FFKM - Perfluoroelastomers
Perfluoroelastomers (FFKM) are the elastomeric form of poly(tetrafluoro ethylene) or PTFE. These elastomers have a fully fluorinated backbone. They are copolymers of tetrafluoroethylene and a perfluorinated ether such as perfluoromethylvinylether (PMVE). Thus, the backbone includes oxygen atoms that are part of the ether groups which provide elasticity. Depending on the type of the ether (marked by the length of the side chain), the fluorine content varies. To vulcanize FFKM, small amounts of a cross-linkable monomer (CSM) are introduced. These are typically cyano-functional vinyl ethers.
FFKM elastomers fill an important niche for applications involving aggressive chemicals at temperatures up to 325°C. They are the most chemically resistant elastomers available on the market and have outstanding high temperature and chemical resistance. They also have excellent steam, ozone and weathering resistance and very low gas permeability. Furthermore, they have a high reliability for static and dynamic loads due to their very low compression set. Some disadvantages are poor abrasion resistance and only moderate mechanical properties that deteriorate rapidly at elevated temperatures, and at temperatures below 0°C. They also have a much higher coefficient of thermal expansion than other elastomers such as NBR or FKM, which could lead to considerable stress at elevated temperatures if expansion of the seal/ O-ring is restricted. Another drawback is their very high price.
COMMERCIAL FFKM Elastomers
Important manufacturers and suppliers of perfluoroelastomers (FFKM) are DuPont, Parker, Solvay, and PPE.
FFKM’s are one of the most expensive elastomer. Typical applications include core sleeves, gaskets, O-rings in chemical processing equipment for applications where the parts are exposed to harsh environments and high temperatures. Some grades are suitable for continuous use at 325°C (620°F), with chemical resistance being almost universal and unrivaled by any other elastomer.