Fluororcarbon, FKM, Viton ® Rubber Compounds

Fluorocarbon, often referred to as Viton ®, rubber offers 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.

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 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.

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1 – Depends on time and service condition.