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Polymers/Compounds
all-categories-product-catalog-polymers
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Nitrile or Buna N Polymer
Nitrile (NBR) is a copolymer of Acrylonitrile and Butadiene rubbers. The ratio of the two polymers affects the properties of a rubber compound. Raising the acrylonitrile content will increase resistance to oil and solvents and improve abrasion resistance. Lowering the acrylonitrile content improves low temperature properties, compression set and fuel resistance.
While Nitrile rubber is considered to be a general purpose material for O-Rings and many other seals, it can be specifically compounded for many purposes. Grades are available for: food processing, use with milk and edible oils, potable water and other specialty applications. Internal lubricants may be added to reduce frictional properties and extend wear. Specialty Nitrile polymers can be produced by carboxylation (see carboxylated Nitrile) or hydrogenation (see HNBR).
The service temperature for PAI Nitrile compounds varies on the low end from -90º to -15º F (-65º to -25º C) depending on acrylonitrile content. On the high side continuous service varies from 225ºF to 300ºF depending on the curing agent used. PAI offers NBR compounds in hardness ranges from 30 to 95 durometer. Black is the standard color, but many other colors are available.
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HNBR Polymer
Hydrogenated Nitrile Butadiene Rubber, also known as Highly Saturated Nitrile (HSN), is produced by hydrogenating acrylonitrile butadiene rubber (NBR).This process improves the heat and ozone resistance, increases tensile strength, and provides superior abrasion resistance. The result is a rubber polymer that performs superior to standard NBR in most sealing applications.
Taking advantage of its inherent properties, HNBR can be compounded to provide excellent service life in applications such as oilfield, automotive, and refrigerants. Dynamic applications requiring long service life or in abrasive environments are especially well suited to HNBR. FDA grades are available. Internally lubricated compounds are superior for extended wear dry air applications.
The service temperature range is generally -40º to 300º F (-40º to 150º C), but can be extended in special applications. PAI offers HNBR compounds in a hardness range from 50 to 90 durometer. Black is the standard color, but other colors are available.
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Carboxylated Nitrile Polymer
Carboxylated Nitrile (XNBR) compounds are similar to NBR compounds with the addition of a carboxyl group included during polymerization. Carboxylation produces a stronger, more abrasion resistant material than standard nitriles.
XNBR compounds generally have higher low temperature ranges than NBR compounds and are less flexible.
PAI offers XNBR compounds in a range from 60 to 90 durometer. Black is the standard color, but we also offer tan and white compounds. Internally lubricated compounds are available for dry air applications.
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Fluoroelastomer Polymer
Fluoroelastomers (FKM) are most commonly known by the trade name Viton®, but are available from several other manufacturers including 3M, Solvay, and Daikin.
General purpose Fluoroelastomers are copolymers of vinylidene fluoride and hexafluoropropylene and usually have a fluorine content of about 66%. These materials have very good high temperature properties and are resistant to a wide range of chemicals and petroleum based oils. Grades are available for food processing, medical and other specialty applications. Black and Brown are the standard colors, but several others are available.
Specialty Fluoroelastomers are typically terpolymers. Many can be used in a range of applications including concentrated acids, water and steam, automotive fuels, and a wider variety of chemicals. Peroxide cured Fluoroelastomers add additional chemical resistance. The fluorine content in specialty FKM polymers varies between 63 and 70%
The service temperature of FKM materials can be as high as 500ºF (260º C) on the upper end. Fluoroelastomers generally do not have especially good low temperature properties, but specialty compounds will perform to -50ºF (-45ºC). PAI offers FKM compounds in a hardness range from 55 to 90 durometer.
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Tetrafluoroethylene Propylene Polymer
Most commonly known as AFLAS® or Viton® Extreme™; Tetrafluoroethylene Propylene (FEPM or TFE/P) is a fluorinated rubber. It has excellent resistance to a wide variety of chemicals, both acids and bases. It works well at elevated temperatures and has very good resistance to petroleum fluids.
The raw material cost for Aflas® is relatively high and it is difficult to process. Like most other fluoropolymers, AFLAS® does not have especially good low temperature properties
The temperature range for compounds is 0º to 475º F (-15 to 245ºC). PAI offers FEPM compounds in a hardness range of 70 to 90 durometer. Black is the standard color, but some others are available.
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Silicone Polymer
Methyl Vinyl Silicone (VMQ) and Methyl Phenyl Vinyl Silicone (PVMQ) are semi-organic elastomers with outstanding resistance to extremes of temperatures. Silicone can provide reliable service at temperatures as low as -175ºF (115ºC) to as high as 480ºF (250ºC) continuously. It also has good resistance to compression set.
