The properties of novel cable insulation systems will rely critically upon the morphology of the material. Here, a blend of high and low density polyethylene was processed in order to generate three sets of samples with different morphologies. The influence of thermo-oxidative ageing at 120 °C was then considered. The resulting chemical changes included the introduction of unsaturation and oxygen-containing groups and was determined by antioxidant consumption and oxygen permeability. Such chemical defects were found to be concentrated in the fraction of each system that was molten at 120 °C and, consequently, served to inhibit recrystallisation following ageing. The resulting spatial distribution of charge trapping sites was therefore strongly dependent on morphology. The electrical conductivity of each system varied non-monotonically with ageing: short times reduced the conductivity; a rapid increase in conductivity over five orders of magnitude occurred beyond a critical ageing threshold. Despite the pronounced structural differences between the morphologically distinct sets of samples, all exhibited comparable conductivity values beyond this threshold, implying that while charge transport is strongly influence by chemical factors, crystallinity is relatively unimportant. This experimental finding appears at odds with theoretical studies of the electronic states in crystalline and amorphous polyethylene.

中文翻译：

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聚乙烯共混物的老化行为：化学缺陷和形态对电荷迁移动力学的影响

新型电缆绝缘系统的性能将严重取决于材料的形态。在此，对高密度和低密度聚乙烯的混合物进行了处理，以生成三组具有不同形态的样品。然后考虑了在120°C时热氧化老化的影​​响。产生的化学变化包括引入不饱和基团和含氧基团，并由抗氧化剂的消耗和氧的渗透性决定。发现这种化学缺陷集中于在120°C熔化的每个系统的馏分中，因此可抑制老化后的再结晶。因此，电荷俘获位点的空间分布强烈依赖于形态。每个系统的电导率随老化而非单调变化：时间短会降低电导率；超过临界老化阈值，电导率迅速增加了五个数量级。尽管在形态上各异的样品组之间存在明显的结构差异，但所有样品均显示出超过此阈值的可比较的电导率值，这表明尽管电荷传输受到化学因素的强烈影响，但结晶度相对而言并不重要。这一实验发现与晶体和非晶态聚乙烯中电子态的理论研究不一致。所有这些都显示出超过该阈值的可比较的电导率值，这意味着尽管电荷传输受到化学因素的强烈影响，但结晶度相对而言并不重要。这一实验发现与晶体和非晶态聚乙烯中电子态的理论研究不一致。所有这些都显示出超过该阈值的可比较的电导率值，这意味着尽管电荷传输受到化学因素的强烈影响，但结晶度相对而言并不重要。这一实验发现与晶体和非晶态聚乙烯中电子态的理论研究不一致。