolerance dimensions to aminimum. Obviously, holding a largenumber of close-tolerance dimensionson any part is much more difficult thangetting a single dimension correct.

Since Texin and Desmopan TPU resins are elastomeric, the suggested toleranceexpectations are outlined in Table 10.

Draft Angle, Length, and Taper RelationshipFigure 19

Length1 in.

2DraftAngle

Taper0.0175 in.

Figure 20 Sprue Design

Orifice Diameter 0.125 0.375 in.0.5 in . / ft.

Taper

0.02 0.08 in. Radius

Nozzle Tip

Sprue Bushing

31 of 60

TOOLING, continued

MaterialTexin and Desmopan

PolyurethanePlus or Minus in

Drawing Dimensions Thousandths of Code (in.) an Inch*

1 2 3 4 5 6 7 8 9 10 11

Table 10 Tolerances for Texin and Desmopan TPU Resins

A = Diameter or Length 0.000B = Diameter or Length 1.000C = Depth 2.000

3.000

4.000

5.000

6.000

6.000 to 12.000 Standard Coarse For each inch over 6.000 add (in.) 0.004 0.006

Over 12.000For each inch over 12.000 add (in.) 0.005 0.007

Height D Single Cavity 0.000 1.000 0.004 0.006Multiple Cavity 0.000 1.000 0.004 0.006

For each inch over 1.000 add (in.) 0.002 0.002Bottom Wall E 0.000 to 0.100 0.003 0.004

0.100 to 0.200 0.003 0.004

0.200 to 0.300 0.004 0.005

Sidewall F Dimension Section thickness to be held relatively constantDraft Allowance 1/ 2 1

COARSE

Data in this chart denote the dimensional tolerances which are considered feasible fordesigning parts of Texin and Desmopan resins.

* These tolerances do not apply to screw threads, gear teeth or fit of mating parts;dimensions in these classifications can generally be held to closer limits. These tolerances do not include allowance for aging characteristics of material.

AF

B

E

C

D

STANDARD

32 of 60

MOLD COOLING

Use molds sufficiently cored for cooling to achieve uniform temperaturesover the mold surface.

Small molds require channels drilled about 2.5 in. (63.5 mm) between centersand 0.43755 in. (11.1 mm) in diameter,with 0.250 in. (6.35 mm) pipe threads for the intake and outlet fittings. Largemolds require channels drilled 4 in.(101.6 mm) between centers and 0.7187in. (18.2 mm) in diameter, with 0.5 in.(12.7 mm) pipe threads for the intakeand outlet fittings.

Molds having long, thin cores may be cooled by using bubblers, baffles, orheat pipes to achieve uniform moldsurface temperatures.

MOLD TYPES2- or 3-Plate Molds

The selection of either two- or three-plate mold construction for processingTexin and Desmopan resins is usuallydetermined by part geometry, produc-tion volume, scrap considerations, cos-metics, and cost.

Single- and Multiple-Cavity Molds

Texin and Desmopan resins can be suc-cessfully processed in both single- andmulti-cavity molds. Which type is usedis dictated by the complexity of the partand the required production volume.

Sprue Bushings

Sprue bushings should be as short as possible with a taper of 0.50 in./ft(0.42 mm/cm) or 0.75 in./ft (0.63mm/cm). A taper of 0.75 in./ft (0.63mm/cm) is preferred for ease ofrelease. If the sprue has little or notaper, it will be difficult to break thesprue from the nozzle. It is importantthat no nicks or undercuts be presenton the surface of the sprue bushing. Avapor-honed type surface finish canbe used for the sprue, if desired. Thesprue bushing spherical radius shouldmatch the nozzle radius and the sprueorifice diameter should be about 20%larger than the nozzle orifice diameter.(See Figure 20.)

Figure 21 Sprue Pullers

Undercut Ring

Sprue

Bushing

Knock-Out Pin

Z Puller Attachedto Knock-Out Plate

Reverse Taper*

5

Knock-Out Pin

End View

Runner

*Exaggerated to show concept.

Front View

33 of 60

TOOLING, continued

Sprue Pullers

Use sprue pullers of any common design, but avoid any that restrict flowof the melt. A 5 reverse-taper spruepuller, as shown in Figure 21, workswell.

