Wednesday, April 22, 2009

The basic compound formula

The specific formulation in Flowing Table has 100 parts of raw gum elastomer and 160.15 parts of total material. After curing for 35 minutes at 140°C its vulcanized properties are indicated as 57 IRHD, with a tensile strength of 30 MPa and elongation at break of 645%. The specific formulation and properties are taken from 'The Natural Rubber Formulary and Property Index published by The Malaysian Rubber Producers Research Association (MRPRA) Rubber chemists use the term phr (parts per hundred rubber), meaning parts of any non rubbery material per hundred parts of raw gum elastomer (rubbery material). They prefer this rather than expressing an ingredient as a percentage of the total compound weight. Parts can mean any unit of weight (kg, lb, etc.) as long as the same weight unit is used throughout the formulation.


Specific Formulation

Material

PHR

For Example

PHR

Raw gum elastomer

100

SMR20

100

Sulfur

from 0 to 4

Sulfur

0.35

Zinc oxide

5

Zinc oxide

5

Stearic acid

2

Stearic acid

2

Accelerators

from 0.5 to 3

MBS

1.4

TMTD

0.4

Antioxidant

from 1 to 3

HPPD

2

Filler

from 0 to 150

N330 Black

45

Plasticizer

from 0 to 150

Aromatic petroleum oil

4

Miscellaneous

None

TOTAL

160.15

PHR is defined as parts by weight of ingredient per 100 parts of raw gum elastomer. The limits given are typical examples and are not intended to be absolute values.


Tuesday, April 21, 2009

The Basic Rubber Compound

The rubber compound was first developed by Goodyear and Hancock and it continues to develop as new materials and new variations on old ones appear in the marketplace. The compound we see everyday as rubber, such as in a tire or pencil eraser, is a mixture of a number of different ingredients. It starts with the raw gum elastomer, supplied by the plantation owner as NR, or by the petrochemical complex converting petroleum products such as ethylene, propylene and butadiene into 'raw' bales or chips of rubbery polymers such as EPDM, BR, SBR, NBR or CR. It is shipped to the rubber processor who blends it with various ingredients. The raw gum elastomer itself has very limited use, although adhesives provide one example. Most are mechanically weak and subject to significant swelling in liquids, and will not retain their shape after molding. Many of its other properties could also benefit from enhancement. It is at this point that the rubber compounder takes over, and all of his art and science is dedicated to modifying the raw gum elastomer, changing it into a more useful material.

Monday, April 20, 2009

Trade names of Rubbers

Trade names

The following, Table is a listing of just a few elastomer types, and some trade names, mainly American and European.


Symbol

Generic name

Some trade names

Company

SBR

Styrene butadiene rubber

Emulsion

Copo

Cariflex

Ameripol-Synpol

DSM Elastomers

Shell

Ameripol Synpol

SSBR

Solution

Duradene

Soloflex

Solprene

Firestone

Soloflex

Housmex

CR

Chloroprene rubber

Neoprene

Baypren

Denka

DuPont Dow Elastomers

Bayer

Denki Kabushiki Kaisha

Kagaku Kogyo

NBR

Nitrile

Nipol

Krynac

Paracril

Chemigum

Perbunan N

Nysyn

Zeon

Bayer

Uniroyal

Goodyear

Bayer

DSM Copolymer

EPDM

Ethylene propylene diene

rubber

Buna EP

Nordel

VistaIon

Royalene

Keltan

Bayer

DuPont Dow Elastomers

Exxon

Uniroyal

DSM Copolymer

IR CIIR BIIR

Butyl

Exxon Butyl

Polysar Butyl

Exxon

Bayer

MQ

Silicone elastomers

Elastosil

Silopren

Wacker Chemie

Bayer FKM (FPM)

HNBR

Highly saturated

(hydrogenated) nitrile

Zetpol

Therban

Zeon

Bayer

FKM

Fluorocarbon

Fluorel

Viton

Tecnoflon

Dyneon

DuPont Dow Elastomers

Montedison

BR

Polybutadiene rubber

Taktene

Budene

Diene

Solprene

Intene

Buna

Bayer

Goodyear

Firestone

Negromex

EniChem

Hils GmbH

ACM

Polyacrylate

HyTemp

Europrene AR

Zeon

EniChem

ECO

Epichlorhydrin ethylene oxide

Hydrin C

Zeon

CSM

Chorosulfonated polyethylene

Hypalon

DuPont Dow Elastomers

EAM(EVM)

