Graphite packing ring manufacturers produce various shapes of sealing products by stamping and cutting with molds or various tools based on various sealing materials (asbestos-free copy board, asbestos-free shrinkage board, asbestos-free rubber board, and other asbestos-free materials) according to various detailed working conditions. Asbestos-free gaskets are roughly classified into asbestos-free rubber board gaskets and asbestos-free copy board gaskets.
They are a series of asbestos-free sealing gaskets made of organic fibers such as aramid and plant fibers, nitrile rubber, and mineral materials. Since the asbestos-free gasket series not only has high strength but also good elasticity and superior impermeability, it is an excellent replacement for asbestos gaskets in automobiles and industrial machinery for ring sealing. Due to the impossibility of perfect machined surfaces, the use of oval gaskets can fill irregularities. When using oval gaskets, pressure and temperature mutually restrict each other. As the temperature rises and the equipment operates for a period of time, the oval gasket material softens, creeps, undergoes stress relaxation, loses mechanical strength, and the sealing pressure decreases.
Asbestos sealing materials are more heat-resistant than asbestos-free sealing materials. The main components of asbestos sealing materials are asbestos, fillers, and rubber, among which asbestos and fillers have high heat resistance. Most non-metallic graphite gaskets are mainly composed of mineral fibers, organic fibers, fillers, and rubber, with the heat resistance of organic fibers typically around 200°C. Currently, asbestos gaskets can withstand temperatures up to around 1000°C.
The mechanical strength of asbestos sealing materials is higher than that of asbestos-free sealing materials. The surface of asbestos fibers is attached with multivalent metal cations, which easily forms a strong interface connection with rubber containing negative charges on its surface, enhancing the connection strength of rubber fibers, i.e., the mechanical strength of the material used in graphite metal spiral wound gaskets. However, the direct affinity of various selected non-asbestos mineral fibers with rubber substrates is inferior to that of asbestos, and thus the contact strength of rubber fibers is also less than that of asbestos.
