FKM
EN FPM · also Fluorel, Fluoroelastomer
FKM is a fluorine-containing elastomer (Viton, FPM) and the standard seal material for aggressive fluids, with about 12 MPa tensile strength, 200 % elongation and service to 200 °C.
FKM grades and fills
FKM is supplied in 6 conditions, soft to hard.
Compare all 6 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
70 Shore A | Most common O-ring hardness: good sealing conformance and low compression load for static and dynamic sealing at low to medium pressure, with 11 MPa tensile and 250% elongation. | 11 | 250 | 22 Shore D | |
Low-temperature | Specify the perfluoromethylvinyl ether low-temperature type (GLT/GFLT class) for aerospace and cold-region fuel and driveline seals: Tg drops to −30 to −40 °C while oil and heat resistance is retained. | 12 | 220 | 25 Shore D | |
80 Shore A | Use this medium hardness for medium- to high-pressure seals or groove designs needing extrusion resistance; conformance is lower than 70 Shore A and elongation falls to 180%. | 13 | 180 | 28 Shore D | |
Peroxide-cured | Substitute peroxide cure with bromine/iodine cure sites for the bisphenol type when service involves hot water, steam or inorganic acids and better hydrolysis resistance is required. | 14 | 190 | 25 Shore D | |
90 Shore A | Pick for high-pressure hydraulic and downhole seals and back-up rings where gap extrusion resistance governs; sealing conformance and low-temperature recovery are poorer, elongation 130%. | 15 | 130 | 38 Shore D | |
70% | Choose the peroxide-cured terpolymer with about 70% fluorine for chemical and fuel-system seals exposed to methanol/ethanol fuels, acids, hot water or temperatures up to 230 °C. | 16 | 180 | 78 Shore A |
Supply forms, finishes and certifications
Ways FKM is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
FDA | FDA / | Certification |
StandardDefault | VDF/HFP 66% 75 Shore A | Standard supply |
What is FKM?
FKM is a fluorine-containing elastomer (Viton, FPM) and the standard seal material for aggressive fluids, with about 12 MPa tensile strength, 200 % elongation and service to 200 °C. Engineers specify it for molded O-rings, oil seals, gaskets and diaphragms in fuel, oil, engine and chemical service, with 70A/80A/90A hardnesses plus peroxide-cured, low-temperature and FDA compounds on file. Cost is well above nitrile, low-temperature flexibility is limited, and ketones, esters and hot amines attack standard grades; FFKM is the step up for those media and for higher temperatures. FKM has a density of 1.82 g/cm³ (0.0658 lb/in³), heavier than 96% of polymer grades. Its glass-transition temperature is -20°C (-4 °F). FKM has a tensile strength of 12 MPa (1.74 ksi), weaker than 76% of polymer grades. Elongation at break is 200% and the elastic modulus is 0.01 GPa (0.0012 Msi).
What is FKM used for?
- Fuel system O-rings
- Rotary shaft oil seals
- Engine and transmission gaskets
- Chemical pump diaphragms
- Valve stem seals
- Aerospace hydraulic seals
- Turbocharger hose couplings
Advantages
- Good corrosion resistance — 95/100, better than 97% of polymer grades
- Good UV / weathering resistance — 95/100, better than 95% of polymer grades
- High service temperature — 200°C (392 °F), better than 87% of polymer grades
- Ductile — tolerates forming and impact — 200%, better than 76% of polymer grades
Limitations
- High mold shrinkage — 3%, worse than 97% of polymer grades
- Heavy — 1.82 g/cm³ (0.0658 lb/in³), worse than 96% of polymer grades
- Difficult to machine — 25/100, worse than 93% of polymer grades
- High embodied carbon — 12 kg CO₂/kg, worse than 91% of polymer grades
- Low stiffness — 0.01 GPa (0.0012 Msi), worse than 82% of polymer grades
FKM properties
Typical room-temperature values in the Standard condition; bars are the position among polymer grades.
Physical3
FKM has a density of 1.82 g/cm³ (0.0658 lb/in³), heavier than 96% of polymer grades. Its glass-transition temperature is -20°C (-4 °F).
Mechanical7
FKM has a tensile strength of 12 MPa (1.74 ksi), weaker than 76% of polymer grades. Elongation at break is 200% and the elastic modulus is 0.01 GPa (0.0012 Msi).
Thermal8
FKM is rated for continuous service to 200°C (392 °F). It conducts heat at 0.21 W/m·K (0.121 BTU/hr·ft·°F), better than 55% of polymer grades. Thermal expansion is 160 µm/m·K (88.9 µin/in·°F).
Electrical5
FKM is an electrical insulator with a dielectric strength of 16 kV/mm (406.4 V/mil) and a resistivity of 2×10¹¹ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (95/100), better than 97% of polymer grades. UV resistance is excellent.
