The glass insulating material is also an electrically insulating glass, and the raw material is silicon dioxide. The main disadvantage is the high melting temperature and the high price. Used as an electrically insulating glass. The most common is to use silica as the main body to add oxides such as boron oxide, aluminum oxide, lead oxide, calcium oxide and sodium oxide to form a highly viscous liquid, which is rapidly solidified under the condition that crystal grains are not precipitated. . The glass has good electrical properties, heat resistance, chemical stability and ease of formability. Glass is classified into quartz glass, soda glass, lead glass, borosilicate glass, fusible glass, glass fiber, etc. according to composition and properties.
Quartz glass is made of pure quartz at 1700 ~ 1800 °C. It has good electrical properties, low thermal expansion coefficient, high heat resistance and impact resistance, and good UV transmission capability. It can be used as a high-frequency insulating material and ultra-high pressure mercury lamp for high temperature resistance and good transparency. Quartz glass can be made into optical fibers for optical communication. The disadvantage is that the melting temperature is high and the price is high.
Sodium glass is melted from silica, sodium oxide, calcium oxide, magnesium oxide, aluminum oxide, and the like. Since the alkali metal oxide such as sodium oxide or potassium oxide is added, the melting temperature can be lowered to about 1400 ° C, the molding processability is also greatly improved, and the price is low, and it is mostly used as a window glass. The addition of an alkali metal oxide significantly reduces the volume resistivity, surface resistivity, and chemical stability of the glass. However, the mechanical strength and thermal stability of soda glass after quenching treatment are greatly improved, and it is suitable for manufacturing high and low voltage transmission and distribution insulators. Sodium glass is also used as an incandescent bulb and a fluorescent tube.
Lead glass is mainly composed of silica, lead oxide, sodium oxide and the like. Its melting point is lower than that of soda glass, its processability is good, and its electrical properties are greatly improved. It can be used as a neon tube or a stem for an electron tube. A glass having a high content of lead oxide has a high dielectric constant and thus can be used as a capacitor medium. Lead glass has a strong absorption capacity for radiation and can be used as a protective material for isolating X-rays and gamma rays.
The borosilicate glass is mainly composed of silica, boron oxide and the like. It has high insulation resistance, low high frequency loss, good thermal shock resistance and chemical stability, and is mainly used as high frequency insulators, lamps, bulbs, etc.
Fusible glass is mainly composed of boron oxide, lead oxide, silicon oxide, zinc oxide and the like. Its softening temperature is lower than 600 ° C, so it is called fusible glass. It can be used as a soldering metal, ceramic, glass solder and electronic components package.
Glass fibers are drawn from molten glass into fibers. Glass fibers used in electricians are required to have high electrical insulation and chemical stability, and are often made of low alkali or alkali-free glass. Compared with natural fibers, it has non-flammability, high chemical stability, low moisture absorption and high mechanical strength. It is widely used as insulation for heat-resistant electromagnetic wires and transformer windings. A cloth and a belt woven from glass wool are often used as a reinforcing material, and are laminated with an organic material to form a laminated insulating sheet and a tube. In recent years, high-strength composite insulators have been made of glass fiber for the construction of high-voltage transmission lines.