低密度聚乙烯/纳米蒙脱土复合材料的水树枝生长特性

低密度聚乙烯是高压电力电缆的主要绝缘材料,水树枝生长特性与聚乙烯高压电力电缆绝缘击穿具有紧密联系。采用熔融插层复合法制备了一种低密度聚乙烯/蒙脱土纳米复合材料;设计制作了纳米复合材料的水树枝老化试样及试验装置,在试验中观测了试样的水树枝生长长度,并对试样的水树枝引发率进行了统计,分析了低密度聚乙烯/蒙脱土纳米复合材料的吸水率对水树枝生长的影响;采用差示扫描热法分析了试样的结晶度和晶粒尺寸均匀性,通过分析低密度聚乙烯/蒙脱土纳米复合材料的结晶行为,说明了纳米蒙脱土对纳米复合材料中水树枝的抑制机理。试验与分析结果表明:掺杂质量分数为3%的纳米蒙脱土粒子能够有效地提高低密度聚乙烯的结晶度,使晶粒尺寸分布均匀,吸水率减小,延缓水树枝在低密度聚乙烯中的引发与生长。

Properties of Water Tree Growing in Low Density Polyethylene/Montmorillonite Nano-composite

Low density polyethylene(LDPE) is a major type of insulation material in power cables.The water tree growing property of polyethylene is closely related to insulation breakdown in high voltage polyethylene cables.We presented a type of LDPE/montmorillonite(MMT) nano-composite prepared by a melting intercalation process.A testing setup and specimens of water trees growth in the nano-composite were designed and made.The lengths of the water trees in these specimens were observed,and the trigger rates of the water trees were counted in the water tree aging experiments.Moreover,the influence of water absorption of the LDPE/MMT nano-composite on property of water tree growing was analyzed,and the mechanism of water trees in the LDPE/MMT nano-composite restrained by MMT nano-particles was illustrated through analysis of crystallization behavior of the nano-composite.The experiments and analysis results show that MMT nano-particles of which the mass fractions are 3% can increase the crystallinity degrees and decrease the grain sizes of LDPE.Therefore,they help to decrease the water absorption,the postpone inception and the growth of water trees.