resin-guidelines-111102132909-phpapp01.doc

RESIN GUIDELINES

Resin Guidelines

RESIN GUIDELINESTABLE OF CONTENTS

ABS (Acrylonitrile Butadiene Styrene)

3

Acetal Homopolymer (Delrin)

4

Acetal Copolymer (Celcon)

5

Acrylic

6

Cellulosics

7

Fluoropolymers

8

Ionomer (Surlyn)

9

Nitrile Resins (Barex)

10

Nylon 6, 6/6, 6/9, 6/10, 6/12, 11 and 12 ( PA-Polyamide)

11

Polybutylene

12

Polycarbonate

13

Thermoplastic Polyester (PBT -(Polybutylene Terephthalate)

15

Thermoplastic Co-polyester (PCTA and PETG)

16

High Density Polyethylene

17

Low Density Polyethylene

18

Linear Low Density Polyethylene

19

High Molecular Weight Polyethylene (HMWPE)

20

Ethylene Copolymers - (EEA, EVA, EMA)

21

Polypropylene

22

Polystyrene

23

Polyurethane

24

Rigid Vinyl (Polyvinyl Chloride - PVC)

25

Flexible Vinyl

26

Thermoplastic Elastomers (TPE or TPR)

27

Vinylidene Chloride (VDC) - "Saran"

28

Thermoset Resins (Phenolics, Alkyd, Polyester Comp., Polyimides)

29ABS (Acrylonitrile - Butadiene - Styrene)

Widely used in sheet, pipe and profile, injection molding and blow molding. ABS exhibits high impact strength and are quite rigid. ABS absorbs moisture and is almost always run vented during the extrusion process and dried for injection molding. ABS is easily processed in most cases.

Screw Design Recommendations:

For extrusion applications, two-stage screw designs generally preferred for sheet and pipe extrusion, although it can be run off on a single stage when resin is properly dried. Usually a very simple screw design with Evolution Mixer for colorants or other compounding is more than adequate.

Higher outputs obtained with barrier screws with distributive mixing will produced excellent results. Screw Material Recommendations:

General recommendation: 4140 HT steel base material

Colmonoy 56 flight lands

Bored thru the feed for screw cooling

Chrome plating .001 thick as an option Barrel Recommendation:Typically, ABS is neither abrasive nor corrosive so X102, 666 or equivalent barrel linings are adequate.Other Information:

Extrusion:Maximum output approximately 10 LB/HP/Hr but speed limited due to overheating, i.e., approximately 100 RPM maximum on a 3.5 extruder.

Injection Molding:There are very good screw designs for when injection molding of very high impact resins are used.

Injection molding of ABS is the principal resin that used for chrome plated plastic parts.

One of the principle ABS manufacturer is Dow Chemical.

Notes: ABS can be foamed in pipe applications and requires special designs. These need to be referred to the Design Group for recommendations.-3-Acetal Homopolymer (Delrin)

Acetal homopolymers are some of the strongest and stiffest of generally used polymers. Most applications are replacements for metal parts. Although there are some extrusion applications, majority of the usage is in injection molding.


Single-stage screw designs are always used. The Evolution Mixer can be used for coloring or compounding applications. Barrier screws have been used with good temperature control, and good melt quality. Recommended for very critical tolerance injections or extrusion applications where unmelts and surging cannot be tolerated.

Screw Material Recommendations:

General Recommendation: 4140 HT steel base material



Chrome plating .001 thick as an optionNo particular wear problems with Delrin.

Other Information:

Maximum output approximately 8-9 LB/HP/Hr for extrusion applications. No limit on screw speed.

There is a wide range of viscosities available so be sure to get manufacturer name and resin number.

Acetal Homopolymer resins not particularly temperature sensitive and generally fairly easy to process.

For extrusion screws, die pressure is important due to generally low viscosity.

Only commercial producer is DuPont.

Notes:

-4- Acetal Co-polymer (Celcon)Acetal copolymers are strong, hard, and highly crystalline polymers that are often used as metal replacements. They have superior creep resistance, corrosion resistance, and a low coefficient of friction.

Acetal Co-polymers are used primarily in injection molding, although it also has extrusion applications in thin films, blowmolding, profiles, and tubing.


Single-stage screws are usually used as there is no drying requirement. Mixing devices are required only for difficult colorant dispersions or special compounding requirements. Primary recommendation is a simple single-stage screw. Any type mixer can be used, but Evolution mixer would be preferred.

A barrier-type screw can be used for good temperature control, good melt quality and also recommended for critical tolerance injection or extrusion applications.


General Recommendation:

4140 HT steel base material



Chrome plating .001 thick as an option Chrome plating not required, but is recommended because formaldehyde can be formed at high temperatures.

No particular wear problems with Celcon.

Other Information:

Maximum output approximately 8-9 LB/HP/Hr. Speed may be somewhat limited due to high melt viscosity and resultant overheating. Requires speeds somewhat similar to rigid PVC.

