Are Viton™ and FKM the same?

Viton™ and FKM are closely related, but they are not technically the same thing.

FKM is the generic material designation for a family of fluoroelastomer rubbers, while Viton™ is a registered trademark used for specific fluoroelastomer products.

Because Viton™ has been widely used in industry for many years, the name is often used as a general term for FKM rubber. You may therefore hear people refer to an FKM seal as a “Viton seal”, even when the material is not actually a branded Viton™ product.

This can cause some confusion when specifying FKM rubber sheet, seals, gaskets and O-rings.

In this guide, we explain the difference between Viton™ and FKM, their properties, applications and what you should specify when ordering a replacement seal or gasket.

What Is FKM?

FKM is a family of high-performance synthetic rubber compounds known as fluoroelastomers.

The material contains fluorine, which contributes to its excellent resistance to:

- High temperatures
- Oils
- Fuels
- Hydrocarbons
- Many chemicals
- Ozone
- Weathering
- Ageing

FKM is commonly used where a standard rubber such as nitrile, EPDM or neoprene may not provide sufficient resistance to the operating environment.

FKM can be manufactured into a wide variety of products, including seals, gaskets, O-rings, rubber sheet, tubing and bespoke rubber components.

What Is Viton™?

Viton™ is a registered trademark associated with fluoroelastomer products.

It is a well-known brand of fluoroelastomer that has been used extensively in demanding sealing applications.

Because of the popularity of Viton™, the name has become widely recognised within industries such as automotive, aerospace, chemical processing, oil and gas and general engineering.

However, Viton™ is a brand name rather than the generic name for all fluoroelastomer rubber.

This means that all Viton™ materials fall within the broad category of fluoroelastomers, but an FKM material does not automatically mean it is a Viton™ branded product.

So, Are Viton™ and FKM the Same?

Not exactly.

The easiest way to understand the difference is:

FKM = generic material designation

Viton™ = specific trademark/brand

Think of it in the same way as other situations where a brand name becomes commonly used to describe a wider class of product.

In everyday conversation, customers and engineers may use “Viton” to describe FKM rubber generally. However, when specifying a component for an important application, it is better to identify the actual material specification and compound rather than relying solely on the word “Viton”.

Why Is FKM Sometimes Called Viton?

Viton™ has been widely used for many years in industrial sealing applications and has become one of the best-known names associated with fluoroelastomer rubber.

As a result, terms such as:

- Viton seal
- Viton gasket
- Viton O-ring
- Viton sheet
- Viton rubber

are often used when the intended material is actually FKM.

This terminology is particularly common when customers are looking for replacement seals.

However, there can be significant differences between individual FKM compounds, even though they are all classified as FKM.

Are All FKM Rubbers the Same?

No.

This is an important consideration when replacing an existing seal.

FKM is a family of materials rather than one single formulation. Different compounds can be formulated to provide different levels of resistance and performance.

Factors that can vary include:

- Fluorine content
- Temperature resistance
- Chemical resistance
- Low-temperature flexibility
- Compression set
- Hardness
- Mechanical properties
- Fuel resistance
- Processing characteristics

Therefore, simply specifying “FKM” may not always be enough for a critical sealing application.

The correct compound should be selected according to the temperature, pressure, fluid, chemicals and operating conditions involved.

What Are the Main Advantages of FKM?

FKM is popular because it combines excellent temperature resistance with very good resistance to oils, fuels and many aggressive environments.

High-temperature resistance

FKM can perform at temperatures where many general-purpose elastomers begin to deteriorate.

Depending on the specific compound, FKM can typically operate at temperatures around 200°C, with some specialist grades capable of higher temperatures.

The actual operating limit should always be taken from the manufacturer's specification for the particular compound.

Excellent oil and fuel resistance

FKM provides excellent resistance to many:

- Mineral oils
- Fuels
- Lubricants
- Hydrocarbons
- Hydraulic fluids

This makes it particularly useful in automotive and industrial sealing applications.

Chemical resistance

FKM provides good to excellent resistance to many chemicals.

However, it is important to remember that FKM is not resistant to every chemical. Compatibility depends on the specific FKM compound as well as the chemical concentration, temperature and exposure time.

Good ageing and weather resistance

FKM generally provides good resistance to ozone, weathering and ageing, making it suitable for demanding outdoor and industrial environments.

What Is Viton™ / FKM Rubber Used For?

FKM and branded fluoroelastomer products such as Viton™ are widely used in demanding applications.

Common applications include:

Automotive

FKM seals are frequently used in automotive applications involving:

- Engine oils
- Fuels
- Lubricants
- High temperatures
- Fuel systems
- Engine components
- O-rings
- Gaskets

Aerospace

FKM is used in selected aerospace sealing applications where resistance to fuels, oils, temperature and environmental conditions is required.

Specific aerospace applications will normally require an approved compound and specification.

Oil and Gas

FKM is commonly used in oil and gas applications because of its resistance to hydrocarbons, oils and elevated temperatures.

Chemical Processing

FKM can be suitable for selected chemical-processing applications where resistance to aggressive fluids and elevated temperatures is required.

Chemical compatibility should always be confirmed before selecting the material.

Industrial Equipment

FKM seals and gaskets are used in machinery, pumps, valves, compressors and other industrial equipment where high-performance sealing is required.

Viton™ vs FKM: Is There a Performance Difference?

There is no simple answer that one is always better than the other.

