FFKMs (according to standard ASTM 1418) (equivalent to FFPMs according to ISO / DIN 1629 standard) are perfluoroelastomeric compounds that contain an even higher amount of fluoride than FKM. The name Kalrez® is a trademark of Dupont.
The material is actually an improved version of Viton with 20% more fluorine in the chains, making it an extremely expensive per fluorocarbon elastomer.
FFKM seals often last longer in demanding chemically aggressive process environments and have better sealing possibilities than other elastomers.
They have improved resistance to very high temperatures to slightly above 300 ° C, chemicals and are even resistant to environments where oxygen-plasma is present for many hours.
FFKMs are used in highly aggressive chemical processes, semiconductor wafer production, pharmaceutical industry, oil and gas extraction and aerospace applications. The long-term performance of FFKM seals can lead to less frequent inspections, repairs and replacement of the seal, which in turn results in increased usability of the process and equipment and longer MTBF with significant cost reduction as the end result.
FFKM seals also help prevent contamination in semiconductor processes by reducing extractables, reducing particulates and providing resistance to degradation in raw plasma. Certain grades have a maximum continuous operating temperature of 327 ° C (621 ° F).
FFKMs are often used to make O-rings and gaskets used in applications where contact with hydrocarbons or highly corrosive liquids is the case, or when a very wide temperature range above the freezing point has to be covered.
For vacuum applications, FFKM offers low gassing and particulate emissions in vacuum sealing applications, as well as high temperature applications (200 – 300 ° C). After production, they are cleaned O-plasma vacuum (and / or vacuum fired) to achieve an aeration performance comparable with Teflon®, while achieving a vacuum density (permeability rates) similar to FKM (Viton®) compounds. Because of this combination of properties, FFKM seals can easily reach UHV pressures without using a metal seal.
However, they are considerably more expensive than standard FKM O-rings.