When choosing sealing materials, the working conditions should be taken into account, and the price factor should be taken into account.

Working medium

Sealing medium is liquid or gas, if it is liquid, it should consider the compatibility of liquid and material; gas should also consider the compatibility of material with lubricant and grease; gas and negative pressure sealing should also pay attention to the permeability. If the sealing material is incompatible with the sealing fluid, it will lead to expansion or contraction of the sealing parts, and failure will occur at the early stage of use. Expansion of seals increases friction resistance and makes seals roll. The shrinkage of seals will cause the reduction of preload and eccentricity compensation until leakage.

Friction factor

Seals have corresponding requirements for friction and wear properties of materials. Material with appropriate friction factor should be selected according to the motion speed. In order to obtain enough service life, the wear resistance of materials should be selected according to the movement speed and stroke. When low speed is required, special attention should be paid to the magnitude of material friction coefficient and the difference between dynamic and static friction coefficient.

structural style

The working principle of seals varies with different structural types (such as extrusion, shaft lip or mechanical seals), which necessarily requires different mechanical properties such as elasticity, strength and deformation rate of materials.

working temperature

Rubber, plastic or graphite and metal sealing rings for mechanical seals vary widely in their applicable temperature range. When selecting materials, it is necessary to accurately grasp the working temperature of sealing parts, especially components in low temperature environment; or according to the working temperature range of materials, to control the temperature rise of components, systems and seals.

Working pressure

Working pressure is the main working parameter of sealing system, which can be changed between 1-400 MPa or in a larger range. The pressure resistance of materials should meet the requirements of working pressure.

work environment

If there is dust pollution in the working environment, it will aggravate the wear of materials, so the wear resistance of materials should be improved.

Vibration shock

If working under vibration or impact conditions, the material should have sufficient strength and elasticity to compensate for the damage of seal and insufficient contact stress caused by vibration offset.

Transfer process

The transfer process of seals and even the structure of seals are related to the deformation ability of materials. Generally, the assembly process should be adapted to the performance of materials, and the assembly performance of seals should be taken into account when selecting materials.

The above eight requirements for sealing materials are often mutually restrictive and cannot be unified. As far as sealing and friction are concerned, the pursuit of one must be at the expense of the other in terms of material properties. At this time, the two performance requirements must be moderately balanced. Therefore, with the proposal of higher sealing requirements, professional materials must be sought according to the use conditions. Even in the same component, according to different requirements, sometimes a variety of sealing materials are selected.