The friction coefficient of PTFE is small (the compression stress is greater than 4MPa, and the friction coefficient is 0.035~0.04), and the gasket is easy to slip outward during pre-tightening, so it is better to use concave and convex flange faces. When a flat flange is used, the outer diameter of the gasket can be contacted with the bolt, and the bolt can be used to prevent the gasket from sliding. Since the glass-lined equipment is sprayed with a layer of enamel on the metal surface and then sintered, the glaze layer is very brittle, and the uneven spraying and flow of the glaze layer make the flange surface flatness poor. The use of metal composite gaskets is easy to damage the glaze layer, so it is recommended to use a PTFE gasket with asbestos board and rubber core material. This kind of packing pad is easy to fit with the flange surface and is also corrosion resistant, and the use effect is good.

Many factories use asbestos rubber sheets to wrap raw polytetrafluoroethylene tapes in strong corrosive media with low temperature and pressure, which are used in manholes and pipelines that are often dismantled. It is very popular because of its easy production and use.