What is FKM?

FKM is a fluoroelastomer that is also referred to as Viton®, Viton® FKM or FPM. They are all one and the same.

  • FKM is the American standard ASTM short form name for Fluoroelastomer.
  • Viton® is a registered trademark of Du Pont, the original developers of the rubber.
  • FPM is the DIN/ISO international abbreviation (1629 standard) for Fluoroelastomer

This family of highly fluorinated carbon-based polymers can be divided into different classes on the basis of chemical composition, fluorine content or their cross-linking mechanism. They are predominantly designed for very high temperature operation and have grown to major importance in the sealing industry.

There are standard and special grades which provide flexibility for custom properties such as:

  • improved low temperature resistance
  • chemical compatibility
  • temperature range
  • low compression set
  • excellent ageing characteristics
  • good oil resistance
  • resistance to arduous conditions with petroleum fuels and mineral-based hydraulic fluids and many solvents.

However the trade-off is, that at high temperatures, they become weaker. They also have limited resistance to steam, hot water, methanol and other highly polar fluids. Trade names include Fluorel®, Viton® and Technoflon®.

One of the special grades we refer to on our site is Viton® Extreme (ETP -600s).  Whilst this is more expensive than standard compounds it is a lot cheaper than FFKM and can compete with some of these polymers in specific chemical exposure applications.

Stainless steel washers bonded to FKM
Stainless steel washers bonded to ETP-600S (Viton Extreme) for arctic aircraft refueling station

What is FKM commonly used for?

  • Aerospace – Today, the vast majority of the world’s commercial and military aircraft depend on the reliability and performance of FKM and FFKM based seals and parts. Seals fabricated with FKM are routinely used in turbine engines, auxiliary power units and hydraulic actuators. This include O-rings used in line fittings, connectors, valves, pumps and oil reservoirs.
  • Food & dairy – FKM,  EPDM & Silicone materials can be suitable where seal failure can lead to potential contamination or line stoppages. Compliance with CIP (Cleaning In Place), SIP (Sterilization In Place) and regulations such as FDA, 3-A, NSF and USP standards can also be achieved.
  • Instrumentation & Electronics – semiconductor manufacturers recognise the quality of FKM for its characteristics to resist a wide range of corrosive chemicals, while subjected to high temperatures during wafer fabrication.
  • Medical –  pumps, tanks, valves, heat exchangers and equipment cleaned using clean-in-place and sterilize-in-place regimes.
  • Motorsport & Specialist Automotive – Fuel seals, head and intake manifold gaskets, quick-connect o-rings, fuel injection seals.
  • Subsea, Oil & Gas – Seals are critical elements within oil and gas systems with HP/HT safety demands and strong resistance to rapid gas decompression requirements.

Fluoroelastomer (FKM) Rubber Property Specifications

Hardness: Shore A
50 – 95
Tensile Strength PSI
500 – 2,000
Tear Resistance
Fair to good
Impact Resistance
Compression Set
Good to excellent
Low Temperature
High Temperature
Intermittent High Temperature
Weather and Sunlight
Good to excellent
Abrasion Resistance
Solvent Resistance
Oils and Gasoline
Adhesion to Metals
Good to Excellent

Rubber materials expertise

The information provided here is only a guide to the primary characteristics and uses of FKM. The relationship between material, product performance and blend options is complex.

At DP Seals we pride ourselves on being able to provide specialist advice in selecting and developing exactly the right blend of materials to meet a vast range of performance requirements.

However we also maintain a large quantity and variety of quality raw materials in stock, enabling us to offer fast turnaround and provide for tight deadlines.

Below you’ll find many free resources to help you think about material selection and we are always on hand to discuss your requirements and provide expert advice.

Find out more about our most commonly used FKM & FFKM materials

Free Resources