| With the development of society and the improvement of people's living standards,China's total annual electricity consumption has gradually increased,and the voltage of power grids in various provinces across the country have also been rising.The rise in voltage level makes the power system's properties requirements for various materials more and more demanding.Among them,the insulating devices made of epoxy composites is an important part of the gas insulated switchger(GIS)circuit breakers.The gas insulated switchger circuit breakers bear the extremely high mechanical load and instantaneous voltage during the operation of open/close in the power system.As the voltage level rises,the insulating devices fracture and electrical breakdown accidents occur frequently.To reduce such accidents,it is necessary to improve the overall properties of the cured epoxy resin.The purposes of this paper is to prepare epoxy resin for extra-high voltage composite insulating devices with the best mechanical,thermal,and electrical properties.The curing cycle and cure kinetic model were established by DSC(differential scanning calorimetry).The optimum content of accelerator dimethylbenzylamine was determined through property tests of epoxy resin curing kinetics,thermal and mechanical properties,on this basis,the self-made modified castor oil was used to toughen the system.Finally,the cured epoxy resin with the best comprehensive properties is prepared,and the optimal formula of the epoxy resin for the insulating devices is determined.According to the formula,the epoxy resin insulating devices were successfully prepared by RTM(Resin Transfer Molding)process,and their properties were characterized.The specific conclusions are as follows:(1)Through non-isothermal DSC scanning test of epoxy resin/anhydride system,the gelation temperature is 68.74?,curing temperature is 147.84?,and post-treatment temperature is 181.90?.According to the three characteristic temperatures and the infra-red spectroscopic analysis of the cured epoxy resin,the curing cycle was determined to be 70?/3h+140?/3h.Using the kissinger and F-W-O method,the apparent activation energy of the system was calculated,its value is 99.14kJ/mol.Using the Malek method,it was found that the Sestak-Berggren model can describe its curing behavior accurately.Finally,the curing kinetic equation of the system can be accurately calculated and derived.(2)When the content of accelerator dimethylbenzylamine is 0.5phr,the cured epoxy resin has the best comprehensive porperties.Among them,the glass transition temperature is 106.3?,the weight loss temperature is 350.7?,the tensile strength is 76.8 MPa,the density is 1.213 g·cm-3,the hardness is 92.5HD,and the cured epoxy resin is orange-red(3)The self-made modified castor oil was synthesized by random interesterification reaction.When castor oil and soybean oil with a mass ratio of 100:35,the modified castor oil synthesized by has the best toughening effect on cured epoxy resin.Adding 10phr modified castor oil to the epoxy resin can optimize the properties of cured epoxy resin,the impact strength of the cured epoxy resin reaches 35.7kJ·m-2,the tensile strength is 75.3MPa,the weight loss temperature is 335.0?,the glass transition temperature is 103.2?.(4)The insulating devices were successfully prepared by the RTM process.The result shows that when the infiltration temperature reaches 80?,the epoxy resin has the best wettability to the aramid fiber and the pull rods have the best quality.Among them,the shaft/radial electrical strength is 17.0kV/mm and the flashover voltage is 185kV(sample length is 43mm),the dielectric constant is 3.53,the dielectric loss factor is 0.0026,the tensile strength is 291.1MPa,the bending strength is 402.3MPa,the density is 1.591g·cm-3,and the water absorption is 0.085%.Comprehensively,the insulating devices has excellent porperties and sufficient safety margin. |
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