When selecting sealing materials, the main consideration should be working conditions, and price factors should also be taken into account.

Working medium

Is the sealing working medium liquid or gas? If it is liquid, the compatibility between the liquid and the material should be considered; The compatibility of materials with lubricants and greases should also be considered for gases; Gas and negative pressure seals should also pay attention to breathability. If the sealing material and sealing fluid are incompatible, it can cause the seal to expand or contract, leading to failure in the early stages of use. The expansion of the seal causes an increase in frictional resistance and also causes the seal to roll. Shrinkage of the seal will cause a decrease in preload, a decrease in eccentricity compensation capability, and eventually lead to leakage.

Friction coefficient

Sealing has corresponding requirements for the friction and wear performance of materials, and materials with appropriate friction coefficients should be selected according to the speed of movement. In order to achieve sufficient service life, the wear resistance of the material needs to be selected based on the movement speed and stroke. When there are requirements for low-speed performance, special attention should be paid to the magnitude of the material's friction coefficient and the difference between the dynamic and static friction coefficients.

structural style 

Different structural types result in different sealing principles (such as extrusion type, shaft lip type, or mechanical seal), which inevitably require different mechanical properties such as elasticity, strength, and deformation rate of the material.

working temperature 

The temperature range of rubber, plastic, graphite, and metal sealing rings used for various sealing rings varies greatly. When selecting materials, it is necessary to accurately grasp the working temperature of the sealing components, especially in low-temperature environments; Or control the temperature rise of components, systems, and seals based on the working temperature range of the material.

working pressure

The working pressure is the main working parameter of the sealing system, which can vary between 1-400MPa or larger. The pressure resistance of the material should meet the requirements of the working pressure.

work environment

If there is dust pollution in the working environment, it will exacerbate material wear, and the wear resistance of the material should be improved.

Vibration impact

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

Transfer process

The transfer process of seals and even the structure of sealing devices are related to the deformation ability of materials. In general, the assembly process should be adapted to the material properties, and if allowed, the assembly performance of seals should be appropriately considered when selecting materials.

The above 8 requirements for sealing materials are often interdependent and cannot be unified. In terms of sealing and friction, pursuing one of them must come at the expense of sacrificing the other in terms of material properties. At this point, it is necessary to strike a moderate balance between the two performance requirements. So with higher sealing requirements, it is necessary to seek professional materials according to the usage conditions. Even within the same component, multiple sealing materials may need to be selected according to different requirements.