Application of Silicone Oil in Lubricating Oil

Silicone oil, also known as polysiloxane, its silicon oxygen bond is very stable, so silicone oil has good thermal stability and oxidation stability. At present, the silicone oils used as lubricating oils 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 grease base oil for special purposes. Ethyl silicone oil is mainly used for precision instrument oil. Methyl phenyl silicone oil is commonly used to make synthetic high temperature grease base oil due to its high temperature resistance, low freezing point and good oxidation resistance. Compared with other silicone oils, chlorosilicone has better lubricity, so it is often used to prepare base oil for medium load grease.

 

The lubricating oil in the lubricating oil system is usually a forced circulation operation mode. Some air is often entered during operation, which will produce foam and bubbles under intense agitation. The larger air bubbles can quickly rise to the surface of the oil, while the smaller The bubbles rise slowly, no matter which form exists in the oil, it will bring adverse effects to the equipment, the oil pressure of the oil pump may not go up, which will affect the oil circulation, destroy the oil film, and cause wear. At the same time, the oil pressure is unstable, which will affect the adjustment. In severe cases, the foam will overflow from the top of the oil tank, threatening the operation of the unit. Therefore, the oil must have anti-foam performance.

 

In order to eliminate the foam produced by the working medium in the equipment system, after long-term observation and research, a variety of defoaming methods have been found, such as physical defoaming method, mechanical defoaming method, chemical defoaming method, etc. The chemical defoaming method has the best effect of adding anti-foaming agent and the method is simple. Therefore, it is widely used at home and abroad. In 1943, Shell Development Company and Gulf Research and Development Company simultaneously discovered that liquid organopolysiloxanes were very effective anti-foaming agents. Methyl silicone oil is still widely used as a lubricating oil anti-foaming agent. Methyl silicone oil is used as an anti-foaming agent, which is related to its following properties: 1. The surface tension is lower than that of lubricating oil, which promotes the desorption of foaming agent, but the surface film strength formed by itself is poor. It has a small solubility in lubricating oil, but it has a certain degree of lipophilicity. The chemical nature is not active, not easy to react with the lubricating oil. ④The dosage is low, the effect is good, and it can effectively eliminate the foam in the lubricating oil even at high temperature. ⑤ Methyl silicone oil has the advantages of low volatility, good viscosity-temperature, high flash point, low freezing point, good thermal stability and long service life. The commonly used viscosity of dimethyl silicone oil that plays a defoaming role in lubricating oil is (25 ℃ kinematic viscosity) 100-100000cs, and the usage amount is 5-50 mg/kg.

 

Silicone oil is a liquid polyorganosiloxane with excellent high and low temperature resistance, chemical stability, shear resistance, viscosity-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 weapon platforms.
The viscosity-temperature coefficient of silicone oil is lower than that of organic polymers with carbon chain structure, which is mainly due to the large bond angle and bond energy of the silicone oxygen silicon bond of the silicone oil molecular chain, large degree of freedom of orientation and good flexibility. Among all kinds of silicone oil, methyl silicone oil has the smallest temperature viscosity coefficient and its viscosity changes with temperature, so it is the most suitable base oil for damping fluid. With the increase of temperature, the viscosity of methyl silicone oil changes greatly in the low temperature section, while the change becomes smaller and smaller in the high temperature section. Thus, methyl silicone oil is a damping material suitable for use at higher temperatures. Silicone oil-based damping fluid has stable damping performance in a wide range of temperature and frequency. 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.
In fact, because the molar mass of the general methyl silicone oil has a certain distribution, it is polydispersity, which indicates that the viscosity-temperature coefficient and the distribution of molar mass are also related, and the required viscosity methyl silicone oil with lower viscosity-temperature coefficient can be formulated with different viscosity methyl silicone oil as the base oil of the damping liquid. The commonly used viscosity (kinematic viscosity at 25 ℃) of dimethyl silicone oil used as damping liquid is 1000-10000cs.