Classification and Performance of Insulating Materials
There are many kinds of insulating materials, which can be divided into three categories: gas, liquid and solid. The common gas insulation materials are air, nitrogen, six sulfur fluoride insulating PC film and so on. Liquid insulating materials are mainly mineral insulating oil, synthetic insulating oil (silicone oil, twelve alkylbenzene, polyisobutylene, Yi Bingji biphenyl, two aryl ethane, etc.) two kinds. Solid insulating materials can be divided into two types, organic and inorganic. Materials include insulation paint, plastic insulation, insulation paper, fiber insulation products, plastics, rubber, paint and linoleum pipe insulation impregnating fiber products, electrical products and composite film, adhesive tape, electrical insulating organic solid laminate. The inorganic solid insulation materials are mainly mica, glass, ceramics and their products. In contrast, the variety of solid insulating materials is also the most important.
The requirements of different electrical equipment on the performance of insulating materials have been emphasized. High voltage electrical equipment, such as high voltage motor, high voltage cable and other insulation materials, require high breakdown strength and low dielectric loss. The main requirements of low voltage electrical apparatus are mechanical strength, elongation at break, heat resistance grade and so on.
The macroscopic properties of insulating materials, such as electrical properties, thermal properties, mechanical properties, chemical resistance, climate change and corrosion resistance, are closely related to their chemical composition and molecular structure.
Inorganic solid insulating material is mainly composed of silicon, boron and various metal oxides, ionic structure, main features of high heat resistance, temperature is generally higher than 180 DEG, good stability, ageing resistance, chemical resistance and long-term aging properties under electric field; but high brittleness. The impact of low strength, high pressure and low tensile strength; poor technology.
Organic materials are generally polymers with an average molecular weight of 104~106, and their heat resistance is usually lower than that of inorganic materials. The heat resistance of the materials containing aromatic ring, heterocyclic ring, silicon, titanium and fluorine is higher than that of general linear chain polymer.
The important factors affecting dielectric properties of insulating materials are the strength of molecular polarity and the content of polar components. The dielectric constant and dielectric loss of polar materials are all higher than those of non polar materials, and it is easy to adsorb impurity ions to increase the conductivity and reduce the dielectric properties. Therefore, in the manufacturing process of insulating materials, we should pay attention to cleaning and prevent pollution. The dielectric requires a high dielectric constant to improve its specific characteristics.