Rubber seals are the only polymer materials with high flexibility and excellent elasticity. The biggest characteristic of rubber is that its modulus of elasticity is very small and its elongation is very high. Secondly, it has good air permeability and resistance to various chemical media and electrical insulation. Some special synthetic rubber have better oil resistance and temperature resistance, and can resist the swelling of fat oil, lubricating oil, hydraulic oil, fuel oil and solvent oil; cold resistance can be as low as - 60 to - 80 degrees C, heat resistance can be as high as + 180 to + 350 degrees C. Rubber also withstands all kinds of flexural and bending deformation, because the hysteresis loss is small. The third characteristic of rubber is that it can be blended, blended and compounded with a variety of materials, and then modified to obtain good comprehensive properties.