绝缘封装用环氧树脂固化物的湿热老化特性

Hydrothermal Aging Characteristics of Cured Epoxy Resin for Insulation Encapsulation

环氧树脂容易受到湿热环境的侵蚀而发生绝缘性能劣化,进而直接影响电力系统运行的安全性与稳定性。为明确环氧树脂材料在湿热环境下的介电性能变化趋势,该研究对环氧树脂固化试样进行湿热老化实验,探究老化温度对其介电性能的影响规律,并对湿热老化机理进行分析。实验结果表明:环氧树脂试样在湿热老化后因吸湿出现质量增加,水分子对环氧树脂基体的塑化作用使其玻璃化转变温度降低。湿热老化后环氧树脂的体积电阻率下降,而相对介电常数和介质损耗因数增大,低频区尤为明显。用瓦格纳热击穿理论解释了环氧树脂试样击穿现象,相对介电常数和介质损耗因数增大都会导致环氧树脂的工频交流击穿强度下降。湿热老化温度升高加速了环氧树脂的吸湿进程,使其平衡状态的吸湿量增大,造成介电性能进一步下降。

Epoxy resins are susceptible to be eroded by hydrothermal environment,which causes deterioration of insulation performance,and directly impairs the safety and stability of power system operation.In order to clarify the change trend of the dielectric properties of epoxy resin materials in hydrothermal ambience,artificial hydrothermal aging experiments were conducted on cured epoxy resin samples to investigate the effect of aging temperature on its electrical properties,and the aging mechanism was analyzed.The experimental results indicate that the mass of epoxy resin samples will augment due to moisture absorption after hydrothermal aging.Plasticizing effect of water molecules on the epoxy resin matrix will lower its glass transition temperature.The volume resistivity of epoxy resin samples will decrease after exposing to hydrothermal ambience,while the relative permittivity and dielectric loss factor will increase especially in the low frequency region.The AC breakdown phenomenon of epoxy resin samples is explained using Wagner’s thermal breakdown theory,and the power frequency AC breakdown strength of epoxy resin will decrease due to the increase in relative permittivity and dielectric loss factor.Higher aging temperature can promote the hygroscopic process of the epoxy resin,which will increase the moisture content in equilibrium state and cause the dielectric properties to further decrease.