Viton™ (FKM) gaskets
Viton™ gaskets for fuels, chemicals and heat.
FKM fluoroelastomer keeps sealing in hot fuels, oils, aromatics and many acids that destroy other rubbers. Ask us about Viton™ and other FKM gaskets and washers cut to your drawing, and we will help you choose the grade for your fluid.
- Typical service range of FKM
- -20°C to +200°C
- Typical fluorine content of FKM grades
- 66% to 70%
What it is
What Viton™ (FKM) is.
FKM is the standard designation for fluoroelastomers: synthetic rubbers in which fluorine atoms shield the polymer chain, much as they do in PTFE. Viton™ is the best-known brand of FKM, and the two names are often used for the same thing. In international standards the material is also called FPM.
The fluorine gives FKM the broadest fluid resistance of any common rubber. It seals mineral and synthetic oils, petrol, diesel and fuel blends, aromatic and chlorinated solvents, and many acids, and it does so up to about 200°C continuously. It also resists ozone and weather, burns reluctantly, and has very low gas permeability and compression set.
Grades differ in fluorine content, typically 66% to 70%: the more fluorine, the better the chemical resistance, and the poorer the flexibility in the cold. Our guide to rubber gasket materials compares FKM with the other elastomers.
Viton™ is a trademark of The Chemours Company. Other names are the trademarks of their owners.
All rubber gasket materialsProperties
FKM properties for gasket design.
These are typical values for a general-purpose FKM gasket compound, for comparing materials at the design stage. Specialised grades extend the cold limit, the steam resistance or the chemical resistance, and the data sheet for the grade supplied applies to your part.
FKM is dense, so a gasket weighs noticeably more than the same part in nitrile, and it is firm: most gasket grades sit around 70 to 80 Shore A.
FKM and other materials comparedFKM fluoroelastomer: typical properties
General values, not a specification
| Property | Typical value |
|---|---|
| General | |
| Polymer | Fluoroelastomer (FKM; FPM in ISO 1629) |
| Fluorine content | 66% to 70%, by grade |
| Density | 1.8 to 2.0 g/cm³ |
| Mechanical | |
| Hardness | 60 to 90 Shore A; 70 to 80 Shore A is common |
| Tensile strength | 7 to 15 MPa, by grade |
| Elongation at break | 150% to 300% |
| Compression set | Very low, including at high temperature |
| Thermal | |
| Service temperature | -20°C to +200°C |
| Short-term peak | About +230°C |
| Low-temperature grades | Flexible to about -40°C |
| Resistance | |
| Oils, fuels, aromatic and chlorinated solvents | Excellent |
| Many mineral acids | Good to excellent |
| Ozone, weather and flame | Excellent; self-extinguishing |
| Attacked by | Ketones, low molecular weight esters and ethers, amines, hot water and steam (standard grades) |
General
- Polymer
- Fluoroelastomer (FKM; FPM in ISO 1629)
- Fluorine content
- 66% to 70%, by grade
- Density
- 1.8 to 2.0 g/cm³
Mechanical
- Hardness
- 60 to 90 Shore A; 70 to 80 Shore A is common
- Tensile strength
- 7 to 15 MPa, by grade
- Elongation at break
- 150% to 300%
- Compression set
- Very low, including at high temperature
Thermal
- Service temperature
- -20°C to +200°C
- Short-term peak
- About +230°C
- Low-temperature grades
- Flexible to about -40°C
Resistance
- Oils, fuels, aromatic and chlorinated solvents
- Excellent
- Many mineral acids
- Good to excellent
- Ozone, weather and flame
- Excellent; self-extinguishing
- Attacked by
- Ketones, low molecular weight esters and ethers, amines, hot water and steam (standard grades)
Typical published values for general-purpose FKM. Ask for the data sheet of the grade supplied.
Ordering
Ordering FKM gaskets cut to your drawing.
FKM costs several times as much as nitrile, so it pays to specify it precisely. Tell us the size, tolerance and quantity, the exact fluid and its concentration, and the highest and lowest temperatures, and we will confirm the grade, thickness and cutting method with the quotation.
If your drawing names Viton™ or another particular grade, say so: we will quote that grade or agree an equivalent FKM with you. Thick sheet and prototypes are usually cut without a tool; our page on laser and water jet cutting explains tool-less cutting.
Cut to your drawing
Gaskets, washers, flat seals and complex profiles.
Grade advice
We check the FKM grade against your fluid and temperature.
FKM gaskets
What to ask us for
| Option | Availability |
|---|---|
| Solid FKM sheet | Thicknesses on request |
| Viton™ or a named FKM grade | On request |
| Low-temperature or steam-resistant grades | Ask us |
| Parts | Gaskets, washers and flat seals |
| Cutting | Die cut or water jet cut, by thickness and quantity |
- Solid FKM sheet
- Thicknesses on request
- Viton™ or a named FKM grade
- On request
- Low-temperature or steam-resistant grades
- Ask us
- Parts
- Gaskets, washers and flat seals
- Cutting
- Die cut or water jet cut, by thickness and quantity
Grades and thicknesses are confirmed with the quotation.