The important point is that Viton™ is a brand of fluoroelastomer, while FKM describes a wider family of materials.

A particular Viton™ compound may have specific performance characteristics that make it suitable for an application. Another FKM compound from a different manufacturer may have different properties.

Therefore, the comparison should really be between the specific compounds, rather than simply “Viton™ versus FKM”.

When replacing an existing seal, it is important to consider the original specification, operating conditions and required performance.

FKM vs Nitrile

FKM is often compared with nitrile rubber (NBR) because both materials are widely used for oil and fuel-resistant seals.

In general:

Nitrile is often an excellent choice for general-purpose oil-resistant sealing applications.

FKM becomes particularly attractive where higher temperatures, improved chemical resistance or demanding fuel/hydrocarbon exposure are involved.

Read our guide to FKM vs nitrile rubber.

FKM Rubber Sheet and Viton™ Sheet

FKM is available in rubber sheet form, which can be used to manufacture gaskets and bespoke sealing components.

FKM sheet can be used in applications requiring resistance to:

- High temperatures
- Oils
- Fuels
- Hydrocarbons
- Many chemicals
- Weathering and ozone

Customers sometimes search for Viton™ sheet when they are actually looking for FKM rubber sheet.

When ordering, it is useful to clarify whether a specific branded Viton™ material is required or whether a suitable FKM compound meeting the required specification is acceptable.

View FKM rubber sheet from TYM Seals & Gaskets.

FKM Seals and Gaskets

FKM is particularly well suited to seals and gaskets because it can retain its properties in demanding environments.

Common FKM sealing products include:

- FKM O-rings
- FKM gaskets
- FKM oil seals
- FKM cord
- FKM tubing
- FKM sheet
- Bespoke FKM seals
- Custom-cut FKM gaskets

When selecting an FKM seal, the material compound, hardness, profile and dimensions should all be considered.

What Should I Specify: Viton™ or FKM?

If you are ordering a replacement seal, simply asking for a “Viton seal” may not provide enough information.

Where possible, provide:

- Existing seal material
- Manufacturer and machine model
- Seal dimensions
- Cross-section
- Hardness
- Operating temperature
- Pressure
- Fluid or chemical being sealed
- Whether exposure is continuous or intermittent
- Any required approvals or specifications

If the original seal is specifically specified as a branded Viton™ product, this should be stated.

If the requirement is simply for a fluoroelastomer with particular performance characteristics, FKM may be the more appropriate material description.

Can FKM Replace Viton™?

In some applications, a suitable FKM compound can be used as an alternative to a branded Viton™ product.

However, this should not be assumed automatically.

The replacement material should meet the performance requirements of the application. Factors such as temperature, chemical compatibility, pressure, compression set and required certification may all need to be considered.

For critical applications, the replacement should be checked against the original material specification.

Choosing the Right FKM Seal or Gasket

The best sealing material depends on the environment in which the component will operate.

At TYM Seals & Gaskets, we supply a range of FKM rubber sheet, seals and gaskets for industrial applications.

If you are unsure whether you need FKM, nitrile, EPDM, silicone or another elastomer, we can help you select a material based on your operating conditions.

Providing details of the temperature, pressure, chemical or fluid exposure and application will help identify the most appropriate material.

FKM Rubber from TYM Seals & Gaskets

TYM Seals & Gaskets is a UK manufacturer and supplier of rubber and silicone sheet, seals, gaskets and bespoke sealing components.

Our range includes FKM, nitrile, EPDM, neoprene and silicone materials for a wide variety of industrial applications.

We can also manufacture bespoke gaskets and sealing components from drawings, dimensions or samples.

If you are looking for FKM rubber sheet, FKM seals or replacement gaskets, contact TYM Seals & Gaskets to discuss your requirements.

Explore FKM rubber sheet.

Frequently Asked Questions About Viton™ and FKM

Are Viton™ and FKM the same?

Not technically. FKM is the generic designation for a family of fluoroelastomer rubbers, while Viton™ is a registered trademark associated with specific fluoroelastomer products.

Is Viton™ better than FKM?

It is not accurate to say that Viton™ is automatically better than FKM. Viton™ is a brand, while FKM is a material classification. Performance depends on the specific compound and its formulation.

Is FKM the same as fluoroelastomer?

FKM is a commonly used designation for fluoroelastomer rubber. The exact terminology can vary by region and material specification.

Is Viton™ rubber heat resistant?

Yes. Fluoroelastomer materials such as Viton™ are known for excellent high-temperature resistance. The actual maximum operating temperature depends on the specific grade and application.

Is FKM resistant to oil?

Yes. Excellent resistance to oils and many hydrocarbons is one of the main advantages of FKM rubber.

Is FKM better than nitrile?

Neither material is universally better. FKM generally offers superior high-temperature and chemical performance, while nitrile is often a more economical option for general oil-resistant applications.

Can FKM be used instead of Viton™?

A suitable FKM compound may be an alternative in some applications, but the material should be checked against the original specification and operating conditions before being used as a replacement.

Can you supply Viton™ or FKM seals?

TYM supplies FKM rubber sheet, seals and gaskets for a wide range of industrial applications. If a specific branded material is required, this should be stated when requesting a quotation.

Need help choosing between FKM, Viton™, nitrile or another rubber? Contact TYM Seals & Gaskets with details of your application and operating conditions and we can help identify a suitable material.