Cold-slug wells are recommended and should be built into the base of the sprueand at every branch or sharp turn in therunner system. This provides a trap forcold, solidified material, keeping it outof the cavity.

RUNNERS AND RUNNERSYSTEMS

Round runner systems are preferred for Texin and Desmopan resins. Full-roundcross sections are best (see Figure 22).A primary runner of 0.250 0.750 in.(6.35 19.05 mm) diameter, withsecondary runners of 0.250 in. (6.35mm) diameter, are commonly used.However, these dimensions can varyaccording to part size and configuration.

Keep runners as short as possible to reduce unnecessary pressure dropsbetween the sprue and gate, and toreduce scrap.

Hot Runner Molds

Texin and Desmopan TPU resin can be successfully molded using insulated orhot runner systems. Hot runner moldscan practically eliminate the use of re-grind because there is no sprue scrap orrunner system with each shot. Hot run-ner molds are more expensive than con-ventional molds but the added cost canbe offset on extended production runswhere the use of regrind might beimpractical.

A diameter of at least 1 in. (2.54 mm)is suggested for insulated runners. Theaddition of cartridge heaters to theinsulated runner block allows start-upwithout going through the procedure ofremoving the solidified runner.

Figure 22 Runner Design

Good Better Best Poor Poor

Figure 23 Gate Designs Which Prevent Jetting

Impinging Edge Gate

Section

Bottom View

Overlap Gate

Side View

Bottom View

Suggested Minimum Gate Dimensions for Parts Molded of Texin and Desmopan TPU Resins

Round

Diameter 0.030 in. 1/2 1/2Thickness Thickness

of Part of PartLand Length 0.030 in. 0.040 in. 0.060 0.080 in.

Rectangular

Thickness 0.030 in. 1/2 1/2Thickness Thickness

of Part of PartLand Length 0.030 in. 0.040 in. 0.060 0.080 in.

34 of 60

The suggested diameter of hot runners is at least 0.50 in. (12.7 mm). The bestresults with hot runner molds have beenobtained by using hot tips in the secondplate. Consult the hot runner moldsuppliers technical staff when selectinga system for Texin and Desmopan resin.

GATING

Gate type and location are determined by the part design. Any of the gatingstyles typically used in injection mold-ing can be used successfully with Texinand Desmopan TPU resin.

Regardless of the type employed, locatethe gate in the thickest section of the partto control sinks, voids, molded-instresses, and/or warpage in the finishedpart. To minimize jetting, position thegate so that the melt flow impinges on acore, core pin, or an opposite wall (see

Figure 23). Also locate the gate to helpprevent the trapping of gas caused bybackflow, which can result in burningor filling difficulty.

Table 11 lists suggested gate dimen-sions for various part thicknesses.

Sprue Gate

Normally, sprue gates are located in the center of the part. If possible, pro-vide a cold slug well in the core sideopposite the sprue gate.

Figure 24 Rectangular Edge Gate

Typically 23 TimesGate Thickness

T- Part ThicknessT

Side View

Max. 0.060 in.0.25 0.65 T

Runner

Bottom View

Thickness

< 0.125 in. 0.125 0.250 in. > 0.250 in.(< 3.175 mm) (3.175 6.35 mm) (> 6.35 mm)

Table 11

Edge Gates

Edge gates, whether rectangular or round, must be large enough to avoidfrictional burning. Examples of edgegate dimensions are shown in Figure 24.Variations of edge gating are shown inFigure 25.

Disc and Ring Gates

This type of gate works particularly well for cylindrical parts with relatively

thick sections. It generally results in lesspart distortion than would several pin-point gates.

Pinpoint Gates

Due to the shear-sensitivity of Texin and Desmopan resins, avoid usingpinpoint gates except for very smallparts.

INSERT MOLDING

Inserts of a variety of materials and design can be used with Texin andDesmopan TPU. Since parts molded of Texin and Desmopan resins, unlikeparts made of rigid plastic, are notprone to crazing, no minimum wallsection is needed around a molded-ininsert. The thickness of the wall isdetermined solely by pull-out or torquestrength. The thicker the wall, thegreater the resistance to pull-out ortorque. The design of the insert neednot be limited to a straight, smoothwall, but can have knurls, splines,reverse tapers, or undercuts.

