Oil seal is an important part of transmission shaft media seal, and its quality and life are directly related to the normal operation of machinery. Oil seals are generally used in dynamic conditions, and are in direct contact with the sealed medium such as oil, so it is required that the oil seal sealant should have good oil resistance, wear resistance and small friction coefficient. Because the friction heat generated between the oil seal and the shaft is very high, especially the lip part is higher, so the heat resistance of the rubber material is better. In addition, it is required that the rubber material flow performance is good to ensure that it is easy to move and fill the whole mold cavity when curing.
The main performance indicators of the oil seal are heat resistance and oil resistance, and the commonly used rubber materials are nitrile rubber (long-term use temperature below 120 ~ C), acrylic rubber (120 ~ C ~ 170℃), fluorine rubber (170℃ ~ 220oC). Under normal use, oil leakage failure occurs in the later stage, mainly due to the hardening of the lip of the oil seal, the loss of elasticity and cracking. In order to improve the service life of the oil seal, the heat resistance of the rubber used in the oil seal must be improved. After the rubber type is determined, the vulcanization system is the key, such as nitrile rubber material, the selection of DCP peroxide vulcanization system and the addition of auxiliary vulcanization agent to improve the heat resistance (such as magnesium methacrylate) can effectively improve the heat resistance.
For the filling and reinforcing system, because the oil seal requires a certain mechanical strength, tear resistance, good wear resistance, high wear resistance furnace black, fast press carbon black, and general carbon black, semi-reinforced carbon black, hot cracking carbon black, spray carbon black and so on are often used. White carbon black is also a common choice of filling and reinforcing agent, such as single white carbon black, in order to improve mechanical strength can add silane coupling agent. Another advantage of the white carbon black material is that it has good adhesion to the metal skeleton material. For fluorine rubber compound, it is not suitable to use fine particle active carbon black, usually use coarse particle hot cracking carbon black or spray carbon black. In order to increase the self-lubricity of the oil seal vulcanizate and reduce the friction coefficient, graphite powder, molybdenum disulfide and other filling materials are often added.
