Silicone fluids in lubricants
Release Time:
2025-05-05
Silicone oil, also known as polysiloxane, has very stable silicone-oxygen bonds, so silicone oil has good thermal and oxidative stability. Currently, the silicone oils used as lubricants mainly include methyl silicone oil, methyl phenyl silicone oil, methyl chlorophenyl silicone oil and ethyl silicone oil. Methyl silicone oil is generally used as damping fluid and special-purpose grease base oil; ethyl silicone oil is mainly used for precision instrumentation oil; methyl phenyl silicone oil is often used to make synthetic high-temperature lubricating grease base oil due to its high-temperature resistance, low freezing point, and good antioxidant properties; chlorosilicone oil is often used to make medium-loaded lubricating grease base oil because of its better lubricating properties compared to other silicone oils.
Lubricating oil in the lubricating oil system is usually a forced circulation mode of operation, the operation of the frequent entry of a portion of the air, in the case of intense agitation will produce foam and bubbles, the larger air bubbles can quickly rise to the surface of the oil, and smaller bubbles rise slower, no matter which form exists in the oil will have an adverse effect on the equipment, may make the oil pump oil pressure does not go up to the impact of the oil cycle, damage to the oil film, Wear and tear, while the oil pressure is unstable, affecting the regulation, serious foam from the top of the tank overflow, threatening the operation of the unit, so the oil must have anti-foam properties.
In order to eliminate the working medium in the equipment system work foam, after a long period of observation and research, found a variety of anti-foaming methods, such as physical defoaming method, mechanical defoaming method, chemical defoaming method, etc., of which the chemical defoaming method of adding anti-foaming agent has the best effect, the method is simple, therefore, has been widely used both at home and abroad. 1943 Shell Development Company and Gulf Research and Development Company at the same time found that liquid organic In 1943, Shell Development Company and Gulf Research and Development Company simultaneously found that liquid organic polysiloxane is a very effective antifoam agent. Nowadays, methyl silicone oil is still widely used as antifoam agent for lubricating oil. Methyl silicone oil as an anti-foaming agent, and its following properties ① surface tension is lower than the lubricating oil, prompting the foaming agent desorption, but it forms its own surface film strength is poor. ② It is less soluble in lubricating oil, but also has a certain degree of lipophilicity. ③ It is chemically inactive and not easy to have chemical reaction with lubricating oil. ④ Low dosage, good effect, even at high temperatures can effectively eliminate the foam in the lubricating oil. ⑤ Methyl silicone oil has the advantages of low volatility, good viscosity and temperature, high flash point, low freezing point, good thermal stability and long service life. The common viscosity of dimethyl silicone oil, which plays an antifoaming role in lubricating oils, is (25℃ kinematic viscosity) 100-100000cs, and the usage amount is 5-50mg.
Silicone oil is a polyorganosiloxane in liquid state, which has excellent resistance to high and low temperatures, chemical stability, shear resistance, viscous temperature characteristics and high compression rate. Silicone oil-based vibration damping products are widely used in electrical and electronic equipment, high-rise buildings, bridges, and weapons platforms.
Silicone oil viscous temperature coefficient than the carbon chain structure of organic polymers is lower, which is mainly due to the silicone oil molecular chain of silicone oxygen silicon bond bond angle and bonding energy of large, large degree of freedom of orientation, good flexibility. Among the various silicone oils, methyl silicone oil has the smallest temperature viscosity coefficient and the smallest change in viscosity with temperature, so it is most suitable for the base oil of damping fluid. As the temperature rises, the viscosity of methyl silicone oil in the low-temperature section of the larger changes, while in the high-temperature section of the change is getting smaller. Therefore, methyl silicone oil is a damping material suitable for use at higher temperatures. Silicone oil-based damping fluid damping is stable over a wide range of temperatures and frequencies. However, in order to further improve the damping performance of silicone oil, it is often necessary to add a certain amount of filler viscosity.
In fact, due to the general molar mass of methyl silicone oil has a certain distribution, is polydisperse, which indicates that the viscosity-temperature coefficient and the distribution of the molar mass is also related to the viscosity-temperature coefficient can be different viscosity of methyl silicone oil formulated with lower viscosity of the required viscosity of methyl silicone oil as a damping fluid base oil. The common viscosity (kinematic viscosity at 25℃) of dimethicone oil used as damping fluid is 1000-10000cs.
Translated with DeepL.com (free version)
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