Insulating sheet materials, also known as dielectrics, are substances that do not conduct electricity or conduct electricity very slightly under the action of direct current voltage. The primary function of insulating sheet materials is to isolate conductors at different potential levels in electrical equipment, allowing current to flow along a specific path. They also serve as mechanical support and fixation, as well as for arc extinction, heat dissipation, energy storage, moisture and mold prevention, and to improve the potential distribution of the electric field and protect the conductors.