In the crude oil, chemical plant, mechanical equipment and other manufacturing industries, when the temperature is low or high, the working pressure is high, and the corrosion energy is strong, silica gel sealing ring cannot be used. At this time, plastic sealing ring can be considered.
1. Plastic sealing ring material
The plastic seal ring is often made of PTFE or polyester. The key of forming method is milling or die forming. PTFE (abbreviated as F4) and polyester and other plastics have poor ductility and high strength, so they are not suitable for vulcanized rubber and leather products as raw materials for forming filler. However, it is still used in some places because of its unique and high-quality characteristics. Taking PTFE sealing ring as an example, it has the advantages of excellent organic chemical reliability, swelling resistance and self wetting, good high temperature and cold resistance, wear resistance and impact resistance, and very low friction resistance. However, because of its large linear expansion coefficient (about 7 times of that of steel), poor heat transfer ability (about 3 / 100 of that of steel), poor physical properties and cold flow conditions, it is required to deal with two key problems in the design scheme, namely, accurately manipulating the pre compression rate of F4 sealing ring and reasonably releasing the friction heat.
2. Design scheme of plastic sealing ring
The key to the design of the plastic seal ring is to improve the material characteristics of the seal ring and update the overall design. The key to improve the properties of plastics is to use the methods of filling plastics, modified engineering plastics and composite plastics. For example, F4 contract F2 and other blending modified materials. F4 can be compounded with vulcanized rubber. F4 is filled with glass fiber, glass powder, porcelain powder, etc. it can improve the wear resistance, compression resistance and reduce the shrinkage. The addition of brass, molybdenum, silver and other powder can improve the heat transfer and physical properties. Adding high purity graphite and vulcanized rubber pliers can improve heat transfer and wear resistance.