1, O-ring seal compound
The O-ring is a kind of sealing product with simple structure, various specifications and a large quantity. The seal quality life of O-rings depends on dimensional accuracy and size. It is generally required that the rubber compound has certain mechanical strength, tear resistance, good heat resistance, oil resistance, chemical resistance, and small compression set under the conditions of use. According to the requirements of use, there are generally heat and oil resistance requirements, and the use of rubber compounds is the most. Acrylate rubber can be used for oil-resistant sealing products with higher temperature (such as 150~C-l90 °C). Fluorine rubber for oil resistant rubber products requiring higher temperature, silicone rubber for heat resistance. When the working pressure is high, the method of increasing the hardness of the O-ring compound is to increase the filling amount of the carbon black, but the filling amount is too high, the mixing is difficult, and the basic physical properties of the vulcanized rubber are damaged, and the glue is also made.
It is prone to scorch. In the case of using the same kind of rubber, such as nitrile rubber, in order to improve heat resistance and oil resistance and reduce compression set, a peroxide (such as DCP) vulcanization system or an effective sulfur vulcanization system (low sulfur high promotion) may be used. . These two vulcanization systems can generate
The carbon-carbon bond cross-linking structure and the monosulfide bond cross-linking structure effectively improve the heat resistance and oil resistance of the vulcanizate and reduce the compression set.
In the filling and reinforcing system of the heat-resistant and oil-resistant rubber compound of the O-ring, the less reactive hot black, spray carbon black or semi-reinforcing carbon black is used, and the carbon black is characterized by coarse particles. The rubber has good elasticity, low heat generation, low compression set and can be filled in a large amount to reduce the cost of the rubber compound. If the O-ring is used under dynamic sealing conditions, it is necessary to increase the tear resistance. A highly wear-resistant carbon black with a higher activity may be used in combination. Fluororubber rubber is a self-reinforcing rubber. If it is filled with activated carbon black, it will reduce the mechanical properties of the rubber. Therefore, it is generally filled with a small amount of hot particles of low activity or hot carbon black.
2, oil seal compound
The oil seal is an important part of the transmission shaft medium seal, and its quality and life are directly related to the normal operation of the machine. Oil seals are generally used under dynamic conditions and are in direct contact with the sealed medium such as oil. Therefore, the oil sealant is required to have good oil resistance, wear resistance and a small friction coefficient. Since the oil seal and the shaft have high heat generation, especially in the lip portion, the heat aging resistance of the rubber material is good. In addition, the flow properties of the rubber compound are required to ensure that it is easy to move and fill the entire cavity during mold clamping. The main performance indicators of oil seals are heat and oil resistance. The commonly used rubber compounds are nitrile rubber (long-term use temperature below 120~C), acrylate rubber (120~C-170°C), and fluororubber (170°C-220oC). Under normal use, the oil seal fails in the later stage, mainly due to the aging and hardening of the oil seal lip, loss of elasticity and cracking. In order to improve the service life of the oil seal, it is necessary to increase the heat resistance of the rubber compound used in the oil seal. After the rubber type is determined, the vulcanization system is the key. For example, a nitrile rubber compound, a DCP peroxide vulcanization system, and a vulcanizing agent (such as magnesium methacrylate) added with heat resistance can effectively improve heat resistance. For the filling and reinforcing system, since the oil seal requires a certain mechanical strength, tear resistance, and good wear resistance, high wear-resistant furnace black, fast-pressing carbon black, general carbon black, and semi-reinforcing carbon are often used. Black, hot black carbon, spray carbon black, etc. Silica is also a commonly used filler reinforcing agent, such as silica alone, and a silane coupling agent may be added to improve mechanical strength. Another advantage of the silica composite is its good adhesion to the metal skeleton material. For the fluororubber compound, it is not suitable to use fine particle activated carbon black, and it is usually selected from the thermal cracking black or the spray carbon black of the coarse particles. In order to increase the self-lubricity of the oil-sealed vulcanizate and reduce the friction coefficient, graphite powder, molybdenum disulfide and other filling materials are often added.
3, rubber sealing strip
The rubber sealing strip is mainly used for various rubber doors of automobiles, airplanes, railways and high-rise buildings to prevent dust, air and water from entering the system. Because rubber seals are mostly used in doors and windows of automobiles, trains, airplanes and high-rise buildings, rubber materials are required to have good weather resistance, aging resistance and good mechanical properties, suitable elongation, compression set and cold resistance. performance. The processing property, fluidity and extrusion performance of the rubber compound are good, the shape is stable, the surface is smooth, and the surface cannot be contaminated or stained. The rubber sealing strip compound is the best for EPDM rubber, and it is also the main rubber compound which is often used. It is characterized by good weather resistance. The rubber filling strip compound formula reinforcement filling system often adopts carbon black varieties with good extrusion performance, small deformation and smooth surface, such as fast extrusion carbon black (N550), or with general-purpose, semi-reinforcing carbon black, spray carbon Black and so on. For high-grade sealing strip products such as cars, the use of carbon black should not only meet the requirements of physical and mechanical properties, processing properties, but also the surface must be smooth and free of particles. Therefore, the content of sieve residue of carbon black is required to be low, and there must be no impurities, namely carbon black. The purity is high.