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Preparation and Characterization of C-grade Solvent-free Silicone Impregnating Resin

Feb 26, 2021

A silicone impregnating resin was synthesized from methylphenyl silane monomer and special silane monomer to prepare organosiloxane prepolymer. The impregnating resin does not contain any organic solvent and is a low-viscosity fluid liquid at room temperature. The structure and physical properties of the impregnated resin were characterized by infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy and gel chromatography. The results show that the polyorganosiloxane containing silicon hydrogen and vinyl groups in the molecular structure of this type of impregnating resin is an oligomer with a relatively small molecular weight.

Electrical insulation impregnating resin is one of the main insulating materials for electrical products, and it is an indispensable insulating material for AC and DC motors, impregnated dry-type transformers, and power transformers. From the 1950s to 1960s, solvent varnishes were commonly used in electrical insulation impregnating resins. They generally contained about 50% solvent and required multiple impregnations, poor internal dryness, long impregnation process time, serious environmental pollution, and poor production safety. In the 1970s, the development and promotion of solvent-free paints began. Most solvent-free paints are styrene type, and they generally contain 30% to 40% styrene. The main function is to solve the problem of dryness in the winding, reduce the number of dipping, and improve production efficiency. However, there is still a large amount of volatile matter during baking and the storage life is short. By the 1980s, under the premise of pursuing higher reliability, heat resistance and environmental resistance of electrical products abroad, vacuum (pressure) was steadily promoted.Impregnation process and form a new generation of low volatile impregnating resin. It is characterized by low vapor pressure, no large amount of volatile matter during vacuum impregnation and thermal curing, good stability, fast curing, and internal filling up to 98% .

In China, this evolutionary process comes late. At present, there are limited varieties of electrical insulating impregnants above H level in China. Solvent silicone resins have been the mainstay for decades, and solvent-free impregnating resin products are relatively few. However, the vacuum impregnated low-volatility solvent-free impregnating resin has good manufacturability (good stability and fast curing), combined with obvious environmental protection characteristics and safety of production and transportation, which effectively improves the reliability of motor products and can meet new requirements. Technical design requirements have received attention and been widely used at home and abroad in the past 10 years.

Solvent-free silicone impregnating resin is a new type of electrical insulation material developed in response to this requirement and trend. It has excellent heat resistance, thermal oxygen stability and excellent insulation properties. It has moisture resistance, water resistance, rust resistance, cold resistance, ozone resistance and weather resistance. It has good corrosion resistance to most water-containing reagents such as dilute acids and alkalis. performance. In addition, the solvent-free silicone impregnating resin also has flame retardancy and environmental protection functions. Its development will undoubtedly provide great support and promotion to the development of high-tech electromechanical products.

Organosilane monomers are pre-polymerized to form low molecular weight prepolymers. The above-mentioned prepolymers are mixed according to the equimolar ratio of the reactive groups, and catalysts and inhibitors are added to promote stable storage at room temperature. At a certain temperature, the vinyl-containing prepolymer and the active hydrogen-containing reactive group are additively polymerized and cross-linked to form a high-grade heat-resistant, flame-retardant, solvent-free and environmentally friendly insulating paint. The characteristics of the process are: no low-molecular substances fall out during curing to form a film, no influence on electrical performance, and no pollution. The specific application curing principle is the following chemical equation.

making process:Take a certain amount of phenyl monomer, methyl monomer, silane monomer and vinyl monomer to dissolve in sufficient toluene and deionized water, hydrolyze at a lower temperature, and then conduct condensation at 120°C; After the reaction is completed, the toluene layer is allowed to stand for layering, and then the toluene layer is washed with water, filtered, and distilled under reduced pressure to remove the toluene to obtain the silicone resin. Take 100 parts of the aforementioned silicone impregnating resin, add an appropriate amount of curing agent and temperature-sensitive inhibitor, and mix evenly to obtain a solvent-free silicone insulating impregnating resin.

The solvent-free silicone impregnating resin synthesis system does not contain any organic solvents, and there is no low molecular weight precipitation during the curing process. It is suitable for the vacuum pressure insulation impregnation treatment of motors, and can obtain a good integrity and air gap-free insulation structure. It is a new type of insulation impregnating resin that is environmentally friendly, fire-resistant and flame-retardant, and has good development prospects.

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