Insulating paper is usually a thin sheet material formed by the deposition of plant fibers, mineral fibers, synthetic fibers or their mixtures on paper machines through water or other media. Insulating paper has high tear resistance, low elongation and good insulation, so it is widely used as insulating material in motor, cable, capacitor and transformer, and is also the main component of laminated products, composite materials and prepreg materials.

In recent years, with the development of electric power industry, modern power generation equipment and transmission equipment are developing towards high voltage and large capacity. With the rapid development of science and technology in the world, a variety of high-performance synthetic fibers have been developed and produced and applied in paper industry, such as polyester fiber paper, polyaromatic amide fiber paper, polysulfone fiber paper, polyoxadiazole fiber paper, etc. They have been successfully applied in batteries and transformers. Voltage transformers, capacitors and other electrical equipment, especially insulation paper, are the most common and successful applications.

Due to the special use of insulating paper, it is required to have some characteristics different from other kinds of paper, mainly including mechanical properties, electrical properties and thermal stability.

Mechanical properties

Insulating paper will be affected by various external forces in the process of use, such as high-voltage and large-capacity generator insulation paper to withstand high-speed rotation, starting and stopping and sudden short circuit caused by the great mechanical stress, so it requires higher mechanical properties, mainly including tensile strength and elongation at break.

Thermal stability

Thermal stability is an important index of insulating paper and a main factor of aging of low voltage insulation, which determines its service life. Under normal operating conditions, the electric field strength has only a slight effect on the aging process of insulation. When insulating paper is used in high temperature environment for a long time, it will become brittle due to thermal aging and gradually lose its mechanical and electrical properties.

Electrical performance

Insulation paper is widely used in electrical equipment, so it needs to meet certain electrical performance. The electrical properties of insulating paper refer to its polarization, conductivity, dielectric loss and breakdown characteristics under the action of electric field.

The properties of insulating paper are interrelated and cannot be viewed separately and in isolation. In the process of selecting and developing materials, the advantages and disadvantages of various materials should be balanced comprehensively. In addition, in order to produce insulating paper with good electrical properties, the existence of impurities such as metal ions, air bubbles and moisture should be avoided as far as possible in the production process, and the insulating paper should have high uniformity.