Ethylene vinyl acetate

Levapren

Bayer

AU

Urethane (ester)

(see chapter 8)

Urepan

Millathane

Vibrathane

Bayer

TSE Industries

Uniroyal

EU

Urethane (ether)

(see chapter 8)

Millathane

Adiprene

Vibrathane

TSE Industries

Uniroyal

Uniroyal


Some other Types of Rubbers

Polybutadiene rubber BR

Although this is a significant elastomer it is most commonly used as a blend with other rubbers. Grades are very much dependent on the architecture of the repeating unit in the polymer chain. BR is traditionally difficult to process on rubber machinery; this difficulty is not apparent when BR is blended with other non polar elastomers such as NR. BR vulcanizates confer high resilience, therefore low heat build up, and good abrasion resistance to blends with other rubbers (its resilience is excellent and it has a low temperature flexibility second only to silicone rubber). In view of the above properties its major application area is in tires. Other applications are golf ball centers, modification of polystyrene to make high impact polystyrene and miscellaneous products needing improvements in abrasion, low temperature and resilience.

Polyacrylate ACM

This family of polymers exhibit oil resistance. Their heat aging temperature limit is between 150°C and 175 °C. The major application areas are automotive engine and transmission seals, gaskets and O-rings. The low temperature properties are not good, although some grades are flexible to -40°C.

Epichlorohydrin ECO CO and GECO

These halogenated polyethers are available in three forms: a homo polymer (CO), a copolymer (ECO) and a terpolymer (GECO). Attributes found within this group are: extremely low gas permeability, good oil and ozone resistance, and a good low and high temperature range. The high temperature performance is better than that of nitrile. They are used for automotive air ducts, fuel line hose tube and cover and some oilfield applications.

Chlorosulfonated polyethylene CSM

Best known as Hypalon this material has excellent ozone, acid, and weathering resistance together with mild oil and heat aging resistance. It is used extensively for roofing, pond liners and applications needing resistance to strong mineral acids.

Polynorbornene

This rubber has an extremely high molecular weight, allowing it to absorb from 150 to 300 phr of plasticizer and still retain good physical properties in very low hardness compounds. It is used for soft feed rolls for copiers and as the tread for dragster tires.

Reference: An Introduction to Rubber Technology by Andrew Ciesielski 1999

Aflas TFE/IP & Kalrez FFKM


Aflas TFE/IP

This is a copolymer of tetrafluoroethylene and propylene. It is a fluoroelastomer and has many of the attributes of FKM. Aflas has generally better resistance to both high temperature steam, and bases such as amines and concentrated alkalis, but poorer resistance to benzene and chlorinated solvents than conventional FKM. Elastomers with a chemistry combining that of Aflas and FKM are available. Aflas has a specialized, small market consisting primarily of oil seals for the automotive industry, wires and cables and oilfield drilling (downhole).

Kalrez FFKM

To the chemist this material is a copolymer of perfluoromethyl vinyl ether and tetrafluoroethylene. The latter monomer is better known in the plastic material polytetrafluoroethylene (PTFE; Teflon is an example). FFKM (Perfluoroelastomer) has a chemical resistance close to the outstanding levels reached by PTFE. Its upper continuous dry heat aging temperature is about 260°C. Applications are those where all other elastomers are unsuitable. In terms of properties (chemical and heat resistance) FFKM is the closest thing to a universal elastomer. FFKM can be used for highly critical oilfield parts and in the chemical industry for parts which have to stand up to highly corrosive chemicals and extreme temperatures. The price, relative to other elastomers is extremely high and molding of Kalrez compounds is usually performed by specialists.


Reference: An Introduction to Rubber Technology by Andrew Ciesielski 1999

Hydrogenated Nitrile HNBR (HSN)


This is a relatively new elastomer, making its first appearance in 1984. The symbol for the generic material is HNBR, although HSN is sometimes used in literature, standing for highly saturated nitrile. It has all the attributes of NBR plus a very much higher heat resistance, dependent on the grade chosen. It also has very good weather and abrasion resistance, plus good mechanical strength. It is used in oilfields where it has resistance to amine corrosion inhibitors and better hydrogen sulfide resistance than NBR. It has established itself in automotive applications for timing belts, gaskets and o-rings, where higher temperature resistant elastomers are needed. Peroxide cured HNBR has heat aging resistance up to 150°C, based on around 1,000 hours, while sulfur donor cured HNBR temperature resistance might drop to 135°C. Cost is somewhat less than conventional fluorocarbon rubber (FKM) on a weight basis, also since the density (using g/cm', which approximates to specific gravity) of HNBR is about half that of FKM, more products can be made for the same weight purchased.

