FKM (Viton)
A fluorinated rubber for heat and chemicals
Typical values for the temper in the title
FKM (fluoroelastomer, trade name Viton) resists high temperatures (about 200 °C and above in continuous service, per the database), oils and fuels, many chemicals, ozone and weather. It is the common material for seals when NBR is no longer enough.
It is used for seals in engines, the chemical and oil industries, pumps and valves, fuel systems and semiconductor fabs. Drawbacks: high cost, poor cold flexibility (in standard grades), and sensitivity to hot water, steam, ketones and amines.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 7-17 MPa | |
| Elongation A | 150-350% | |
| Density ρ | 1.80-1.85 g/cm³ | |
| Max service temperature | 200°C | |
| Machinability | Die-cut / Molded | relative rating in the site database |
Structure and family
| Feature | Value | Meaning |
|---|---|---|
| Type | fluoroelastomer | heat and chemical resistance |
| ASTM D1418 code | FKM | |
| Typical hardness | Shore A 60–90 | by compound |
Typical values per producer data.
Grades and versions
In rubber, the polymer type is chosen first (by fluid and temperature), then hardness (Shore A) and compound. In ASTM D2000 the code gives the service temperature (first letter) and oil resistance (second letter).
| Version | Properties | When to choose it |
|---|---|---|
| Standard FKM | heat and oils | most uses |
| Low-temperature FKM | flexible at lower temperatures | aerospace, outdoors |
| FFKM (perfluoro) | extreme chemical resistance, very expensive | harsh chemicals, semiconductors |
Applications
- Engine seals
- Chemical and oil industry seals
- Pump and valve seals
- Fuel systems
- Semiconductor fabs
Fabrication
Suitable for
Oils, fuels, many acids, aromatic and chlorinated solvents, ozone, heat.
Not suitable for
Hot water and steam (standard grades), ketones (such as acetone), amines, glycol-based brake fluid, extreme cold.
Production
Molding and curing (vulcanization), die-cutting from sheet, or extrusion. Machining rubber is not common.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| NBR (Nitrile, Buna-N) | 15-25 MPa | — | NBR: cheap, for lower heat · material page |
| EPDM | 7-20 MPa | — | EPDM: for steam and water, not oil · material page |
| Silicone (VMQ) | 4-10 MPa | — | silicone: for cold and heat, mechanically weak · material page |
Common mistakes
Using standard FKM in steam
It is damaged. For steam, EPDM or a special grade.
Using it with acetone or ketones
It swells.
Installing in extreme cold
It hardens and loses sealing. For cold, a special grade.
Equivalents, standards and supply
| ASTM | D1418: FKM / D2000: HK |
|---|---|
| DIN | ISO 1629: FKM |
| Standards | ASTM D2000 HK / ASTM D1418 / ISO 1629 |
| Forms | O-rings · seals · gaskets |
| Producers | Chemours Viton · Daikin · 3M Dyneon |
Learn more
Values are typical for a compound and for comparison only. In rubber, properties depend strongly on the compound (filler, cure, hardness). For seals, design to a chemical compatibility chart and producer data. Sources: ASTM D1418, ASTM D2000, ISO 1629, producer data, and the METAL HUB materials database.
Updated: October 31, 2026