The development process of my country's hydraulic (including hydraulic, the same below), pneumatic and sealing parts industry can be roughly divided into three stages.

Hydraulic seals have pressure requirements and require a certain smoothness of the joint surface. The sealing elements are mostly made of rubber, and the sealing effect is achieved through the local deformation of the seals.

The friction of seals, especially the phenomenon of hysteretic creep caused by seals, can be intentionally influenced by changing the chemical composition of the material. In the process of changing seal materials, the designer must have a firm grasp on changes in seal wear and crush performance.