Reference: An Introduction to Rubber Technology by Andrew Ciesielski 1999

Fluorocarbon rubber FKM (FPM)


In the United States fluorocarbon rubber is well known by its trade name of Viton (Based on vinylidene fluoride and hexafluoro-propylene the grades available differ in the chemical building blocks which were used to construct the polymer. Like silicone rubber, FKM has excellent high temperature resistance with an upper continuous heat aging temperature limit of 205°C. DuPont literature quotes continuous dry heat service to be >3,000 hours at 232°C decreasing to >48 hours at 316 0C. At the opposite end of the scale Nagdi points out that conventional FKM is usually serviceable at temperatures down to -20°C in dynamic applications, while for static use the temperature can be lower, although this will depend on the grade chosen. A primary variable in FKM grades is the level of fluorine in the elastomer molecule, FKMs being fluorohydrocarbons. Terpolymers tend to have higher fluorine content than copolymers and therefore have better resistance to various media. In general, fluoroelastomers have excellent resistance to oxidation, ozone, fuels and petroleum oils and are resistant to most mineral acids at high concentrations. Although FKM has good resistance to many chemicals, excessive swelling occurs in some polar solvents such as low molecular weight ethers, esters and ketones. Chemicals such as alkalis and amines should be used with caution, with standard fluorocarbon grades, especially at higher temperatures because alkalis harden the general purpose FKM, which will eventually embitter and then crack. FKM has a tendency to self extinguish when a flame is removed. This is of benefit in situations where the results of a fire would be catastrophic, for example in a coal mine. Other elastomers might burn out of control, when the source of the originating flame (such as methane gas explosion) is removed. Applications for FKM include automotive fuel hose liners and seals and flue duct expansion joints, where high temperatures and acidic products from gas desulfurization are involved. The relative cost of FKM is high, also a high specific gravity (around 1.8) means less cured product (volume) per unit weight A recent addition to the FKM family is an 'alloy' of a polar ethylene copolymer with a fluoroelastomer which optimizes cost, oil and heat resistance.

Reference: An Introduction to Rubber Technology by Andrew Ciesielski 1999

Silicone Rrubber MQ MPQ MVQ and MPVQ

As you can see, a number of symbols have been designated for significant variations within the silicone rubber family. The reader may refer to ASTM D 1418 for abbreviations for elastomeric materials. Since all of the symbols for silicone rubber end in Q, this is the convention that will be used for silicone rubber in general. Most elastomers have a carbon main chain, while Q has a silicone oxygen backbone. Silicone has an upper continuous heat aging temperature in the region of 205°C. Caprino and Macander give a table of estimated service life for Q as follows: 40 years at 90°C, 2-5 years at 200°C and two weeks at 315 °C. Moisture, such as might be found in a poorly ventilated environment, can be a problem at high temperature. Silicone is among the best elastomers for both high and low temperature resistance. PVMQ heads the low temperature list at around -100°C. Silicone rubber has excellent ozone, weather resistance and electrical insulation. Like CR, Q has a measure of flame retardant ability. Mechanical properties such as tensile strength, are low, but change very little when measured at higher temperatures; at 150°C, it is catching up with other elastomers. Oil resistance is about the same as that of CR, acid and alkali resistance are not good. Applications include aerospace, medical, food contact, and automotive ignition cable. The cost of the raw gum elastomer is higher than any of the rubbers mentioned so far.

