FFKM is an abbreviation for perfluorinated rubber. Another abbreviation commonly seen, often in Europe, is FFPM. In industry, the name Kalrez is routinely used as a synonym for FFKM. Kalrez is the trade name of DuPont de Nemours, under which the company markets its FFKM products. DuPont de Nemours primarily sells finished parts, whereas compounds of FFKM can only be purchased from other producers like Daikin Industries of Japan.
The media and temperature resistance of FFKM is broadly like that of PTFE (polytetrafluoroethylene, also known under the trade name Teflon). Due to its high crystallinity (meaning it is unyielding and inflexible) PTFE belongs to the thermoplastics, but has properties that would justify its classification as a duroplastic (you can find out more about the difference between elastomers, thermoplastics and duroplastics here).
Essentially, by incorporating monomers, an elastomer can be produced with resistance properties almost the same as those of PTFE. When partially fluorinated monomers are used, then you get fluoroelastomers (FKM). However, if completely fluorinated, that is, hydrogen-free monomers are used, the result is a perfluoroelastomer FFKM.
Cross-linking agents for FFKM compounds can be diamines, bisphenol or peroxides. Triazine cross-linking is also an option. The type of cross-linking significantly impacts the thermal and chemical resistance of an FFKM compound. This is something that must be taken into account when selecting the correct FFKM compound. It makes good sense to work closely with the manufacturer regarding the application specifications for the material.
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