Elastomer Seals: FKM vs. FFKM in High Vacuum

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For decades, elastomer seals have formed the backbone of high vacuum systems, offering remarkable sealing capabilities and durability. At ANCORP, we specialize in providing the highest quality elastomer seals designed to withstand the demands of high vacuum applications.

Elastomer Seals in Vacuum

Elastomer seals are an essential component of the vacuum technology world. Their ability to create a leak-tight seal is paramount for high vacuum applications, where even the smallest leak can result in diminished system performance.

Elastomer materials create a seal by undergoing deformation in vacuum which fills microscopic irregularities on a flange sealing surface, thereby creating a virtually impermeable seal by vacuum standards. The performance of an elastomer seal is heavily influenced by material compatibility between the elastomer and process conditions. Conditions that affect the elastomer are a result of both the inherent properties of the material and the environment of the vacuum.

Elastomer seals are generally found in ISO flanges and fittings and ASA flanges and fittings but also various valves and traps. Each incorporates high-quality elastomer seals designed to provide optimal performance and durability as shown in the ISO clamps featured below.

Material compatibility is an essential factor to consider when selecting the appropriate seal. It involves a deep understanding of the chemical nature of the elastomer and its interaction with the surrounding environment, which may include a range of fluids, gases, and temperatures. At a molecular level, elastomers are long-chain polymers that have cross-links between the chains. These cross-links provide the elasticity and resilience that are characteristic of elastomers and influence compatibility. Among the numerous types of elastomers available, Fluorocarbon elastomers (FKM) and Perfluoroelastomers (FFKM) are the most commonly used in high vacuum applications.

FKM and FFKM: Different Elastomers for Different Applications

Fluorocarbon elastomers (FKM) and Perfluoroelastomers (FFKM) are examples of elastomers widely used in high vacuum applications, and each has a different chemical compatibility due to their unique molecular compositions.


FKM is characterized by carbon atoms fully or partially surrounded by fluorine atoms. The strong carbon-fluorine bonds lend FKM excellent chemical and thermal resistance. This molecular structure makes FKM seals compatible with a wide range of chemicals, including hydrocarbons, oils, and some acids, but less suitable for polar solvents like ketones and amines.

FFKM, on the other hand, has a structure where all backbone carbon atoms are surrounded by fluorine atoms. This results in even higher chemical resistance than FKM, making FFKM compatible with virtually all chemical media, including polar solvents, and even more extreme temperatures.

However, no elastomer is universally compatible with all media and conditions. Factors such as the media’s concentration, exposure duration, temperature, and pressure also play a role in determining compatibility. Hence, the selection of elastomer materials in high vacuum applications often involves a thorough understanding of the specific environmental constraints of the application.

ANCORP: Empowering your High Vacuum Applications

Elastomer seals are used extensively across ANCORP’s wide range of high vacuum components, including our ISO flanges and ASA flanges. These seals are critical in maintaining the high vacuum environment required in industries ranging from semiconductor manufacturing to materials science research and aerospace applications.

The choice of elastomer seal will depend on the specific application and process. As mentioned above, FKM seals may be used in high vacuum applications where exposure to harsh chemicals is limited. And, FFKM when the system will be exposed to extreme temperatures or aggressive chemical environments.

We are committed to helping our customers navigate these complexities, using our understanding of vacuum science to guide you towards the best elastomer solution for your specific application. Whether you’re dealing with high temperatures, corrosive chemicals, or other challenging conditions, our team can help you navigate elastomer seal selection for your specific application. Reach out to our sales team today to learn more about our range of elastomer seals.