电缆中间接头硅橡胶绝缘的理化特性研究

Physical and Chemical Characteristics of Silicone Rubber Insulation for Cable Intermediate Joint

为了研究硅橡胶绝缘材料理化特性随电缆接头服役时间的变化规律,对不同服役年限10 kV冷缩电缆中间接头硅橡胶绝缘层的密度、热延伸、力学性能、动态热力学性能和热稳定性进行测试。结果表明:在电缆接头服役过程中,由于长期电、热联合作用,硅橡胶材料的交联键出现一定程度的断裂,分子链部分断裂,致使其密度逐渐降低,但高温负荷下伸长率变化较小,具有良好的回弹性;硅橡胶材料的拉伸强度和断裂伸长率随运行时间的增加出现明显的下降;运行后硅橡胶材料表现出起始储能模量大幅下降的降解现象,聚合物基体与填料微粒的粘附力逐渐减弱,出现双损耗峰特征并且降解速率加快,热稳定性下降,残炭量降低;硅橡胶材料的老化状态取决于力学降解和结构硅氧化过程的竞争效应。

In order to study the change laws of physical and chemical characteristics of silicone rubber insulating materials with the service time of cable joint,we tested the density,thermal elongation,mechanical properties,dynamic thermo-mechanical properties,and thermal stability of the silicone rubber insulation layer in 10kV cold-shrinkable cable intermediate joints with different service years.The results show that in the service process of cable joint,due to the long-term combination of electricity and heat,the cross-linking bond of the silicone rubber material is broken to a certain extent,the molecular chain is degraded partially,resulting in the gradual reduction of its density,while its elongation changes a little under high temperature load,which has good resilience.With the increase of the operation time,the tensile strength and elongation at break of the silicone rubber material decrease significantly.After operation,the silicone rubber material exhibits a degradation phenomenon that the initial storage modulus decreases significantly,the adhesion force between the polymer matrix and filler particles is weakened gradually,the characteristic of double-loss peak occurs,the degradation rate is accelerated,the thermal stability decreases,and the carbon residue reduces.The ageing state of the silicone rubber material depends on the competitive effect of mechanical degradation and structural silicon oxidation process.