FKM

In brief

FKM (fluoro rubber) is a synthetic elastomer for applications with high temperature and media exposure.

The material is used where seals, moulded parts or semi-finished products need to remain stable over the long term against oils, fuels, solvents and many chemicals.

For typical delivery forms in operation, an FKM sheet serves as the semi-finished product, while an FKM seal takes on the sealing function in the component.

• Temperature: suitable for permanently elevated operating temperatures (material-dependent).
• Media resistance: high resistance to many oils, fuels and chemical media.
• Ageing: high resistance to ozone and weathering.
• Permeation: low gas permeability for many sealing tasks.

Fundamentals and properties of FKM

FKM belongs to the group of fluoro rubbers and is used where classic elastomers such as NBR or EPDM reach their thermal or chemical limits.

Temperature behaviour

FKM is designed for permanently elevated operating temperatures. Depending on the compound and duration of use, the material remains dimensionally stable and functional even at high temperatures.

FKM is therefore suitable for applications in the engine environment, in the process industry and at thermally stressed sealing points.

Chemical resistance

The material shows very high resistance to:

• mineral oils and synthetic oils
• fuels and additives
• greases and lubricants
• many solvents and chemical media

The specific media resistance always depends on the compound and should be tested for the respective application.

Ageing and weathering resistance

FKM is largely insensitive to ozone, oxygen and UV radiation. As a result, elasticity is retained even under long-term outdoor or continuous exposure.

Gas permeability

Compared with many other elastomers, FKM has low permeation. This makes the material suitable for sealing tasks with increased requirements for tightness and media containment.

For application-oriented designs, both FKM sheets as semi-finished products and ready-designed FKM seals are available.

Limits of FKM and differentiation

FKM is used specifically for demanding applications. However, the material is not suitable for every technical or economic requirement.

Typical limits of FKM

Despite its high performance, FKM has material-related limitations:

• limited resistance to hot water and steam
• reduced elasticity at low temperatures compared with other elastomers
• higher material costs compared with standard elastomers

Suitability should therefore always be assessed in the interaction of temperature, medium and mechanical load.

Differentiation from NBR

NBR is frequently used for oil- and fuel-resistant applications at moderate temperatures. FKM is chosen when higher temperatures, aggressive media or longer service lives are required.

Differentiation from EPDM

EPDM is particularly suitable for hot water, steam and weathering. FKM is preferred when the focus is on oil, fuel or chemical resistance.

Differentiation from HNBR

HNBR represents a technical intermediate solution. FKM offers, beyond that, higher chemical stability and temperature resistance for particularly demanding operating conditions.

For the selection of suitable semi-finished products or finished components, the overview of elastomers serves as an objective decision-making aid.

Typical areas of application of FKM

FKM is used where components are permanently exposed to thermal and chemical loads and a stable sealing function is required.

Automotive and drive technology

In the engine and drive environment, FKM is used for seals that come into contact with fuels, oils or exhaust gases. The material remains dimensionally stable even at permanently high temperatures.

Mechanical and plant engineering

In industrial plants, FKM is used wherever aggressive media, lubricants or process chemicals are relevant to sealing.

Chemical and petrochemical industry

FKM is used for sealing points in pipelines, pumps and reactors where solvents, acids or other chemical media occur.

Aerospace technology

In specialised aerospace applications, FKM is used because of its media and ageing resistance.

Energy and process engineering

In thermally stressed processes as well as in oil- and fuel-carrying systems, FKM takes on the sealing function over long service lives.

Depending on the design, both cut-to-size FKM sheets and individually manufactured FKM seals are used.

Delivery forms and processing of FKM

FKM is available in various delivery forms and is processed as a semi-finished product or as a finished component depending on the application.

FKM sheets and semi-finished products

FKM sheets serve as the starting material for individual cut pieces and components. They are manufactured in various thicknesses and qualities and allow flexible further processing.

Typical applications are flat gaskets, covers or special cut pieces to drawing.

FKM seals

FKM seals are manufactured application-specifically. These include flat gaskets, frame and special seals for static and dynamic sealing points.

The design is based on medium, temperature, pressure and mechanical stress.

Moulded parts and custom-made products

FKM moulded parts are used for complex geometries. These are produced tool-specifically and tailored to the respective application.

Processing and machining

FKM can be punched, cut and waterjet cut. The choice of process depends on component geometry, quantity and tolerance requirement.

For an economic implementation, the coordination between material, manufacturing process and operating conditions is decisive.

As a starting basis for individual solutions, FKM sheets serve, while ready-designed FKM seals are used directly in the application.

Selection notes and decision criteria

The selection of FKM is based on clearly defined technical parameters. A blanket assessment is not expedient, as properties depend strongly on the compound.

Temperature and duration of use

The decisive factors are the permanently applied operating temperature as well as possible temperature peaks. In addition, the planned service life influences the selection of the suitable FKM quality.

Media contact

Type, concentration and temperature of the medium determine the chemical suitability. Alternating media or cleaning cycles must also be included in the assessment.

Mechanical load

Pressure, movement, surface pressure and possible relative movements have a direct effect on service life. Static and dynamic applications require different material designs.

Seal geometry

Shape, wall thickness and installation situation influence resilience and deformation. Tight radii or small installation spaces can restrict the choice of material.

Economic efficiency

FKM is used when technical requirements justify a higher material quality. In less stressed applications, alternative elastomers are often more economical.

For implementation, cut-to-size FKM sheets serve as the basis or directly ready-to-install FKM seals, depending on design and quantity.

Frequently asked questions about FKM

What does FKM stand for?

FKM stands for fluoro rubber and denotes a group of synthetic elastomers with high temperature and media resistance.

Which temperatures does FKM cover?

FKM is designed for permanently elevated operating temperatures. The specific application limit depends on the respective compound and the planned duration of use.

Is FKM oil- and fuel-resistant?

FKM shows very high resistance to mineral oils, synthetic oils, fuels and additives and is suitable for corresponding sealing tasks.

How does FKM behave towards chemicals?

The material offers broad chemical resistance to many solvents and process media. The exact suitability is tested on an application-specific basis.

Is FKM suitable for water and steam applications?

For applications with water or steam, alternative elastomers are frequently chosen. The material overview of elastomers supports the pre-selection.

In which forms is FKM available?

FKM is available as a semi-finished product and as a finished component, for example as an FKM sheet or as an individually designed FKM seal.