With the development of modern industry, the working conditions of seals are becoming more and more demanding, requiring seals to have high temperature resistance, high pressure, high speed and low friction, low wear, long service life and high sealing reliability. In terms of reciprocating seals, in recent years, many seals for imported equipment have used slip ring seals filled with PTFE and rubber, so the combination seal made of PTFE is universally recognized. For the application of effective sealing components in reciprocating hydraulic systems.

Polytetrafluoroethylene (PTFE), the main material of the slip ring type combination seal, is a copolymer of polytetrafluoroethylene monomer. The excellent performance of PTFE is highlighted in several aspects. Wide range of high and low temperature use. It can work for a long time at a high temperature of 260 ° C, or satisfactorily used at a low temperature of -250 ° C; high chemical stability. Strong acid, strong alkali, strong oxidant, organic liquid, etc. have no effect on it; abnormal self-lubricity. It has an extremely low coefficient of friction of only 0.03, and the dynamic and static friction coefficients are almost equal; the protruding surface is not sticky. Almost all viscous substances cannot adhere to its surface; it is resistant to high pressure.

Polytetrafluoroethylene is an aggregate composed of a ribbon crystal between a crystalline sheet and a disordered amorphous phase. The molecules between the two phases are extremely weak, and the wear resistance and thermal conductivity are poor, soft and easy to flow. These are not sufficient to hinder its use, so various fillers need to be added to the PTFE to improve some of its mechanical and physical properties. At present, whether it is from the formulation of PTFE, the sintering process, or the structural design and processing technology of the slip ring combination seal, it has been perfected and matured. The reciprocating slip ring type combination seal "shaft step ring" and "hole square ring" have been widely used in the loader industry, and the rotary type slip ring type combined seal "shaft revolving square ring" and "hole" have been produced. The use of a revolving square ring has also been promoted and used in the excavator industry, and has been applied on many devices and has been affirmed. The service life is close to the level of the imported seal.