Viton (FKM) Properties
Viton (FKM) is the premium elastomer for high temperatures and aggressive chemicals. Learn its strengths, limitations, and when the extra cost is justified.
Overview
FKM (fluoroelastomer), commonly known by the DuPont trade name Viton, is a high-performance synthetic rubber. It excels in high temperatures and aggressive chemicals where standard elastomers like EPDM and nitrile fail. The trade-off is cost — FKM is 5–10× more expensive than standard elastomers.
Key Properties
| Property | Value |
|---|---|
| Density | 1800 kg/m³ |
| Max service temperature | 200°C (continuous), 230°C (intermittent) |
| Min service temperature | -20°C |
| Hardness range | 50–90 Shore A |
| Tensile strength | 10–15 MPa |
Advantages
- Excellent high temperature resistance: 200°C continuous — significantly higher than EPDM (150°C) or nitrile (120°C).
- Outstanding oil and fuel resistance: The standard choice for seals in petroleum products, fuels, and synthetic oils.
- Good chemical resistance: Resists acids, alkalis, and many solvents that destroy standard elastomers.
- Good compression set resistance: Maintains seal force at elevated temperatures.
- Low permeability: Resists gas permeation — used in vacuum and gas sealing.
Limitations
- High cost: 5–10× the cost of standard elastomers — justified only where the performance is needed.
- Poor low temperature flexibility: Stiffens below -20°C — not suitable for cryogenic or arctic applications.
- Not for steam: While FKM can handle intermittent steam, EPDM is better for continuous steam service.
- Not for hot water: FKM degrades in hot water above 100°C — use EPDM for hot water.
- Not for ketones and esters: Swells in acetone, MEK, and ethyl acetate — use silicone or PTFE.
Typical Applications
- O-rings for chemical and petroleum service
- Valve stem seals in chemical plants
- Gaskets for fuel and oil systems
- Seals in high-temperature process equipment
- Aerospace and automotive seals
- Semiconductor manufacturing seals
Chemical Compatibility
| Chemical | Rating |
|---|---|
| Mineral oils | Excellent |
| Fuels (petrol, diesel, jet) | Excellent |
| Synthetic oils | Excellent |
| Acids (dilute) | Good |
| Alkalis | Good |
| Steam (intermittent) | Fair |
| Hot water | POOR — use EPDM |
| Ketones (acetone, MEK) | POOR — do not use |
| Esters | POOR — do not use |
| Aromatic hydrocarbons | Good |
How CHI can help
Ask CHI about Viton (FKM) properties and to determine whether the higher cost is justified for your application. The CHI assistant can recommend the right material for your specific application, explain chemical compatibility, and flag when a material is unsuitable for your operating temperature or environment.