界面多应力作用下乙丙橡胶的特性变化及破坏机理

Performance Change and Failure Mechanism of Ethylene Propylene-Diene Monomer under Interfacial Multi-Stresses

为了深入研究电缆附件绝缘材料在电、热和机械等多种应力耦合作用下的破坏机理,以110kV预制式电缆中间接头用三元乙丙橡胶为研究对象,搭建了模拟电缆附件绝缘界面应力作用状况的多应力耦合试验装置。对交联聚乙烯-乙丙橡胶界面中的橡胶试样施加不同的机械拉伸和电应力,应力作用不同时间后,采用显微观察、机械性能测量、体积电阻率及交联度测试、衰减全反射傅里叶红外光谱和X射线光电子能谱等手段对试样进行了观察及测试。研究结果显示,乙丙橡胶表面分子中的部分原有基团在电应力作用下被破坏并氧化,生成—OH、CO等氧化基团,机械拉伸应力对上述反应具有一定的协同促进作用,而机械性能、体积电阻率和交联度等反映材料体积特性的参数变化幅度不大。这表明,上述多应力耦合作用对乙丙橡胶的破坏主要停留在表面,并未深入体积内部,原因可能是乙丙橡胶材料中的大量添加物和填料暴露在表面后,阻挡了放电粒子和活性基团对试样内部的进一步破坏。

To investigate the failure mechanism of cable accessory insulation under the coupling effects of electrical,thermal and mechanical stresses,ethylene propylene-diene monomer(EPDM)rubber in 110 kV prefabricated cable joints is taken as the research object,and a multi-stress experimental device is constructed to simulate the insulation interface of cable accessories.Different mechanical tension and/or electrical stresses are applied to the rubber samples in the interface composed of XLPE-EPDM.After being stressed for preset time periods,the samples are observed by scanning electron microscope(SEM),and their mechanical property,volume resistivity,crosslinking degree,attenuated total reflectance Fourier infrared spectrum(ATR-FTIR)and X-ray photoelectron spectroscopy(XPS)are measured.It is shown that some chemical bonds of EPDM at the sample surfaces are destroyed and oxidized under the electrical stress,with the generated oxidation groups such as—OH and CO.The mechanical tensile stress promotes this reaction,on the contrary,those parameters involved in material volume characteristics,including mechanical property,volume resistivity and crosslinking degree,only are slightly changed,which indicates that the damage effect of the coupled multi-stresses on EPDM samples remains on the surface and does not go deep inside the volume.It is explained as that the large number of additives and fillers in the EPDM material exposed at the surface prevent the further damage of sample interior by the discharge particles and active groups.