FKM; aka Viton®

Clwyd Compounders have been at the forefront of fluoroelastomer compounding for over 30 years. We have a dedicated internal mixer and mixing line for fluoroelastomer compounds which benefits from our decades of experience, improving the process, to provide the most consistent compound on the market.

Fluoroelastomers are often considered to be a single polymer type, but fluoroelastomers can be further subdivided on the basis of their monomer type(s). Different fluoroelastomer subtypes offer different compound properties (dependent on their constituent monomers and cure systems), which can lead to significant differences in compound performance. This large family of elastomers include polymers that are capable of resisting oils, methanol, caustic or corrosive chemicals, steam and extremes of temperatures (as low as -50°C or as high as 320°C). As fluoroelastomer specialists, we can help guide you to the most suitable fluoroelastomer subtype for your needs.


  • Excellent chemical resistance
  • Outstanding thermal stability


  • Restricted low temperature capability

Typical Applications

  • ‘O’ Ring Applications
  • Seals for automotive fuel lines
  • Hydraulic pumps

FFKM; aka Kalrez®

The ultimate elastomer for applications where only outstanding performance is good enough; suitable for use over a temperature range of -40 to 320°C.

Applications include:

  • Seals for cabinets used in the manufacture of semiconductors, where plasma resistance is essential
  • Reaction column seals for the chemical industry
  • Deep well drilling applications, requiring prolonged performance at temperatures > 250°C and resistance to high pressure steam and amines
  • Food industry applications where there is a requirement for high performance whilst undergoing high pressure steam cleaning


  • Exceptional chemical resistance in harsh conditions
  • Thermal stability from -25°C to 320°C
  • Ultimate in sealing performance


  • Poor compression set
  • Can be difficult to process

All perfluoroelastomers compounds are produced in a dedicated clean room facility, and vacuum packed into foil bags for dispatch to avoid contamination.

Clwyd Compounders have extensive experience of compounding these materials, and will take into account the full range of factors which may affect compound performance under these extreme conditions, so that you can order these very expensive materials with confidence.