Reference: An Introduction to Rubber Technology by Andrew Ciesielski 1999

Sunday, April 19, 2009

Butyl Rubber IIR and Halobutyl Rubber CIIR and BIIR


Butyl rubber is a copolymer of isobutylene and isoprene, hence IIR. Its grades vary in isoprene content and viscosity, which is related to molecular weight. If a halogen, such as chlorine or bromine, is introduced into the polymer architecture, it becomes CIIR or BIIR, respectively. IIR has some properties similar to those of EPDM, such as good mineral acid and base resistance (like EPDM some concentrated mineral acids are a problem), and weather resistance which is similar to that of EPDM. IIR has excellent resistance to permeability by gases. For example, Fusco mentions its permeability to air being as low as 10% that of NR, at 65°C. Like EPDM, the polarity of IIR is low which means poor resistance to petroleum oils and conversely low swell in many polar solvents, such as ketones. Resilience is poor, which translates to good damping ability. The upper continuous heat aging temperature limit is around 121°C, which can be distinctly improved with IIR compounds containing resin (polymethylol-phenol) cure systems. For low temperature properties the vulcanizate becomes stiff and leathery at around -18°C, although it is not brittle until around -70 0C, Applications naturally following from these properties include mounts and bumpers for vibration and shock prevention, roof and tank linings, curing bladders and inner tubes for tires. A significant use is inner liners for tubeless tires, where halobutyl is preferred due to improved interply adhesion with the rest of the inner tire. Halobutyls can be blended with unsaturated elastomers such as NR, whereas for IIR it is not recommended. Blending is not recommended for IIR since the rate of cure of the 'other elastomer' in the blend is often much faster than the rate of cure of the IIR, resulting in under cured IIR in the blend. IIR and halobutyl are used for pharmaceutical closures using high purity zinc oxide as the curative. Zinc oxide, is 'generally regarded as safe' by the United States Food and Drug Administration, i.e., has historically been in common use in contact with food or skin for many years without ill effect. Recent elastomer modifications (from Exxon) are p-methylstyrenelisobutylene copolymers, which have the low permeability and high damping of IIR with the environmental and aging resistance of EPDM, and 'star branched' butyls, which have improved processing properties, prior to cure.

Reference: An Introduction to Rubber Technology by Andrew Ciesielski 1999

Thursday, April 16, 2009

Nitrile NBR


To the chemist this rubber is known as acrylonitrile butadiene rubber, to others it is called Buna-N but to many people in the industry, simply, nitrile. It is the workhorse of the marketplace for its oil resistant properties. The grades offered differ in the percentage of acrylonitrile (ACN) in the polymer chain as well as the overall viscosity of the polymer. The higher the amount of ACN in the elastomer the better the oil resistance; the lower end of the ACN distribution range being approximately equivalent to the oil resistance of CR and therefore only having a moderate level of oil resistance. NBR also has superior fuel resistance. The terms oil and fuel used here refers loosely to those products derived from petroleum. The weather resistance of NBR is poor, similar to NR and SBR, although it can be enhanced by blending with the plastic, polyvinyl chloride (PVC), at some 'cost' to its low temperature properties. This latter attribute of NBR also varies with ACN content; the lower the percentage of ACN in the polymer, the better the low temperature flexibility, and the poorer the oil resistance. A compound which has a nitrile raw gum elastomer in it, with a medium (33%) ACN content would have good oil resistance and low temperature resistance down to the region of -40°C. A low ACN (18%) nitrile would be useful down to -55°C. NBR has better heat aging resistance than CR and is in the region of 107°C for continuous (defined approximately as 1,000 hours) use. Special compounding ingredients can be added to increase heat aging resistance. Like SBR, NBR needs reinforcing fillers to give good mechanical properties.

NBR use is dominant in the oilfield, used in blowout preventions, packers and seals. However, sour gas wells containing hydrogen sulfide and amine corrosion inhibitors have been a problem for NBR based components because both chemicals can degrade nitrile elastomers causing embrittlement. The other major use for NBR is in the automotive sector. However, as 'under the hood' temperatures increase with reduced airflow and smaller engine compartments, NBR producers are searching for ways of increasing this elastomer's upper region of heat aging resistance. The term sour gas is also used in automotive applications, but here it means hydro peroxides (rather than hydrogen sulfide), which sometimes form in unleaded gasoline; this can be damaging to the 'average' NBR. Very high ACN NBR or NBRJPVC might be used in this situation. The use of alcohol (methanol and ethanol) in gasoline, the so called oxygenated fuels, has made NBR processors look very closely at the effect of such a mixture on this elastomer, since alcohol concentrations at a certain level (around 10%) could be a problem. The alcohol causes NBR in contact with the gasoline alcohol blend to swell significantly. Blends above 5% should be treated with caution unless a resistant rubber type is used. It is worth noting that many applications of NBR exclude contact with oxygen (from the surrounding air), since the product is immersed in oil. This can increase the heat aging resistance temperature mentioned above. NBR is a distinctly polar rubber; hence it’s excellent resistance to non polar petroleum oils. This also means that NBR has poor resistance to polar liquids such as ketones, esters, chlorinated solvents, and highly aromatic solvents such as benzene
and toluene.

