PTFE envelope gasket are type of static seal. It is composed of elastic materials such as compressed non-asbestos sheet ,rubber,Ceramics, etc., and a PTFE envelope cove 　　PTFE has superior properties against chemical (not affected by all chemicals except molten alkali metal and fluorine at elevated temperature) and a wide working temperature range. (from ?80~260℃) the coefficient of static and dynamic friction of PTFE are very low. PTFE is the best of the ?on-stick?materials. It has excellent weathering and aging characteristics. 　　Application:PTFE envelope gasket is used to seal pipe flanges glass lined, PVC or FRP. Low bolt torque effecting a seal and chemical compatibility is a main characteristic of this type of gasket.