紫外辐照高温硫化硅橡胶的红外光谱分析和老化机理

doi:10.3964/j.issn.1000-0593(2020)04-1063-08

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摘要：高温硫化(HTV)硅橡胶复合绝缘子广泛应用于特高压输电线路，其抗紫外老化性能越来越受到人们的关注。采用自行设计的可调式紫外老化试验箱对两个厂家的高温硫化硅橡胶样品进行了紫外辐照(0, 500和1 000 h)加速老化实验，辐照光波长范围为320～750 nm。对辐照前后试样进行傅里叶变换衰减全反射红外光谱(ATR-FTIR)测试，分析谱峰的变化与试样(表面)官能团的关系，辅以扫描电子显微镜（SEM）和憎水性、体积电阻率的测试来研究HTV硅橡胶的老化机理。结果表明：高温硫化硅橡胶FTIR全谱图中1 260 cm^-1处Si—CH₃反射峰和800 cm^-1附近Si—(CH₃)₂反射峰强度随辐照时间的增加而逐渐减弱，1 000～1 100 cm^-1处的Si—O—Si反射峰强度随辐照时间的增加先减弱后增强；扫描电镜观察到辐照后的样品表面出现大颗粒和坑洞、粗糙度变大，其主要元素O，Si和Al重量百分比略增加；喷水分级法在表面形成的水珠随着样品辐照时间的延长由均匀分布变得不均匀且出现合并，憎水性有明确下降；体积电阻率略微降低。分析认为：辐照后紫外线切断了HTV硅橡胶部分Si—C，C—C和C—H键，对称排列的非极性甲基基团—CH₃从硅氧主链上脱落，减弱了对主链强极性的屏蔽作用，使Si—O—Si峰强度减弱，且少量侧链被氧化，形成C—O和—OH（COOH）；而主链之间因裸露出来的自由基—Si·发生进一步的交联反应，使得Si—O键相对含量增加，使Si—O—Si峰强度再增强。二方面结果均导致高温硫化硅橡胶表面极性增强，憎水性下降。水本身具有微弱的电离，憎水性下降的高温硫化硅橡胶易吸收空气中的水使其表面载流子浓度增加体积电阻率略有下降。通过红外光谱分析，紫外线是通过切断高温硫化硅橡胶表面的部分Si—C，C—C，C—H键，使其生成新的自由基并发生交联和氧化而使其老化的。红外光谱的应用对于高温硫化硅橡胶复合绝缘子老化研究及其在特高压输电线路上的挂网应用均具有重要意义。

关键词：高温硫化硅橡胶；紫外辐射加速老化；傅里叶变换红外光谱；扫描电子显微镜；憎水性；体积电阻率

Abstract：High temperature vulcanized (HTV) silicone rubber composite insulators are widely used in UHV transmission lines, and more and more attention has been paid to their ultraviolet aging resistance. In this paper, the samples of high temperature vulcanized silicone rubber come from two manufacturers, and the testing instrument is a self-designed adjustable ultraviolet aging test chamber, with 320~750 nm ultraviolet radiation as experiment condition. Then aging test by ultraviolet radiation (0, 500, 1 000 h) was carried out. Fourier transform attenuated total reflection infrared spectroscopy (ATR-FTIR) was used to analyze the relationship between the change of spectral peak and the functional group of sample (surface) before and after radiation, which was supplemented by SEM, hydrophobicity and volume resistivity measurement. Thus the aging mechanism of HTV silicone rubber was studied. The results showed that with the increase of ultraviolet radiation time, the reflection peak intensity of HTV silicone rubber side chain Si—CH₃ and Si— (CH₃)₂ decreases, and the main chain Si—O—Si reflection peak intensity increases, the hydrophobicity decreases clearly, and the volume resistivity decreases slightly. Scanning electron microscope (SEM) showed that large particles and potholes appear on the surface of the irradiated, and the weight percentage of Al, O, Si increases. The results showed that ultraviolet light cut off the part of Si—C bond of HTV silicone rubber and removed the nonpolar methyl group from the main chain of Si—O—Si, which weakened the shielding effect on the strong polarity of the main chain. The exposed free radical —Si· was further oxidized and crosslinked, which enhanced the binding of Si—O—Si, enhanced the polarity of molecular chains, and decreased the hydrophobicity. The decrease of hydrophobicity made HTV silicone rubber easy to absorb water in the air, and the weak ionization of water itself increased the carrier concentration, resulting in a slight decrease in volume resistivity. According to the infrared spectrum analysis, the following conclusions were drawn: ultraviolet ray accelerated the aging of high temperature vulcanized silicone rubber by cutting off the functional groups on the surface of high temperature vulcanized silicone rubber; The application of infrared spectroscopy is of great significance to the study of aging of silicone rubber composite insulators at high temperature and its application in UHV transmission lines.

Key words：High temperature vulcanization silicone rubber; Ultraviolet radiation accelerated aging; Fourier transform infrared spectroscopy; Scanning electron microscope; Hydrophobicity; Volume resistivity

收稿日期: 2019-03-20 修订日期: 2019-07-16

中图分类号:

TM215.2

基金资助: 国家自然科学基金项目（51462017）资助

通讯作者: 虞澜 E-mail: yulan000@hotmail.com

作者简介: 李敬敬，1981年生，昆明理工大学材料科学与工程学院博士研究生 e-mail: ljjing1981@163.com

引用本文:

李敬敬，张辉辉，李国芳，张善刚，刘颜，董鹍，祖恩东，虞澜. 紫外辐照高温硫化硅橡胶的红外光谱分析和老化机理[J]. 光谱学与光谱分析, 2020, 40(04): 1063-1070.
LI Jing-jing, ZHANG Hui-hui, LI Guo-fang, ZHANG Shan-gang, LIU Yan, DONG Kun, ZU En-dong, YU Lan. Aging Mechanism Analysis of High Temperature Vulcanization Silicone Rubber Irradiated by Ultraviolet Radiation Based on Infrared Spectra. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2020, 40(04): 1063-1070.

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