Rubberrubber

Fluoroelastomer (FKM)

The chemical elastomer. Handles the fuels, hot oils and acids that swell everything else on this list, and costs roughly five to ten times what nitrile does per kilogram.

Stock forms — Sheet, moulded washer section and extruded cordtmoulded or calenderedsheetODCSwasher⌀ dcord
Fluoroelastomer (FKM) — stock formsSymbols only — no stock sizes are published

Properties

Family
Rubber
Category
rubber
Density
1.85 g/cm³ · 1850 kg/m³

Densityhow fluoroelastomer (fkm) compares

Density of Fluoroelastomer (FKM) — 1.85 g/cm³Fluoroelastomer…1.85Water1.00Aluminium2.700369g/cm³
1.85 g/cm³ — 1850 kg/m³Water 1.00 · Aluminium 2.70

Rubber propertiesFluoroelastomer (FKM / Viton family) · family range, not a compound guarantee

ASTM designation
FKM · D2000 HK
Shore A hardness
70 · the sealing default, selected for the gland rather than the polymer
Service temperature
-26 to 204 °C · -15 to 399 °F
Typical media
Fuels, hot oils, acids, aggressive chemistry

Family screening range from Parker O-Ring Handbook ORD 5700, §2.2 — the range for the polymer family, not for any one compound. Within a family the filler and cure system move the limit by tens of degrees, so the compound data sheet governs the finished part.

The grey figures are converted at °F = °C × 9/5 + 32; the Celsius numbers are the published ones.

Applicationswhere fluoroelastomer (fkm) is normally specified

Engine and fuel system sealsChemical process sealsHot oil serviceAerospace sealsSemiconductor equipment

Service & sealingtrade experience, not measured values

Oil & fuel
Excellent at temperature — hot oils, fuels and lubricants that destroy nitrile above about 100 °C.
Weather & ozone
Excellent. Weathering, ozone and ageing are not the constraint; cold is, on the standard grades.
Sealing
Static and dynamic seals in engine, fuel, chemical and semiconductor service. Use it where the media would kill everything else on this list, and budget for it accordingly.

These lines are not measurements: no units, no single source. They describe how the family is generally found to behave — which media it survives and what it will seal — rather than what any one compound is guaranteed to do. The media a joint will meet decides the family before the temperature does.

Practical notes

  • Viton is a Chemours trademark for one family of FKM — not a synonym for all of them
  • Densest of the common rubbers, by a wide margin
  • Poor low-temperature performance for the price; check the end of the range first

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