Perfluoroelastomer
ASTM D1418, ISO 1629 Designation: FFKM
ASTM D2000, SAE J200 Type/Class: JK, HK
Standard Color: Black
Trade Names:
- Aegis® (International Seal Company)
- Chemraz® (Greene, Tweed & Company)
- Kalrez® (DuPont Dow Elastomers)
Relative Cost: Very High
General Temperature Range: -35° to +500° F
The majority of perfluoroelastomers are terpolymers of tetrafluoroethylene (TFE), perfluorovinyl ether (PVE), and a cure site monomer. The fully-fluorinated monomers contained in perfluoroelastomers endow them with superior chemical resistance. There are currently three main commercial compounds:
Aegis offers both superior chemical resistance and thermal stability. Composed of high-purity ingredients, Aegis also boasts low permeation and outgassing. Parts made of Aegis have found wide use in the semiconductor industry and as components in analytical instruments.
Chemraz offers superior chemical compatibility coupled with outstanding steam resistance. Chemraz is resistant to almost every chemical compound, including fuels, ketones, esters, alkalines, alcohols, aldehydes, and both organic and inorganic acids.
Kalrez is a highly resistant perfluoroelastomer that features both the chemical resistance of Teflon® and the high temperature stability of a fluoroelastomer like Viton®. Resistant to over 1,600 solvents, chemicals, and plasmas, Kalrez exhibits minimal swell and can function in almost any chemical or petrochemical situation. Kalrez offers low compression set, and it doesn’t get hard and brittle in temperatures up to 600° F (316° C). Kalrez is less likely to cold flow than Teflon. Kalrez seals are most common in the oil exploration and refining industries. It is also used for seals in analytical and process control equipment, as well as for chemical processing and transportation seals.
On the down side, Kalrez’s compression set increases as temperature increases. Despite its overall chemical resistance, Kalrez can swell when in contact with uranium hexafluoride, fully halogenated Freon®, and some fluorinated solvents. Kalrez should never be exposed to molten or gaseous alkali metals, and gland volume may need to be increased to allow for expansion in higher temperatures. Processing is difficult, so much so that DuPont (which normally deals in raw polymers rather than finished products) took the lead in producing finished Kalrez articles since other manufacturers did not want to tackle it.
FFKM performs well in:
- Most chemical and petrochemical situations
FFKM does not perform well in:
- Uranium hexafluoride
- Fully halogenated freons
- Some fluorinated solvents
