| The three-dimensional cross-linked network formed by the reaction of epoxy resin and curing agent has the advantages of excellent insulation,good mechanical properties,easy processing,small shrinkage and low cost,and is widely used in power system.With the rapid development of ultra-high voltage,the properties of domestic produced epoxy resin insulation materials have been difficult to meet the needs of ultra-high voltage electrical equipment.Especially,how to give consideration to the good thermal and mechanical properties is the urgent problem to be solved in development and modification of epoxy resin materials for high voltage insulation.The thermal mechanical properties of epoxy resin have become the bottleneck to further improve the reliability of ultra-high voltage electrical equipment.In order to improve the comprehensive performance of epoxy resin for high voltage insulation,this paper explores the relationship between the microstructure and the macro performance of epoxy resin,so as to provide theoretical basis and method guidance for the preparation of epoxy resin with excellent comprehensive performance for high voltage insulation.By using molecular dynamics(MD)simulation method,two sets of 8 groups of epoxy resin cross-linked structures for high voltage insulation were designed,and the properties of the designed epoxy system in this paper was comprehensively evaluated,and the effectiveness of the selection system was demonstrated and the application was analyzed.The main work of this paper is as follows:For the epoxy-anhydride system for high voltage insulation,a general automatic crosslinking program is designed.Taking the epoxy-anhydride system commonly used in the field of high voltage insulation as an example,a group of epoxy-anhydride cross-linked system is constructed,and the accuracy of the general crosslinking method of epoxy-anhydride system is verified by experiments.Then,based on the model,the effects of crosslinking densities,molecular number and cooling rate on the macroscopically properties of the cross-linked system were studied.Finally,it is determined that the crosslinking density is 89%,the cooling rate is 20K/100ps,and the molecular number is different according to the actual analysis.The results show that after determining the crosslinking density,the accuracy of the cross-linked model can be further improved by reasonable selection of molecular number and cooling rate.Six groups of cross-linked models of epoxy-anhydrides were constructed by using the general method of crosslinking model of epoxy-anhydrides system with the variables of epoxy resin monomer and curing agent monomer.Then,the influence of epoxy resin monomer and curing agent monomer on the microstructure and macro properties of epoxy resin curing products was investigated,and the relationship between the microstructure and macro properties of epoxy-anhydride system was analyzed.Finally,two kinds of alicyclic epoxy resin and one kind of anhydrides curing agent are determined for the design of epoxy resin cross-linked network for high voltage insulation.Based on the mechanism of polymer blending modification,the optimized epoxy resin monomer and curing agent monomer are modeled together with the monomer molecules in the epoxy-anhydride system commonly used in the field of high voltage insulation.Two sets of 8 groups of epoxy resin cross-linked networks for high voltage insulation were designed according to the design principle which the molar ratio of epoxy resin to anhydride resin was 9:1,8:2,7:3 and 6:4 respectively,and the molar ratio of epoxy groups to anhydride groups was 1:1.Then,the influence of the ratio on the structure and properties of the cross-linked network of epoxy resin for high voltage insulation was studied.Finally,according to the design scheme,the test samples are synthesized and the key performance is tested,and the experimental feasibility of the design scheme is demonstrated.The performance evaluation index system of epoxy resin for high voltage insulation is established,and the performance evaluation model of epoxy resin for high voltage insulation based on fuzzy comprehensive evaluation method is established.Then,taking the epoxy-anhydride system commonly used in the field of high-voltage insulation as the comparing system,and together with eight groups of epoxy resin cross-linked systems designed in this paper,the case analysis of performance evaluation is carried out,and two sets of epoxy resin systems with the best comprehensive performance in the design scheme are selected respectively.Then,by MD simulation method,nano-SiO2 was modified on the selected epoxy resin substrate with excellent comprehensive performance,and the performance of the composite was predicted and analyzed,so as to demonstrate the effectiveness and application analysis of the selection system. |
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