GIL中聚酯薄膜在电热作用下裂解机理的分子动力学模拟  

Molecular Dynamics Simulation of the Pyrolysis Mechanism of Polyester Films in Gas Insulation Lines Under Electrothermal Stresses

作　　者：辛喆 赵彤[1] 韩智云 邹亮[1] 张黎[1] Xin Zhe;Zhao Tong;Han Zhiyun;Zou Liang;Zhang Li(School of Electrical Engineering Shandong University Jinan 250061 China)

机构地区：[1]山东大学电气工程学院,济南250061

出　　处：《电工技术学报》2018年第22期5196-5205,共10页Transactions of China Electrotechnical Society

基　　金：国家自然科学基金(51737005);山东省重点研发计划(2018GGX104009);山东大学基本科研业务费专项资金(2017JC012)资助

摘　　要：聚酯(PET)薄膜在气体绝缘封闭线路(GIL)中用作电极覆膜以降低金属微粒对GIL的威胁。PET薄膜会在电、热等因素作用下逐渐老化最终导致绝缘失效。本文通过反应分子动力学模拟方法(ReaxFF),分析PET薄膜在高温和高电场强度下的微观动态反应路径和主要产物形成过程,得到其绝缘老化失效的微观机理。PET薄膜中大量反应活性较高的酯基在电热的作用下易发生断裂,进而导致PET聚合度降低,对电场耐受能力下降。在热裂解中,它产生大量对苯二甲酸根,C_2H_4等小分子,其中前者容易与氢离子组合形成对苯二甲酸(PTA)。在较高的反应温度下,PTA脱羧作用增强,CO_2产生速率明显加快。C_2H_4、CO_2和CO等气体产物积聚在PET薄膜的内部以形成微孔,易发生局部放电从而破坏PET薄膜的绝缘。模拟了不同聚合度PET薄膜分子链的电裂解反应,结果显示在电场力的作用下分子被极化拉伸,内部作用力被削弱,形态遭到破坏,同时热稳定性和机械强度下降。Polyethylene terephthalate(PET)is used as an electrode coating in gas insulation lines(GIL)to reduce the threat of metal particles to GIL operation.PET will gradually age under the influence of electricity,heat and other factors,eventually leading to insulation failure.In this paper,the micro-dynamic reaction path and the main product formation process of PET at high temperature were analyzed via ReaxFF,and the microscopic mechanism of PET insulation failure at high temperature and high field strength were obtained.A large number of highly reactive ester groups in PET are prone to fracture under the action of electricity and heat,which in turn leads to a decrease in the degree of polymerization of PET and the resistance to field strength.In the thermal cracking,it produces a large number of terephthalate,C2H4 and other small molecules,in which the former is easily combined with hydrogen ions to form PTA.At higher reaction temperatures,terephthalate decarboxylation is enhanced and the rate of CO2 production is significantly accelerated.The main gas products such as C2H4,CO2 and CO are accumulated in the interior of PET to form micropores.The local discharge will easily occur in the micropores and eventually lead to the breakdown of PET due to insulation failure.The electro-cracking reaction of PET chains with different degrees of polymerization was simulated.The results show that,the molecules are polarized and the internal force is weakened under the action of the electric field force.The morphology is also destroyed,and the thermal stability and mechanical strength are decreased.

关 键 词：电极覆膜 聚酯薄膜 裂解 微观机理 反应分子动力学 

分 类 号：TM215.1[一般工业技术—材料科学与工程]