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Silicone Resins are also Commonly used on Fire-resistant Mica Tapes

Mar 3, 2022

Solvent-free impregnating varnish is widely used in the VPI insulation treatment of motor coils in high-end fields such as high-voltage motors, high-speed traction motors, and spacecraft engines. Silicone materials have the advantages of high temperature resistance and corona resistance, and are more suitable for insulation in the above fields deal with. With the continuous development of my country's high-speed railway, subway, light rail, and magnetic levitation technology, insulating materials with higher and better performance have been widely used, so the market prospect of solvent-free silicone impregnating paint will be optimistic and the sales potential will be huge.

The amount of organic silicon used in the country is also increasing year by year. In 1996, the total output of organic silicon monomers in the country was less than 1kt, which was far from meeting the increasing domestic demand, and only relying on large amounts of imports. According to customs statistics, my country’s imports of primary polysiloxanes totalled 18416t in 1996, an increase of 22% over 1995 and more than four times the domestic output. From January to June 1997, my country’s primary polysiloxane imports totaled 13,268t, an increase of 56% over the same period in 1996. The annual import volume is expected to exceed 20000t. 1999 was a year of rapid development of China's silicone industry, and its monomer output increased by 50% compared with 1998; it was also a year of rapid expansion of China's silicone market, and the import volume of polysiloxane in the mainland increased compared with 1998. 40%, reaching 43435t. In other words, in 1999, the consumption of organic silicon in China's mainland exceeded 60kt/a, with a growth rate of over 40%. In the same year, the import volume of siloxane in Taiwan Province only increased by 4% to 23970t/a. a. From January to June 2000, the import volume of polysiloxane was 24158t, an increase of 24% over the same period in 1999. It can be seen that China's organic silicon market continues to maintain a strong growth momentum


At present, the solvent-free impregnating varnishes used on foreign motors mainly include epoxy solvent-free impregnating varnish, polyester imine solvent-free impregnating varnish and solvent-free organic silicon impregnating varnish. Manufacturers are mainly in Japan, Europe and the United States. Now only a few companies sell 700 to 800 tons of silicone resins in China each year. The main application areas are high-temperature coatings, electronic insulating materials, mica tape and mica board adhesives, and insulating impregnating varnishes. In Europe, railway traction motors are mainly silicone impregnating varnishes. In China, because the synthesis technology of solvent-free silicone impregnating varnishes (silicone resins) has not made a breakthrough, the organic silicon impregnating varnishes are mainly solvent-based. Solvent organic silicon paint has not been used by the railway traction motor industry because of its long drying time and not suitable for vacuum pressure impregnation. At the same time, it is not suitable for VPI dipping process. Domestic railway traction motors are now using modified diphenyl ether series solvent-free impregnating varnishes, and about 300 tons of modified diphenyl ether solvent-free impregnating varnishes are shared by all railway newly built and repaired motors throughout the year. The mica tape and mica board used in the motor are also matched with modified diphenyl ether impregnating varnish as the adhesive. With the introduction and digestion of AC drive locomotives and the advancement of localization, modified diphenyl ether solvent-free impregnating varnish will be eliminated, solvent-free silicone impregnating varnish will be promoted and used, and mica tape adhesive for traction motors will also be changed to organic Silicone adhesive. At present, the H-class winding type dry change requires flame retardancy and moisture resistance, and at the same time, the winding type dry change impregnating paint is required to have flame retardancy, moisture resistance, toughness and good adhesion. 

At present, the epoxy-polyester solvent-free impregnating varnish used in China is difficult to meet the requirements. Now Yunnan Segme Transformer Co., Ltd. has begun to use silicone resin for dry transformers. The application effect is good and it has won a good reputation in the transformer industry. Therefore, silicone Lacquer and glue have good prospects for promotion and application in the H-class winding dry change industry. At present, about 150 tons of H-grade solvent-free impregnating varnish is used for H-grade winding type dry change every year. 

Silicone resins are also commonly used on fire-resistant mica tapes. About 60 tons of silicone resins are used for fire-resistant mica tapes each year. In addition, silicone resins are used in high-temperature resistant coatings, road waterproof coatings, and protective coatings for electronic circuit boards. widely used. At present, there is no domestic manufacturer that can produce solvent-free silicone dipping varnish on a large scale. Domestic users all import from abroad. Importing solvent-free silicone dipping varnish from abroad is expensive and long ordering time. It is difficult to meet the production requirements in time, so they are seeking localization. . Therefore, the solvent-free organic silicon dipping varnish has a good prospect for promotion and application in China.

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