Metal Inserts

Inserts of steel, aluminum, brass, zinc, and other metals can be molded intoTexin and Desmopan elastomers. Inmany cases, sufficient bond strengthcan be obtained simply by degreasingthe inserts, applying an adhesive to theinserts, and heating them to 220250F (104 121C) before placingthem in the mold. Polyurethane-basedadhesives work well. Consult a BayerCorporation Technical Group represen-tative for Texin and Desmopan resinsfor a list of adhesives that may be used.

35 of 60

TOOLING, continued

Figure 25 Variations of Edge Gating

Width = Typically 2 3 D

Radius

0.020 in. 0.060 in. Land

C

D= 25% 65% C

PartingLine

C = Part ThicknessD = Gate Depth

36 of 60

Additional mechanical anchoring that is, using an insert with knurls,splines, reverse tapers, or undercuts can help ensure additional reliability. If mechanical anchoring cannot beprovided, then roughen the contactsurface of the metal, giving it a tooth.

Nonmetal Inserts/Over-Molding

Texin and Desmopan TPUs can be joined to many nonmetallic materials,including other thermoplastics to ob-tain a molded part with both flexibleand rigid components. Usually, therigid substrate (molded part) is pro-duced first and placed, after a shorttime (less than 3 hours to be sure ofproper bonding), in an injection mold

and the flexible component injectedonto it. This rigid-to-flexible sequenceis used because the more rigid materialgenerally accounts for the greater massof the finished part.

The success of bonding Texin andDesmopan TPU with another thermo-plastic by injecting one materialdirectly onto the other is dependent on three factors:

1. Chemical affinity (adhesion).

2. Mechanical anchoring potential ofthe substrate material.

3. Processing order.

A suggested pairing of a number of combinations of Texin and DesmopanTPU with other engineering thermo-plastics on the basis of their processingorder is provided in Table 12.

The processing order of the material isa function of the application and thedesign of the part, too. The followingprocessing considerations are alsocrucial to achieving a good bond:

l The two materials should be joinedtogether in the freshly molded state.

l The second material must be able topartially melt the substrate material.

l Both materials should contain justenough mold release for demoldingthe final part.

Bonding Properties of Different Materials

ABS TPU Good AdhesionPC TPU Good AdhesionPC/ABS Blend TPU Good AdhesionRigid PVC TPU Good AdhesionRigid TPU TPU Good Adhesion

PBT TPU Inadequate AdhesionPA TPU Inadequate Adhesion

TPU ABS Good AdhesionTPU PC Good AdhesionTPU PC/ABS Blend Good AdhesionFlexible TPU Rigid TPU Good Adhesion

TPU PBT Better Adhesion, Depending on Type

TPU PA Better Adhesion, Depending on Type

PE TPU No AdhesionPP TPU No AdhesionTPU PE No AdhesionTPU PP No Adhesion

Material InjectionSubstrate Molded to Substrate Assessment

Table 12

Figure 26 Examples of Rigid/Flexible Designs

37 of 60

TOOLING, continued

Problems can occur in the rigid-flexiblebond if too much time (several hours oreven days) has elapsed between moldingthe rigid substrate and the over-moldingflexible component. These defectsusually are due to one or more of thefollowing substrate problems:

l Blooming of additives to the surface.

l Excessive release agent.

l Post-mold shrinkage (tightness of the part in the mold cavity andchanges in part dimensions).

l Problems with partial melting (dueto aging).

l Surface contamination.

If the substrate will be produced andplaced in intermediate storage before re-inserting it into a mold for injectionof the second material, then some pro-visions for mechanical anchoring areessential. This is particularly importantif the second material will not partiallymelt the substrate material.

The layout of the contact surfaces is another important consideration for anoptimum connection (see Figure 26).The contact surfaces should be aslarge as possible. In addition, the wallthickness of the material injected ontothe substrate should be ample, and theflow paths as short as possible. Other-wise, the heating capacity of themolten material may be inadequate tosufficiently melt the substrate for agood bond.