Resin degrades at high temperatures, requiring care in the screw design.

Notes:

-5-

Acrylic

(PMMA)Acrylic resins are used primarily where high light transmittance is desirable. They are available in general purpose and impact grades. Acrylics absorb moisture, and two-stage screws are usually used for extrusion applications. However, single stage screws are used for injection molding applications if the resins are dried. Generally, the acrylic resins are easily processed. Screw Design Recommendations

Conventional screws (single or two stage) work well, although 30:1 L/D is a minimum length for optical parts. Evolution Mixers are recommended for good mixing and temperature homogeneity. There is no particular advantage to barrier screws for processing acrylics, although they have been used from time to time. A Evolution Mixer can be used at the tip to homogenize for improved optical properties.





Chrome plating .001 thick as an optionNo particular wear or corrosion problems when processing Acrylic., because Acrylics are seldom used with fillers. Other Information:

Sheet and profile extrusion are common for acrylic and injection molding is a large process for this polymer.

Notes:

-6-

Cellulosics

There are three general types of cellulosics that are in common use and are processed using single screws. These are cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. They are used for a wide variety of extrusion and injection applications. In general, they are difficult resins to process in extrusion but are easily injection molded.


The primary extrusion problem with cellulosics is surging, and we have been largely successful in solving that problem with a barrier-type screw and a spiral UCC mixer. A simple single-stage design can be used if low outputs are acceptable. In injection molding where surging is of less importance, conventional screws work satisfactorily. Mixers of any type can be used for coloring.


There is no wear or corrosion problem in processing cellulosics.





Chrome plating .001 thick as an optionCellulosics are seldom used with fillers since their principal attributes clarity, gloss and transparency.

Other Information:

Cellulosics are sold in various hardnesses much like flexible PVC. The processors will know them by these hardness codes such as H=Hard, S=Soft, MH=Medium Hard. This hardness value also indicates the polymer's melt flow characteristics. Be sure and get these values.

Since cellulosics are so sensitive to surging, it is important in the design to know what the expected die back pressure might be. If that is not available, be sure and obtain the cross sectional area of the extruded part.

Notes:

-7-

Fluoropolymers

Fluoropolymers have exceptional mechanical, chemical, and temperature properties. Consequently, they are typically used in hostile environments of temperature or corrosion. They also have a very low coefficient of friction and have a self-lubricating quality. they are commonly called Teflon, although that is strictly a DuPont brand name.


Single-stage conventional screws are used almost universally to process Fluoropolymers. Mixing sections can be used, although the Fluoropolymers are seldom colored but may have fillers. Outputs are generally low as compared to most polymers on a given size screw due to the requirement to develop such a high temperature.


Fluoropolymers are extremely corrosive in the melt state, and require special screw (and barrel) materials.

General Recommendation: Hastelloy, unhardened flights No cooling bore.

Colmonoy 56 is easily applied to Hastelloy for a premium wear resistance O.D.

4140 HT steel with electrolysis nickel plating has been used successfully with Fluoropolymers but not highly recommended.

Other Information:

Principal resin suppliers are DuPont, Allied Chemicals, and 3M Company.

Types of Fluoropolymers typically processed are FEP, PFA, PCTFE, and ECTFE.

Bores should only be used when necessary due to the difficulty in drilling Hastelloy.

Outputs limited usually by melt quality. Horsepower is seldom a limiting factor as output/HP is greater than 10 LB/HP/Hr.

Notes:

-8-

Ionomer (Surlyn)Principal application is food packaging due to barrier properties. Ionomers have exceptional cut, abrasion and impact resistance. Typical uses are golf ball covers, wear strips, footwear, athletic equipment, etc. The main commercial resin is DuPont's "Surlyn".


Ionomers process easily and, although conventional single-stage screws are usually used, spiral UCC mixing screws and barrier-type screws work well. Just about any type mixer could be used.

Ionomers are seldom colored or compounded with fillers so mixing requirements are pretty much nil.


Ionomer is comparable to LDPE and hardsurfacing may be required for extended wear life.

General Recommendation: 4140 HT steel


Cored for cooling thru feed section of screw Other Information:

The major new market for Ionomer is in coextruded film, blowmolding and injection molding, especially for golf ball skinsNotes:

-9-

Nitrile Resins (Barex)

Nitrile resins are typically used for food and non-food packaging because of their excellent barrier properties. Blowmolding and injection-blowmolding are the principal processing techniques. There is also sheet extrusion for thermoformed packaging.

Nitrile resins are similar to rigid vinyl with respect to processing.


Single-stage and two-stage screws are used depending on whether venting is necessary. Mixing pins are recommended when there is a mixing requirement. UCC sections cannot be used.

Chrome plating is recommended, as nitriles can be somewhat corrosive if degradation occurs.

Nitriles pose no wear problem and are not filled.


4140 HT Steel


Cored full length for internal cooling

Chrome plated .002 thick

Other Information:

Since nitriles process similar to rigid vinyl, the screws are very deep flighted. Consequently, screw speed and horsepower are important. Maximum screw speeds to avoid overheating should be 60 RPM or less.