Most silicone is non-toxic; therefore grades are available for food processing, use with milk and edible oils, and for use in medical devices including grades for long and short term bodily implantation. Specialty grades are available for static dissipation and fire retardation.
Low physical strength and poor abrasion resistance combined with high friction, generally limit silicone to static seals. Although it swells considerably in petroleum lubricants, this is not usually detrimental in most static sealing applications.
PAI offers silicone compounds in a hardness range of 20 to 80 durometer. Salmon or orange is our standard color, but a rainbow of other colors is available. Translucent and clear compounds are possible too.
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Fluorosilicone Polymer
Fluorosilicones (FVMQ) combine most of the attributes of silicone with resistance to petroleum oils & hydrocarbon fuels typical in Fluoroelastomers. As a result, they are often used in aircraft fuel systems.
Low physical strength and poor abrasion resistance combined with high friction, usually limit Fluorosilicone to use as static seals. Fluorosilicones are suitable for use over a temperature range of -85º to 350ºF (-65º to 175ºC).
PAI offers Fluorosilicone compounds in a hardness range of 40 to 80 durometer. Blue is the standard color but others are available.
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EPDM Polymer
Ethylene-propylene (EPDM) compounds are prepared from ethylene, propylene and a third monomer. These compounds are used frequently to seal phosphate ester fire resistant hydraulic fluids such as Skydrol. They are also very effective in brake systems, and for sealing hot water and steam. Ethylene-propylene compounds have good resistance to mild acids, alkalis, silicone oils and greases, ketones, and alcohols. They are not recommended for petroleum oils or diester lubricants.
Ethylene-propylene has a temp range of -65º to 300ºF (-55º to 150ºC). It is compatible with polar fluids that adversely affect other elastomers.
PAI offers EPDM compounds in a hardness range of 40 to 90 durometer. Black is the standard color, but many other colors are available.
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Chloroprene Polymer
Chloroprene rubber (CR) is more commonly know by the trade name Neoprene®.
Chloroprene is unusual in that it is moderately resistant to both petroleum oils and weather (ozone, sunlight, oxygen). This qualifies Neoprene® for O-ring service where many other elastomers would not be satisfactory. It is also used extensively for sealing refrigeration fluids. FDA grades are available. Neoprene® has good compression set characteristics, abrasion resistance, and a temperature range of -65º to 285ºF (-55º to 140ºC).
PAI offers Neoprene® compounds in a hardness range of 40 to 90 durometer. Black is the standard color, but many other colors are available.
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Perfluoroelastomer Polymer
Perfluoroelastomer (FFKM) is most commonly known by the DuPont trade name Kalrez®. Perfluoroelastomer compounds offer the widest range of chemical and solvent resistance as well as very high operating temperatures (up to 575º F / 300ºC). Food and medical grades are offered.
The price of products made from Perfluoroelastomers tend to be very high due to the raw material cost, so this polymer is used for specialty applications only. The low temperature range is only -20º to +20ºF depending on the compound. Thermal expansion needs to be considered when using Perfluoroelastomers at elevated temperatures.
P-REX™, Precision Associates’ family of Perfluoroelastomer compounds are available in hardness range of 70 to 90 durometer. Black is the standard color, but white is available.
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Urethane Polymer
Precision Associates manufactures products in both Polyester (AU) and Polyether (EU) Millable Gum Urethane rubber compounds.
Polyurethane compounds exhibit outstanding tensile strength and abrasion resistance in comparison with other elastomers. Fluid compatibility is similar to that of nitrile at temperatures up to approximately 160ºF (70ºC). Below 160º, Polyurethane seals offer outstanding performance in high pressure hydraulic systems with abrasive contamination, high shock load, and related adverse conditions. At higher temperatures, polyurethane has a tendency to soften and lose both strength and fluid resistance advantages over other elastomers.
Food and dairy grades of Polyether Urethane are available. Polyether materials tend to do better in water and petroleum based oils, while Polyester urethanes do better in fuels.
Polyurethanes are suitable for use over a temperature range of -65º to 250ºF (-55º to 120ºC). PAI offers Urethane compounds in a hardness range of 40 to 90 durometer. Black is the standard color but others are available.
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Epichlorohydrin Polymer
Epichlorohydrin (ECO) (CO) compounds, also known as Hydrin®, provide excellent resistance to fuels and oils, excellent weather resistance, and good low temperature properties.
Epichlorohydrin compounds exhibit fair compression set properties and poor resistance to sour gas. Epichlorohydrin can be corrosive to some metals.
