Rubber Compounds of O-Rings - Viton, Neoprene, EPDM, Nitrile

Rubber Compounds O Rings

Rubber Compounds of O-Rings

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N Nitrile E EPDM C Neoprene G SBR S Silicone B Butyl  
O Polyacrylate H Hypalon V Viton P Polyurethane F Fluorosilicone A Aflas K Chemraz

Nitrile (Buna-N, NBR)

Nitrile rubber is the general term for acrylonitrile butadiene terpolymer. The acrylonitrile content of nitrile sealing compounds varies considerably (18% to 50%) and influences the physical properties of the finished material. The higher the acrylonitrile content, the better the resistance to oil and fuel. At the same time, elasticity and resistance to compression set is adversely affected. In view of these opposing realities, a compromise is often drawn, and a medium acrylonitrile content selected. Nitrile has good mechanical properties when compared with other elastomers and high wear resistance. Nitrile is not resistant to weathering and ozone.
Heat resistance

  •     Up to 212°F (100°C) with shorter life at 250°F (121°C).


Cold flexibility

  •     Depending on individual compound, between –30°F and –70°F (–34°C and –57°C).


Chemical resistance

  •     Aliphatic hydrocarbons (propane, butane, petroleum oil, mineral oil and grease, diesel fuel, fuel oils) vegetable and mineral oils and greases
  •     HFA, HFB and HFC fluids
  •     Dilute acids, alkali and salt solutions at low temperatures
  •     Water (special compounds up to 212°F (100°C)).

Not compatible with:

  •     Fuels of high aromatic content (for flex fuels a special compound must be used)
  •     Aromatic hydrocarbons (benzene)
  •     Chlorinated hydrocarbons (trichlorethylene)
  •     Polar solvents (ketone, acetone, acetic acid, ethyleneester)
  •     Strong acids
  •     Brake fluid with glycol base
  •     Ozone, weather and atmospheric aging.

 

EPDM (Ethylene Propylene, EPM)

EPM is a copolymer of ethylene and propylene. Ethylenepropylene-diene rubber (EPDM) is produced using a third monomer and is particularly useful when sealing phosphate-ester hydraulic fluids and in brake systems that use fluids having a glycol base.
Heat resistance

  •     Up to 300°F (149°C) (max. 400°F (204°C) in water and/or steam).


Cold flexibility

  •     Down to approximately –70°F (–57°C).


Chemical resistance

  •     Hot water and steam up to 300°F (149°C) with special compounds up to 400°F (204°C)
  •     Glycol based brake fluids up to 300°F (149°C)
  •     Many organic and inorganic acids
  •     Cleaning agents, soda and potassium alkalis
  •     Phosphate-ester based hydraulic fluids (HFD-R)
  •     Silicone oil and grease
  •     Many polar solvents (alcohols, ketones, esters)
  •     Ozone, aging and weather resistant.


Not compatible with:

  •     Mineral oil products (oils, greases and fuels).

 

Neoprene (Chloroprene, CR)

Neoprene was the first synthetic rubber developed commercially and exhibits generally good ozone, aging and chemical resistance. It has good mechanical properties over a wide temperature range.
Heat resistance

  •     Up to approximately 250°F (121°C).


Cold flexibility

  •     Down to approximately –40°F (–40°C).


Chemical resistance

  •     Paraffin base mineral oil with low DPI, e.g. ASTM oil No. 1
  •     Silicone oil and grease
  •     Water and water solvents at low temperatures
  •     Refrigerants
  •     Ammonia
  •     Carbon dioxide
  •     Improved ozone, weathering and aging resistance compared with nitrile rubber.


Limited compatibility

  •     Naphthalene based mineral oil (IRM 902 and IRM 903 oils)
  •     Low molecular aliphatic hydrocarbons (propane, butane, fuel)
  •     Glycol based brake fluids.


Not compatible with:

  •     Aromatic hydrocarbons (benzene)
  •     Chlorinated hydrocarbons (trichloroethylene)
  •     Polar solvents (ketones, esters, ethers, acetones).

 

SBR (Styrene-Butadiene)

SBR probably is better known under its old names Buna S and GRS (government rubber styrene.) SBR was first produced under government control between 1930 and 1950 as a replacement for natural rubber. The basic monomers are butadiene and styrene, with styrene content approximately 23.5%. About one third of the world output of SBR is used in tire production. SBR is mostly used in seals for non-mineral oil based brake fluid applications. Heat resistance

  •     Up to approximately 225°F (107°C).


Cold flexibility

  •     Down to approximately –70°F (–57°C).


Compatible with:

  •     Water, alcohol, glycol and certain ketones (acetone)
  •     Non-mineral oil based brake fluid
  •     Silicone oil and grease
  •     Diluted water solutions, weak acids.