Currently Barex by Vistron is the only commercial nitrile resin.

Notes:

-10-

Nylon 6, 6/6, 6/9, 6/10, 6/12, 11 & 12

(Polyamide PA)Nylons constitute a family of resins all having similar chemical structure. The differences in structure are essentially described by the numbers such as 6, 6/12, etc. Nylons generally are characterized by their toughness, chemical resistance, and good frictional properties. Applications are very broad ranging from wire coating to brush bristles.


Nylons absorb moisture and must be well dried before processing. Despite the moisture problem, single-stage screws are used almost universally. This is probably due to the difficulty of venting nylon due to its low melt viscosity.

Nylon is very stable and any kind of mixing device can be used, although mixers are seldom required.

Barrier screws work very well.


General: 4140 HT steel base material


NOTE: Many nylon compounds are now fiber and/or mineral filled. The screws require root as well as O.D. protection and therefore tool steels are typically used for screw smaller than 70mm in diameter Other Information:

Nylons have a high melting point and low melt viscosity. As a result, outputs are low per RPM and high screw speeds are typical. Output per horsepower, however, is high, i.e., 9-10 LB/HP/Hr.

Two-stage vented designs can be designed also successfully if necessaryNotes:

-11-

Polybutylene

(PB)Polybutylene is a polyolefin having exceptional flexibility, resistance to creep, and stress crack resistance. Its primary application is in water pipe, with blown film being the secondary application.

PB total usage at this time is quite small.


The resin processes very much like polypropylene. Except for minor modifications in the profile, PB can be treated like polypropylene.

Barrier type screws with Evolution Mixer will process PB very well.Screws should be bored in the feed section for improved solids conveying.


4140 HT steel base metal


Cored for cooling thru feed section of screwChrome plating is not required.

Other Information:

Screw wear would be typical for a polyolefin in that hard surfacing is recommended.

Notes:

-12-

Polycarbonate

Polycarbonate has exceptionally high impact strength, rigidity, and dimensional stability. Since PC is also transparent, it has major usage as a glazing material. Other principal applications are in blowmolding film and injection molding.


Polycarbonate is hydroscopic and requires drying or vented screws. Generally, single-stage screws are used because PC is hard to devolatilize due to its exceptionally high melt viscosity. Single and two-stage screws have been designed successfully.If mixing is required the Evolution Mixer should be used. Due again to the high viscosity, it is very important to have correct screw speed and horsepower.




Chrome plated

Large channel radius to eliminate dead spots and degradation

Cored for cooling for improved solids conveyingOther Information:

Sabic "Lexan" and Bayer "Merlon" are the principal resins.

Glass-filled polycarbonate is widely used and causes extreme screw wear, therefore it is recommended that the screw channels are fully encapsulated with Stellite 6 and Colmonoy 56 flight lands. Nitriding can also be used.If tinted sheet or products are being made, then mixing is absolutely required to insure that no streaking occurs in the finish product.

Notes:

-13-

Thermoplastic Polyester (Polybutylene Terephthalate-PBT)

PBT is a crystalline resin that exhibits good tensile strength, toughness, dimensional stability, and a low coefficient of friction. Principal application is in injection molding with increasing activity in sheet and film. Due to its sharp melting point and low melt viscosity, PBT is difficult to process in extrusion applications and melt pump should always be used.Screw Design Recommendations:

Single-stage barrier screws are typically used, although PBT is hydroscopic and must be dried. Two-stage screws usually present no design problems.

For extrusion applications, our best recommendation is a barrier-type screw with a Evolution Mixer.

Bores are recommended in thru feed section.

PBT is used with glass fiber fillers frequently in injection moldingScrew Material Recommendations:

General Recommendation: 4140 steel based material


Cored for cooling

Chrome Plating is an optionOther Information:

Sabics "Valox" is the principal resin.

Valox is sold in many glass-filled grades and caused high screw wear. We recommend that the most economical protection is to nitride the screw geometry, but for maximum protection the screw geometry should have full encapsulation with Stellite 6 in the high wear areas. HVOF tungsten carbide coating has been successful but are very expensive.

Notes:

-14- Thermoplastic Polyester

(Polyethylene Terephthalate-PET)

PET is a crystalline resin that, when oriented, excels in strength, toughness and clarity. Principal applications are beverage bottles and oriented cast films. Other areas are paper coating, oriented strapping, and injection blowmolding.

There are two distinct screw design situations. Beverage bottles require different designs than other applications.

Screw Design Applications:

For Injection Molding of Beverage Bottles, a barrier type screw with an Evolution Mixer produces excellent results

In extrusion applications barrier-type screws is recommended with the Evolution Mixers, although for small extrusion screws (2 and smaller) a single-stage conventional screw with an Evolution Mixer can be used.

