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What are the classifications of silicone oils? What are the main characteristics, advantages and disadvantages?

2019-11-03 5

What are the classifications of silicone oils? What are the main characteristics, advantages and disadvantages?


Silicone oil generally refers to a linear silicone product that remains in a liquid state at room temperature. Generally divided into methyl silicone oil and modified silicone oil. The most commonly used silicone oil-methyl silicone oil, also known as ordinary silicone oil, has all organic groups as methyl groups. Methyl silicone oil has good chemical stability, insulation and good hydrophobic properties. It is obtained by hydrolysis of dimethyldichlorosilane with water to obtain a polycondensation ring, and the ring body is obtained by cracking and rectifying to obtain a low ring body, and then the ring body, the heading agent and the catalyst are put together to be condensed to obtain each. A mixture of different degrees of polymerization can be obtained by removing low boilers by distillation under reduced pressure.
Classification


According to the chemical structure, there are methyl silicone oil, ethyl silicone oil, phenyl silicone oil, methyl hydrogen silicone oil, methyl phenyl silicone oil, methyl chlorophenyl silicone oil, methyl ethoxy silicone oil, methyl trifluoropropyl Silicone oil, methyl vinyl silicone oil, methyl hydroxy silicone oil, ethyl hydrogen silicone oil, hydroxyl hydrogen silicone oil, cyanide-containing silicone oil, etc.;


According to the use, there are damping silicone oil, diffusion pump silicone oil, hydraulic oil, insulating oil, heat transfer oil, brake oil and so on.


Main characteristics


Silicone oil has excellent heat resistance, electrical insulation, weather resistance, hydrophobicity, physiological inertness and small surface tension. In addition, it has a low viscosity temperature coefficient, high compression resistance, and some varieties are also resistant to radiation. Performance.


Silicone oil has many special properties, such as oxidation resistance, high flash point, low volatility, no corrosion to metals, and no toxicity.


Advantages and disadvantages


Advantage


Silicone oil atlas (1) Excellent shear stability, absorption vibration, vibration transmission prevention function, can be used as damping fluid.




(2) Excellent thermal oxidation stability, such as thermal decomposition temperature >300 °C, low evaporation loss (150 ° C, 30 days, evaporation loss is only 2%), oxidation test (200 ° C, 72 h), viscosity and acid value change small.


(3) Excellent electrical insulation, volume resistance, etc. do not change in the range of normal temperature to 130 ° C (but not in water).


(4) It is an oil which is non-toxic and has low foaming property and strong anti-foaming property, and can be used as a defoaming agent or the like.


(5) The viscosity-temperature performance is the best among liquid lubricants, and the viscosity change is small in a wide temperature range. Its freezing point is generally less than -50 ° C, and some as high as -70 ° C, long-term storage at low temperatures, the appearance of oil, viscosity does not change, it is a base oil with high temperature, low temperature, wide temperature range.


Disadvantage


(1) The surface tension is small (easy to leak from the machine).


(2) The gas solubility is large (it is difficult to design a gas seal device).


(3) Silicone oil has a large thermal expansion coefficient (probability of overpressure).


(4) The lubricity of silicone oil is not good, especially for the friction of steel steel.


(5) Certain hygroscopicity (after the water content is higher than 100×10-6, the electrical performance drops sharply)


Use


Commonly used as high-grade lubricants, anti-vibration oils, insulating oils, defoamers, mold release agents, polishing agents and vacuum diffusion pump oils. Among the various silicone oils, methyl silicone oil is the most widely used, and is the most important type of silicone oil, followed by methylphenyl silicone oil. In addition, there are ethyl silicone oil, methylphenyl silicone oil, nitrile-containing silicone oil, and the like. Various functional silicone oils and modified silicone oils are mainly used for special purposes.