FKM and FPM Elastomer

Fluorine Kautschuk Material (FKM) is related to fluorocarbon-based elastomer materials defined by ASTM International standard D1418 and ISO standard 1629. FKM polymer is made from vinylidene monomers (VDF) with a high concentration of fluorine and carbon-based monomers. It is commonly called fluorine rubber or fluoro-rubber. FKM and FPM are interchangeable abbreviations that often refer to the same family of fluorocarbon-based materials. In some countries, FPM is a more commonly used abbreviation. At ERIKS, we give priority to the ISO abbreviation: FKM.

Fluorocarbon elastomers have grown to major importance in the sealing industry. Due to its wide range of chemical compatibility, temperature range, low compression set, and excellent ageing characteristics, fluorocarbon rubber is one of the most significant single elastomers developed in recent history. 

FKM and the Viton™ brand

FKM was originally developed by DuPont and Chemours under the brand name Viton™. Now several FKM manufactures exist, and some have their own brand names: Dai-El (Daikin), and Tecnoflon (Solvay). People often ask for ‘’viton’’, when they are specifically looking for the Viton™ brand. Dyneon®/Fluorel® (3M) is also a well known fluoroelastomer, but will be retracted from the market by 2025.

If you are looking for fluorine rubber materials for use in high-tech industries where low outgassing and low particle emissions of the materials are required, for example in the optics or semicon industries, then have a look at our SCVBR® offering. 

FKM materials differ from each other by:

  • Polymer structure: copolymer (two monomers), terpolymer (three monomers) or tetrapolymer (four monomers).
  • Fluorine content
  • Chemical composition
  • Curing agent

 

Generally, with increasing fluorine content, resistance to chemical attack is improved while low temperature characteristics are diminished. There are, however, specialty grade fluorocarbons that can provide high fluorine content with low temperature properties. 

The differences have a significant impact on chemical resistance and temperature performance. The ASTM D1418 designation is a way of categorizing FKMs, but they are often named as type A-B-F-GF-GLT (type names defined by Chemours for the Viton™ brand).

ASTM D1418

Common Used Names

Cure System

Fluorine Content %

Description

ASTM D1418

Type 1

Common Used Names

Viton™ A

Cure System

Bisphenol or amine

Fluorine Content %

66 %

Description

General purpose with good compression set

ASTM D1418

Type 2

Common Used Names

Viton™ B, F or GF

Cure System

Bisphenol, amine or peroxide

Fluorine Content %

66-70 %

Description

Improved solvent, coolant and hot water resistance

ASTM D1418

Type 3 

Common Used Names

Viton™ GLT

Cure System

Peroxide

Fluorine Content %

64-67 %

Description

Improved low-temperature resistance, but reduced chemical resistance

ASTM D1418

Type 4

Common Used Names

Aflas®

Cure System

Peroxide

Fluorine Content %

55 %

Description
ASTM D1418

Type 5

Common Used Names

Viton™ ETP

Cure System

Peroxide

Fluorine Content %

67 %

Description

Improved resistance to amines

ASTM D1418

-

Common Used Names

Ultra-Low Temp

Cure System

Peroxide

Fluorine Content %

66 %

Description

Improved low-temperature resistance compared to Type 3

Strengths & Limitations

Temperature Resistance

  • Low temperatures to -50°C (depending on the type)
  • High temperatures: +200°C (higher peaks)

 

Chemical & Aging Resistance

Strengths

  • Strong organic and inorganic acids and bases (except low-molecular acids such as formic and acetic acids)
  • Most vegetable and mineral oils and fats
  • Ozone, UV, and sunlight
  • Mineral-oil-based hydraulic fluids
  • Alkali, mildly acidic
  • Low temperatures up to -50°C for special types of FKM LT material

 

Limitations

  • Steam resistance (for Type I and Type A copolymers)
  • MEK resistance
  • Range of solvents. Check out our Chemical Resistance Guide below.
  • Unstable with regard to low-molecular organic acids such as formic and acetic acids
  • Low-temperature resistance for Type 1 and Type A copolymers

 

Material Comparison

  • FKM has better mineral oil and grease resistance
  • FKM offers much higher temperature resistance
  • FKM A type has less low temperature resistance
  • FKM displays much better overall chemical resistance
  • FKM has much better ageing resistance in ozone, UV, and sunlight

  • FKM offers less steam resistance
  • FKM has less overall chemical resistance
  • FKM exhibits reduced resistance at higher temperatures
  • FKM has lower overall cost

  • FKM provides better overall chemical resistance
  • VMQ has much better low temperature flexibility

 

FEPM Compound Overview

Ask Our Specialists

For more information on Fluoro-elastomers or one of our other o-ring materials, please contact one of the ERIKS Sealing & Polymer locations or fill out the form below.

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