| As a high-performance paper-based material,aramid paper is widely used in rail transit and other electrical insulation fields as the main insulation material.The aramid paper in traction motor,traction transformer and other electrical equipment of rail transit still relies heavily on imports for a long time.There are large defects in the structure design of domestic aramid paper.The aramid paper has an “open”microstructure,low interface bonding,low electrical insulation performance and large fluctuation,which can not meet the requirements of high insulation,high heat resistance and low dispersion and other special requirements in the field of rail transit.In order to overcome the problem of low interface bonding in the “open”microstructure,this paper has carried out the design,preparation,characterization and performance research of “sealed” microstructure aramid paper.The research work of this paper aims to realize the preparation and engineering application of aramid paper with high electrical insulation performance.The main research contents and conclusions of the paper are as followed:(1)The idea of “sealed” microstructure of aramid paper to construct dense and less defective fiber bonding interface was proposed.Starting from material design,the microscopic characteristics and performance characteristics of floc with different spinning processes and fibrid with different beating degrees were investigated,and the formula design of aramid paper was carried out to determine the appropriate fiber ratio.The results showed that the best electrical insulation and mechanical properties of aramid paper with the ratio of dry spinning floc:self-made high-pulp precipitated fibrid(wt.%)=40:60.The tensile strength and tensile index of the prepared paper were1.41 k N/m and 34.73N·m/g,the breakdown voltage and electrical strength were 1.32 k V and 9.0 k V/mm,respectively.(2)The concept of agglomeration factor was introduced.The fourdrinier wire forming technology was innovatively applied to the forming of aramid paper.The effects of forming concentration,high frequency shaking,slurry/wire ratio,vacuum degree and dispersant additives on the forming process were studied.The suitable hot calendering parameters were determined by orthogonal test and single factor test.The experimental results showed that the best forming effect can be obtained when the forming concentration was 0.10%,the high frequency shaking frequency was400r/min,the amplitude was 10 mm,the slurry/wire ratio was 0.93,the vacuum degree was-30 KPa,and 1.0% acrylamide dispersant(ks1040)was used.The suitable hot calendering process parameters were 290?,20 MPa and 15m/min.(3)On the basis of structural design and material preparation,the differences in composition,structure and performance between self-made aramid paper and representative aramid paper at home and abroad were systematically evaluated by using a variety of advanced characterization techniques.The results showed that the composition of the self-made aramid paper was basically the same as that of the imported aramid paper and domestic aramid paper.The internal structure of the self-made aramid paper was compact with few defects,formed the “sealed” microstructure.The electrical strength of self-made aramid paper is 18.4kv/mm and the dispersion coefficient is3.01%,which achieved the research goal of high insulation and low dispersion.The air permeability of the self-made aramid paper sample was 0.003 ?m/Pa·s,the pressure retention rate was 83.5% after immersion,and the temperature index(TI)was223 °C.The thermal oxidative aging behavior of self-made aramid paper in contact with copper/aluminum metal conductor was consistent with that of imported products,which was better than that of domestic paper. |
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