Envelope gaskets are one of the earlies development of a PTFE gasket material that has sought to eliminate the cold flow problems of pure PTFE material. The product is old-fashioned and does not have current approvals for sealant use. For example, new environmental requirements require the use of BAT and verified tightness values, which are missing so we do not recommend using the material as a sealant. Envelope gaskets have been effectively replaced with the most modern gasket option, KLINGER® top-chem 2000 PTFE.
We do not recommend using this material as a sealant