高压电缆绝缘用LDPE分子结构与电气性能研究

Research on Molecular Structure and Electrical Properties of LDPE for High Voltage Cable Insulation

选取改进前后3种国产高压电缆绝缘用低密度聚乙烯(LDPE),通过凝胶渗透色谱(GPC)和核磁(NMR)等手段对比分析相对分子质量与分布、双键含量和长链支化度等结构参数;测试并分析改进前后LDPE和交联聚乙烯(XLPE)的直流电气性能。结果表明:改进后的LDPE相对分子质量较大,分布较窄,双键含量和长链支化度均有一定提高,改进后的LDPE体积电阻率、电阻率温度系数、直流击穿等电气性能提升明显,特别是高温体积电阻率。改进后LDPE制备的XLPE体积电阻率整体高一个数量级,90℃体积电阻率高两个数量级,电阻率温度系数大幅下降,直流击穿场强提升约30%,且高电场下几乎无空间电荷。

Three kinds of domestic LDPE before and after improvement for high voltage cable insulation are tested by means of GPC and NMR.The structural parameters such as molecular weight and distribution,double bond content and long⁃chain branching degree are compared and analyzed.The DC electrical properties of LDPE and cross⁃linked polyethylene are tested.The results show that the improved LDPE has a larger molecular weight,a narrower molecular distribution,a certain increase in double bond content and long⁃chain branching degree.There are significant improvements in electrical properties such as volume resistivity,temperature coefficient of resistivity,and DC breakdown strength.The overall volume resistivity of the XLPE prepared by the improved LDPE is one order of magnitude higher,and the volume resistivity at 90℃is two orders of magnitude higher.The temperature coefficient of resistivity is greatly reduced,and the DC breakdown strength is increased by about 30%.