Preparation And Characterization Of Polyurethane Acrylate Modified Organic Silicon Impregnating Varnish

Insulating impregnating varnishes are mainly used to impregnate the windings,insulating parts of motors and electrical appliances,to fill gaps and microholes.After the impregnated paint curing,the impregnated surface can form a continuous and smooth coating,and the winding can be bonded into a solid whole,which can improve the moisture resistance,thermal conductivity,breakdown strength and mechanical strength of the insulation structure.At present,the common silicone insulating impregnating paint has some disadvantages,such as poor adhesion and poor mechanical properties,which limits its wide application in the field of insulation.The research and development of silicone insulating impregnating varnish with higher performance is of great application value.This thesis mainly carries on the research work from the following several aspects.1.The Methyl / phenyl silane monomers and vinyl chlorosilane are reacted to make low molecular weight organosiloxane prepolymer,and then the prepolymer was mixed according to the molar ratio of reaction group.An additive silicone insulating impregnating resin without organic solvent and low viscosity was prepared by adding appropriate amount of platinum catalyst.Through the characterization of resin structure,molecular weight,thermal decomposition temperature,and the determination of the properties of the cured film,the successful preparation of solvent-free silicone impregnated resin was determined.The optimum mass ratio of silicon-containing vinyl matrix resin to hydrosilyl crosslinking agent is 2.2: 1,its molecular weight is 1022,its molecular weight distribution width is 1.95,and the thermal decomposition temperature is 108℃.2.Polyurethane acrylic prepolymer was prepared by using HDI and pentaerythritol triacrylate as raw materials,DBTDL as catalyst and MEHQ as inhibitor.Through the characterization of molecular weight and distribution,glass transition temperature,thermal decomposition temperature and structure of the prepolymer,the successful preparation of polyurethane acrylate prepolymer was confirmed.The molecular weight is 1265,the molecular weight distribution width is 1.5,the glass transition temperature is-35,and the thermal decomposition temperature is 479 ℃.3.In order to further improve the toughness of silicone paint film,modified silicone insulating impregnating paint was prepared by using polyfunctional polyurethane acrylate(PUA)prepolymer and hydrosilyl polysiloxane containing active hydrogen.The modification mechanism,the compatibility of impregnating paint and the effect of polyurethane acrylate prepolymer content on the thermal stability,electrical properties and mechanical strength of the film were investigated.It is determined that when the amount of polyurethane-acrylate is 5%,the electrical properties,thermal stability and mechanical properties of the film are the best.