Known for high media and temperature resistance, Perfluoroelastomers or FFKM has a wide range of chemical stability for use where extreme safety standards are required and where high maintenance and repair costs exceed the costs of quality seals. FFKM materials are elastomeric compounds designed with high fluorine content to offer extreme chemical resistance, similar to PTFE, and also offer rubbery-elastic qualities of an elastomer with flexibility and resilience.
The chemical resistance prevents the molecular breakdown of the rubber. The resilience and spring back allow for continued sealing during thermal changes and joint movement. Dupont was the first to offer this solution with their Kalrez product line. Since then, other competitors including Parker, Freudenberg, and Minnesota Rubber introduced FFKM O-Rings to their product lines.
Advantages of FFKM
- Wide temperature range (-55°C – 330°C)
- Excellent chemical resistance – Resists over 1,800 different chemicals
- Good mechanical properties, maintains seal integrity
- Excellent gas and liquid permeation resistance
- Excellent weather ability and ozone resistance
- Self-extinguishing and non-flammable in air
- Reduces maintenance and operating costs
- Meets safety standards for pharmaceutical and food processing
Disadvantages of FFKM
- Can swell significantly in fluorinated solvents
- Should not be used with molten or gaseous alkali metals
- Thermal coefficient larger than other elastomers, so seal housing size may need modifying
- High cost, so generally used when no other elastomer is appropriate
FFKM materials are found in markets such as chemical, industrial, oil and gas, semiconductor, food & pharmaceutical, medical, and aerospace applications. These industries often have critical sealing applications where high-end elastomers prevent costly downtime and provide safe seals to prevent exposure to strong chemicals and high temperatures. In many cases, specific formulations of FFKM are created depending on the industry’s needs. Specific formulations depend on the industry’s need in a specific process.
SEMICONDUCTOR INDUSTRY
Within the Semiconductor industry, there are specific FFKM compounds depending on whether the need is for Plasma Etch, Thermal Oxidation and Diffusion, or Wet Etching processes. These compounds are designed as pure as possible. Any impurity will result in defective integrated microchips. Some of these processes involve strong acids so chemical resistance is important. Equipment downtime can result in massive production costs so going with a premium elastomer is nothing compared to knowing the part will work the first time and last longer than lower-performing alternatives.
CHEMICAL INDUSTRY
Within the Chemical Industry, there are specific formulations available that are designed for optimal temperature and compression set resistance. In other cases, steam and strong chemical resistance have been prioritized. Most of these properties far exceed any other rubber elastomer solution available on the market today.
FOOD INDUSTRY
Within the Food and Drug Administration, there are compounds designed for compliance with USP Class VI and FDA regulation 21 CFR 177.2600 which meet low extractable compatibility.
STANDARD SOLUTIONS
Kalrez 7075 has the highest temperature rating of any elastomer solution available. It also offers the greatest compression set resistance and strong acid resistance in addition to the high-temperature capability.
Kalrez 4079 is an industry-standard, particularly with a new AMS formulation for the aerospace market. It offers high temperature and compression set resistance. Kalrez 4079AMS offers high thermo-oxidative stability in gas turbine engines and meets the requirements of AMS 7257.
SHARE YOUR APPLICATION FOR A PRODUCT RECOMMENDATION
It is so important to understand all needs of the seal regardless of the industry, so the best compound can be selected. Sharing as much of this information with Sealing Devices Applications Engineers will result in the best product selection in the shortest amount of time.
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FFKM Seals: Frequently Asked Questions
What is FFKM and why is it used for extreme sealing?
FFKM (perfluoroelastomer) is a family of high-fluorine elastomer compounds that combines the chemical resistance of PTFE with the elasticity of rubber. This allows FFKM O-rings to withstand very aggressive media and high temperatures while still maintaining flexibility and sealing force, even as equipment cycles and joints move.
What temperature range can FFKM O-rings handle?
Typical FFKM compounds can operate from around -55°C up to approximately 330°C (about -67°F to 626°F), depending on the specific material grade. This wide temperature window makes FFKM a strong choice when other elastomers like standard fluoroelastomers or EPDM can’t survive the application.
How is FFKM different from FKM (Viton™) and other elastomers?
FKM (e.g., Viton™) and other fluoroelastomers offer excellent chemical and temperature resistance, but FFKM takes performance a step further. FFKM compounds are formulated with higher fluorine content, so they resist a broader range of chemicals and perform at higher temperatures than typical FKM, nitrile, or EPDM materials. FFKM is often selected when all other elastomers have failed.
Which industries commonly use FFKM seals?
FFKM seals are widely used in:
- Semiconductor manufacturing
- Chemical processing
- Oil and gas
- Pharmaceutical and food processing
- Medical devices
- Aerospace and other high-reliability industrial applications
These environments demand low contamination, tight emissions control, and long service life, where seal failure can be very costly or unsafe.
Are FFKM O-rings suitable for food and pharmaceutical applications?
Yes. There are FFKM compounds formulated to meet key regulatory and safety standards, including FDA 21 CFR 177.2600 and USP Class VI. These low-extractable materials help limit contamination risk and support strict cleanliness requirements in food, beverage, and pharmaceutical processing.
What are the main advantages of FFKM seals?
FFKM seals offer:
- Very wide operating temperature range
- Exceptional resistance to a large number of chemicals
- Good mechanical strength to maintain seal integrity
- Low gas and liquid permeation
- Strong resistance to weathering and ozone
- Non-flammability in air
By reducing seal failures, FFKM can also help minimize unplanned downtime and maintenance costs in critical equipment.
Are there any limitations or drawbacks to FFKM?
Yes. FFKM is not suited for every application. Some compounds can swell significantly in fluorinated solvents, FFKM should not be used with molten or gaseous alkali metals, and its higher thermal expansion may require housing redesign. The material cost is also higher than standard elastomers, so it’s typically chosen when performance and uptime outweigh the initial seal cost.
What are Kalrez® 7075 and Kalrez® 4079, and when are they used?
Kalrez® 7075 is a perfluoroelastomer compound with one of the highest temperature ratings of any elastomer, plus strong resistance to compression set and aggressive acids. Kalrez® 4079 is a widely used FFKM compound, including an AMS-qualified formulation (Kalrez® 4079AMS) for aerospace applications requiring high thermo-oxidative stability, such as gas turbine engines.
How do I know if my application really needs FFKM?
You may need FFKM if your seals are exposed to:
- Very high or very low temperatures
- Highly aggressive chemicals, acids, or solvents
- Applications where contamination must be minimized
- Processes where seal failure leads to major downtime or safety risks
If you’re unsure, share your media, temperatures, pressures, and service conditions with Sealing Devices’ Applications Engineering team so they can recommend whether FFKM is the best fit or if a lower-cost elastomer will perform reliably.
Can Sealing Devices help select the right FFKM compound for my process?
Absolutely. Sealing Devices works with leading suppliers such as DuPont (Kalrez®), Parker, Freudenberg, and Minnesota Rubber and can help match your process conditions—media, temperature, pressure, and cleanliness requirements—to the right FFKM compound and seal design. Providing detailed application information upfront helps ensure a fast, accurate recommendation.