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What is FKM and FFKM rubber?

Among the other rubber classes, fluoro-elastomers (FKM or FPM and FFKM) show the best properties in terms of resistance to fire and to chemical agents due to the high content of fluorine and to the intrinsic stability of the carbon-fluorine bond. Commercial grades of fluoro-elastomers are obtained from the radical polymerization of vinyl monomers. The most common are: difluoroethylene (VDF), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoromethylvinylether (PMVE), 2-methoxyethylvinyl ether (MOVE), ethylene and propylene. The proper polymer in-chain dosing of groups with different steric hindrance and properties together with the employment of specific terminal chains allow modulating mechanical properties, their behavior at low temperature, chemical resistance, the type of reticulation and processability. Fluroelastomer-based formulations are generally characterized by the use of non‑ or weak‑reinforcing fillers, both carbon blacks and white fillers, and by a low content of process aids.

performance additives scientist

Properties of Fluoro-elastomers (FKM/FFKM)

These are some of the properties of fluoro-carbon rubber compounds:

  • Steady service temperature up to +320°C 
  • Dynamic employment at low temperatures up to -45°C with some specific grades
  • High compatibility with all type of fuels
  • Excellent resistance to blow-by condensates
  • High resistance to solvents, oils, acids and bases, both organic and inorganic
  • Low gas permeability
  • Excellent dielectric properties
  • High resistance to fire

Material processing

Fluoro-carbon rubber compounds are generally processed through compression or injection moulding depending on the type of article. Frequently, fluoro-elastomers are overmolded on metal parts. Another typical application is the preparation of hoses and tubes, by means of extrusion or wrapping and autoclave curing. The complex macromolecular architecture permits taking advantage of ionic reticulation mechanism using appropriate diamines or bisphenol curatives combined with specific activators, or radical reticulation mechanism using appropriate organic peroxides.

What is FKM & FFKM rubber typically used for?

Typical applications for fluoro-elastomers (FKM/FFKM) compounds

  • O-ring for fuel distribution, lubricant and chemical agents
  • Rotary shaft seals
  • Manifold seals
  • Valve seals
  • Gaskets
  • Hoses and tubes for fuel and lubricant systems
  • Turbo charge hoses
  • Fuel tank bladders
  • Rolls
  • Component parts for the semiconductor industry
FKM and FFKM automotive rubber compounds

Rubber Application Matrix

HEXPOL’s rubber compounds can be used in a variety of different applications. Download our Application Matrix to see which compounds can fit your application.

Rubber Application Matrix

Contact Us to discuss FKM & FFKM

Sara Cotelli

High Performance Compounding, Europe, Middle East, Asia, and India
+39 (0) 35 42 52 000
Gary Moore

Gary Moore

Advanced Rubber & High Performance Compounding, Americas
+1 682 215 7096
Marc Pignataro

Marc Pignataro

Advanced Rubber & High Performance Compounding, Americas
+1 440 391 4318

High performance compounds

Learn more about typical high performance polymers in our material range.

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