摘要
为了从微观角度探究物理改性和化学改性提升热稳定纸抗热老化性能的机制,对纤维素改性相关的几种模型分子、热稳定剂、小分子酸、水分子和氧气进行了量子化学计算,获取了相关分子的最高占用轨道(highest occupiedmolecular orbital,HOMO)能量、最低未占用轨道(lowestunoccupied molecular orbital,LUMO)能量及3种-D-吡喃葡萄糖分子的Mulliken布局分布。通过反应分子间的前线轨道能隙和亲电亲核反应位点来考察不同分子间的反应活性及活性点。结果表明:热稳定纸中胺基热稳定剂先与水分子、小分子酸和氧气这些老化因子反应,从而保护了纤维素链;化学改性使得纤维素的抗氧化性能有小幅提升,但化学稳定性却被降低,由于变压器运行温度远小于起始分解温度,热解难以进行;热稳定纸的亲水性差使得纸中水分含量少,加上有机酸的消耗,纤维素水解反应进行缓慢,这在热老化实验中纸的聚合度下降较少上得到了印证。
In order to shed some light on the mechanism of anti-thermal ageing performance improvement of physically and chemically modification in thermally upgraded insulation paper from microscopic scale ,several modeling molecules, thermal agents, small molecule acids, water molecule and oxygen molecule were computed with quantum chemistry method to get the information about HOMO and LUMO energy and Mulliken population distribution of three 13-D-glucopyranose molecules. The reactivity of those molecules and the active sites were investigated by energy gaps between frontier orbitals, electrophilic reaction sites and necleophilic reaction sites respectively. The results show that the cellulose molecules are protected by reaction between thermal agents and small molecule acids, water and oxygen in thermally upgraded insulation paper. Moreover, the anti-oxidation performance of chemically modified paper is improved slightly whereas the chemical stability decrease, which may lead to thermal decomposition.Actually, pyrolysis is difficult to happen due to transformer operation temperature is much lower than the initial decomposition temperature of chemically modified cellulose. As to depolymerization process in cellulose hydrolysis, the rate will be retarded by depletion of water and acids when comparison with kraft insulation paper.
出处
《中国电机工程学报》
EI
CSCD
北大核心
2013年第25期196-203,28,共8页
Proceedings of the CSEE
基金
国家重点基础研究发展计划项目(973项目)(2011CB209401)
国家创新研究群体基金(51021005)
国家自然科学基金项目(51077136)~~
关键词
热稳定纸
密度泛函
物理改性
化学改性
抗热老化
最高占用轨道
最低未占用轨道
thermally upgraded insulation paper
densityfunction
physically modification
chemically modification
anti-thermal ageing
highest occupied molecular orbital（HOMO）
lowest unoccupied molecular orbital（LUMO）
