What Is FKM Rubber? Properties, Uses, Temperature Resistance and Applications

FKM rubber is a high-performance synthetic elastomer known for its excellent resistance to high temperatures, oils, fuels, chemicals and aggressive operating environments.

FKM is widely used to manufacture seals, gaskets, O-rings, sheets, tubing and other rubber components where standard rubber materials such as nitrile or EPDM may not provide sufficient resistance.

You may also hear FKM referred to as fluorocarbon rubber, fluoroelastomer or Viton®. Viton® is a well-known trade name for fluoroelastomer products, while FKM is the general material designation used for this family of high-performance elastomers.

At TYM Seals & Gaskets, we supply FKM rubber in a range of forms and specifications for demanding industrial applications.

What Does FKM Stand For?

FKM is the material designation commonly used for fluoroelastomer rubber.

The "F" refers to fluorine, while the "KM" designation relates to the classification used for this type of elastomer.

FKM contains a significant proportion of fluorine within its polymer structure. This fluorine content is one of the reasons FKM has such strong resistance to heat, oils, fuels and many chemicals.

FKM is particularly useful where a rubber component needs to maintain its sealing properties in environments involving elevated temperatures, hydrocarbons or aggressive chemicals.

Is FKM the Same as Viton®?

The terms FKM and Viton® are often used interchangeably, but technically they are not exactly the same.

FKM is the generic material designation for a family of fluoroelastomers.

Viton® is a registered trademark associated with fluoroelastomer products manufactured by Chemours and its predecessors.

As a result, an FKM rubber product may be made from an FKM compound without being a Viton® branded product.

This distinction can be important when specifying replacement seals or rubber components. If a particular branded material is required, the specification should state this rather than simply specifying FKM.

What Are the Properties of FKM Rubber?

FKM is chosen for applications where a combination of temperature, chemical and fluid resistance is required.

Typical properties of FKM include:

- Excellent high-temperature resistance
- Excellent resistance to oils and fuels
- Very good resistance to many chemicals
- Good resistance to mineral oils
- Good resistance to many hydrocarbons
- Good resistance to ozone and weathering
- Low gas permeability
- Good compression set resistance at elevated temperatures
- Good ageing resistance
- Good mechanical properties across a wide temperature range

The exact performance of an FKM product depends on the particular compound, hardness, formulation and operating conditions.

For this reason, FKM should be selected according to the application rather than simply assuming that every FKM product will perform identically.

What Temperature Can FKM Rubber Withstand?

One of the main reasons FKM is used instead of conventional rubber materials is its ability to withstand high operating temperatures.

Depending on the compound and application, FKM can typically operate at temperatures around 200°C, with some specialist grades capable of higher short-term or continuous temperatures.

The exact temperature range depends on the specific FKM formulation and the conditions under which it is being used.

When specifying FKM, it is important to distinguish between:

- Continuous operating temperature
- Intermittent or short-term temperature
- Exposure to temperature combined with chemicals or fluids
- Low-temperature requirements

High-temperature resistance is only one part of material selection. A seal operating at high temperature while simultaneously exposed to fuel, oil or chemicals may require a different FKM compound from one used in a dry environment.

What Is FKM Rubber Used For?

FKM is used extensively across industries where conventional elastomers may not provide sufficient performance.

Common applications include:

Automotive

FKM is widely used in automotive applications because of its resistance to fuels, oils, lubricants and elevated temperatures.

Applications can include:

- Engine seals
- Fuel system seals
- Oil seals
- O-rings
- Gaskets
- Valve seals
- Turbocharger applications
- Fuel hoses and components

Aerospace

FKM is used in aerospace applications where sealing components can be exposed to high temperatures, fuels, lubricants and demanding environmental conditions.

Material selection for aerospace applications is highly specification-dependent, so the appropriate approved compound should always be used.

Oil and Gas

The combination of chemical, oil and temperature resistance makes FKM useful in oil and gas applications.

It can be used for seals and gaskets exposed to hydrocarbons, fuels, lubricants and other demanding fluids.

Chemical Processing

FKM can provide excellent resistance to many chemicals, making it suitable for selected chemical-processing applications.

However, FKM is not resistant to every chemical, so compatibility should always be checked before use.

Industrial Machinery

FKM seals and gaskets are used throughout industrial equipment where high temperatures, oils or aggressive fluids are present.

FKM Rubber Sheet

FKM is available as rubber sheet, allowing it to be converted into bespoke gaskets, seals and other components.

FKM sheet can be used where a gasket needs to withstand conditions that may be too demanding for standard nitrile, EPDM or other rubber materials.

Applications can include:

- Flange gaskets
- Chemical-resistant gaskets
- Oil-resistant gaskets
- High-temperature gaskets
- Industrial seals
- Custom-cut components
- Equipment maintenance and replacement parts

FKM sheet is available in different thicknesses and hardnesses depending on the material specification and application.

View FKM rubber sheet from TYM Seals & Gaskets.

FKM Seals and Gaskets

FKM is particularly well suited to sealing applications because it can maintain its properties when exposed to high temperatures and many oils, fuels and chemicals.

FKM can be manufactured into a wide range of sealing products, including:

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

The correct profile, hardness and compound should be selected according to the application.

