FKM rubbers are available in various grades, which differ mainly in the polymer composition and fluorine content. In combination with the cure system (diamines, bisphenol or peroxides) the properties of the compound can be influenced to meet the requirements of the application. In general FKM has an outstanding resistance to high temperatures, it’s elastomeric properties in hot air are maintained up to 204°C with peak temperatures up to 300°C. FKM elastomers exhibit excellent resistance to swelling in a wide variety of oils, fuels, solvents and chemicals.

They are recommended for:

• Petroleum oils and hydrocarbon fuels

• Organic ester based lubricants

• Silicate ester based lubricants

• Aromatic hydrocarbons (benzene, toluene, xylene)

• Halogenated hydrocarbons (trichloroethylene, carbon tetrachloride)

Despite their excellent resistance to a wide variety of fluids, there are certain chemicals that severely attack FKM compounds.

The use of FKM elastomers is not recommended for:

• Polar solvents, ketones (acetone, MEK) and esters (ethyl acetate)

• Low molecular weight organic acids (formic acid, acetic acid)

• Hot water and steam, unless compounded with lead oxide

• Skydrol fluids

• Glycol based automotive brake fluids

• Anhydrous ammonia and amines

• Hot hydrofluoric or chlorosulphonic acids

The fluid resistance of FKM types improves with increasing fluorine levels. However, as the fluorine content increases the low-temperature flexibility of the polymer decreases, and a compromise must be made between fluid resistance and low temperature flexibility of the final vulcanizate. The low-temperature properties of conventional FKM elastomers are, in general, moderate. For low-temperature applications special FKM types have been developed.