Classification and performance of insulating materials

There are many types of insulating materials, which can be divided into three categories: gas, liquid and solid. Commonly used gas insulating materials include air, nitrogen, sulfur hexafluoride, insulating PC film, etc. Liquid insulating materials mainly include mineral insulating oil and synthetic insulating oil (silicon oil, dodecylbenzene, polyisobutylene, isopropyl biphenyl, diaryl ethane, etc.).

Solid insulating materials can be divided into organic and inorganic categories. Organic solid insulating materials include insulating varnish, insulating glue, insulating paper, insulating fiber products, plastics, rubber, varnished paint tubes and insulating impregnated fiber products, electrical films, composite products and adhesive tapes, electrical laminated products, etc. Inorganic solid insulating materials mainly include mica, glass, ceramics and their products. In contrast, solid insulating materials are the most diverse and the most important.

Different electrical equipment has different requirements for the performance of insulating materials. Insulating materials used in high-voltage electrical equipment such as high-voltage motors and high-voltage cables require high breakdown strength and low dielectric loss. The main requirements of low-voltage electrical appliances are mechanical strength, elongation at break, heat resistance grade, etc.

The macroscopic properties of insulating materials such as electrical properties, thermal properties, mechanical properties, chemical resistance, climate change resistance, corrosion resistance and other properties are closely related to its chemical composition and molecular structure. Inorganic solid insulating materials are mainly composed of silicon, boron and various metal oxides.

They are mainly ionic structures. Good chemical resistance and long-term aging performance under the action of electric field; but high brittleness, low impact strength, high pressure resistance and low tensile strength; poor processability. Organic materials are generally polymers with an average molecular weight between 104 and 106, and their heat resistance is usually lower than that of inorganic materials. The heat resistance of materials containing aromatic rings, heterocyclic rings, silicon, titanium, fluorine and other elements is higher than that of general linear chain polymer materials.

The important factors affecting the 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 higher than those of non-polar materials, and it is easy to absorb impurity ions to increase conductance and reduce its dielectric properties. Therefore, attention should be paid to cleanliness during the manufacturing process of insulating materials to prevent pollution. The dielectric used in capacitors requires a high dielectric constant to improve its specific characteristics.