The role of insulating materials in electrical equipment is the electric potential of different live parts to isolate. Therefore, electrical insulating materials should first have a high insulation resistance and compressive strength , and to prevent leakage, breakdown and other accidents . Second heat resistance is better to avoid overheating and long-term deterioration of aging ; Furthermore, it should have good thermal conductivity, convenient lightning resistant to moisture resistance and high mechanical strength and processing technology and so on.

According to the requirements, performance indicators are commonly used insulating material dielectric strength , tensile strength , density, expansion coefficient . Insulation compressive strength: the voltage applied to both ends of the insulator is higher, the electric field within the material by the force of the charge , the more prone to impact ionization , causing insulation breakdown. So that the minimum breakdown voltage of the insulator is called the breakdown voltage of the insulator . 1 mm thick insulation breakdown voltage kV need to add that number called the compressive strength of the insulating dielectric material , referred to as the dielectric strength . Because of electrical insulating material has a certain dielectric strength, electrical equipment , various security tools ( pliers , voltage tester , insulated gloves, insulated rods, etc. ) , all kinds of electrical materials, manufacturers are allowed to use certain specified voltage , referred to the rated voltage. When using withstand voltage must not exceed its rated voltage, in order to avoid accidents. Tensile strength: unit cross-sectional area of ??the insulating material is able to withstand tension, e.g. per square centimeter cross section area of ??the glass can withstand 1400 Newton tension. Insulating material insulating properties and temperature are closely related . The higher the temperature , the worse insulating properties of the insulating material . To ensure the insulation strength , each insulating material has a proper maximum allowable operating temperature, at this temperature, can be safely used long term , beyond this temperature will rapidly aging. According to the degree of heat , the insulating material is divided into Y, A, E, B, F, H, C and other levels.