FKM

FKM, or fluorinated rubber, is a family of fluorocarbon-based elastomers used primarily for seals, gaskets, and other highly demanding elastomeric parts. The main base polymers are copolymers of vinylidene fluoride (VDF) and hexafluoropropylene (HFP); terpolymers that include tetrafluoroethylene (TFE) are also common. A related group, known as perfluoroelastomers (FFKM or FEPM), contains higher fluorine content and provides enhanced chemical resistance for extremely aggressive media. FKM materials are widely marketed under brand names such as Viton.

FKM elastomers are distinguished by high temperature stability, excellent resistance to oils, fuels, hydrocarbons, and many solvents, and low permeability to gases. Continuous service temperatures typically range from about -20°C to 200–250°C, with specialized grades approaching higher temperatures. They maintain good elasticity and compression set characteristics in demanding environments and offer broad chemical compatibility, making them popular for dynamic and static sealing applications.

Processing and performance considerations vary by grade. FKM is generally cured using specialized cure systems rather than sulfur-based cures, and processing requires appropriate equipment and controls due to the materials’ chemical resistance and curing behavior. Availability spans a range of hardness, fluorine content, and fluorinated co-monomers, enabling formulations for automotive, aerospace, chemical processing, oil and gas, and some food and pharmaceutical applications (including FDA-compliant grades).

Limitations include higher cost compared with many other elastomers, reduced flexibility at very low temperatures for some grades, and susceptibility to swelling or degradation in certain polar solvents and ketones. Choosing the right grade depends on the specific chemical exposure, temperature, and mechanical requirements of the application.