通过向低密度聚乙烯(LDPE)中加入不同质量分数的过氧化二异丙苯(DCP),制备了不同交联度的XLPE试样,用热延伸实验法对交联度进行表征;利用水刀电极法对试样进行水树枝老化,并采用光学显微镜观测其水树枝的生长形貌;采用差示量热扫描仪(DSC)对试样的结晶度进行测试,并分别通过偏光显微镜(PLM)和扫描电子显微镜(SEM)观察其结晶形貌,研究交联度对交联聚乙烯(XLPE)水树枝老化特性的影响机理.结果表明:提升XLPE的交联度可以显著增强其耐水树枝能力;虽然交联反应抑制了XLPE球晶和片晶的生长,使其结晶度下降,导致无定形区域面积增大,但形成的三维网状结构限制了材料内部水分沿电场方向发生形变挤压形成水树枝的能力,交联度越高,这种抑制能力越强.相比于结晶的影响,三维网状结构对提高材料耐水树枝能力的影响更明显.
XLPE samples with different crosslinking degrees were prepared by adding different mass frac-tion of dicumyl peroxide (DCP) to low density polyethylene (LDPE), and the crosslinking degree was characterized via thermal stretching experiment. The XLPE samples were aged by liquid electrode meth-od, and the growth feature of water trees was observed through optical microscope. The crystallinity of the samples was tested through differential calorimeter scanner (DSC), and the crystal morphology was observed via polarizing microscope (PLM) and scanning electron microscope (SEM), respectively. The influence mechanism of crosslinking degree on the water tree ageing characteristic of XLPE was studied. The results show that the increase of crosslinking degree of XLPE can significantly enhance its anti-wa-ter tree characteristic. The crosslinking reaction inhibits the growth of spherulites and lamellae of XLPE, make the crystallinity decrease and the amorphous area enlarge, but the formed three-dimensional network structure would restrict the water deform along the electric filed direction to form water trees. And the higher the crosslinking degree, the stronger the restrict ability is. Compared to the effect of crystalliza-tion, three-dimensional network structure has more remarkable effect in improving the anti-water tree char-acteristic of materials.
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