Applications
Where FKM gaskets earn their price.
FKM is chosen where a cheaper rubber would swell, harden or crack, and a failed seal costs far more than the gasket.
- Aerospace
Aerospace
Aircraft fuel and lubrication
Seals and washers in hot fuel, lubricating oil and hydraulic systems.
- Automotive
Automotive
Engines and fuel systems
Gaskets that meet hot oil and modern fuel blends under the bonnet.
- Industrial
Process
Chemical and process plant
Pump, valve and flange gaskets for solvents, acids and hydrocarbons.
- Energy & Renewables
Energy
Oil, gas and power
Seals for hot oils, sour hydrocarbons and turbine lubrication.
Vacuum
Vacuum and gas equipment
Low-permeability seals for vacuum chambers and gas handling.
- Security & Defence
Defence
Military vehicles and equipment
Fuel and lubricant seals that must not fail in the field.
Limits
Limits of FKM: ketones, esters, hot water and cold.
FKM's resistance is broad but not universal. Ketones such as acetone and MEK, low molecular weight esters and ethers, and amines swell or attack it, and so do glycol-based brake fluids and phosphate ester hydraulic fluids, which are better sealed with EPDM. Strong alkalis and hot ammonia attack standard grades.
Hot water and steam are a second limit: standard grades degrade in them, and special peroxide-cured grades are needed.
Cold is the third. A standard FKM gasket stiffens at about -15°C to -20°C and may leak if the joint moves while it is cold. Low-temperature grades help, at a price. If the joint sees severe cold or strong chemicals, PTFE gaskets may be the better answer.
Talk to our technical teamAlternatives
FKM, nitrile or PTFE for your gasket?
Nitrile costs least, FKM goes hotter and resists more fuels and chemicals, and PTFE resists almost everything but is not a rubber. Choose what the gasket meets to see which qualifies.
What does the gasket meet?
Choose properties to find the right material. 3 materials compared.
| Requirement | FKM | Nitrile | PTFE |
|---|---|---|---|
| Mineral oils and diesel | Yes | Yes | Yes |
| Aromatic fuels and solvents | Yes | No | Yes |
| Continuous heat above 150°C | Yes | No | Yes |
| Ketones and esters | No | No | Yes |
| Hot water and steamSpecial FKM grades only. | No | No | Yes |
| Cold below -30°CLow-temperature FKM and nitrile grades extend the range. | No | No | Yes |
| Elastic recovery at low bolt loadPTFE creeps and needs a firm, steady load. | Yes | Yes | No |
| Lowest material cost | No | Yes | No |
General guidance for each material family. The data sheet for the grade supplied applies.
Viton™ gasket FAQs
Viton™ gasket questions, answered.
Can't find what you need? Our technical team is happy to help.
What is the difference between Viton and FKM?
FKM is the generic designation for fluoroelastomer rubber, set out in ASTM D1418; ISO 1629 calls it FPM. Viton™ is a brand of FKM made by The Chemours Company. Other manufacturers make FKM too. If your drawing specifies Viton™ by name, tell us; otherwise we can quote an equivalent FKM grade.
What temperature can Viton gaskets withstand?
General-purpose FKM is typically used from about -20°C to +200°C, with short peaks to about +230°C. Standard grades stiffen around -15°C to -20°C, and low-temperature grades stay flexible to about -40°C. The data sheet for the grade supplied gives its rated limits.
Is Viton better than nitrile?
It is more capable, not always better. FKM resists higher temperatures, aromatic fuels, solvents and ozone that nitrile cannot, and it has lower compression set. Nitrile costs a fraction of the price, is more flexible in the cold, and is perfectly adequate for most mineral oil and diesel service. Our guide to nitrile gaskets covers when it is enough.
Which chemicals attack Viton?
Standard FKM is attacked by ketones such as acetone and MEK, low molecular weight esters and ethers, amines, glycol-based brake fluids, phosphate ester hydraulic fluids, strong alkalis and hot water or steam. Special grades extend the resistance to some of these. Tell us the exact fluid, and we will check it.
Is Viton sponge available?
FKM sponge exists, but it is a specialist, costly material, made by fewer manufacturers and in fewer thicknesses than solid sheet. For a low-load seal that must resist fuels or heat, ask us: we will check whether FKM sponge is available for your part, or suggest an alternative.
Need FKM gaskets for a demanding joint?
Send us the drawing, the exact fluid, the temperatures and the quantity, and our technical team will confirm a suitable grade and quote for the cut parts.
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