界面缺陷加速高温硫化硅橡胶在酸热环境下的老化开裂研究

Research on Aging and Cracking of High Temperature Vulcanized Silicone Rubber Accelerated by Interfacial Defects in Acid-heat Environment

高温硫化(high temperature vulcanized,HTV)硅橡胶(silicone rubber, SIR)具备优良的憎水性和抗污闪性能,并作为复合绝缘子的护套被广泛用于输电线路的绝缘装置。护套与芯棒间的界面状态是决定复合绝缘子长时间稳定运行的重要因素,而界面缺陷会严重影响复合绝缘子运行的可靠性。为此设计了含不同尺寸界面缺陷的HTV硅橡胶–环氧玻纤试样板,分别在80℃水、硫酸和硝酸溶液下进行人工老化。结果表明:经80℃硝酸溶液处理4 d后,含界面缺陷的试样表面出现大量裂纹,且随着老化时间增长其表面裂纹逐渐扩大。而无缺陷试样在相同老化条件下8 d后表面仍保持光滑。结合微观形貌结果与理化性能检测分析,裂纹是由缺陷试样的界面应力引起的。此外,经过80℃硝酸溶液处理后,含缺陷试样的拉伸性能和介电性能相比于无缺陷试样均显著下降。80℃硝酸溶液处理8 d后,试样抗拉强度和断裂应变分别从4.58 MPa和470%下降到2.07 MPa和130%。同时由于裂纹加速水分入侵导致缺陷试样在102~104Hz的频率范围内出现了新的介电损耗峰。该研究通过对含人工界面缺陷的HTV硅橡胶进行酸热老化,探究了在酸热应力下,界面缺陷加速HTV硅橡胶的老化开裂机理,可为今后研究复合绝缘子护套的开裂机理及相应的老化特性提供理论支持。

High temperature vulcanized(HTV)silicone rubber(SIR),as the sheath of composite insulators,is widely used as the insulation device in transmission lines due to their excellent hydrophobicity and pollution flashover resistance.However,the interfacial defects of insulators and severe operating environment will accelerate the aging of HTV SIR sheath,seriously impairing the operation reliability of electrical equipment.Herein,the samples designed with different sizes of interfacial defects are aged under water,sulfuric acid,and nitric acid at 80℃,respectively.The results show that a large number of cracks appear on the surface of HTV SIR samples with interfacial defects after nitric acid treatment at 80℃for more than 2 days,meanwhile,samples with no interfacial defects aged under same condition for 8 days maintain unchanged.According to the results of the micro morphology of the sample,the crack is caused by the interfacial stress of the sample.In addition,after nitric acid treatment,the tensile and dielectric properties of HTV SIR with interfacial defects decrease significantly.The tensile strength and fracture strain decrease from 4.58 MPa and 470%to 2.07 MPa and 130%,respectively,proving that cracks caused by interfacial defects can critically weaken the mechanical properties and thermal stability of HTV SIR.Also,an extra dielectric loss peak appears in the frequency range of 102 Hz~104 Hz,which is attributed to water invading and the MWS polarization at cracks.By aging HTV SIR with artificial interfacial defects under thermal and acid stress,the HTV SIR cracking phenomenon of composite insulators under severe operating environment is successfully simulated.This work can provide theoretical support for studying the cracking mechanism and the corresponding aging characteristics of HTV SIR used in composite insulators.