FKM vs Nitrile Rubber

FKM and nitrile rubber (NBR) are both widely used for oil-resistant sealing applications, but they have different performance characteristics.

Nitrile can be an excellent choice where cost-effective oil and fuel resistance is required.

FKM is generally worth considering when higher temperatures, more demanding chemical environments or improved resistance to fuels and aggressive fluids are important.

Read more about the difference between FKM and nitrile rubber.

FKM vs EPDM

FKM and EPDM have very different strengths.

EPDM provides excellent resistance to water, steam, weathering, ozone and many polar chemicals, while FKM is generally much better suited to applications involving oils, fuels and many hydrocarbons.

As a general guide:

- Choose FKM for oils, fuels, hydrocarbons and high-temperature applications.
- Choose EPDM for water, steam, weathering and many outdoor applications.
- Always check chemical compatibility for the specific application.

Neither material should be considered universally better than the other. The correct choice depends on the operating environment.

Is FKM Rubber Resistant to Chemicals?

FKM provides excellent resistance to many chemicals, oils, fuels and hydrocarbons.

However, FKM is not chemically resistant to everything.

Its compatibility can vary depending on:

- The specific chemical
- Concentration
- Temperature
- Exposure time
- Pressure
- FKM formulation
- Other environmental conditions

Some chemicals and operating environments can cause FKM to swell, harden, soften or otherwise deteriorate.

If a seal or gasket will be exposed to a specific chemical, compatibility should be confirmed before the material is selected.

Is FKM Suitable for High-Temperature Applications?

Yes. High-temperature performance is one of the major advantages of FKM.

It can retain useful sealing properties at temperatures where many general-purpose elastomers begin to deteriorate.

However, high temperature combined with other factors can affect service life. For example, an FKM seal exposed continuously to high temperature and aggressive chemicals may have a very different service life from one operating at a lower temperature in a clean environment.

For critical applications, the complete operating environment should therefore be considered when selecting the material.

What Are the Limitations of FKM Rubber?

Although FKM is a high-performance elastomer, it is not suitable for every application.

Potential limitations include:

- Higher cost than many general-purpose rubber materials
- Poorer low-temperature flexibility than some alternative elastomers
- Limited resistance to certain chemicals
- Not generally the first choice for hot water or steam applications
- Not suitable for every amine, ketone or other aggressive chemical environment

The correct rubber should always be selected based on the actual operating conditions, rather than simply choosing the highest-specification material available.

How Do You Choose the Correct FKM Grade?

There are many different FKM compounds available, and choosing the correct one involves more than specifying "FKM".

Important factors include:

- Operating temperature
- Fluid or chemical exposure
- Required hardness
- Pressure
- Compression
- Seal design
- Continuous or intermittent operation
- Required certifications
- Expected service life
- Manufacturing method

For example, an FKM gasket used with automotive fuel may require a different compound from an FKM seal used in a high-temperature industrial chemical application.

Providing your supplier with as much information as possible will help ensure the correct material is selected.

FKM Rubber from TYM Seals & Gaskets

TYM Seals & Gaskets supplies FKM rubber sheet, seals, gaskets and other rubber products for demanding industrial applications.

Our range of rubber materials includes FKM, nitrile, EPDM, neoprene and silicone, allowing customers to select the material most appropriate for their particular operating environment.

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

If you need help choosing between FKM, nitrile, EPDM or another rubber material, provide us with details of the temperature, pressure, fluids, chemicals and application, and we can help identify a suitable material.

Explore FKM rubber sheet.

Frequently Asked Questions About FKM Rubber

What is FKM rubber?

FKM is a family of fluoroelastomer rubbers known for excellent resistance to high temperatures, oils, fuels and many chemicals. It is widely used for seals, gaskets, O-rings, sheet and other industrial rubber components.

Is FKM the same as Viton®?

No. FKM is the generic designation for fluoroelastomers, while Viton® is a registered trademark associated with certain fluoroelastomer products. The terms are often used interchangeably in industry, but technically they are not identical.

Is FKM rubber heat resistant?

Yes. FKM has excellent high-temperature resistance. Depending on the compound, it can typically operate at temperatures around 200°C, with some specialist grades capable of higher temperatures.

Is FKM resistant to oil?

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

Is FKM better than nitrile?

Not necessarily. FKM generally offers better high-temperature and chemical performance, while nitrile can provide excellent oil resistance at a lower cost and may offer better low-temperature flexibility. The best material depends on the application.

Is FKM resistant to water and steam?

FKM can have limitations with hot water and steam and is not normally the first-choice material for these applications. EPDM is often more suitable for hot water and steam, depending on the conditions.

Can FKM be used for gaskets?

Yes. FKM is widely used to manufacture gaskets where resistance to high temperatures, oils, fuels or chemicals is required.

Can you supply FKM rubber sheet?

Yes. TYM Seals & Gaskets supplies FKM rubber sheet in a range of specifications and can also manufacture bespoke gaskets and sealing components from FKM and other rubber materials.

Need help choosing the right rubber? Contact TYM Seals & Gaskets with details of your application, temperature and chemical or fluid exposure and we can help identify a suitable material.