What are the common graphite materials used in mechanical seals, and what are their respective characteristics?

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Graphite is produced by compressing coke powder and graphite powder (or carbon black) using asphalt as a binder, and then sintering it at high temperatures. Depending on the raw materials used, as well as the sintering temperature and time, graphite with different physical and mechanical properties can be produced. One type is known as high-strength graphite, also called carbon graphite; it is characterized by being hard and brittle, having a low thermal conductivity, and being difficult to process. The other type is graphitized graphite, also known as electrographite; it is soft, has low strength, but exhibits good self-lubricating properties. During the production of graphite, high-temperature sintering causes the pitch to evaporate, resulting in the formation of pores; therefore, it must be impregnated before it can be used. Impregnated graphite has no significant effect on thermal conductivity, but its strength and hardness are significantly improved. In addition to the graphite mentioned above, there is also resin graphite, which is made by using synthetic resin as a binder, mixing it evenly with graphite powder, pressing it into shape, and then raising the temperature to the point at which the resin solidifies. This type of graphite allows for a relatively low PV value to be used; it is less utilized in the petrochemical industry, and its advantage is its low cost.