Application of silicone products in the lubricant industry
Lubrication is defined as: adding lubricant between two contact surfaces in relative motion, so that a lubricant film is formed between the two friction surfaces, separating the directly contacting surfaces, and drying the friction into the interior of the lubricant molecules Friction, to reduce friction, reduce wear and prolong the service life of mechanical equipment.
The role of lubricating oil:
1. Reduce friction
2. Reduce wear
3. Cooling effect
4. Antirust effect
5. Transmit power
6. Sealing effect
7. Shock absorption
8. Cleansing effect
Composition of lubricating oil: base oil + additives
Common types of additives are as follows:
Common base oils: mineral base oils, synthetic base oils, vegetable oils and silicone oils.
The lubricating oil in the lubricating oil system is usually a forced circulation operation mode, and some air is often entered during operation. Foam and bubbles will be generated under the condition of intense agitation. Bubbles rise slowly, no matter which form is present in the oil, it will have an adverse effect on the equipment, which may make the oil pressure of the oil pump not affect the oil circulation, damage the oil film, and cause wear. In severe cases, the foam overflows from the top of the tank, threatening the operation of the unit, so the oil must have anti-foam properties.
In order to eliminate the foam generated by the working medium when the equipment system is working, after long-term observation and research, a variety of defoaming methods have been found, such as physical defoaming, mechanical defoaming, chemical defoaming, etc. The antifoaming agent added in the foaming method has the best effect and the method is simple, so it is widely used at home and abroad. In 1943, Shell Development Company and Gulf Research and Development Company also found that liquid organopolysiloxane was a very effective antifoaming agent. Methyl silicone oil is still widely used as lubricating oil antifoaming agent. Methyl silicone oil is used as an anti-foaming agent, which is related to the following properties: ① The surface tension is lower than that of lubricating oil, which promotes the desorption of the foaming agent, but the surface film formed by itself has poor strength. ②It has low solubility in lubricating oil, but it has certain lipophilicity. ③ The chemical property is inactive, and it is not easy to chemically react with lubricating oil. ④The dosage is low, the effect is good, even in the high temperature, it 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 used for defoaming in lubricating oil is (25 ° C kinematic viscosity) 100-100000cs, and the usage amount is 5-50mg / kg.
The viscosity-temperature coefficient of silicone oil is lower than that of organic polymers with a carbon chain structure. This is mainly due to the large bond angle and bond energy of the silicon-oxygen-silicon bonds of the silicone oil molecular chain, large degree of freedom of orientation, and good flexibility. Among various silicone oils, methyl silicone oil has the smallest temperature-viscosity coefficient and its viscosity changes minimally with temperature, so it is most suitable as the base oil for damping fluid. With the increase of temperature, the viscosity of methyl silicone oil changes greatly in the low temperature section, and becomes smaller and smaller in the high temperature section. Therefore, methyl silicone oil is a damping material suitable for use at higher temperatures. The damping performance of the silicone oil-based damping fluid is stable over a wide temperature and frequency range. However, in order to further improve the damping performance of silicone oil, it is often necessary to add a certain amount of filler to increase the viscosity.