FFKM O-Rings (Perfluoroelastomer)
The ultimate elastomer for extreme temperatures, aggressive chemicals, and critical sealing applications where FKM is not enough.
Overview
FFKM (Perfluoroelastomer) is a fully fluorinated elastomer that combines the chemical resistance of PTFE with the elastic recovery of rubber. It is the only elastomer capable of sealing continuously above +300C while resisting virtually every industrial chemical, including concentrated acids, ketones, esters, and amines that attack FKM.\n\nFFKM is specified in semiconductor fabrication, chemical processing reactors, pharmaceutical autoclaves, and oil & gas downhole tools where seal failure costs far more than the seal itself. Commercial names include Kalrez, Chemraz, and Perlast — all are perfluoroelastomers with the same base chemistry, though individual compounds are optimized for temperature, chemical, or steam resistance.\n\nAt O-Ring Supply Co., we supply FFKM O-rings to AS568 and ISO 3601 dimensions, with compound selection guidance based on your specific temperature and media requirements. Lead time is typically 2-6 weeks depending on size and grade.
Material Properties
| Temperature Range | -15C to +325C (grade dependent) |
| Hardness Range | 65-90 Shore A |
| Chemical Resistance | Near-universal (approaches PTFE) |
| Tensile Strength | 10-20 MPa |
| Compression Set (70h/200C) | <=25% |
| Color (standard) | Black, white, or translucent |
Typical Applications
Semiconductor
Wafer processing seals, plasma chambers, CVD and etch equipment
Chemical Processing
Reactor seals, valve stems, and pump seals in concentrated oxidising acids and ketones
Oil & Gas
Downhole seals, wellhead packers, and BOP seals above +200C
Pharmaceutical
Autoclave and clean-steam seals requiring USP Class VI and temperatures above 200C
Aerospace
Engine hot-section seals and fuel nozzle seals in extreme temperature environments
Chemical Compatibility Summary
Compatible With
- - Virtually all chemicals except molten alkali metals
- - Concentrated oxidising acids
- - Ketones and esters
- - Aromatic and chlorinated solvents
- - Steam (grade dependent)
Incompatible With
- - Molten alkali metals
- - Fluorine gas at high temperatures
- - Some liquid alkali metals
- - Practically none in standard industrial use
Compare Nearby Materials
Spring Energized Seals
Strong alternative for vacuum, cryogenic, and low-friction service.
View Spring Energized SealsFurther Reading
Best Material for Semiconductor Equipment
Why FFKM becomes the default elastomer answer in many critical semiconductor tools.
Read articleKey Advantages
Widest Temperature Range of Any Elastomer
Continuous service to +275C and short-term exposure to +325C — 100C beyond standard FKM limits.
Near-Universal Chemical Resistance
Resists ketones, esters, amines, concentrated acids, and steam — chemicals that destroy FKM.
Elastic Recovery Unlike PTFE
Unlike PTFE, FFKM compresses and recovers like rubber, enabling true dynamic sealing in extreme environments.
Ultra-High Purity Grades
Semiconductor-grade compounds are formulated for low outgassing and minimal particle generation.
Frequently Asked Questions - FFKM
Is FFKM the same as Kalrez?
Kalrez is DuPont's brand name for FFKM. FFKM is the generic ISO/ASTM designation for perfluoroelastomer. All Kalrez products are FFKM, but other manufacturers also produce equivalent compounds under different brand names.
Can FFKM replace FKM directly?
Yes. FFKM O-rings to AS568 or ISO 3601 dimensions are dimensionally interchangeable with FKM. No groove modification is required.
Why is FFKM so expensive?
FFKM uses fully fluorinated monomers and complex curing chemistry. Production volumes are low, and the manufacturing process is inherently costly. The price reflects real material and processing cost, not margin.
Does FFKM work in steam service?
Certain FFKM grades are specifically formulated for steam resistance to 200C+, outperforming FKM significantly. Specify steam conditions when ordering so we can recommend the correct grade.
What is the lead time for FFKM O-rings?
Because FFKM is made to order in most sizes, lead time is typically 2-6 weeks depending on compound grade and dimensions. Stock of common AS568 sizes in standard grades may be available faster.