Right

Right

Right

Wrong

Blisters can form on the surface of thepart from moisture in the resin or trappedair in the mold. Splay marks, whichappear as silver-white marks generallyfollowing the flow paths of the melt, alsocan be the result of wet resin or resinthat has overheated.

l Wet material.

l High melt temperature.

l Check drying procedure.l Measure moisture content of resin

pellets in hopper.

l Reduce material temperature by:t Lowering cylinder zone temperatures.t Decreasing screw speed.t Reducing back pressure.

Description of Problem Possible Causes Possible Corrective Action

BLISTERS AND SPLAY MARKS

Figure 27 Blister and Splay Marks

TROUBLESHOOTING GUIDE

38 of 60

39 of 60

l High injection velocity.


l Decrease injection speed.l Increase gate size. l Change gate position.

l Check for overheated bands or nozzle heaters.


Burn marks appear as a brown blush orstreaks of discoloration on the surface.

BURN MARKS

Figure 28 Burn Marks

40 of 60


l Lower injection pressure.l Decrease injection speed.l Reduce overall cycle time.

l Lower material temperature by:t Increasing cylinder zone temperatures

10F (18C).t Decreasing screw speed.t Reducing back pressure.

l Check mold closure and lockup.l Check platen alignment.

l Increase clamp tonnage.

l Improve mold venting.

l Incorrect processing.


l Mold setup.

l Insufficient clamp pressure.

l Excessive vent depth.

FLASH

Flash is a thin, surplus web of plasticmaterial attached to the molded partalong the parting line. Flash formation isdependent on the fit of the mold at theparting line, the applied clamping force,and the viscosity of the resin melt.

Figure 29 Flash

41 of 60

TROUBLESHOOTING GUIDE, continued

Insufficiently or incompletely filled partsare symptomatic of short shots.

l Insufficient melt temperature.

l Insufficient injection pressure.

l Insufficient injection speed.

l Insufficient feed.

l Undersized nozzle orifice.

l Raise material temperature by:t Raising cylinder zone temperatures.t Increasing screw speed.

l Increase injection pressure.

l Increase injection speed.

l Increase resin feed.

l Increase size of nozzle, sprue, runner system.


SHORT SHOTS

Figure 30 Short Shots

42 of 60

Depressions in the surface of the partare generally caused by either insuffi-cient injection pressure or an excessive-ly high melt temperature. Other possiblecauses are degradation of the materialthrough moisture and insufficient gatesize. Increasing injection pressure mayresult in excessive flash, requiring anincrease in clamping force.

l Insufficient injection pressure.

l Excessively high melt temperature.

l Wet material.

l Insufficient gate size.

l Increase injection pressure.

l Reduce melt temperature.

l Check drying procedure.

l Increase size of nozzle, sprue, runner system.

l Move gates closer to thick sections.


SINKS

Figure 31 Sinks

43 of 60



Parts that do not eject freely will preventmolding machines from cycling auto-matically. Efficiency and productivitysuffer. Insufficient cooling, improperejector design, highly polished orchrome-plated mold surfaces, andmoisture are the most common causes of part sticking.

l Insufficient cooling.

l Improper ejector design.

l Highly polished or chrome-plated mold surfaces.

l Wet material.

l Lower melt temperature.

l Lower mold temperature.

l Increase cooling time.

l Check drying procedure.l Measure moisture content of pellets in

hopper.

STICKING PARTS

Figure 32 Sticking Part

44 of 60

Voids occur when moisture from in-sufficiently dried resin vaporizes andbecomes trapped in the hot melt. Afrothy or excessively dark shot indi-catesthat the melt is overheating and mayresult in voids in the molding.

Note: Avoid large-increment tem-perature changes when molding withTexin resins. Change the temperature insteps of 5 10 F (9 18 C) until theproper melt condition is achieved.

l Wet material.

l Overheating.

l Check drying procedure.

l Reduce heat, back pressure, or screw speed.

l Check heater bands and controller for malfunction.


