FKM Compounds

Common Name: Viton®, FKM
Chemical Name: Fluorocarbon
ASTM D1418 Designation: FKM

General Characteristics

Hardness Range (Shore A): 60-90
Tensile Strength Range (psi): 500-2000
Elongation (Max %): 130-300
Compression Set: Good
Resilience-Rebound: Fair
Abrasion Resistance: Good
Tear Resistance: Good
Solvent Resistance: Excellent
Oil Resistance: Excellent
Low Temperature: -10°F
High Temperature: 400°F to 600°F1
Aging, Weathering-Sunlight: Excellent

Advantages

  • Resistant to a wide range of chemicals, fuels, oils and solvents specifically aliphatic and aromatic solvents, halogenated hydrocarbons, acids, animal and vegetable oils.

Disadvantages

  • Not recommended for food applications or exposure to aromatic hydrocarbons.
  • Not recommended for keytones, low molecular weight esters and nitro containing compounds.

Fluorocarbon (FKM) rubbers offer increased oil, solvent and chemical and heat resistance than other common elastomers. FKM (Type A) O-rings are readily available off the shelf in black or brown color.

FKM’s heat resistance makes it optimal for application that exceed +400°F temperatures and where excellent chemical resistance is required. Because FKM is a saturated compound, no double bonding between atoms, it offers excellent resistance to sunlight, weathering and ozone. FKM is used in a variety of demanding aerospace, industrial and automotive application. FKM is commonly used in O-rings, seals, gaskets, liners, hoses, diaphragms.

FKM compounds are classified into 4 categories, Type A, B F and Specialty compounds. Types A, B and F are a saturated co- or terpolymer of vinylidene fluoride (VF2), hexafluoropropylene (HFP), tetrafluoroethylene (TFE) with a bisphenol cure. A, B and F have 66%, 68% and 70% fluorine content respectively. As the fluorine content increases so does the fluid resistance, however, compression set and low temperature flex resistance decreases.

The specialty types are a terpolymer of VF2, TFE, perfluoromethylvinylester (PMVE)and propylene  with a peroxide cure.

Fluorocarbon Types

  • Type A is a copolymer of vinylidene fluoride and  hexafluoropropylene with a bisphenol cure and contains around 66% fluorine content.
  • Type B is a terpolymer of vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene with a bisphenol cure and contains around 68% fluorine content.
  • Type F is a terpolymer of vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene with a bisphenol cure and contains around 70% fluorine content.
  • Specialty Types GB, GF, GLT, GFLT are a terpolymer of VF2, TFE, perfluoromethylvinylester (PMVE)and propylene with a peroxide cure.

Viton® is a registered trademarks of DuPont Dow Elastomers.

1 – Depends on time and service condition.

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