Material Descriptions

Temperature Range: -30°F (-34°C) to 250°F (121°C)

Hardness (Shore A) Range: 40 to 90

Also Know As: Buna-N, Breon, Butakon®, Chemigum®, Hycar®

Class: BF, BG, BK, CH

ESP Recommended Shelf Life: 15 Years

Description: Nitrile is the combination of butadiene and acrylonitrile. Butadiene provides elasticity and low temperature flexibility, resistance to heat, chemicals and oxidation. Acrylonitrile provides hardness, tensile strength and creates resistance to abrasion, fuel and oil. A standard general-purpose nitrile compound usually contains 34% ACN (Acrylonitrile).

Advantages: Excellent tensile strength, abrasion, tear and compression resistance. It is used in water and steam applications (below 212°F), petroleum oils and fuels, silicone oils and greases, propane, ethylene glycol, butane, vegetable, mineral oils and greases, and dilute acids.

Disadvantages: Low resistance to ozone, sunlight and weathering. Incompatible with benzene, toluene, xylene, halogen derivatives (carbon tetrachloride, trichloroethylene), ketones (MEK, acetone), phosphate ester hydraulic fluids (Skydrol, Pydraul), strong acids and glycol.

Polytetrafluoroethylene (PTFE, Teflon) offers superior chemical resistance to oils, solvents, acids and salts. High temperature resistance and low friction are also advantages compared to other elastomers.

With the addition of appropriate fillers, PTFE has excellent mechanical properties, favorable for applications where low lubrication could be a problem.

Fluorocarbon (Viton, Fluorel, Kel-F) elastomers are selected for high underlip temperatures and excellent chemical resistance. Fluorocarbon carries the ASTM designation of FKM and is covered by the ASTM D2000 / SAE J200 - HK classification.

Low temperature resistance is not favorable for dynamic applications. For temperatures below -30°F (-34°C) an alternate elastomer should be selected.

Fluorocarbon elastomers have good resistance to the swelling and deteriorating effects of aromatic solvents, aliphatic hydrocarbons, halogenated hydrocarbons such as carbon tetrachloride, trichloroethylene, diester oils, silicate ester oils, petroleum oils, and many mineral acids. They are also highly recommended in applications involving ozone combined with heat, as in electric motors and electrical equipment.

Fluorocarbons are not recommended for use with highly polar fluids such as hydrazine, ketones, phosphate esters like Skydrol, anhydrous ammonia, low-molecular- weight esters and hot hydrofluoric or chlorosufonic acids.

Polyacrylate elastomers are most commonly selected for higher operating temperatures or extreme pressure (EP) lubricants. Polyacrylate carries the ASTM designation ACM and is covered by the ASTM D2000 / SAE J200 - DF, DH or EH classification.

The main advantage Polyacrylate has over Nitriles is a higher temperature range and additional resistance to ozone and weather attack.

It is not compatible with glycol based brake fluids, aromates, chlorinated hydrocarbons, hot water / steam, acids, alkalis, amines and is not to be used in dry running applications.

Silicone elastomers are generally selected for use in low friction, high temperature applications. Silicone carries the ASTM designation of VMQ and is covered by ASTM D2000 / SAE J200 - FC, FE or GE classifications.

Silicone elastomers are compounded from dimethyl silicone polymers, and will deteriorate if used with silicone oils or greases. Various additives have extended the functional temperature range of silicone rubber beyond any other elastomer. Flexibility below -175° F and service above 700°F for short periods of time have been demonstrated.

Silicone is recommended for the following media: engine and transmission oil; animal and vegetable oils and greases; high molecular weight chlorinated aromatic hydrocarbons; diluted salt solutions and water.

It is not compatible with hydrocarbon based fuels; aromatic hydrocarbons; acids and alkalis; steams and oxidized oils.

Ethylene Propylene is not commonly used in the radial shaft seal industry because of its chemical reaction to oils, greases, and fuels. It is however extremely effective for glycol based brake fluids and phosphate ester hydraulic oils. Ethylene Propylene carries the ASTM designation of EP or EPDM and is covered by the ASTM D2000 / SAE J200 - CA, BA, AA or DA classifications.

EPDM is compatible with alcohols; ketones; esters; organic and inorganic acids; cleaning agents; glycol based brake fluids; hot water / steam.

Hydrogenated Nitrile (HNBR) is a synthetic polymer that results from the hydrogenation of Nitrile rubber. The affect is an increase resistance to lip hardening at higher temperatures. It also provides improved tensile strength, abrasion and ozone resistance. HNBR should not be used in low temperature applications.

Carboxylated Nitrile (XNBR) is a syntetic polymer compounded for highly abrasive operating conditions. It is used for applications involving abrasive materials such as scale, sand, grit or other abrasive material that is likely to collect at the point of shaft contact. Carboxylated nitrile has many of the same fluid compatability characteristics as nitrile.