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Experimental and molecular level analysis of natural ester delaying degradation of cellulose insulation polymer
High Voltage ( IF 4.4 ) Pub Date : 2021-09-24 , DOI: 10.1049/hve2.12151
Jian Hao 1 , Wenyu Ye 1 , Chenyu Gao 1 , Mengzhao Zhu 2 , Lijun Yang 1 , Ruijin Liao 1
Affiliation  

Developing green insulation materials has become an important direction for future research. As a new environmental insulation liquid, natural ester can effectively delay cellulose insulation polymer ageing. Mastering the mechanism of natural ester delaying the cellulose ageing could promote its application in power transformers. In this study, based on the accelerated thermal ageing of pressboard immersed in natural ester and 25# mineral oil at 120°C for 221 days, the thermal ageing rate and the levelling off degree of polymerisation (LODP) for two kinds of oil-impregnated pressboards were compared. The molecular level mechanism of natural ester delaying cellulose degradation and keeping higher LODP value was proposed using molecular dynamics simulation. At the early stage of thermal ageing, cellulose with a higher degree of polymerisation (DP) can form many hydrogen bonds with hydronium ions, and their binding energy is stronger, which can accelerate the acid hydrolysis of cellulose, causing the DP of pressboard immersed in natural ester and mineral oil to decrease rapidly. With the breaking of the cellulose molecular chain, the number of hydrogen bonds and binding energy between cellulose and hydronium ions becomes smaller and the thermal ageing rate decreases gradually. At the end stage of ageing, it is difficult for the hydronium ions to enter the crystalline cellulose, acid hydrolysis of crystalline cellulose is hard to conduct, leading to the occurrence of the LODP phenomenon. The degradation rate of cellulose in natural ester is only 50% of that in mineral oil. The cellulose LODP value in natural ester is over 200 larger than that in mineral oil. Compared with the mineral oil-cellulose system, natural ester can form hydrogen bonds with hydronium ions and lead to fewer hydronium ions in cellulose, fewer hydrogen bonds and smaller binding energy between cellulose and hydronium ions, which can reduce the acid hydrolysis reaction of cellulose. This study provides a theoretical explanation for natural esters to delay the ageing of insulation paper.

中文翻译:

天然酯类延缓纤维素绝缘聚合物降解的实验及分子水平分析

开发绿色绝缘材料已成为未来研究的重要方向。天然酯作为一种新型环保绝缘液,能有效延缓纤维素绝缘聚合物的老化。掌握天然酯类延缓纤维素老化的机理,可促进其在电力变压器中的应用。本研究以纸板在天然酯和 25#矿物油中 120 ℃ 221 d 的加速热老化为基础,研究了两种油浸板的热老化率和流平聚合度(LODP)。对纸板进行了比较。通过分子动力学模拟,提出了天然酯延缓纤维素降解并保持较高LODP值的分子水平机制。在热老化的早期,聚合度较高的纤维素(DP ) 能与水合氢离子形成许多氢键,它们的结合能更强,能加速纤维素的酸水解,引起DP纸板浸入天然酯和矿物油中迅速下降。随着纤维素分子链的断裂,纤维素与水合氢离子之间的氢键数目和结合能变小,热老化率逐渐降低。在老化的最后阶段,水合氢离子难以进入结晶纤维素,结晶纤维素的酸水解难以进行,导致LODP现象的发生。天然酯中纤维素的降解率仅为矿物油的50%。天然酯中的纤维素LODP值比矿物油大200以上。与矿物油-纤维素体系相比,天然酯可以与水合氢离子形成氢键,导致纤维素中的水合氢离子更少,纤维素与水合氢离子之间的氢键较少,结合能较小,可降低纤维素的酸水解反应。本研究为天然酯类延缓绝缘纸老化提供了理论解释。
更新日期:2021-09-24
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