This is a class of synthetic rubber designed for very high temperature operation. FKM provide extraordinary levels of resistance to chemicals, heat and oil, while providing useful service life above 200°C. FKM are not a single entity but a family of fluoropolymer rubbers. Fluoroelastomers or FKM can be classified by their fluorine content, 66%, 68%, & 70% respectively. This means that FKM rubber having higher fluorine content have increasing fluids resistance derived from increasing fluorine levels.

Properties of Fluoroelastomers (FKM)

• They have excellent resistance to chemical attack by oxidation, by acids and by fuels.
• They have good oil resistance.
• They have limited resistance to steam, hot water, methanol, and other highly polar fluids.
• The outstanding heat stability and excellent oil resistance are due to the high ratio of fluorine to hydrogen, the strength of the carbon-fluorine bond, and the absence of unsaturation.
• The latest FKM polymers have a much broader fluids resistance profile than standard fluoroelastomers.
• They are able to withstand strong bases and ketones as well as aromatic hydrocarbons, oils, acids, and steam.
• Peroxide cured fluoroelastomers have inherently better water, steam, and acid resistance.

Application
FKM provides premium, long-term reliability even in harsh environments. A list of its applications is given below:

• Aerospace
  • O-ring seals in fuels, lubricants
  • Valve stem seals
  • Fuel hoses
  • Fuel Injector O-rings
  • In tank and quick connect
  • Flue duct exp. Joints
  • Valve liners
  • Roll covers
  • Sheet stock/cut gaskets
• Automotive
  • Shaft seals
  • Check valve balls
  • Diaphragms
  • Military flare binders
  • Electrical connectors
  • Tire valve stem seals
  • Clips for jet engines
  • Lathe cut gaskets
• Industrial
  • Hydraulic o-ring seals and hydraulic systems
  • Manifold gaskets
  • Fuel tank bladders
  • Firewall seals
  • Engine lube siphon hose fuel system seals
  • Gaskets (valve & manifold)

Viton
Viton® is a registered trademark for fluroelastomer by DuPont Performance Elastomers L.L.C. This fluoroelastomer was introduced in 1957 to meet the requirements in the aerospace industry for a high-performance elastomer. The use of Viton® has spread quickly to many other industries, including the fluid power, automotive, appliance and chemical industries. Viton® is the most specified fluoroelastomer, well known for its excellent heat resistance, excellent resistance to aggressive fuels and chemicals. This popular fluroelastomer has worldwide ISO 9000 and ISO/TS 16949 registration.

Conclusion
FKM is of high value in use as a class of synthetic rubber which provides extraordinary levels of resistance to chemicals, oil and heat. This type of rubber can be fabricated into seals, o-rings, and hoses for a variety of high performance applications in the automotive, aerospace, and petrochemical industries.