Engineering: Chemical Resistance: Teflon Encapsulated O-Ring

The Teflon® FEP or PFA encapsulation is the essential component of the ENCAP-O-SEAL, Teflon® encapsulated o-rings which are resistant to practically all chemicals. Within normal use temperatures, FEP or PFA resins are attacked by so few chemicals that it is more practical to describe the exceptions rather than to tabulate the chemicals with which they are compatible. Molten alkali metals, fluorine, and several complex halogen compounds (chlorine trifluoride) are incompatible with FEP/PFA resins. In some instances, at or near the suggested service limit temperature of FEP (204 C/400 F) and PFA (260 C/500 F), a few chemicals at high concentrations have been reported to be reactive. Attack has been produced at such high temperatures by 80% NaOH or KOH, metal hydrides such as boranes (e.g. B2 H6), aluminum chloride, ammonia (NH3), and certain amines (R-NH2) and imines (R=NH). Also, slow oxidative attack has been observed by 70% nitric acid under pressure at 250C/480 F. Special testing is required when such extremes of reducing or oxidizing conditions are approached.