PET must be thoroughly dried before processing, but should not be run on vented screws due to dramatic IV drop when exposed to atmospheric conditions.Screw Material Recommendations:

There is no wear problems or corrosion with PET.

General Recommendation: 4140 HT base material


Cored thru feed section of the screw for screw cooling

Chrome plating is optionalOther Information:

Notes:

-15-

Thermoplastic Co-polyester (PCTA & PETG)

The commercial types of thermoplastic co-polyesters are PCTA and PETG. However, PETG constitutes most of the volume due to difficulty in processing the PCTA and its price.

PCTA and PETG are considered to be rigid vinyl replacements and are used primarily for blister packaging and blowmolding.

Screw Design Recommendations

We have had outstanding success with a single-stage Barrier-type screws for processing PETG. A Evolution mixer can be used for good temperature homogeneity and where coloring is required.

Eastman (EB062) and Indorama both have several grades of co-polyster resins which are used for blow-molding applications. These resins can be difficult to process and low shear barrier type screw with an Evolution Mixer must be used.


No wear or corrosion problems.




Chrome plating .001 thick as an optionOther Information:

Both PCTA and PETG are made by Eastman Chemical. PCTA is known as Kodar A-150 and PETG is Kodar 6763. There are also new co-polyesters made by Eastman (EB062) and Invista that are used in blow molding.Many screws over the years for processing co-polyesters resins using barrier type screw technology, especially for PETG. Primarily, the benefits are very high output in extrusion, and lower melt temperatures in blowmolding.

Notes:

-16-

High Density Polyethylene (HDPE)

HDPE is processed by many different processing techniques. The largest application is blowmolding, with other high volume applications in film, injection molding, pipe, and sheet.

HDPE is a difficult polymer to process in that it is a highly crystalline resin. Because of the crystalline nature and melting characteristics, HDPE requires greater HP/LB than most resins despite a relatively low melting point.


Most HDPE can be processed on single stage UCC mixing screws at very good rates but in todays technology very seldom recommended. Our optimum design has been a Barrier screw with a Evolution Mixer for improved melt temperature and energy efficiency at improved throughput rates and lower melt temperatures.

For applications where improved coloring mixing, low gels count, or compounding of additives is necessary, a dispersionary mixer such as a spiral UCC section should be added to the Barrier screw. For Barrier screws where blends or regrind are run, the Evolution Mixer section works well.


HDPE presents the most screw O.D. wear of any unfilled polymer. There is no corrosion problem.


4140 HT Base material


Colmonoy 83 flight lands for premium wear resistance

Cored for cooling thru the feed section for improved solid conveying is recommended.

Chrome plating is optional

Other Information:

HDPE has a very wide range of viscosities that affect screw design. The viscosity is indicated by the melt index. Be sure to obtain this information or the resin MFG and resin number so that viscosity information can be obtained.

Use 5 to 6 LB/HP/Hr as maximum outputs.

High molecular weight polyethylene is a type of HDPE that requires special screw designs.

Notes:-17-

Low Density Polyethylene

(LDPE)

LDPE is the highest volume thermoplastic. Over half goes into blown film. Other large applications are wire coating, injection molding, and paper coating.

LDPE is a less difficult resin to process in that it has medium crystallinity and unusual melting characteristics. LDPE requires greater HP/LB than most resins but less that HDPEScrew Design Recommendations:

LDPE has been processed almost universally on barrier-type screws with UCC mixing screws in many years. Barrier screws provide lower melt temperatures and better energy efficiency.

Spiral UCC mixing sections can also be used with the Barrier screw for coloring, low gels, or compounding of additives. For processing blends or regrind, the Evolution Mixer works well.

Bores are required for LDPE for improve stability and solids conveying.


LDPE in low head pressure applications has a low wear problem. There is no corrosion problems with LDPE.

General Recommendation 4140 HT steel base material

Colmonoy 56 flight lands. Colmonoy 83 should be used for premium wear requirements, but an Xaloy 800 or Wexco 777 bi-metallic lined barrel has to be used with the Colmonoy 83Other Information:

Die pressure is also important in film applications as it has a significant effect on output.

Use 6 to 7 LB/HP/Hr as maximum output.

LDPE resins are often blended with EVA resins which affect screw design and a dispersionary mixer is recommended.Notes:

-18-

Linear Low Density Polyethylene(LLDPE)LLDPE is a type of low density polyethylene, but the properties are quite different from conventional LDPE. The primary difference is related to its viscosity as far as screw design is concerned. The result being a much greater horsepower requirement. Almost all LLDPE goes into blown film applications.


Best results have been obtained with the barrier-type screw with a Evolution Mixing section. Generally, a UCC mixing section is recommended to reduce gels and provide mixing when blends of LLDPE and LDPE are used.


LLDPE causes extreme flight wear. There is no corrosion problem.