Reference: An Introduction to Rubber Technology by Andrew Ciesielski 1999 Page 18

Sunday, April 12, 2009

Some Types of Rubbers and their Properties

BUTYL RUBBER (IIR)

BUTYL RUBBER (IIR) has very low permeability rate, good electrical properties, resistance to weathering and Ozone.

TEMP: ­400C to 1200C

Chemical Resistance: Hot Water, Steam, Ozone, Ageing, & Weather Resistance, Silicon Oil & Grease.

POLYTETRAFLUOROETHYLENE (PTFE­TEFLON ®)

PTFE exhibits outstanding chemical resistance to the harshest media, Non flammable, inert, self lubricating are some of its special properties.

TEMP: ­2000C to 2600 C

Other Filled grades of PTFE viz. BRONZE, CARBON, GLASS, MOS2 have better mechanical properties than virgin PTFE.

NATURAL RUBBER (NR)

The oldest rubber available having outstanding resistance to tear, abrasion and cut growth.

Chemical Resistance: Water Oxidation, Alcohol and Ketones, Moderate Resistance to Acids, Alkalis.

O­Rings are manufactured from over 15 different Polymers which include Nitrile (NBR), Fluorocarbon (Viton®), Silicon (VMQ), Fluorosilicone (FVMQ), Polyurethane, PTFE (Teflon®), Natural Rubber (NR), Ethylene Propylene (EPDM), Hydrogenated Nitrile Rubber (H­NBR), Carboxylated Nitrile Rubber(X­NBR), Styrene Butadiene Rubber (SBR), Perfluoroelastomer (FFKM), Chloroprene (Neoprene®).

ETHYLENE PROPYLENE RUBBER (EPDM)

EPDM is a Co­Polymer of Ethylene and Propylene and is mostly used in Break systems having Glycol based Fluids.

TEMP: ­550C to 1500C

Chemical Resistance: Hot Water and Steam, Glycol based brake fluids, Organic And Inorganic Acids, Phosphate Ester Based Fluids, Soda, Potassium, Silicon Oil and Grease, Ozone, Aging and weather resistant.

O­Rings are manufactured from over 15 different Polymers which include Nitrile (NBR), Fluorocarbon (Viton®), Silicon (VMQ), Fluorosilicone (FVMQ), Polyurethane, PTFE (Teflon®), Natural Rubber (NR), Ethylene Propylene (EPDM), Hydrogenated Nitrile Rubber (H­NBR), Carboxylated Nitrile Rubber(X­NBR), Styrene Butadiene Rubber (SBR), Perfluoroelastomer (FFKM), Chloroprene (Neoprene®).


ACRYLONITRILE BUTADIENE (NBR ­NITRILE)

Nitrile Rubber (NBR) is the general term for Acrylonitrile Butadiene Polymer. Acrylonitrile content varies from 18 to 50%. Higher the Acrylonitrile content, better the resistance to fuel and oil, at the same time affecting elasticity & compression set.

TEMP: ­300C to 1000C

Chemical Resistance: Propane, Butane, Petroleum, Mineral Oil, Grease, Diesel Fuel, Fuel Oils, HFA, HFB, HFC Fluids, Dilute Acids, Alkali, Salt Solutions and Water.

CARBOXYLATED NITRILE (XNBR)

Carboxylated Nitrile has proven tear and abrasion resistance compared to NBR. It is often used for dynamic applications.

TEMP: ­300C to 1000C

HYDROGENATED NITRILE (HNBR)

NBR compounds exhibits improved heat resistance to the general NBR compounds. They also possess superior mechanical properties particularly high strength.

TEMP: ­400C to 1500C

FLUOROCARBON (FKM ­VITON ®)

FLUOROCARBON (FKM ­VITON ®) has excellent resistance to High temperature, Ozone, Oxygen, Mineral Oils, Aliphatic and Aromatic Hydrocarbons and many chemicals.

TEMP: ­200C to 2040C

Chemical Resistance: Mineral Oil, Grease, Non Flammable Hydraulic Fluids, Aliphatic and Aromatic Hydrocarbons, Ozone Weathering, Aging, High Vacuum, Steam and Alcohol.

