First of all, let's talk about the application of insulating materials. The role of insulating materials is to isolate the charged parts with different potentials in electrical equipment. Therefore, the insulating material should first have a high insulation resistance and withstand voltage strength, and can avoid leakage, breakdown and other accidents. Secondly, the heat resistance is better to avoid aging and deterioration due to long-term overheating; in addition, it should have good thermal conductivity, moisture resistance and lightning protection, high mechanical strength and convenient processing. According to the above requirements, the performance indicators of commonly used insulation materials include insulation strength, tensile strength, specific gravity, expansion coefficient, etc.

Insulation withstand voltage strength: the higher the voltage applied to both ends of the insulator, the greater the electric field force of the charge in the material, and the more prone to ionization collision, resulting in insulator breakdown. The lowest voltage at which an insulator breaks down is called the breakdown voltage of the insulator. When a 1mm thick insulating material breaks down, the number of kilovolts to be added is called the insulation withstand voltage strength of the insulating material, referred to as insulation strength. As the insulation materials have a certain insulation strength, all kinds of electrical equipment, all kinds of safety appliances (electrician's pliers, electric pen, insulating gloves, insulating rods, etc.), all kinds of electrical materials, manufacturers have stipulated a certain allowable voltage, called rated voltage. The voltage used shall not exceed its rated voltage value to avoid accidents.

Tensile strength: insulating material unit cross-sectional area can withstand tension, such as glass per square centimeter cross-sectional area can withstand 1400 Newton tension.

The insulation properties of insulating materials are closely related to temperature. The higher the temperature, the poorer the insulating performance of the insulating material. In order to ensure the insulation strength, each insulating material has an appropriate maximum allowable working temperature, below which it can be safely used for a long time, and will age rapidly beyond this temperature. According to the degree of heat resistance, the insulation materials are divided into Y, A, E, B, F, H, C and other levels. For example, the maximum allowable working temperature of A- class insulation materials is 105 ℃, and most of the insulation materials in distribution transformers and motors are A- class.