VOIDS

Figure 33 Voids

45 of 60



Due to variations in part geometry andwall thickness, sections of a molded partcool at different rates from the ejectedmelt temperature to room temperature.Differential shrinkage occurs and the parttends to become concave on the sidethat cooled last, most likely around thegate area.

l Unequal mold-half temperatures.

l Distortion upon ejection.

l Material not set up completely prior to ejection.

l Check for uniform mold temperature.

l Check for uniform part ejection.

l Decrease injection speed.l Decrease injection pressure.l Increase cooling time.l Lower material temperature.

WARPAGE

Figure 34 Warpage

46 of 60

GENERAL

Wear safety glasses and/or face shields when processing Texin and Desmopanresins, especially during purging, anduse proper gloves and other appropriategarments when handling hot tools andauxiliary equipment. Material SafetyData Sheets (MSDS) are available andshould be consulted prior to processingTexin and Desmopan polyurethaneelastomer resins.

HEALTH AND SAFETYPRECAUTIONS

Appropriate literature has been assem-bled which provides information con-cerning health and safety precautions thatmust be observed when handling BayerCorporation products mentioned in thispublication. Before working with any of these products, you must read andbecome familiar with the available in-formation on their hazards, proper use,and handling. This cannot be over-emphasized. Information is available inseveral forms, e.g., Material Safety DataSheets (MSDS) and product labels.Consult your local Bayer Corporationrepresentative or contact the ProductSafety and Regulatory Affairs Depart-ment in Pittsburgh, Pennsylvania at 412-777-2000.

For materials that are not Bayer Corporation products, appropriateindustrial hygiene and other safetyprecautions recommended by theirmanufacturer(s) should be followed.

SAFETY CONSIDERATIONS

47 of 60

GENERAL INFORMATION

Corporation representative or the BayerCorporation Regulatory Affairs Managerin the Health, Environment, and SafetyDepartment in Pittsburgh, Pennsylvania.

STERILIZATION INFORMATION

The sterilization method and the numberof sterilization cycles a part made fromTexin and Desmopan TPU resins canwithstand will vary depending upon thetype and grade of resin, part design, andprocessing parameters. Therefore, themanufacturer must evaluate each appli-cation to determine the sterilizationmethod and the number of cycles forexact end-use requirements. Partsmolded from Texin and Desmopan TPUresins are sterilizable using ethyleneoxide, radiation, or dry heat. Steamsterilization methods must not be usedwith aromatic grades of Texin andDesmopan TPU resins because possiblehydrolysis of solid urethane mayproduce aromatic amines, such asmethylene dianiline (MDA).

DEVELOPMENTAL PRODUCTINFORMATION

Any product in this publication with a grade designation containing the lettersDP, KU, or KL is classified as a devel-opmental product and is not consideredpart of the Bayer Corporation line ofstandard commercial products. Com-plete commercialization and continuedsupply are not assured. The purchaser/user agrees that Bayer Corporationreserves the right to discontinue supplyat any time.

REGULATORY COMPLIANCE

Some of the end-uses of the products described in this brochure must complywith the applicable regulations, such asthe FDA, NSF, USDA, and CPSC. Ifyou have questions on the regulatorystatus of Texin and Desmopan resins,please contact your local Bayer Corpo-ration representative or the BayerCorporation Regulatory AffairsManager in Pittsburgh, Pennsylvania.

MEDICAL GRADE INFORMATION

It is the responsibility of the medicaldevice, biological product, or pharma-ceutical manufacturer to determine thesuitability of all component parts andraw materials, including Texin andDesmopan TPU resins, used in its finalproduct in order to ensure safety andcompliance with FDA regulations. Thisdetermination must include, as appli-cable, testing for suitability as animplant device and suitability as tocontact with and/or storage of solu-tions/ liquids, including, without limita-tion, medication, blood, or other bodilyfluids. Under no circumstances, how-ever, may Texin and Desmopan TPUresins be used in any cosmetic recon-structive or reproductive implant appli-cations, nor may any Bayer Corpora-tion resin be used in any other bodilyimplant applications for greater than 29 days, based on Tripartite GuidanceTests. Furthermore, for aromatic gradesof Texin and Desmopan TPU resins,longer term uses are not permissiblebecause possible hydrolysis of solidurethane may produce aromatic amines,such as methylene dianiline (MDA). Ifyou have any questions on the regula-tory status of Texin and Desmopanresins, please contact your local Bayer

48 of 60

BIOCOMPATIBILITY INFORMATION

The medical grades of Texin andDesmopan TPU resins have met the biocompatibility requirements for U.S. Pharmacopoeia Procedure 23Class VI, with human tissue contacttime of 29 days or less.

