Requirements for sealing materials of vacuum pump are as follows:
1. Vacuum pump should have enough low saturated vapor pressure. In general, the saturated vapor pressure at room temperature shall be less than 1.3 × 10-1 ~ 1.3 × 10-2Pa in low vacuum and 1.3 × 10-3 ~ 1.3 × 10-5pa in high vacuum.
2. Good chemical and thermal stability. In the sealing part, it will not soften due to reasonable temperature rise, chemical reaction or volatilization will occur, or even be broken by the atmosphere.
3. It has certain mechanical and physical properties. The solid sealing materials hardened after cooling, plastic sealing materials or sealing wax hardened after drying shall be able to smoothly cling to the sealing surface without bubbles and wrinkles. When the temperature changes, there is no strain embrittlement or crack. Liquid or colloidal sealing materials shall maintain the original viscosity.
4. Some sealing materials shall be soluble in some solvents. So that it can be easily cleaned out during replacement.
In addition to the above requirements, in some cases, the materials used in vacuum pumps must also consider their electrical properties, insulation properties, optical properties, magnetic properties and thermal conductivity properties.
Of course, in addition to the above properties of materials, we should also consider the cost, utilization rate and the possibility of purchasing materials.