Material Guide: FKM

Learn what FKM rubber is, its advantages, disadvantages, typical uses, and applications.

What is FKM rubber?

FKM (Fluoroelastomer) is a type of synthetic rubber known for its excellent resistance to chemicals, oils, and heat. It’s a high-performance elastomer that’s often used in applications where traditional rubber materials cannot withstand extreme conditions.

Fluorinated polymers contain chemically inert fluorine-carbon bonds that deliver a high level of resistance to chemicals. By the latter stages of the 1950s, FKM types 1 and 2 were commercially available offering increased chemical resistance. The fluorine content increased dramatically from around 26.7% (for the precursor to FKM) to 66% – 68%.

Depending on the type of FKM, the chemical composition varies to give differing characteristics. Varying amounts of VF2 (2-fluoroethene), HFP (hexafluoropropylene), TFE (tetrafluoroethylene), PAVE/PFVE (perfluoro (methyl vinyl ether)), ethylene and propylene are combined resulting in a range of material properties. Further details on the types of FKM can be found below.

FKM was originally developed during this time under the name Viton™ by DuPont, though it is now owned by Chemours. It was created to meet the increasing demands of the aerospace industry. Today, Viton™ remains one of the most popular brands of FKM, but TRP supply a range of non Viton™ FKM’s for a wider range of properties including high hot tear resistance and low temperature grades.

Polymer design has continued to improve due to a greater understanding of the polymer architecture.

What are the advantages of FKM rubber?

Excellent compression set

  • FKM rubber maintains its shape and sealing properties even after prolonged compression at elevated temperature.

High-temperature resistance

  • FKM rubber can withstand temperatures ranging from -55°C to 200°C (-4°F to 392°F).
  • For short time periods, a higher service temperature may be applied.

Good resistance to chemicals

  • FKM rubber is resistant to a variety of chemicals, including acids, fuels, oils, and industrial solvents.

High mechanical strength

  • FKM rubber offers good mechanical properties, including flexibility and resilience.
  • It can also be formulated for explosive decompression resistance and for use in food processing including with CIP & SIP systems and FDA compliance.

Low permeability

  • Low permeability is a key property of FKM rubber. This makes it suitable for applications where sealing against fluids is critical.
  • TRP have developed a novel FKM material that has half the typical permeability of an FKM in high temperature sea water.

What are the disadvantages of FKM rubber?

Cost

  • FKM has a higher initial cost than non-fluorinated hydrocarbons.

Which applications use FKM rubber?

Due to its high resistance to chemicals, oils, and heat, FKM rubber is widely used in a number of industries and applications. They include:

 

  • Aerospace – FKM rubber is used in aircraft and spacecraft for seals, gaskets, and O-rings because of its ability to withstand high temperatures and extreme conditions. TRP have formulated materials to meet various standards for aerospace seals, such as MIL specs, SAE specs and DTD 5612A.

 

  • Automotive – Seals, gaskets, and O-rings are also used in the automotive industry due to their excellent oil and fuel resistance. It is widely used in motor sport applications including Formula 1 engines.

 

  • Chemical processing & transport – As a rubber for chemical processing, Fluoroelastomers are used for seals and gaskets that come into regular contact with corrosive chemicals. Specifying FKM can reduce the need for changing seals as it can be used with a far wider range of chemical than cheaper alternatives.

  • Oil and gas – Oil and gas applications use FKM rubber for seals and gaskets in pipelines, valves, drilling equipment, pipelines, and other components that are regularly exposed to aggressive fluids and high temperatures. TRP offers RGD-resistant oil seals and O-rings, approved to NORSOK M-710 and ISO 23936-2.

 

  • Pharmaceutical and food processing – Due to its high chemical resistance and the ability to meet stringent hygiene standards, FKM rubber is used in equipment and machinery in pharmaceutical and food processing applications. TRP offer food-safe polymers in grades approved to 21CFR177.2600 (d, e & f), EC1934/2004 and USP Class 6.

 

  • Military and defence – FKM rubber is also used in a wide variety of military and defence applications, including with vehicles and aircraft where durability and reliability are absolutely essential.

Frequently asked questions about FKM

  • Are Viton™ and FKM the same?

    Viton™ is a type of FKM. Viton™ was the original name for FKM when it was first created in the 1950s by DuPont but is now owned by Chemours. While Viton™ and FKM are sometimes used interchangeably, Viton™ refers to a specific brand of FKM supplied by Chemours, while FKM refers collectively to the material type.

  • What are the types of FKM?

    The primary types of FKM are:

    • Type 1 – These FKMs contain 66% fluorine content and are formed using vinylidene fluoride (VDF) and hexafluoropropylene (HFP). These are good for general-purpose use across various industries.
    • Type 2 – These have a fluorine content between 68 and 69% and are created using VDF, HFP, and tetrafluoroethylene (TFE). These are good for use with fuels and oils, having an enhanced resistance to heat and chemicals.
    • Type 3 – Type 3 FKM contains a fluorine content between 62 and 68%. Formed with VDF, TFE, and perfluoro (methyl vinyl ether) (PMVE), they offer better low-temperature flexibility in comparison to other copolymers and terpolymers.

  • What compounds of FKM are available at TRP?

    TRP have a vast range of FKM compounds, please see our material datasheets for more information. The grades offered include:

    • F214 – This compound offers a temperature range of -55°C to 200°C and is suitable for use with many fuels, oils, and chlorinated solvents.
    • F366 – As a black, bisphenol-free fluorocarbon compound, F366’s high resistance to sterilisation in place (SIP) and clean in place (CIP) processes make it an ideal option for food production applications.
    • F131 – A Viton™ FKM, Daisy 80 is suited for nuclear seals with an impressive temperature range of -15°C to 200°C and high chemical resistance.

Contact our Engineers

For further information, please contact one of our technical experts today, and we will be pleased to offer advice and guidance.

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