General Recommendation 4140 HT steel base material

Colmonoy 56 flights. Colmonoy 83 should be used for premium wear requirements, but an Xaloy 800 or Wexco 777 bi-metallic lined barrel has to be used with the Colmonoy 83 Cored for cooling thru the feed for improved solids conveying

Notes

We would expect 5 to 5.5 LB/HP/Hr with LLDPE. Notes:

-19-

High Molecular Weight Polyethylene

(HMWPE)

HMWPE is simply HDPE having a higher average molecular weight. Due to HMWPE's high melt viscosity, it necessitates special screw designs wherein drive power and melt temperature can be effectively controlled. Applications are growing rapidly in blown film, sheet, blowmolding, and pipe. Any HDPE having a melt index of less than .2 can be considered HMWPE.


A low compression Barrier-type screw with an Evolution Mixer has performed very well on HMWPE. UCC sections cannot be used without overheating.

As with most polyolefins, the horsepower requirement is large to it's important to know screw speed and horsepower before designing the screw.


HMWPE causes high flight wear, but there are typically no corrosion problems.

General Recommendation: 4140 HT steel base material (28-32 Rc)


Colmonoy 83 should be used for premium wear requirements, but an Xaloy 800 or Wexco 777 bi-metallic lined barrel has to be used with the Colmonoy 83 Cored for cooling for improved solids conveyingOther Information:

It is necessary to obtain actual resin data, if possible, or manufacturers' resin numbers if no data is available, as HMWPE covers a very broad range. Notes:

-20-

Ethylene Copolymers

Ethylene-Ethyl Acrylate (EEA)

Ethylene-Vinyl Acetate (EVA)

Ethylene-Methyl Acetate (EMA)

Three ethylene copolymers are widely used both as extrusion resins themselves, and as blending agents to modify HDPE and LDPE. In general, they are very similar to LDPE except for a lower melting point. All three are manufactured with a range of ethylene to co-monomer ratios, giving a fairly wide range of processing parameters, i.e., they range from rubbery, low melting polymers to being very similar to LDPE.


Evolution Mixing screws are recommended for all three ethylene copolymers.

These resins process very easily. Due to softness and low melting point, barrier type screws offer little advantage. Most of the time these material are process on small extruders and therefore barrier type screw are not usually used.Screw Material Recommendations:By themselves, none of the ethylene copolymers are particularly prone to cause high flight wear. However, when blended with HDPE and LDPE, the wear may be more like HDPE or LDPE. There is no corrosion problem.


Colmonoy 56 flight lands. Cored for cooling is recommended for improved solids conveying


EFA, EVA, and EMA are typically used in blown film, cast film, and extrusion coating.

Notes:

-21-

Polypropylene (PP)

Polypropylene is a high volume resin with primary applications in film, fibers, sheet, blow molding, injection molding and strapping. Polypropylene is a difficult resin to process in that it is difficult to feed and has a higher melt point than other polyolefins, i.e., LDPE and HDPE. PP has a low specific gravity of .90 gm/cc whereas HDPE has a specific gravity of .96 gm/cc in the solid form.Screw Design Recommendations:

Barrier-type screws work very well on PP, although the screw profile is not the standard barrier-type profile, whereas they will have longer feed section in order to develop better solids conveying. Bores are recommended in the feed section in order to improve solids conveying..

Since PP has such a low specific gravity and poor feeding, the expected outputs are typically 30% to 35% lower that when process in other polyolefins.

The primary characteristic that makes PP difficult to process is because of its low coefficient of friction which complicates feeding.


PP has similar high flight wear characteristics as the polyethylenes, although not as severe. There is no corrosion problem.

General Recommendations: 4140 HT steel base material (28-32 Rc)

Colmonoy 56 flight lands Colmonoy 83 should be used for premium wear requirements, but an Xaloy 800 or Wexco 777 bi-metallic lined barrel has to be used with the Colmonoy 83Other Information:

Notes:

-22-

Polystyrene

(GPS or HIPS)Polystyrene is sold in two basic types. Crystal or "GP" is unmodified. Crystal is injection molded (plastic glasses) and extruded (light diffusers). Impact styrene or "HIPS" is rubber modified crystal which is also primarily injection molded (appliances) and extruded (refrigerator liners) and packaging applications. In addition, there is a large market in PS foams (egg cartons), where GP and HIPS are used.


Polystyrene does not absorb moisture but is still run vented in many cases, although venting is not essential. Regardless, most screw designs for PS are two stage, even if venting is not required. A decompression design can be used, however, be substituted for a two-stage design with no difficulty. Barrier screws can be used for PS, but there is no advantage except stability. PS resins are easily processed in most cases. Refer to Engineering for PS foam design information.


There are no wear or corrosion problems with PS.

General Recommendation: 4140 HT Steel base material (28-32 Rc)

Colmonoy 56 flight lands Cored for cooling thru feed section is recommended

Other Information:

PS outputs can exceed 10 LB/HP/Hr, so rates are very good in most cases.

Notes:

-23-

Polyurethane

(PU)Polyurethanes are a relatively limited application as far as screw processing. Most PU's are chemical foams, spray-able coating, or are cast from liquids. Principal applications for screw processing are tubing, wire coating, and some profiles. Extrudable Polyurethanes cover a wide range due to the resin's ability to be plasticized. Polyurethans are relatively difficult to process due to their poor feeding characteristics.