TECHNICAL SUPPORT

To get material selection and/or designassistance, just write or call and let usknow who you are and what your needsare. So that we can respond efficientlyto your inquiry, here are some of thepoints of information we would like toknow: physical description of yourpart(s) and engineering drawings, ifpossible; material currently being used;service requirements, such as mechani-cal stress and/or strain, peak andcontinual service temperature, types ofchemicals to which the part(s) may be

exposed, stiffness required to supportthe part itself or another item, impactresistance and assembly techniques;applicable government or regulatoryagency test standards; tolerances thatmust be held in the functioningenvironment of the part(s); and anyother restrictive factors or pertinentinformation of which we should beaware.

In addition, we can provide processingassistance nationwide through a net-work of regional Field TechnicalService Representatives. We can helpcustomers optimize the quality and per-formance of their parts by offering thefollowing types of assistance: on-siteprocessing, equipment, and productivityaudits; startup and troubleshootingsupport; and tool design.

Upon request, Bayer Corporation will furnish such technical advice or assis-tance it deems to be appropriate inreference to your use of our Texin andDesmopan products. It is expresslyunderstood and agreed that, since allsuch technical advice or assistance isrendered without compensation and is

based upon information believed to bereliable, the customer assumes andhereby expressly releases Bayer Corpo-ration from all liability and obligationfor any advice or assistance given orresults obtained. Moreover, it is yourresponsibility to conduct end-use test-ing and to otherwise determine to yourown satisfaction whether Bayer Corpo-ration products and information aresuitable for your intended uses andapplications.

For assistance, contact any of our regional sales offices listed on the backcover, or call or write us at the follow-ing address:

Bayer CorporationPolymers Division, PlasticsTexin Product Management100 Bayer Road, Building 8Pittsburgh, PA 15205-9741Phone: 412-777-2000

49 of 60

APPENDIX A:LIST OF TABLES

Page No. Description Table No.

5 Texin and Desmopan TPU Table 1Injection Molding Resins

6 Grade Composition and Designations Table 2for Texin and Desmopan Resins

6 Performance Additives and Designations Table 3for Texin and Desmopan Resins

17 Dehumidifying Hopper Dryer Table 4Troubleshooting Guide

19 Suggested Starting Conditions for Table 5Processing Texin and Desmopan TPU Resins

20 Barrel Heating Temperatures Table 6a

20 Nozzle Temperatures Table 6b

21 Melt Temperatures Table 6c

22 Injection Pressures Table 7a

22 Hold Pressures Table 7b

22 Injection Speed Table 7c

Page No. Description Table No.

23 Injection Cushion Table 7d

23 Back Pressure Table 7e

23 Screw Speed Table 7f

24 Clamp Tonnage Table 7g

24 Mold Temperature Table 7h

28 Suggested Starting Conditions for Table 8Processing Texin and Desmopan TPU Resins

29 Shrinkage Values for Parts Molded of Table 9Texin and Desmopan TPU Resins

31 Tolerances for Texin and Desmopan Table 10TPU Resins

34 Suggested Minimum Gate Dimensions for Table 11Parts Molded of Texin and Desmopan TPU Resins

36 Bonding Properties of Different Materials Table 12

50 of 60

Page No. Description Figure No.