Not compatible with:

  •     Mineral oils
  •     Petroleum greases and fuels
  •     Aliphatic hydrocarbons like benzene, toluene, xylol
  •     Chlorinated hydrocarbons - such as chloroform, trichlorethylene, carbon tetrachloride
  •     Oxidizing media like nitric acid, chromic acid, hydrogen peroxide, chlorine, bromine.

 

Silicone (VMQ)

The term silicone covers a large group of materials in which vinyl-methyl-silicone (VMQ) is often the central ingredient. Silicone elastomers as a group have relatively low tensile strength, poor tear and wear resistance. However, they have many useful properties as well. Silicones have good heat resistance up to 450°F (232°C), good cold flexibility down to –75°F (–59°C) and good ozone and weather resistance as well as good insulating and physiologically neutral properties.
Heat resistance

  •     Up to approximately 400°F (204°C) (special compounds up to 450°F (232°C)).


Cold flexibility

  •     Down to approximately –75°F to –65°F (–59°C to –54°C) with special compounds down to –175°F (–115°C).


Chemical resistance

  •     Engine and transmission oil (e.g.: ASTM oil No.1)
  •     Animal and vegetable oil and grease
  •     Brake fluid (non-petroleum base)
  •     Fire-resistant hydraulic fluid, HFD-R and HFD-S
  •     High molecular weight chlorinated aromatic hydrocarbons (including flame-resistant insulators, and coolant for transformers)
  •     Moderate water resistance
  •     Diluted salt solutions
  •     Ozone, aging and weather resistant.


Not compatible with:

  •     Superheated water steam over 250°F (121°C)
  •     Acids and alkalis
  •     Low molecular weight chlorinated hydrocarbons (trichloroethylene)
  •     Aromatic mineral oil
  •     Hydrocarbon based fuels
  •     Aromatic hydrocarbons (benzene, toluene).

 

Butyl (IIR)

Butyl rubber is produced by many companies in different types and varies widely in isoprene content. Isoprene is necessary for proper vulcanization. Butyl has a very low permeability rate and good electrical properties.
Heat resistance

  •     Up to approximately 250°F (121°C).


Cold flexibility

  •     Down to approximately –75°F (–59°C).


Chemical resistance

  •     Hot water and steam up to 250°F (121°C)
  •     Brake fluids with glycol base
  •     Many acids (see Fluid Compatibility Table)
  •     Salt solutions
  •     Polar solvents, e.g. alcohols, ketones and esters
  •     Poly-glycol based hydraulic fluids (HFC fluids) and phosphate-ester bases (HFD-R fluids)
  •     Silicone oil and grease
  •     Ozone, aging and weather resistant.


Not compatible with:

  •     Mineral oil and grease
  •     Fuels
  •     Chlorinated hydrocarbons.

 

Polyacrylate (ACM)

ACM or simply acrylate rubber consists of a polymerized ester and a curing monomer. Ethyl acrylate rubber has a good resistance to heat and mineral oil; on the other hand butyl acrylate has a better cold flexibility. Polyacrylate has a good resistance to mineral oil, oxygen and ozone even at high temperatures. The water compatibility and cold flexibility of ACM are significantly worse than with NBR.
Heat resistance

  •     Shortened lifetime up to approximately 350°F (177°C).


Cold flexibility

  •     Down to approximately –5°F (–21°C).


Chemical resistance

  •     Mineral oil (engine, gear box, ATF oil)
  •     Ozone, weather and aging resistance.


Not compatible with:

  •     Glycol based brake fluid
  •     Aromatics and chlorinated hydrocarbons
  •     Hot water, steam
  •     Acids, alkalis, amines.

 

Hypalon (Chlorosulfonated Polyethylene, CSM)

The polyethylene polymer contains additional chlorine and sulfur groups. Chlorine gives the material resistance to flame and mineral oil and also improves the cold flexibility.
Heat resistance

  •     Up to 250°F (121°C).


Cold flexibility

  •     Down to approximately –20°F (–29°C).


Chemical resistance

  •     Many acids
  •     Many oxidizing media
  •     Silicone oil and grease
  •     Water and water solvents
  •     Ozone, aging and weathering resistance.


Limited compatibility

  •     Low molecular aliphatic hydrocarbons (propane, butane, fuel)
  •     Mineral oil and grease
  •     Limited swelling in aliphatic oils (ASTM oil No. 1)
  •     High swelling in naphthene and aromatic base oils (IRM 902 and IRM 903 oils)
  •     Polar solvents (acetone, methyl ether, ketone, ethyl acetate, diethyl ether, dioxane)
  •     Phosphate-ester based fluids.


Not compatible with:

  •     Aromatic hydrocarbons (benzene)
  •     Chlorinated hydrocarbons (trichloroethylene).

