PTFE is prone to internal cooling and stress relaxation under stress and continuous high temperature, so it is generally used for low voltage, medium temperature, strong etching and substances that do not allow environmental pollution, such as strong alkali, strong acid, Halogen lamp, drugs, etc. The safety application temperature is 150 ℃, and the working pressure is below 1MPa. Although polytetrafluoroethylene has higher compressive strength, its application temperature does not exceed 200 ℃ and its corrosion resistance is reduced. PTFE gaskets working pressure generally does not exceed 2MPa.

Due to the increase in temperature, the raw materials experience stress relaxation, resulting in a significant decrease in the sealing working pressure. Even if the temperature is not raised, with the increase of time, the internal stress of the protruding surface clamping will also decrease, resulting in a stress relaxation condition. This condition can be caused in various gaskets, and only the stress relaxation condition of polytetrafluoroethylene gaskets is relatively serious, which should be paid attention to.

The friction resistance of polytetrafluoroethylene is relatively small (the clamping internal stress exceeds 4MPa, and the friction resistance is 0.035-0.04), and the gasket is easy to move outward when torque is applied. Therefore, a convex concave flange surface should be selected. When selecting a plan flange, the diameter of the gasket can be touched by the anchor bolt, and the anchor bolt can be used to prevent the gasket from sliding outward. Because the glass lined equipment is made by calcining a layer of enamel on the metal surface after painting, the glaze layer is too brittle, coupled with uneven painting and fluidity of the glaze layer, the flatness of the flange surface is weak. Choosing a metal material mixed gasket can easily damage the glaze layer, so it is recommended to use a PTFE gasket with a core plate made of asbestos rubber and silicone. This type of gasket is very easy to fit with the flange surface and resistant to corrosion, with excellent application efficiency.

Many factories use asbestos rubber sheets wrapped with polytetrafluoroethylene raw tape for frequently disassembled access holes and pipelines in strong corrosive substances with low temperature and working pressure. Because it is made and convenient to use, it is quite popular.