无外界干预下硅橡胶电树枝自恢复特性的研究

Study on self-recovery characteristics of silicon rubber electrical tree without external interventions

为深入理解硅橡胶(SiR)电树枝的自恢复机理,本文对SiR电树枝自恢复特性进行研究,观测SiR电树枝自恢复过程中的形貌变化,表征SiR试样在电树枝自恢复过程中弹性模量和交联密度的变化,并对SiR电树枝自恢复机理进行分析。结果表明:在没有外电场以及修复填料等外界干预下,SiR电树枝表现出自恢复特性,其部分分支会逐渐退化并最终消失,分形维数逐渐降低,自恢复速率呈现先快后慢的阶段性特征。在电树枝自恢复过程中,SiR试样的弹性模量略有增加,由0.964 MPa增大至0.977 MPa;交联密度略有减小,由1.886×10^(-4) mol/g减小为1.883×10^(-4) mol/g。自恢复后电树枝劣化区域的物理交联密度略有提升,由0.55×10^(-4) mol/g提升至0.58×10^(-4) mol/g。结合SiR电树枝生长机理,分析认为SiR电树枝的自恢复过程本质是树枝通道的弹性收缩过程,受控于通道内的气体流动,并伴随着氢键的重建过程。

To deeply understand the self-recovery mechanism of electrical tree in silicone rubber(SiR),the self-recovery characteristics of SiR electrical tree were studied in this paper.The morphology variation during the self-recover process of electrical tree in SiR were observed,the elastic modulus and crosslinking density of SiR during the self-recovery process of electrical tree were tested,and the self-recover mechanism of SiR electrical tree was analyzed.The results show that the electrical trees in SiR exhibit self-recovery characteristics without external interventions including external electrical field and healing fillers,wherein some branches of electrical tree gradually degrade and eventually disappear,meanwhile the fractal dimension gradually decreases,and the rate of self-recovery exhibits the stage characteristics of fast at first and then slow.During the self-recovery process,the elastic modulus of SiR sample increases slightly from 0.964 MPa to 0.977 MPa,and the crosslinking density decreases slightly from 1.886×10^(-4) mol/g to 1.883×10^(-4) mol/g.After recovery,the physical crosslinking density of electrical tree deteriorated area increases slightly from 0.55×10^(-4) mol/g to 0.58×10^(-4) mol/g.Combined with the growing mechanism of SiR electrical trees,it is analyzed that the self-recovery process of SiR electrical tree is essentially the elastic contraction of tree channel,which is controlled by the gas flow in the channel and accompanied by the reconstruction of hydrogen bond.