Effect of Chopped Fiber Concentration on PMIA Paper Properties and Analysis of Structure-Activity Relationship Mechanism
Fan Xiaozhou1,2, Yang Rui1, Fan Sidi1,2, Liu Yunpeng1,2, Lü Fangcheng1,2
1. College of Electrical and Electronic Engineering North China Electric Power University Beijing 102206 China; 2. Hebei Key Laboratory of Power Transmission Equipment Security Defense North China Electric Power University Baoding 071003 China
Abstract In order to study the effect of chopped fiber concentration on the insulation and mechanical properties of PMIA paper and its structure-activity relationship mechanism, samples of PMIA paper with different chopped fiber concentration were prepared, tensile strength, Young's modulus, breakdown strength, conductivity and charge trap were tested, the test results of samples with different fiber concentration were compared, and the structure-activity relationship mechanism was analyzed by combining phase field breakdown simulation and molecular dynamics simulation. The results showed that with the increase of chopped fiber concentration, the mechanical properties of meta-aramid paper initially increased and then decreased, with the optimum performance reached at a weight fraction of 20% of chopped fiber, and the tensile strength and Young's modulus reached 31.9 MPa and 2.39 GPa, respectively. When the weight fraction of chopped fiber reaches 30%, the chopped fiber forms a "layered cross-linking" structure, which enhances its hindering effect on carrier migration, and its breakdown strength is higher than that of pure pulp paper, reaching 180.9 kV/mm. Firstly, the PMIA paper was prepared using the wet-laid method with tunable chopped fiber concentration. 2 000 mL of DI water, 130 mL of PEO solution (weight fraction = 0.052%), and precipitated fibers are mixed together into a fiber dissociator and dissociated at a rate of 30 00 r/min for 5 minutes. The chopped fibers are then added together and the dissociation is continued for 25 minutes. Next, the suction filtration and paper making are performed. The prepared paper is dried in a vacuum at 110℃ for 20 minutes to remove most of the moisture. The as prepared paper is then placed on a heating plate for flatness and kept for completely dry before taking it out for later use. Finally, the paper was hot pressed three times using a flat vulcanizer and a chrome plated mold with parameters of 270℃, 10 MPa, and 10 s. The composite paper prepared by this process has a diameter of (200±2) mm and a thickness of (0.16±0.02) mm. We prepared samples of meta aramid insulation paper with different chopped fiber contents, and tested their microstructure, mechanical properties, and electrical properties. We used phase field simulation and molecular dynamics calculations to explain the mechanism of their structure-activity relationship, and obtained the following conclusions: (1) The surface of meta aramid paper without chopped fibers presents a very dense structure. With the introduction of chopped fibers, obvious defects begin to appear between the chopped fibers and at the interface with the pulp. At the same time, the hot pressing process brings a layered structure to the meta aramid paper, which is severely damaged when the weight fraction of chopped fibers reaches 40%. But when the weight fraction of chopped fibers is 30%, a cross-linked layered structure appears in the sample. (2) The sample without chopped fibers exhibited the worst mechanical properties. As the content of chopped fibers is increased, the tensile strength of the paper is gradually increased, and reached its best at a weight fraction of 20%. Its tensile strength and Young's modulus are increased by 31.8% and 30.6%, respectively, compared to pure pulp paper. (3) The optimal insulation performance of the meta aramid paper sample occurs when the short cut weight fraction is 30%, and its breakdown strength reaches 180.9 kV/mm. At the same time, it also exhibits the highest trap depth and the lowest conductivity. Its cross-linked structure compensates for the interface defects and brings more effective hindrance to carrier migration.
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2024, Vol. 39 
