硝酸对硅橡胶的老化作用机理研究

doi:10.19595/j.cnki.1000-6753.tces.200809

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摘要在硅橡胶复合绝缘子的运行过程中,硝酸的产生、渗透和老化会降低硅橡胶的性能,并影响到电网设备的安全运行。该文结合多种表征技术系统研究硝酸对硅橡胶的老化作用机理。气相色谱-质谱（GC-MS）结果表明,硅橡胶中聚二甲基硅氧烷（PDMS）在硝酸的作用下裂解,导致硅橡胶中D₄~D₇为主的环状硅氧烷小分子增多。硝酸溶液浸泡600h的硅橡胶内D₄是未老化时的30倍,有机组分相对含量下降了9.19%。傅里叶红外光谱（FTIR）和X射线光电子能谱（XPS）的结果表明,硝酸老化后硅橡胶表面Si-C键断裂并被氧化,生成无机硅氧结构Si-O₃和Si-O₄,导致表面C元素含量降低;同时甲基中的C-H键断裂并引入极性羟基。由试验结果可知,硝酸主要从以下两方面引起硅橡胶老化：一是H⁺作用于PDMS中的Si-O键,使硅橡胶中的PDMS网络结构解聚;二是强氧化性的NO₃^-作用于表面PDMS中的基团,导致硅橡胶表面由非极性转为极性。这些是引起硅橡胶阻隔性能及憎水性下降的主要原因。

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关键词 ：硅橡胶, 硝酸, 硅氧烷小分子, 化学结构

Abstract：During the running of a silicone rubber composite insulator, the formation and permeation of nitric acid will reduce the properties of silicone rubber, which threatens the safety of the insulation device in power grid. In this paper, the aging mechanism of nitric acid on silicone rubber was systematically studied by several material characterization techniques. The results of GC-MS show that the polydimethylsiloxane (PDMS) in silicone rubber breaks into low molecular weighted siloxanes (LMW), resulting in the increase of the D₄~D₇. Moreover, the concentration of D₄ in the 600h nitric acid aged sample is 30 times that of the virgin one, and the left relative content of PDMS decreases by 9.16%. The results of FTIR and XPS show that the Si-C bond is broken and oxidized after aging with nitric acid, leading to the increase of Si-O₃ and Si-O₄, while the content of carbon element is reduced. At the same time, the C-H bond breaks and polar hydroxyl groups are introduced into methyl group. It can be seen that nitric acid mainly causes the aging of silicone rubber from two aspects: one is that the H⁺ acts on the Si-O bond in PDMS, which depolymerizes the PDMS network structure in silicone rubber; the other is that the highly oxidized NO₃^- acts on the groups in PDMS, which causes the surface of silicone rubber to change from non-polarity to polarity. These are the main reasons for the decrease in barrier and hydrophobicity of silicone rubber.

Key words： Silicone rubber nitric acid low-molecular-weight siloxane chemical structur

收稿日期: 2020-07-06

PACS:

TM85

基金资助:南方电网公司科技项目（GDKJXM20200403）、中国博士后科学基金项目（2020M682609）、广东省电力装备可靠性企业重点实验室开放基金项目（GDDKY2020KF01）资助

通讯作者: 方鹏飞男,1971年生,教授,博士生导师,研究方向为高电压绝缘材料老化表征与微观测试技术、纳米结构电介质等。E-mail：fangpf@whu.edu.cn

作者简介: 张妮女,1992年生,硕士,研究方向为高电压绝缘材料。E-mail：1095302527@qq.com

引用本文:

张妮, 汪政, 杨粤, 彭向阳, 方鹏飞. 硝酸对硅橡胶的老化作用机理研究[J]. 电工技术学报, 2021, 36(22): 4820-4828. Zhang Ni, Wang Zheng, Yang Yue, Peng Xiangyang, Fang Pengfei. Study on the Nitric Acid Induced Aging Mechanism in Silicone Rubber. Transactions of China Electrotechnical Society, 2021, 36(22): 4820-4828.

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