A barrier-type screw design works very well on polyurethanes because of its inherent low surge capabilities. Surging is the output limit on most PU extrusion applications.

Conventional single-stage screws can be used if low outputs are acceptable.

Cooling bores are recommended thru the feed section to improve solids conveying.


There are no wear or corrosion problems with PU as a general rule. However, there are so many methods used to plasticize Polyurethane that it is best to use chrome plating in case there is some polymer degradation and a corrosive medium is formed and it also is beneficial for solids conveying.


Cored for cooling thru the feed section of the screw


Chrome plating.

Other Information:

Notes:

-24-

Rigid PVC (Polyvinyl Chloride-PVC)

Rigid vinyl is essentially unmodified PVC. It has some difficult processing characteristics such as heat sensitivity and high viscosity that have to be considered. Due to the high viscosity, it is essential that adequate horsepower is available at low speeds. Maximum screw speed on rigid vinyl is approximately 50 RPM without polymer degradation.


Rigid vinyl is typically supplied as pellets for single screw extrusion and injection molding, but for some rare occasion it can be used in a powder form. In almost all cases, powder is run vented and two-stage screws are required. Usually powder screws have a plastic screw mixer or a Plasti-Screw section in the first stage. RPVC screws are typically single stage and range and a special barrier-type screw with a spiral UCC mixer is recommended. Bores are required full length. Hollow bored removable noses are also used in most cases so that the tip of the screw can be heated to reduce degradation on the screw tip. Also the removable nose should have an offset to also help eliminate tip degradation.Screw Material Recommendations:

Rigid vinyl degrades during processing to form free chlorides which are very corrosive. Chrome plating is required in many cases (.002" thickness is preferred). Stainless steel screws work very well also for small screws to aid in corrosion resistance and high torque requirements. Nitriding also provides good corrosion protection. Rigid vinyl (unfilled) presents no wear problem.

General recommendation:

4140 HT steel base material (28-32 Rc) or

17-4 Ph Stainless Steel (this does not require chrome plating)


Cored full depth

Removable cored offset nose (made from 17-4 Ph Stainless Steel)

Chrome plating .002 thick for 4140 HT screwsOther Information:

When mineral fillers are used, screw flight wear is greatly increased. Colmonoy 83 flights are recommended with fillers. Highly filled compounds can result in extreme flight wear.

The biggest single screw application for rigid PVC is profiles with other also a large market in blowmolding.

Powdered vinyl is commonly called dry blend.

Outputs for rigid vinyl are generally on the low side because of the limit on screw speed.

-25-

Flexible Polyvinyl Chloride

(FPVC)Flexible vinyl is rigid vinyl with various types of plasticizers and lubricants added to reduce the hardness and melt viscosity. Flexible PVC ranges from very soft, rubbery materials back up to being almost rigid. This broad range of properties makes it important to get as much information on a particular resin formulation as possible. Key information is hardness (Shore A of D) and specific gravity.


Design of screws is pretty much related to hardness. For soft compounds, i.e., < 90 Shore A, barrier-type screw with a Evolution Mixer works very well. Barrier-type screws provide the highest output on soft compounds. In general, soft PVC is easy to process in pellet form on single-stage screws. In powder form, vented screws are often required. Bores are not required but usually supplied for harder compounds, i.e., > 90 Shore A. The materials act more like rigid vinyl and are often called semi-rigid. Basically, these compounds can be treated the same as RPVC.


The softer resins are much easier to process in that they are less heat sensitive and have lower viscosity. As a result, corrosion is a lesser problem and regular chrome plating is adequate. The harder resins (semi-rigid) have the same requirements as rigid vinyl.

Flexible vinyl (unfilled) presents no wear problem, and 4140 steel with flame hardened flights is recommended.



17-4 Ph Stainless Steel (this does not require chrome plating)


Cored full depth

Removable cored offset nose (made from 17-4 Ph Stainless Steel)

Chrome plating .002 thick for 4140 HT screws

Other Information:

When mineral fillers are used, screw flight wear is greatly increased. Colmonoy 83 flights are recommended with fillers. Highly filled compounds can result in extreme flight wear.

Powdered vinyl is commonly called Dry Blend.

Principal markets for flexible vinyl is almost entirely extrusion with profiles, wire coating, and sheet being the main applications.

Outputs are usually very high with flexible vinyl, as horsepower and screw speed seldom limit rate.

Notes:

-26-

Thermoplastic Elastomers

(TPE or TPR)

Thermoplastic elastomers are polymers that have the general properties of rubber but can be processed as thermoplastics. There are a wide variety of these TPE resins, but they all process in a similar fashion. For most situations and resin types, they process like flexible vinyl except for their tendency to feed better.


