Fluoropolymers / Alfa Chemistry

Structure and performance of FFKM

  • Perfluoroelastomers (FFKM) represent a special subgroup of fluorocarbon elastomers, which are essentially rubber derivatives of polytetrafluoroethylene (PTFE).
  • FFKMs are based on the copolymerization of perfluoromethyl vinyl ether (PMVE) and other perfluoro (alkoxy/alkyl) vinyl ethers with TFE monomers. Perfluoro (alkoxy/alkyl) vinyl ethers form the most stable bond after PTFE. The glass transition temperature (Tg) and crystallinity depend on the type and quantity of these monomers. The typical Tg range of TFE/PMVE copolymers is -25 to 25°C. Compared with other elastomers, the Tg of FFKM is relatively high. Care must be taken in applications that use FFKM at operating temperatures close to or equal to Tg, and cyclic applications at temperatures close to or below Tg.
  • The thermal stability of fluorocarbon elastomers also depends on their molecular structure. Perfluorinated copolymers, such as those of TFE and PMVE, are thermally stable at temperatures up to 300°C. In addition, with heat aging, this FFKM becomes more elastic rather than brittle. The thermal stability of FFKM is much higher than that of fluorocarbon elastomers that contain hydrogen in their structure. For example, the long-term maximum use temperature of FFKM is 315°C, while the long-term maximum use temperature of fluoroelastomers (FKM) is 215°C.
  • Operating temperature range of fluoroelastomersFigure 1. Operating temperature range of fluoroelastomers [1]

  • FFKM have almost unparalleled resistance to many chemicals other than fluorinated solvents. But they will be adversely affected by hydraulic oil, diethylamine, and fuming nitric acid, resulting in elastomer swelling of 41%, 61%, and 90%, respectively.


  • FFKM can be used for sealing parts of semiconductor wafer processing equipment, which need to function in harsh chemical environments and process temperatures of 25 to 300 °C. FFKM has extraordinary chemical and heat resistance, allowing it to withstand almost any process medium, including reactive plasmas with temperatures up to 316 °C. In addition, these seals provide cleanliness and pollution-free, maintain the sealing function in corrosive media, but also need to withstand "wet" and "dry" process chemistry applications including etching, ashing, peeling, copper plating and chemical vapor deposition.
  • Comparison of the weight loss percentage of FFKM, FKM and silicone rubber in reactive plasmaFigure 2. Comparison of the weight loss percentage of FFKM, FKM and silicone rubber in reactive plasma [2]

  • Seals used in the food and beverage manufacturing and processing industries need to cope with a series of harsh conditions and must also comply with many hygiene standards and regulations. Among them, for very high temperature applications, FFKM may be the most suitable elastomer material choice.

Table 1. Comparison of commonly used elastomers and their applicability in different foods [3]

  Suitability for use
Material typeMaterial description Dry food Aqueous food Fatty food
CRChloroprene rubber**
NBRAcrylonitrile butadiene rubber**
VMQSilicone rubber**

Note: √Generally suitable; *Could be suitable, dependent on grade.


  1. Jiri George Drobny, Technology of Fluoropolymers, 2009, p97.
  2. Shuhong Wang, John M. Legare, Journal of Fluorine Chemistry 122 (2003) 113–119.
  3. Nathan Peel, Sealing Technology 2008 (2008) 11-14.
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