Methyl silicone oil is a linear polyorganosiloxane with Si-O-Si as the main chain and two methyl and trimethylsiloxy-terminated caps connected to Si. It is liquid at normal temperature. Its structural formula is as follows:

Methyl silicone oil is generally colorless, odorless, non-toxic,
Volatile liquid, insoluble in water, methanol, ethylene glycol, miscible with benzene, dimethyl ether, carbon tetrachloride or kerosene, etc., slightly soluble in acetone, dioxane, ethanol and butanol. Because methyl silicone oil has a small intermolecular force, the molecular chain is helical, and the organic groups can rotate freely, so it has excellent spreading properties, lubricity, high and low temperature resistance, weather resistance, radiation resistance, high flash point, Low surface tension and physiological inertia are widely used in daily chemical, mechanical, electrical, textile, coating, pharmaceutical and food industries.

Characteristics of methyl silicone oil

Methyl silicone oil has many special properties:

■ Good heat resistance

Since the main chain of the silicone oil molecule is composed of -Si-O-Si-bonds, it has a structure similar to that of inorganic polymers, and its bond energy is high, so it has excellent heat resistance.

■ Good oxidation stability and weather resistance

■ Good electrical insulation

Silicone oil has good dielectric properties, and its electrical characteristics change little with temperature and frequency. The dielectric constant decreases with increasing temperature, but changes little. Silicone oil has a low power factor, which increases with temperature, but it has no regularity with frequency. The volume resistivity decreases with increasing temperature.

■ Good hydrophobicity
Although the main chain of the silicone oil is composed of a polar bond Si-O, the non-polar alkyl groups on the side chain are oriented outward, preventing water molecules from entering the interior and acting as a hydrophobic. The interfacial tension of silicone oil to water is about 42 dyne / cm. When it is diffused on glass, due to the water repellency of silicone oil, a contact angle of about 103 ° is formed, which is comparable to paraffin.

■ Low viscosity temperature coefficient
Silicone oil has a low viscosity and a small change with temperature, which is related to the helical structure of the silicone oil molecules. Silicone oil is a type of oil with the best viscosity-temperature characteristics of various liquid lubricants. This characteristic of silicone oil is very meaningful for damping equipment.

■ High compression resistance
Due to the helical structure and large intermolecular distance of silicone oil molecules, it has high compression resistance. Utilizing this property of silicone oil, it can be used as a liquid spring, and its volume can be greatly reduced compared with a mechanical spring.

■ Low surface tension
Low surface tension is a characteristic of silicone oils. Low surface tension indicates high surface activity. Therefore, silicone oil has excellent defoaming and antifoaming properties, isolation properties and lubricating properties from other substances.

■ Non-toxic, tasteless and physiologically inert
From a physiological point of view, silicone polymers are one of the least reactive compounds known. Dimethicone is inert to living organisms and has no rejection reaction with animal organisms. Therefore, they have been widely used in the departments of surgery and internal medicine, medicine, food and cosmetics.

■ Good lubricity
Silicone oil has many excellent properties as a lubricant, such as high flash point, low freezing point, thermal stability, small change in viscosity with temperature, does not corrode metals, and has no adverse effects on rubber, plastics, coatings, organic paint films, and low surface tension. Easy to spread on metal surfaces. In order to improve the lubricity of silicon oil steel to steel, a lubricity additive miscible with silicone oil can be added. The introduction of chlorophenyl on the siloxane chain or the replacement of dimethyl with trifluoropropylmethyl can greatly improve the lubricating properties of silicone oils.