聚乙烯分子链结构差异对其介电性能的影响

Effect of molecular chain structure of polyethylene on its dielectric performance

为探究国内外聚乙烯电缆料性能差异产生的原因,本文通过凝胶渗透色谱(GPC)、旋转流变测试以及自成核退火热分级(SSA)等方法测试了材料的分子量分布、长支链含量以及短支链含量,探讨了一种国产和两种进口500kV交联聚乙烯电缆料的分子链结构与其介电性能的关系。结果表明:聚乙烯体内长支链含量从小到大的顺序为:国产样品、进口B样品、进口A样品;短支链含量从小到大的顺序为:进口B样品、进口A样品、国产样品。其中,进口A样品中较高的长支链含量,有利于分子有序排列和结晶的形成,进而提高其耐压等级;国产样品过高的短支链含量会阻碍分子结晶,导致其击穿场强较低。此外,3种聚乙烯分子链结构的差异对其介电常数、介质损耗因数和电阻率影响不大。

In order to explore the reasons for the differences in the properties of polyethylene cable materials at home and abroad,the molecular weight distribution,long branch chain content and short branch chain content of the materials were measured by gel permeation chromatography(GPC),rotational rheological test,and self-nucleation annealing thermal classification(SSA),and the relationship between the molecular chain structure of one domestic and two imported 500 kV cross-linked polyethylene cable materials and their dielectric properties were discussed.The results show that the order of long-chain chain content in polyethylene from small to large is:domestic sample,imported B sample,imported A sample.The order of short chain content from small to large is:imported sample B,imported sample A,domestic sample.Among them,the imported sample A has higher content of long-chain chains,which is conducive to the formation of ordered molecular arrangement and crystallization,and further improve its withstand voltage level.Excessive short chain content in domestic samples can hinder the molecular crystallization,resulting in lower breakdown strength.In addition,the differences in the molecular chain structure of the three types of polyethylene have little effect on their dielectric constant,dielectric loss factor,and resistivity.