7 Texin and Desmopan Resin Pellets Figure 1

8 Label Information for Texin and Desmopan Figure 2Thermoplastic Polyurethane Resins

9 Typical Injection Molding Machine Figure 3

10 Screw Profile Figure 4

11 Free-Flowing, Sliding Check-Ring Figure 5Style Non-Return Valve

11 Flow Characteristics of the Figure 6Non-Return Valve

12 Removable and Non-Removable Figure 7Nozzle Tips

12 Internal Flow Channel of a Standard Figure 8Nozzle Tip

13 Internal Flow Channel of a Reverse- Figure 9Taper Nozzle Tip

14 Moisture Absorption Rate of Figure 10Texin and Desmopan Resins

14 Typical Desiccant Dehumidifying Figure 11Hopper Dryer System

15 Desiccant Dehumidifying Hopper Figure 12Dryer System Airflow

16 Bubble Formation During Purging Figure 13

18 Temperature Zones/Machine Figure 14Cross Section

21 Making an Accurate Melt Temperature Figure 15Reading

Page No. Description Figure No.

24 Measuring Mold Temperature Figure 16

26 Regrind Pellets Figure 17

26 Mechanical Cleaning of the Screw Figure 18

30 Draft Angle, Length, and Taper Figure 19Relationship

30 Sprue Design Figure 20

32 Sprue Pullers Figure 21

33 Runner Design Figure 22

33 Gate Designs Which Prevent Jetting Figure 23

34 Rectangular Edge Gates Figure 24

35 Variations of Edge Gating Figure 25

37 Examples of Rigid /Flexible Designs Figure 26

38 Blister and Splay Marks Figure 27

39 Burn Marks Figure 28

40 Flash Figure 29

41 Short Shots Figure 30

42 Sinks Figure 31

43 Sticking Part Figure 32

44 Voids Figure 33

45 Warpage Figure 34

APPENDIX B:LIST OF FIGURES

Aadditives, 37blooming, 37

after-cooler, 17air control butterfly valve,

dehumidifying hopper dryer, 17air duct(s), 17air ejection, 30air shot(s), 21, 26, 27air temperature, drying hopper inlet air, 15airflow, 15, 17airflow, reactivation, 17annealing, 27

procedure, 27temperature control, 27

appearance of the melt, 21appearance of the molded part, 18applications, 5, 6, 25, 47, 48

automotive, 6consumer, 6industrial-mechanical, 6load-bearing, 5low-deflection, 5medical, 6

automotive components, 6cams, 6exterior applications, 6gears, 6mechanical parts, 6

B

back pressure, 12, 23, 38, 40, 44frictional heat, 12

Back Pressure (Table 7e), 23baffles, 32bags, 8

opening and resealing, 8

51 of 60

INDEX

brown blush, 39Bubble Formation During Purging

(Figure 13), 16bubblers, 32bulk trucks, 8burn marks, 39

troubleshooting guide, 39Burn Marks (Figure 28), 39burning, 11, 34, 35bushings, 29, 32

C

cartons, 8, 14opening and resealing, 8

cartridge heaters, 33changeover temperature, 17changing material, 27channeling of the pellets, 15charred pellets, 13chrome-plated mold surfaces, 43clamp/clamping force, 9, 40, 42clamp pressure, 40clamp tonnage, 24, 40clamping pressure, 24cleaning, 26closed-loop control systems, 13cold slug, 11, 34cold slug well(s), 33, 34color(s), 7, 8color blend, 8color concentrate(s), 7color designation, 7color dispersion nozzle, 7color quality, 25colorant(s), 7, 8coloring molded parts, 8

barrel, 9, 11, 13, 20, 25, 26, 27capacity, 13heater bands, 20heating, frictional, 20heating zones, 20liner, 9temperature, 20

Barrel Heating Temperatures (Table 6a), 20Bayer Corporation products, 46

hazards, proper use, and handling, 46Bayer Corporation Regulatory Affairs, 47Bayer Corporation Technical Group

representative for Texin and Desmopanresins, 6, 7, 8, 25, 29, 35

biocompatibility information, 48biological product suitability,

determining, 47black specks, 16blend uniformity, 6blending, 6, 7blisters, 38blisters and splay marks, 38

troubleshooting guide, 38Blisters and Splay Marks (Figure 27), 38block/blocking, 15blooming of additives, 37blower rotation, 17Bonding Properties of Different Materials

