Methyl silicone oil is a linear polyester with Si-O-Si as the main chain and two methyl and trimethylsiloxy groups connected to the Si. Organosiloxane is liquid at room temperature and its structural formula is as follows:
Methyl silicone oil is generally a colorless, odorless, non-toxic, non-volatile liquid, insoluble in water, methanol, and ethylene glycol, and can be mixed with benzene and dibenzoic acid. It is soluble in methyl ether, carbon tetrachloride or kerosene, and slightly soluble in acetone, dioxane, ethanol and butanol. Because the intermolecular force of methyl silicone oil is small, the molecular chain is spiral-shaped, and the organic groups can rotate freely, it has excellent spreading properties, lubricity, high and low temperature resistance, weather resistance, radiation resistance, high flash point, With the characteristics of low surface tension and physiological inertness, it is widely used in daily chemical, machinery, electrical, textile, coating, pharmaceutical and food industries.
Characteristics of methyl silicone fluid
Methyl silicone oil has many special properties:
■ Good heat resistance
Since the main chain of silicone oil molecules 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 resistance and weather resistance
■ Good electrical insulation
Silicon oil has good dielectric properties, and its electrical properties change very little with changes in temperature and cycle number. The dielectric constant decreases with increasing temperature, but the change is small. The power factor of silicone oil is low, increases with temperature, but changes with frequency without rules. Volume resistivity decreases as temperature increases.
■ Good hydrophobicity
Although the main chain of silicone oil is composed of polar bonds Si-O, the non-polar alkyl groups on the side chains are oriented outward, preventing water from The molecules enter the interior and act as hydrophobic. 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
Silicon oil has low viscosity and changes little with temperature, which is related to the spiral structure of silicone oil molecules. Silicone oil is a type of oil with the best viscosity and temperature characteristics among various liquid lubricants. This characteristic of silicone oil is very meaningful for damping equipment.
■ High compression resistance
Due to the spiral structure characteristics of silicone oil molecules and the large distance between molecules, it has high compression resistance. This characteristic of silicone oil can be used as a liquid spring. Compared with mechanical springs, the volume can be greatly reduced.
■ Low surface tension
Low surface tension is a characteristic of silicone oil. Low surface tension indicates high surface activity. Therefore, silicone oil has excellent defoaming and anti-foaming properties, isolation properties from other substances, and lubrication properties.
■ Non-toxic, odorless and physiologically inert
From a physiological point of view, silicone polymers are among the most inactive compounds known. Dimethicone is biologically inert and has no rejection reaction with animal bodies. Therefore, they have been widely used in the surgical and internal medicine, pharmaceutical, food and cosmetic sectors.
■ Good lubricity
Silicone oil has many excellent properties as a lubricant, such as high flash point, low freezing point, thermal stability, small viscosity change with temperature, non-corrosive to metals, and good for rubber, plastics, coatings, organic The paint film has the characteristics of no adverse effects, low surface tension, and easy spreading on the metal surface. In order to improve the lubricity of silicone oil on steel, lubricity additives that are miscible in silicone oil can be added. The lubrication properties of silicone oil can be greatly improved by introducing a chlorophenyl group into the siloxane chain or replacing the dimethyl group with trifluoropropylmethyl.
The lubricant has many excellent properties, such as high flash point, low freezing point, thermal stability, small viscosity change with temperature, non-corrosion to metals, no adverse effects on rubber, plastics, coatings, and organic paint films, low surface tension, and easy bonding on metals. Surface spreading and other properties. In order to improve the lubricity of silicone oil on steel, lubricity additives that are miscible in silicone oil can be added. The lubrication properties of silicone oil can be greatly improved by introducing a chlorophenyl group into the siloxane chain or replacing the dimethyl group with trifluoropropylmethyl.
