Gasket sheets are produced with finished materials obtained by paper mill process (latex in aqueous suspension) or calendering. Paper mill process gives materials with a more restricted range of application, they are more economical and compressible compared with materials obtained by calendering process which provides excellent products with optimal thermal properties and resistance to pressure. Asbestos was substituted introducing glass fibers (little used) and Kevlar fibers. Through the cutting of these materials, two kinds of gaskets are produced:
• Gaskets for less heavy uses. For example gaskets used in sewerage or water supply
• High performance gaskets able to work at high temperatures and in contact with acids and corrosive fluids
To further improve gaskets’ application range after the cutting it is possible cover the inner edge with a metal, usually copper, producing what are commonly defined as envelope or coated gaskets. The metal aims to isolate the asbestos free gasket from the aggressive fluid, allowing the work in otherwise non suitable situations.