Sustainability4
Producing a kilogram of FKM takes about 200 MJ of energy and emits 12 kg of CO₂ — more than 89% of polymer grades. Typical recycled content is 0%.
Manufacturability4
FKM's machinability is poor (25/100, worse than 93% of polymer grades).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the polymer family
Yield strength against density for every polymer grade FabDigit runs. FKM is highlighted; hover a dot for its name, or open the interactive family chart.
Working with FKM
Is FKM easy to machine?
Not suited to conventional cutting; seals are compression or injection molded and deflashed by cryogenic tumbling. If machining is unavoidable, turn pre-cured blanks with very sharp tools at low speed and cool the part thoroughly.
Can FKM be welded?
Not heat weldable; splice joints with uncured gum stock vulcanized in place, or bond with fluoroelastomer-specific adhesives applied over the matching primer.
Can FKM be formed, bent or molded?
Compression, transfer or injection molded with a press cure at 175–190 °C, followed by a 200–230 °C post-cure for 16–24 h to lower compression set and drive off volatiles.
Manufacturability
The process limits FabDigit applies to FKM. Every FKM part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
Injection molding
| Mold shrinkage | — |
|---|---|
| Wall thickness | — – — |
| Recommended draft | — |
| Pre-drying | — |
FKM chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| vinylidene fluoride (VDF, )main-chain monomer | 45 – 70 | 60 |
| hexafluoropropylene (HFP, )provides amorphous elasticity | 25 – 45 | 40 |
| tetrafluoroethylene (TFE, )added in terpolymer (high-fluorine); 0 in standard dipolymer | 0 – 30 | 0 |
| fluorine contentmass fraction of fluorine in the polymer | 65 – 70 | 66 |
| carbon black (N990/N550 )share in the compound (about 20-30 phr) | 10 – 30 | 20 |
| curative + Ca(OH)2 / MgObisphenol AF + phosphonium salt or peroxide/TAIC system | 3 – 10 | 6 |
What surface finishes work on FKM?
Surfaces can be graphite, PTFE or silicone coated to cut friction and installation stiction; bonding to metal inserts requires plasma or chemical pretreatment plus a fluoroelastomer-specific primer.
Surface treatments FabDigit runs on polymer parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Injection Molding Coating
Metallization / Functional
Equivalent designations
Standards and trade names that resolve to FKM in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- EN / DIN / Werkstoff-Nr.
- FPM
- Trade names
- FluorelFluoroelastomerViton
How much does FKM cost?
FKM is a standard-cost polymer ($$), cheaper than about 60% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
FKM — frequently asked
What is FKM used for?
FKM is typically used for fuel system O-rings, rotary shaft oil seals, engine and transmission gaskets, chemical pump diaphragms, valve stem seals and aerospace hydraulic seals. In short: high-temp chemical fluoroelastomer.
What is the tensile strength of FKM?
FKM has a typical tensile strength of 12 MPa (1.74 ksi) — weaker than 76% of polymer grades. Strength varies by condition: see the 6 listed tempers.
Is FKM easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of polymer grades). Not suited to conventional cutting; seals are compression or injection molded and deflashed by cryogenic tumbling. If machining is unavoidable, turn pre-cured blanks with very sharp tools at low speed and cool the part thoroughly.
Can FKM be welded?
Not heat weldable; splice joints with uncured gum stock vulcanized in place, or bond with fluoroelastomer-specific adhesives applied over the matching primer.
What surface finishes work on FKM?
Surfaces can be graphite, PTFE or silicone coated to cut friction and installation stiction; bonding to metal inserts requires plasma or chemical pretreatment plus a fluoroelastomer-specific primer.
Can FKM be formed, bent or molded?
Compression, transfer or injection molded with a press cure at 175–190 °C, followed by a 200–230 °C post-cure for 16–24 h to lower compression set and drive off volatiles.
What is the maximum service temperature of FKM?
FKM is rated for continuous use to about 200°C (392 °F), and briefly to 275°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does FKM cost?
FKM is a standard-cost polymer ($$), cheaper than about 60% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in FKM?
Yes — FKM is available for injection molding; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM D1418 — Rubber and Rubber Latices Nomenclature (FKM) — ASTM (2022)
- ASTM D2000 — Classification System for Rubber Products in Automotive Applications — ASTM (2020)
- Viton™ Fluoroelastomer Product & Chemical Resistance Guides — Chemours / DuPont (2023)
- Tecnoflon® FKM Product Selection Guide — Solvay Specialty Polymers (2022)
- Engineered Materials Handbook Vol.2 — Engineering Plastics & Elastomers — ASM International (1988)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.