 

Viton (Fluorocarbon, FKM)

Fluorocarbon rubber has excellent resistance to high temperatures, ozone, oxygen, mineral oil, synthetic hydraulic fluids, fuels, aromatics and many organic solvents and chemicals. Low temperature resistance is normally not favorable and for static applications is limited to approximately –15°F (–26°C) although in certain situations it is suitable down to –40°F (–40°C). Under dynamic conditions, the lowest service temperature is between 5°F and 0°F (–15°C and –18°C). Gas permeability is very low and similar to that of butyl rubber. Special fluorocarbon compounds exhibit an improved resistance to acids, fuels, water and steam.
Heat resistance

  •     Up to 400°F (204°C) and higher temperatures with shorter life expectancy.


Cold flexibility

  •     Down to –15°F (–26°C) (some to –40°F (–40°C)).


Chemical resistance

  •     Mineral oil and grease, low swelling in ASTM oil No. 1, and IRM 902 and IRM 903 oils
  •     Non-flammable hydraulic fuels in the group HFD
  •     Silicone oil and grease
  •     Mineral and vegetable oil and grease
  •     Aliphatic hydrocarbons (fuel, butane, propane, natural gas)
  •     Aromatic hydrocarbons (benzene, toluene)
  •     Chlorinated hydrocarbons (trichlorethylene and carbon tetrachloride)
  •     Fuels, also fuels with methanol content
  •     High vacuum
  •     Very good ozone, weather and aging resistance.


Not compatible with:

  •     Glycol based brake fluids
  •     Ammonia gas, amines, alkalis
  •     Superheated steam
  •     Low molecular organic acids (formic and acetic acids).

 

Polyurethane (AU, EU)

One must differentiate between polyester urethane (AU) and polyether urethane (EU). AU type urethanes exhibit better resistance to hydraulic fluids. Polyurethane elastomers, as a class, have excellent wear resistance, high tensile strength and high elasticity in comparison with any other elastomers. Permeability is good and comparable with butyl rubber.
Heat resistance

  •     Up to approximately 180°F (82°C).


Cold flexibility

  •     Down to approximately –40°F (–40°C).


Chemical resistance

  •     Pure aliphatic hydrocarbons (propane, butane, fuel)
  •     Mineral oil and grease
  •     Silicone oil and grease
  •     Water up to 125°F (50°C) (EU type)
  •     Ozone and aging resistant.


Not compatible with:

  •     Ketones, esters, ethers, alcohols, glycols
  •     Hot water, steam, alkalis, amines, acids.

 

Fluorosilicone (FVMQ)

Fluorosilicone rubber contains trifluoropropyl groups next to the methyl groups. The mechanical and physical properties are very similar to silicone rubber. However, fluorosilicone offers improved fuel and mineral oil resistance but poor hot air resistance when compared with silicone.
Heat resistance

  •     Up to 350°F (177°C) max.


Cold flexibility

  •     Down to approximately –100°F (–73°C).


Chemical resistance

  •     Aromatic mineral oils (IRM 903 oil)
  •     Fuels
  •     Low molecular weight aromatic hydrocarbons (benzene, toluene).

 

Aflas (Tetrafluoroethylene Propylene, FEPM)

This elastomer is a copolymer of tetrafluoroethylene (TFE) and propylene. Its chemical resistance is excellent across a wide range of aggressive media.
Heat resistance

  •     Up to approximately 450°F (232°C).


Cold flexibility

  •     Down to approximately 25°F (–4°C).


Compatible with:

  •     Bases
  •     Phosphate esters
  •     Amines
  •     Engine oils
  •     Steam
  •     Pulp and paper liquors.


Not compatible with:

  •     Aromatic fuels
  •     Ketones
  •     Carbon tetrachloride.

 

Chemraz (Perfluoroelastomer, FFKM)

The name "perfluoroelastomer" is somewhat misleading. An actual perfluorinated material with a high molecular weight is polytetrafluoroethylene or PTFE which has the chemical formula "(CF2)n." The molecular carbon chain is shielded by the chemical inertness of the large bonded fluorine atoms. Perfluoroelastomer is produced by the copolymerization of tetrafluoroethylene (TFE) and a perfluorinated ether, e.g. perfluoromethylvinylether (PMVE). The differing resistance to volume swell of the different perfluoroelastomers is due to the perfluorinated ether element, where the side-chain can consist of up to four perfluorinated carbon atoms. The extraordinary chemical resistance is partly due to the fluorine atoms shielding the carbon chain, and partially due to the vulcanization system.
Heat resistance

  •     450°F to 600°F (232°C to 316°C) depending on compound.


Cold flexibility

  •     0°F to –15°F (–18°C to –26°C).


Chemical resistance

  •     Aliphatic and aromatic hydrocarbons
  •     Chlorinated hydrocarbons
  •     Polar solvents (acetone, methylethylketone, ethylacetate, diethylether and dioxane)
  •     Inorganic and organic acids
  •     Water and steam
  •     High vacuum with minimal loss in weight.


Not compatible with:

  •     Fluorinated refrigerants (R11, 12, 13, 113, 114, etc.).
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