FEP/PFA Encapsulated O-Rings
Elastomeric, rubber O-Rings are susceptible to high friction and limited resistance to aggressive chemicals. Solid PTFE O-Rings are rigid with no effective memory and high compression set. FEP or PFA Encapsulated O-Rings combine the resilience and sealing force of an elastomer with the chemical resistance of PTFE. This is accomplished by the use of an elastomeric core of silicone or FKM with a relatively thin encapsulation of FEP or PFA fluoropolymer plastic. The result is an elastomeric PTFE seal with enhanced sealing capability.
Hercules OEM's Chem-RING FEP or PFA Encapsulated O-Rings are solvent-resistant and chemically inert (except for attack by alkaline metals, fluorine and some halogenated compounds at high temperatures), yet have an elastomeric memory near that of rubber O-Rings. The more commonly specified FEP encapsulation also has an extremely low coefficient of friction (.1 to .2) and very low permeability to gases, making CHEM-RINGS virtually a universal seal for use in hostile environments. PFA encapsulated O-Rings have increased maximum temperature limits over FEP encapsulated seals.