Abstract: Polypropylene is a type of insulating material with excellent performance, which has received significant attention in the field of high-voltage cable insulation. However, its insulating properties decrease significantly after aging, particularly in conjunction with the harsh actual operating environment. This can result in the phenomenon of surface discharge occurring from time to time. In order to investigate the impact of polar groups on the along-surface discharge characteristics of polypropylene at the microscopic level, this paper employs a microscopic analysis of the aforementioned parameters, including the geometrical structure, orbital energy level, density of states, depth of traps, and excited states of different polypropylene molecular chains under the electric field, based on the density functional theory. The results demonstrate that the introduction of polar groups leads to an increase in the degree of curling of the molecular chain, an elevation in the dipole moment, and the formation of a polarized charge on the surface of the material. The depth of the molecular traps is increased by the action of the electric field, with those containing polar groups having a smaller depth, which is favourable for electron de-trapping and increases the number of discharges. The electrophilic activity of the polar group region renders the trapped electrons relatively active, and the accumulated electrons in the region during the process of along-surface discharge. The strong activity will promote the development of electron avalanche. Molecules containing polar groups will experience a significant reduction in excitation energy, with the polar group region becoming the main place of electronic excitation and counter-excitation. In the process of electron and hole composite emission photons, the formation of a luminescence centre will accelerate material ageing, and the formation of space photoionisation in the air gap on the surface of the material will increase the probability of along-surface discharges.
李亚莎, 曾跃凯, 赵光辉, 田泽, 王璐敏, 吴雕. 外电场下极性基团对聚丙烯单分子链沿面放电影响的研究[J]. 材料导报, 2025, 39(13): 24050193-8.
LI Yasha, ZENG Yuekai, ZHAO Guanghui, TIAN Ze, WANG Lumin, WU Diao. Study of Effect of Polar Groups on the Discharge of Polypropylene Monomolecular Chains Along the Surface Under External Electric Field. Materials Reports, 2025, 39(13): 24050193-8.
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2025, Vol. 39 