(Table 12), 36bonding Texin and Desmopan TPU with

other thermoplastics, 36-37combinations, 36 defects, 37factors affecting, 36layout of the contact surfaces, 37problems with partial melting, 37processing considerations, 36substrate problems, 37

coloring the resin, 7color concentrates, 7dry blending, 7

compression ratio, 9compression set, 27condensation, moisture, 14

preventing accumulation on resins, 14consumer applications, 6

in-line skate boots, 6shoe components, 6ski goggle frames, 6

Consumer Product Safety Commission (CPSC), see regulatory agencies/organizations

contaminated material, 25contamination, 8, 25, 26, 37

dust, dirt, 8moisture, 8surface, 37

controller, 44controls, 11, 13

closed-loop, 13process, 11

cooling or solidification of the melt, 11cooling requirements of a part, 25cooling time, 13, 18, 25, 43, 45copolymers, 5creep, 27curing, 27

ambient air, 27elevated temperature, 27

cycle time, 12, 20, 24, 25, 40cylinder, 12, 13, 26, 27cylinder temperature, 12cylinder wall, 12, 13cylinder zone temperatures, 38, 40, 41cylindrical parts, 35

desiccant, 14, 15, 17replacing, 17worn-out, 17

desiccant beds, 17desiccant dehumidifying

hopper dryer, 14, 15Desiccant Dehumidifying Hopper Dryer

System Airflow (Figure 12), 15design assistance, 48Design Manual for Engineering Resins, 29developmental products/product

information, 47dew point, 15, 17diagnostic devices, 6differential shrinkage, 45dimensional tolerances, 18dimensional uniformity, 13dimensions, molded part, 18dimethyl acetamide, 26dip dying, 8dirt, 8disc and ring gate(s), 35discolored material, 25distorted part(s), 25DP resin grade designation, 47draft, 30Draft Angle, Length, and Taper

Relationship (Figure 19), 30drool, 10drums, 8, 14dry blending pigments, 7dry cycling the hopper dryer, 15, 17dry heat sterilization, 47dryer, 14-17drying, 7, 14, 16, 21, 25

hot air oven, 16pigments or dyes, 7resin, 14

D

deep-flighted screws, 12degradation, 9, 10, 12, 13, 25, 27, 42

material, 25, 27, 42melt, 12resin, 9

dehumidifying hopper dryer, 17after-cooler, 17air control butterfly valve, 17air duct(s), 17airflow, 15blower rotation, 17changeover temperature, 17desiccant beds, 17drying air temperature, 17electrical connections, 17filter, 17heater, 17hopper inlet airflow, 15hose connections, 17inlet airflow, 17inlet-air hose, 17material residence time, 17process air heating elements, 17process air temperature, 17regeneration cycle timer, 17return air line, 17return air temperature, 17temperature controller, 17thermocouple, 17

Dehumidifying Hopper Dryer Troubleshooting Guide (Table 4), 17

demolding, 36depressions in part surface, 42

52 of 60

drying air temperature, 17drying equipment, 14-15drying procedure, 38, 42, 43, 44drying the desiccant, 15drying time, 15dust, 8dyes, 7, 8

E

edge gate(s), 35dimensions, 35variations, 35

ejector pins, 27electrical connections, dehumidifying

hopper dryer, 17end-use performance, 25end-use testing, 48equipment assistance, 48ester-based TPU, 27ethylene oxide sterilization, 47Examples of Rigid/Flexible Designs

(Figure 26), 37excessive flash, 42excessive heat, 13, 25excessive transparency of the melt, 21excessively high melt temperature, 42external heat/heaters, 11, 12, 18

F

feedstock, 8Field Technical Service Representatives, 48filling difficulty, 34filter(s), dirty or clogged, 17filter(s), dehumidifying hopper dryer, 17final molding conditions, 27finished part, 8, 30, 34, 36

53 of 60

INDEX, continued

grade, resin, 5, 6, 7, 13, 24, 47designation, 6, 47rigid, 5unreinforced general-purpose, 5

Grade Composition and Designations for Texin and Desmopan Resins (Table 2), 6

H

hardness, hardness value, 5, 6Shore A, 6Shore D, 6

health and safety precautions

Documents

PU-BAYER