STEMA · TECHNICAL INSIGHTS

PTFE O-Rings vs FEP/PFA Encapsulated O-Rings – Key Differences

Compare solid PTFE O-rings with FEP/PFA encapsulated silicone or FKM O-rings for chemical resistance, food contact and static sealing.

A solid PTFE O-ring is not the same as an FEP- or PFA-encapsulated O-ring. Encapsulated rings use a fluoropolymer jacket over an elastomer core, commonly silicone (VMQ) or FKM.

These products are usually intended for static sealing. The jacket can be damaged by stretching, abrasion or unsuitable installation. Confirm the exact grade for food-contact or chemical service.

Solid PTFE versus FEP/PFA jacketed elastomer

Solid PTFE has low elastic recovery. FEP/SIL and PFA/SIL contain silicone cores; FEP/FKM and PFA/FKM use fluorocarbon elastomer cores. Always evaluate the complete assembly, not only the jacket.

Encapsulated seals are generally intended for static service. Food-contact suitability must be documented for the exact product and operating conditions.

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General technical guidance, not approval for a specific application. Confirm material grade, dimensions and suitability for actual operating conditions.

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