Main performance requirements for oil seals
When the structural parameters of the oil seal is determined, the oil seal material is an important factor affecting its sealing performance and service life. It directly affects the oil seal of the three key parameters, namely: oil seal on the shaft of the radial force; Oil Seals the amount of interference; lips in the borrowed contact area. Therefore, the main performance requirements of the oil seal compound are: ① chemical stability with the sealing medium is good, the compound in the sealing medium (mainly oil) does not occur swelling, hardening and other phenomena, otherwise the radial force Reduce, change the size of the interference, resulting in sealing failure. ② has a good heat resistance, wear resistance, friction coefficient is small, which is more high linear speed oil seal is particularly important. ③ has a moderate elasticity, can adapt to the roughness of the shaft and eccentricity of the changes, the dynamic eccentric have a better ability to follow (follow-up).
Recipe design points
Manufacture of oil seal mainly rubber nitrile rubber, acrylic rubber, fluorine rubber and silicone rubber. What specific choice of rubber, depending on the type of oil and the working temperature may be. Usually in the general fuel, hydraulic oil, oil, no special additives in the lubricating oil, Oil Seals the temperature in the -40 ~ +120 ℃, the choice of nitrile rubber; -20 ~ + 150 ℃ in the gear oil can be used acrylic Rubber; in -40 ~ +120 ℃ of various oils and corrosive medium can choose fluorine rubber; in -100 ~ +250 ℃ high temperature, high speed oil seal, the choice of silicone rubber. Regardless of which rubber is used as the main material of the oil seal, shrinkage due to the expansion of the oil and the withdrawal of the binder in the vulcanizate are caused. If the oil entering the rubber is more than the extracted components, the vulcanizate will expand; otherwise, shrink. Oil Seals Shrinkage of the General Assembly to reduce the amount of lip and shaft interference, follow-up decline. And the expansion is too large, will change the structure of the oil seal size, so that the radial force decreased, resulting in sealing failure. Therefore, the volume change rate of the oil seal compound in the sealing medium should be reduced as much as possible. It is generally believed that a slight amount of expansion is advantageous for sealing performance and service life of the oil seal.
① vulcanization system: nitrile rubber should use low sulfur or sulfur-free, Oil Seals or effective curing system and peroxide composition of the complex system. Acrylic rubber commonly used sodium stearate, potassium stearate or both as a vulcanizing agent. Fluorine rubber is generally vulcanized with 3 # vulcanizing agent, while the compression of permanent deformation requires a higher oil seal, available double into the A and with benzyl triphenyl phosphorus chloride curing system. Silicone rubber is still used for vulcanization of peroxide.
② reinforcement, filling system: reinforcing agent generally used in the particle thermal cracking carbon black, spray carbon black or with carbon black, general carbon black, semi-reinforced carbon black, high wear-resistant carbon black and use. In order to reduce the coefficient of friction of the oil seal compound, the compound can be filled with the appropriate amount of graphite powder, molybdenum disulfide, silicon nitride and other self-lubricating materials as filler.
③ plasticizer, antioxidant: should not be easily selected by the sealing medium, Oil Seals such as polyester plasticizer, reactive antioxidant to ensure the stability of the size of the oil seal, will not cause excessive contraction, damage the seal of the oil seal performance.