News dynamics
Development history of insulation materials
Release time:
2019-05-14 17:37
The earliest insulating materials used were natural products such as cotton, silk, mica, and rubber. In the early 20th century, industrial synthetic plastic phenolic resin first came out, which has good electrical properties and high heat resistance. Later, urea-formaldehyde resin and alkyd resin with better performance appeared one after another. The emergence of trichlorobiphenyl synthetic insulating oil made a leap in the specific characteristics of power capacitors (but it was later discontinued because it was harmful to human health). Sulfur hexafluoride was also synthesized during the same period.
Since the 1930s, synthetic insulating materials have developed rapidly, mainly including acetal resin, chloroprene rubber, polyvinyl chloride, styrene-butadiene rubber, polyamide, melamine, polyethylene and polytetrafluoroethylene, which has excellent performance and is known as the king of plastics. The emergence of these synthetic materials has played a major role in the development of electrical technology. For example, acetal enameled wire is used in motors to improve their operating temperature and reliability, while greatly reducing the size and weight of the motors. The successful development of glass fiber and its braided tape and the synthesis of silicone resin have added the H-level heat resistance level to motor insulation.
After the 1940s, unsaturated polyester and epoxy resin came into being. The emergence of powdered mica paper helped people get rid of the plight of the scarcity of mica resources.
Since the 1950s, new materials based on synthetic resins have been widely used, such as unsaturated polyester and epoxy insulation glues for high-voltage motor coil impregnation. Polyester series products are used in motor slot lining insulation, enameled wire and impregnation varnish, and E-class and B-class low-voltage motor insulation have been developed, further reducing the size and weight of the motor. Sulfur hexafluoride began to be used in high-voltage electrical appliances, and developed towards large-capacity miniaturization. Air insulation of circuit breakers and oil and paper insulation of transformers were partially replaced by sulfur hexafluoride.
In the 1960s, heat-resistant resins containing heterocyclic and aromatic rings were greatly developed, such as polyimide, polyarylamide, polyarylsulfone, polyphenylene sulfide and other materials with H-class and higher heat-resistant grades. The synthesis of these heat-resistant materials created favorable conditions for the development of F-class and H-class motors in the future. Polypropylene film was also successfully used in power capacitors during this period.
Since the 1970s, there has been relatively little research and development of new materials. During this period, the focus was on various modifications of existing materials and expansion of their application range. A new method was used to refine mineral insulating oil to reduce its loss; epoxy mica insulation has made many improvements in improving its mechanical properties and achieving air gap-free to improve its electrical properties. Power capacitors have transitioned from paper-film composite structures to full-film structures. 1000 kV ultra-high voltage power cables have begun to study the use of synthetic paper insulation to replace traditional natural fiber paper. Pollution-free insulating materials have also developed rapidly since the 1970s, such as replacing toxic chlorinated biphenyls with non-toxic dielectric isopropyl biphenyl and ester oils, and expanding the application of solvent-free paints. With the popularization of household appliances, major fire accidents caused by the ignition of their insulating materials have occurred repeatedly, so research on flame retardant materials has attracted attention.
