Perfluoroelastomers FFKM

FFKM perfluoroelastomers are only used when the ultimate heat and oil resistance combination is absolutely needed and cost is not a barrier. These elastomers represent the most expensive rubber commercially available. This class of elastomer represents the highest level of fluorination available, with a fluorine content of 73%. FFKM molecular chains are fully fluorinated. The fluorine bonds present impart a unique level of chemical inertness to these polymers, which can impart excellent chemical inertness to the rubber compound in many situations. 

The price of these elastomers can be 2,000 to 3,000 per pound. They are only used when the ultimate combination of heat and oil resistance is needed. Commonly, FFKM is used in critical sealing applications. 

FFKM is a perfluorinated polymethylene rubber with fluoro, perfluoroalkyl, and/or perfluoroalkoxy groups on the polymer chain, likely with a small fraction of perfluorinated monomer units containing functionality to enable vulcanization. 

Perfluoroelastomers FFKM (official ASTM abbreviation) Perfluorocarbon elastomers PFR 

There is no standard classification system for FFKM. This technology is very proprietary. 

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Perfluoroelastomers (FFKM), such as KALREZ, are particularly suited for extreme service conditions. They are resistant to more than 1,500 chemical substances, including ethers, ketones, esters, aromatic and chlorinated solvents, oxidizers, oils, fuels, acids, and alkali and are capable of service at temperatures up to 316°C (600°F).55 Because of the retention of resilience, low compression set, and good creep resistance, they perform extremely well as static or dynamic seals under conditions where other materials, such as metals, FKM, PIPE and other elastomers, fail. Parts from FFKM have very low outgassing characteristics and can be made from formulations, which comply with FDA regulations.56 Primary areas of application of perfluoroelastomers are paint and coating operations, oil and gas recovery,... 

Perfluoroelastomers represent a special subgroup of fluorocarbon elastomers. They are essentially rubbery derivatives of PTFE and exhibit exceptional properties, such as unequaled chemical inertness and thermal stability. Currently, there are two types of known commercial perfluoroelastomers, KALREZ and PERLAST . These have ASTM designation FFKM. 

Perfluoroelastomers (ASTM designation FFKM) are essentially copolymers of two perfluorinated monomers, TFE and PMVE with a CSM, which is essential for cross-linking. Perfluoroelastomers can be cured by ionizing radiation without any additives. The advantage of radiation cured FFKM is the absence of any additives, so that the product is very pure. The disadvantage is the relatively low upper-use temperature of the cured material, typically 150°C, which limits the material to special sealing applications only [32]. 

Perfluoroelastomers (ASTM designation FFKM) such as copolymers of tetrafluoro-ethylene (TEE) and perfluoromethylvinyl ether (PMVE) can maintain their thermal stability to temperatures as high as 300°C (572°F) or even higher, with a maximum continuous service temperature of 315°C (599°F). Moreover, instead of hardening, the elastomer becomes more elastic with aging [13]. 

The longer the polymer chain is, the better is the resistance to compression set because of the improved ability to store energy. In Figure 8.3, the sealing compounds are NBR (nitrile rubber), EPDM (ethylene-propylene diene rubber), FVMQ (fluoro-vinyl-methyl [fluorosilicone]), VMQ (vinyl-methyl silicone), FKM (fluroelastomers), and FFKM (perfluoroelastomers). 

FFKM Perfluoroelastomer Fully fluorinated fluorocarbon Best fluid resistance of any elastomer Fluorocarbon-containing refrigerants cause minor effects... 

Another category of fluoroelastomers, called FEPM has been created recently for base resistant fluoroelastomers. For higher temperature and chemical resistance fiiUy fluorinated materials, called perfluoroelastomers, are available in the form of molded seals and parts, such as Kalrez perfluoroelastomers parts and Chemraz Perfluoroelastomer Compounds. They bear the classification of JK or HK depending on supplier and compound offered, JK offering a continuous service temperature of 315°C. FFKM compounds are available from most FKM suppliers but gums are rarely available and in this chapter we focus on fluoroelastomers FKM and FEPM. 

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