O­Rings are manufactured from over 15 different Polymers which include Nitrile (NBR), Fluorocarbon (Viton®), Silicon (VMQ), Fluorosilicone (FVMQ), Polyurethane, PTFE (Teflon®), Natural Rubber (NR), Ethylene Propylene (EPDM), Hydrogenated Nitrile Rubber (H­NBR), Carboxylated Nitrile Rubber(X­NBR), Styrene Butadiene Rubber (SBR), Perfluoroelastomer (FFKM), Chloroprene (Neoprene®).

SILICON (VMQ)

Silicon has best Cold flexibility, Excellent heat resistance, Good Insulating properties, Good Ozone and weathering resistance, as well being neutral in its properties.

TEMP: ­500C to 232 0C Chemical Resistance: Ozone, Aging, Weathering, Animal & Vegetable oil, Grease, Moderate Resistance to Mineral Oil.


FLUOROSILICONE (FVMQ)

Fluorosilicone (FVMQ) offers improved fuel and oil resistance in comparison to regular Silicon (VMQ), Mechanical and Physical properties being the same. TEMP: ­700C to 1750C

POLYURETHANE (AU)

POLYURETHANE have the highest Wear resistance, Tensile strength and Elasticity. They have high volume applications in seals for hydraulic cylinders.

TEMP: ­300C to 800C

Chemical Resistance: Ozone, Aging, Mineral Oil, Aliphatic Hydrocarbons, Water (upto 500C)

STYRENE­BUTADIENE RUBBER (SBR)

SBR previously known as ' BUNA S' was first produced as a replacement to natural rubber.

TEMP: ­400C to 1050C

Chemical Resistance: Water, Alcohol, Non­Mineral Oil fluid, Silicon oil and Grease, Weak Acids.

O­Rings are manufactured from over 15 different Polymers which include Nitrile (NBR), Fluorocarbon (Viton®), Silicon (VMQ), Fluorosilicone (FVMQ), Polyurethane, PTFE (Teflon®), Natural Rubber (NR), Ethylene Propylene (EPDM), Hydrogenated Nitrile Rubber (H­NBR), Carboxylated Nitrile Rubber(X­NBR), Styrene Butadiene Rubber (SBR), Perfluoroelastomer (FFKM), Chloroprene (Neoprene®).

CHLOROPRENE RUBBER (CR ­NEOPRENE®)

Chloroprene popularly known as NEOPRENE exhibits good Ozone, Aging, chemical, Abrasion & Flex Fatigue Resistance.

TEMP: ­400C to 1200C

Chemical Resistance: Silicon Oil And Grease, Water and its solvents, Refrigerants, Ammonia and Carbon Dioxide, Ozone, Weathering and Aging.

CHLOROSULFONATED POLYETHYLENE (CSM ­HYPALON ®)

Chlorine in the Polymer imparts resistance to Flame and Mineral Oils and also improves cold flexibility. TEMP: ­200C to 1200C Chemical Resistance: Oxidising Media, Water, Aging, Grease, Many Acids.


PERFLUOROELASTOMER (FFKM)

PERFLUOROELASTOMER (FFKM) exhabits unique resistance even in the harshest environments. It exhabits unbeatable resistance to Acids, Alkalis, Steam, Ketones.

TEMP: ­250C to 3000C

Chemical Resistance: Aliphatic, Aromatic and Chlorinated Hydrocarbons, Organic And In­Organic Acids, Water, Steam and Vacuum.

TETRAFLUOROETHYLENE ­PROPYLENE (TFP­E)

TFE­P has excellent chemical resistance to a wide range of materials

TEMP: ­50C to 2320C

Chemical Resistance: Bases, Engine Oil, Steam, Radiation, Amines Phosphate Esters.

O­Rings are manufactured from over 15 different Polymers which include Nitrile (NBR), Fluorocarbon (Viton®), Silicon (VMQ), Fluorosilicone (FVMQ), Polyurethane, PTFE (Teflon®), Natural Rubber (NR), Ethylene Propylene (EPDM), Hydrogenated Nitrile Rubber (H­NBR), Carboxylated Nitrile Rubber(X­NBR), Styrene Butadiene Rubber (SBR), Perfluoroelastomer (FFKM), Chloroprene (Neoprene®).