Methyl silicone oil is a linear polyorganosiloxane with Si-O-Si as the main chain and 2 methyl groups and trimethylsiloxy end-capped on Si. It is liquid at room temperature and its structural formula is as follows:

Methyl silicone oil is generally colorless, odorless, non-toxic and non-volatile liquid, insoluble in water, methanol, ethylene glycol, miscible with benzene, dimethyl ether, carbon tetrachloride or kerosene, slightly soluble in acetone, Dioxane, ethanol and butanol. Because the intermolecular force of methyl silicone oil is small, the molecular chain is helical, and the organic group can rotate freely, so it has excellent spreading performance, lubricity, high and low temperature resistance, weather resistance, radiation resistance, high flash point, With the characteristics of low surface tension and physiological inertia, it is widely used in daily chemical, machinery, electrical, textile, paint, medicine and food industries.

Properties of methyl silicone oil

■ Good heat resistance

Since the main chain in 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 very 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 properties change little with temperature and cycle number. The dielectric constant decreases with increasing temperature, but the change is small. The power factor of silicone oil is low and increases with temperature, but there is no rule with frequency. The volume resistivity decreases with increasing temperature.

■ Good hydrophobicity

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

■ Small viscosity-temperature coefficient

The viscosity of silicone oil is low and the change with temperature is small, which is related to the helical structure of the silicone oil molecule. Silicone oil is a kind of oil with the best viscosity-temperature characteristics among various liquid lubricants. This characteristic of silicone oil is very meaningful for damping equipment.

■ High compression resistance

Due to the helical structure characteristics of silicone oil molecules and the large intermolecular distance, it has high compression resistance. Using this characteristic of silicone oil, it can be used as a liquid spring, and the volume can be greatly reduced compared with mechanical springs.

■ Low surface tension

Low surface tension is characteristic of silicone oils. Low surface tension means high surface activity, therefore, silicone oil has excellent defoaming and anti-foaming properties, isolation properties from other substances and lubricating properties.

■ Non-toxic, odorless and physiologically inert

From a physiological point of view, silicone polymers are among the most inactive compounds known. Dimethicone is inert to 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 lubricants, such as high flash point, low freezing point, thermal stability, small viscosity change with temperature, no corrosion of metals, no adverse effects on rubber, plastics, coatings, organic paint films and low surface tension, Features such as easy spreading on metal surfaces. In order to improve the lubricity of silicone oil-based steel to steel, lubricity additives that are miscible with silicone oil can be added. Introducing chlorophenyl groups or replacing dimethyl groups with trifluoropropylmethyl groups on the siloxane chain can greatly improve the lubricating properties of silicone oils.