The temperature range for Epichlorohydrin is -65º to 275ºF (-55º to 135ºC).
PAI offers black Epichlorohydrin compounds in a hardness range of 50 to 90 durometer.
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Butyl Polymer
Chlorobutyl (CIIR) and Isobutylene Isoprene (IIR) compounds provide superior gas permeation and excellent weather resistance. They are also useful for their energy absorption properties. Food grades are available.
Butyl rubbers do not provide good petroleum oil or fuel resistance and are not especially good at compression set resistance.
PAI offers Butyl compounds in a hardness range of 30 to 70 durometer. Black is the standard color, but some white compounds are available.
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Styrene Butadiene Polymer
Styrene Butadiene Rubber (SBR), also known as Buna S, was developed just before WW II and was used extensively by the United States during WW II due to the unavailability of Natural rubber during those years. It is still widely used in tires.
SBR is reasonably priced, has good abrasion resistance and fair weathering properties. It is not especially good with chemicals or solvents.
The temperature range for SBR compounds is -60º to 250º F. PAI offers Black SBR compounds in a hardness range of 40 to 80 durometer. Some white compounds are also available.
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Chlorosulfonated Polyethylene Polymer
Once known by the trade name Hypalon®, Chlorosulfonated Polyethylene (CSM) compounds demonstrate excellent resistance to oxygen, ozone, heat and weathering.
Chlorosulfonated Polyethylene does have poor tear, abrasion resistance and compression set properties.
The operating temperature range for CSM is -65º to 275ºF (-55º to 125ºC). PAI offers CSM compounds in a hardness range of 50 to 80 durometer. Black is the standard color, but some white compounds are available.
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Natural Rubber / Polyisoprene Polymer
Natural Rubber (NR) is harvested as latex from Hevea rubber trees. Polyisoprene (IR) is a synthetic version of Natural Rubber. These polymers are known for having excellent elongation, rebound, and energy absorption properties.
Because it is an organic product, Natural Rubber does have more problems with consistency from lot-to-lot than most man made polymers. Individuals with Latex allergies can respond negatively to Natural Rubber. Both Natural Rubber and Polyisoprene tend to revert when used at elevated temperatures.
The operating temperature range for these polymers is -50º to 180ºF (-45º to 80º C). PAI offers compounds in a hardness range of 30 to 70 durometer. Black is the standard color, but several other colors are available.
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Polyacrylate Polymer
Polyacrylate (ACM) compounds retain their properties when sealing petroleum oils at continuous temperatures as high as 350ºF (175ºC). Polyacrylate seals are used extensively in automatic transmission and other automotive applications.
Polyacrylate materials provide excellent weather resistance, but only fair resistance to water when submersed for extended periods. Polyacrylate also provide fair compression set resistance as well as low temperature performance
PAI offers black ACM compounds in a hardness range of 50 to 80 durometer.
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Hydrogenated Carboxylated Butadiene Acrylonitrile Polymer
Hydrogenated Carboxylated Acrylonitrile-Nitrile Rubber (HXNBR) exhibits significantly higher tear strength at high temperatures when compared to regular HNBR and higher tensile strength and higher elongation at break than either regular HNBR or XNBR. This material has improved heat and ozone resistance compared to XNBR while providing superior abrasion resistance - better than both HNBR & XNBR.
HXNBR can provide excellent service life in applications such as oilfield, automotive, and refrigerants. Dynamic applications requiring long service life or in abrasive environments are especially well suited to HXNBR. Internally lubricated compounds are outstanding for extended wear dry air applications.
The service temperature range is generally -40º to 300º F (-40º to 150º C), but can be extended in special applications. PAI offers HXNBR compounds in a hardness of 90 durometer. Black is the standard color.
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Ethylene Acrylate Polymer
Also know by the trade name Vamac®, Ethylene Acrylate (EA) provides the highest heat resistance commercially available in a moderately priced weather-resistant polymer. The heat resistance along with good oil resistance makes this polymer a popular choice for under hood automotive applications. Good ozone resistance makes EA a good choice for weather resistant compounds.
Compression set resistance is only fair, along with poor resistance to organic solvents or highly aromatic fluids.
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Chlorinated-Polyethylene Polymer
Chlorinated Polyethylene (CM) is derived by the random chlorination of high density polyethylene. It demonstrates resistance to ozone, weather, acids and bases. This polymer has reasonable resistance to petroleum based oils.
The operating temperature range for CM materials is -50º to 300ºF (-45º to 150ºC). PAI has a 80 durometer black Chlorinated Polyethylene compound, but will develop others upon request.