Barrier-type screws are used most frequently, but single spiral UCC mixing screws can be used for small screws (2 and smaller) also work well. Generally, mixing does not seem to be a problem, but almost any type mixer can be used.


TPE typically has no wear or corrosion problems, so 4140 steel with Colmonoy 56 flights is recommended.

If fillers are used, Colmonoy 83 flights are recommended.




Cored for cooling thru feed section of the screw


There are three general classifications of TPE:

1)Styrene block copolymers.

2)Urethane and polyester/polyether block copolymers.

3)Polyolefin blends which is typically PP basedIt is important to get the resin designation as there is considerable variation in their melt properties.

Principal applications are in molded footwear, wire coating, insulation, and hose.

Notes:

-27-

Poly-vinylidene Chloride(PVDC)

"Saran"

PVDC is a vinyl type polymer that has exceptional gas and liquid barrier properties. It is used almost entirely in food and chemical packaging. Most of the volume is in film and coextruded sheet.


The screw designs are mostly conventional single-stage screw. Since PVDC is very easily degraded at temperatures over 400 F, processing is very critical.

Mixing devices are not used normally with PVDC.

Screws are usually bored full length with removable bored noses.


PVDC is very corrosive in the melt condition and requires special screw materials. The most common material is Duranickel which has been used mostly with Colmonoy 56 hardsurfacing.

An alternate that is less expensive and shows promise of giving reasonable screw life is 4140 steel base material with Colmonoy 56 flights and electroless nickel plating.General recommendation:

Duranickel or equivalent nickel base material

Cored full depth

Removable offset nose made of DuranickelOther Information:Dow Chemical manufacturers "Saran" and is the most common commercial resin in the United States.

Notes:

-28-

Thermoset Resins

(Phenolics, Alkyd, and Polyester Compounds, Polyimides)Thermoset resins are processed like thermoplastic resins and most commonly injection molding, very seldom extruded. But due to the high temperatures of processing, an irreversible chemical reaction takes place which permanently "cross links" the polymer chains. The thermoset resin cannot be reprocessed once the cross linking has occurred.


All thermoset screws can be termed general purpose, as little work has been done on high performance screws. They are always single-stage conventional design except for the flighted tapered nose. Typically, the L/D's vary from 12:1 to 20:1.

Bores are seldom used.


Thermosets do not present high wear unfilled, but since they are almost always highly filled, high screw wear is prevalent in thermoset processing. Nitrided screws work well, with tool steel screws being superior to nitrided.

Corrosion is not severe in most thermosets, but with certain catalysts corrosion problems can exist. Generally, plating is not recommended.

Other Information:

Notes:

-29- Popular Screw Designs

1.Single Stage - The most basic of all the screw designs, generally consisting of a feed, transition, and metering section. Other renditions of the single stage is the feed/transition and the transition/metering.

2.Two-Stage* - The two-stage screw is basically two single-stage screws end to end, and any combination of single stages.

The main reason for the two-stage design is that after the resin is melted in the first stage and the melted polymer is pumped into the vent section. In this section the volatiles can be extracted from the melted polymer, then the second transition and metering section pump the resin through the die.

*In some applications, it is found that in order to improve the appearance of the product, volatiles such as gases, moisture or even air, have to be removed from the melt at a point prior to the discharge end of an extruder or injection molding machine. This is done by venting and the use of the two-stage screw.

3.Zero Metering - This design is used on injection screws. Its purpose is to generate less shear heat which in turn translates into cooler melt temperature and it allows for faster recovery times.

4.Plasti-screw Design (developed by NRM) - This design has a secondary flight, actually a spiral dam, makes approximately one less complete turn while the main flight makes two to four turns. The polymer is forced over the high shear dam. The Plasti-Screw is basically a very short barrier screw section5. Barrier-Type Screws:

The following designs are all variations of Barrier type screws. Uniroyal and Maillefer developed the first true barrier-type screws. The barrier design works in the following manner: Most designs have conventional feed and metering sections, the same as the single-stage screw. The difference is in the transition section where at the end of the feed section a secondary flight is introduced. This flight continues through the transition section until it gets to the metering section where it is terminated in one way or another. This secondary flight is undercut somewhat to that of the main flight, and as the polymer is conveyed through the main channel it gradually melts and the melted polymer forms against the barrel surface. The melted polymer then flows over the barrier flight into the auxiliary channel where it is then conveyed to the metering section. So actually what the barrier flight does is separate the melted polymer from the unmelted polymer.

Barr ET and VET Design

This design uses open-ended melt and solids channels to reduce localized shear melt hang-up and degradation. A homogenization section is located at the end primary flight to provide low-shear blending to avoid temperature gradients. Some of these patents are still active so there are cases where the screw can not be reversed engineered.Barrier or "Max-Melt" Design (patented by Hoover Universal)

Forms the auxiliary channel by having the auxiliary starting from the front side of the primary flight and at the same lead as the primary flight. At the same time, the back side of the primary takes off at a slower lead to form the auxiliary channel then returns to the same lead as the auxiliary flight, which is normally the square lead of the screw.

