Outstanding resistance to heat, weather, ozone, oxygen and oxidisers. Very low gas permeability. PPE FKM (FPM) seal materials includecopolymer, terpolymer and tetrapolymer grades and bisphenol and peroxide cure systems.
FKM elastomers are highly fluorinated polymers containing few compounding ingredients. They are stable at very high temperatures (they can withstand 200°C / 400°F indefinitely, in service). By comparison, conventional elastomers would become brittle in 24 hours at this temperature, in air. FKM vulcanisates, in general, have outstanding resistance to oxygen, ozone, weather, flame and oxidative chemicals, and excellent resistance to swelling in a wide variety of media. However, they are not compatible with polar solvents (e.g. M.E.K.), some organic acids (e.g. Formic acid), certain methanol and ester based hydraulic fluids (e.g. Skydrol), ammonia and some amines. They are suitable in high-energy radiation environments up to about 106 Rads. Special grades of FKM may be required for use in hot water and steam applications.
FKM elastomers provide high compression set resistance if compounded with bisphenol cure systems. Generally they are serviceable down to –30°C, but specialist grades (such as Endura® V91A) can provide effective sealing down to –45°C. Electrical insulation properties are not particularly outstanding, but would be adequate for sheathing wher elevated temperatures, ozone, chemical and flame resistance are required (e.g. shaft seals, O-rings and gaskets, diaphragms and cable sheathing).