Material

FKM / FPM (Fluoroelastomer)

FKM (fluorocarbon elastomer), widely known by the trade name Viton®, is a fluorine-containing synthetic rubber engineered for aggressive chemical and thermal service. With outstanding resistance to mineral oils, fuels, acids, and temperatures up to 200°C continuous, FKM is the go-to elastomer when NBR reaches its limits. FITCO supplies standard, low-temperature and peroxide-cured FKM compounds selected for chemical compatibility, explosive decompression resistance and continuous-service temperature.

FKM O-rings built for chemical and high-temperature service.

Material Data Sheet

Temperature range

-20°C to +200°C (short excursions to +230°C; special low-temp grades to -40°C)

Hardness range

55–90 Shore A

Tensile strength

10–17 MPa

Elongation

150–300%

Compression set

15–25% (70 h at 200°C)

Resists

Mineral & vegetable oils, fuels, aromatic & chlorinated solvents, many acids, ozone, weathering, UV

Avoid with

Ketones, esters, amines, hot water/steam (standard grades), low-molecular-weight organic acids

Standards

AS568, ISO 3601, BS 1806, JIS B2401

Performance

Key advantages of FKM

Chemical Resistance

Excellent resistance to mineral oils, fuels, aromatic and chlorinated solvents, many inorganic acids, and a broad range of industrial chemicals. Significantly wider chemical compatibility than NBR or EPDM.

High-Temperature Service

Continuous service up to 200°C with short excursions to 230°C. Excellent aging characteristics — maintains seal force and elasticity over years of high-temperature operation.

Weather & Ozone

Outstanding resistance to ozone, oxygen, sunlight, and weathering. Rated excellent for outdoor and UV-exposed applications where NBR would crack and fail.

Low Compression Set

Maintains sealing force over time with low compression set values, ensuring reliable long-term performance in critical sealing applications under sustained loading.

Vacuum Compatibility

Very low gas permeability makes FKM ideal for high-vacuum applications, semiconductor equipment, and systems requiring minimal outgassing.

Regulatory Compliance

Available in FDA 21 CFR 177.2600, USP Class VI, 3-A Sanitary, and WRAS approved grades for food, pharmaceutical, and potable water applications.

Compound Grades

FKM types and selection

Grade	Type	Key Feature	Typical Application
Viton A / FKM Type 1	Dipolymer (66% fluorine)	General-purpose, good fuel resistance	Automotive, general industrial
Viton B / FKM Type 2	Terpolymer (68% fluorine)	Better chemical resistance than Type A	Chemical processing, oil & gas
Viton GBL-S	Peroxide-cured	Superior steam and amine resistance	Sour-gas service, refinery
Viton GFLT	Low-temperature	Flexible down to -40°C	Cold-start automotive, Arctic service
Viton Extreme ETP	Specialty	Broad fluid and base resistance	Aggressive mixed-chemical service

FITCO also supplies equivalent FKM compounds from Daikin (Dai-El) and 3M/Dyneon, allowing us to match the exact fluid resistance, temperature floor and regulatory approval your application requires.

Limitations

Where FKM is not recommended

Ketones & Esters

Standard FKM grades swell significantly in ketones (acetone, MEK), esters, and low-molecular-weight organic acids. Use FFKM for these media.

Amines & Alkalis

Standard bisphenol-cured FKM is attacked by amines and strong alkalis. Peroxide-cured grades (GBL-S type) offer improved resistance but are not universal.

Hot Water & Steam

Standard FKM grades show limited resistance to hot water and steam above 150°C. EPDM or specialty peroxide-cured FKM should be specified instead.

Cost

FKM is 5–10× the cost of NBR. Where petroleum oils are the only concern and temperature is below 120°C, NBR is the more economical choice.

Applications

Where it's used

Oil & Gas

Downhole and surface seals, wellhead equipment, BOP seals, pipeline fittings, compressor seals — anywhere petroleum products, H₂S or high temperatures are present.

Automotive

Fuel injector seals, emission control systems, turbocharger seals, transmission seals, exhaust gas recirculation (EGR) systems, and engine oil seals.

Aerospace

Fuel system seals, hydraulic actuator seals, engine seals, and environmental control system components requiring high-temperature chemical resistance.