Efficient Design / Dray-Lawrence Patent (patented by New Castle Industries, Inc. / Xaloy)

The basis of this patent is that the auxiliary channel is established by introducing the auxiliary flight of a lead greater than the lead of the flight in the feed section and that channel widths of the feed and transition sections are of equal and constant width.This patent has expired and therefore is public domain and can be made by any one."Kim" Design

This barrier-type screw was licensed by B.F. Goodrich. It is very similar to the "Efficient" design except, instead of the barrier flights lead increasing and then remaining constant through the transition, in the "Kim" design the lead of auxiliary and primary flights increases with each turn, keeping the main channel constant with the auxiliary channel getting wider and closing off at the end of the transition section.This patent has expired and therefore is public domain and can be made by any one.

DSB, DSB II and others (patented by Davis Standard)

This is a barrier screw similar in design as the Kim screw and uses a Spiral UCC mixer on the end. This has been Davis Standards primary barrier technology for many years. The original DSB (Davis Standard Barrier) patent has expired but there have been other versions that have been patented.Wave Screw (Patented by HPM)The Wave screw technology is a type of barrier mixing section typically located at the beginning of the metering section of the screw. The root of the screw has an oscillating deep to shallow channel on either side of a barrier flight. When the channel is deep on one side of the barrier flight, directly opposite from the deep channel the channel is shallow. This oscillation happens every 120 or 180 of rotation. And multiple times down the length of the metering section.

There are two primary designs of Wave Screws, there is the Double Wave and also the Triple Wave, which is just another version of the same technology. The initial Double Wave patent has expired but there are some of patents have may be still active, if the maintenance fees have been paid by Taylor Industries as of this writing on 3/29/11.Fusion Screw (Patented by Xaloy)The Fusion Screw is a unique barrier screw technology which combines a barrier section in the transition of the screw (Dray-Lawrence patent) along with a wavy root metering section. This design allows for high throughput rates, low melt temperature and excellent power efficiency. This technology has been patented in three different version, the original Fusion, which is not patented outside the US, the Fusion II Screw which does have international patent protection and finally the PP Fusion Screw which has a modification for improved solids conveying for processing PP.WARNING: Before offering to duplicate a customers existing screw design, check the screw thoroughly for any type of marking for patent numbers. If the screw has a patent number stamped on it, then the screw can not be reversed engineered.Screw Materials

4140 Heat Treated Steel -Most screws built in the USA are made of this material. Its base hardness as we receive it is between 28-32 Rc. This material has poor abrasion and corrosion resistance.4M95 Is a carbon steel made by Timken and others which very similar to 4140 HT steel, but has better through hardness, less internal stresses and therefore stays straighter during the manufacturing of the screw, and 4% sulfur which makes it easier to machine and weld. This is a superior material to 4140 HT and typical costs less per pound.Tool Steel -Normally the CPM-9V grade of tool steel is used in screw manufacturing. It has much higher torsional strength than any other screw material. After the screw is completely machined it is air hardened, which is a thru hardening, to around 64 Rc. Tool steel has a very good abrasion resistance on the entire surface of the screw, but it has poor corrosion resistance. Another drawback of tool steel is that it is most generally limited to the smaller screws (2 1/2" diameter (65mm) and under).

Duranickle & Hastelloy -Duranickle and Hastelloy are both excellent materials to use when corrosion is a problem. The most common resins that require these materials are fluoropolymers (teflon) and Saran. Most screws are hard surfaced.

Nitralloy 135-M -Nitralloy when nitrided has good abrasion resistance and fair corrosion resistance. This is primarily used where the screw is processing a polymer which has abrasive filler.17-4 PH Stainless Steel This grade of stainless steel is commonly used for corrosive applications and also for screws that are 2.5 (65mm) in diameter when torsional strength is required. 17-4 has a yield strength of 175Kpsi whereas 4140 HT only has a yield strength of 95-100 Kpsi.Screw Coatings and Treatments

Flame Harden -This is the most common type of heat treatment used for hardening the bearing section and mixer outside diameters of carbon based screws. A surface hardness of 48-52 Rc can be achieved.

Nitriding -Nitriding is a process where Nitrogen gas is inducted into the material, either 4140 or Nitralloy. There is also another method of Nitriding which is known as Ion-nitriding which is not quite as hard, but is done at a lower heat and therefore causes less distortion to the screw material.Chrome Plating - Chrome plating is used mostly for corrosion resistance, although if applied in suitable thicknesses, it offers abrasion resistance also. Screw are typically plated .001 thick over the flighted length of the screw. All screws which are designed for processing PVC must be chrome plated a minimum of .002 thick to ensure corrosion protection.Nickel Plating -Nickel plating is excellent for corrosion resistance and can be applied more evenly than chrome.

Tungsten Carbide - is a surface treatment where a tungsten carbide spray (HVOF) is put on the screw where very high abrasion occurs. Normal deposit of this spray is.0005"-.001" thick.

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