反应型抗氧剂接枝改性XLPE直流介电性能研究

Crosslinked polyethylene (XLPE) insulated high voltage direct current (HVDC) cables have broad application prospect. However, the performance of insulation materials is one of the main factors that restrict its development. At present, only rare Multi-National Corporations master the key technology of the industrialization of these materials. The additive antioxidant used in XLPE cable insulation is easy to form space charge and remove, which would affect the operation stability of direct current (DC) cables. Therefore, this project will put forward the idea to improve DC dielectric properties of XLPE insulation by designing molecular structure. The functional antioxidants containing polar groups will be grafted onto XLPE molecular chain, which makes the polar groups of antioxidants distribute in XLPE uniformly and has the effect of suppressing space charges. The internal relationships between the polar groups, grafting content of antioxidants and the space charge distribution, DC conductivity and DC breakdown strength of the modified XLPE will be investigated by deep and systematical research. The mechanism of the improvement of functional antioxidants to DC dielectric properties of XLPE will be revealed by the research of trap distribution and charge behavior. The functional antioxidants will be designed and synthesized for developing crosslinkable polyethylene insulation materials used in HVDC cables. This project not only has important scientific significance, but also can be expected to obtain favorable economic and social benefits.

交联聚乙烯（XLPE）绝缘高压直流电缆应用前景广阔，绝缘材料性能是制约其发展的主要因素之一，目前只有极少数跨国公司掌握了该材料生产的关键技术。XLPE电缆绝缘中所使用的添加型抗氧剂易形成空间电荷，迁移析出，影响直流电缆的稳定运行。因此本项目提出通过分子结构设计改善XLPE绝缘直流介电性能的思想，将含有极性基团的反应型抗氧剂接枝到XLPE分子链中，使得抗氧剂的极性基团均匀分布在XLPE中，起到抑制空间电荷的作用。拟通过深入、系统的研究，揭示抗氧剂的极性基团种类和接枝量与其改性XLPE的空间电荷分布、直流电导特性和直流击穿强度的内在联系，通过陷阱分布特性及电荷行为的研究探明反应型抗氧剂改善XLPE直流介电性能的机理，并设计、合成出可用于制备高压直流电缆用可交联聚乙烯绝缘材料的反应型抗氧剂。本项目研究不仅具有较重要的科学意义，而且有望获得良好的经济和社会效益。

空间电荷的产生与积聚是制约XLPE绝缘材料应用于高压直流电缆的主要因素之一。本项目选取含有极性基团的两类反应型抗氧剂受阻酚和受阻胺，通过熔融接枝将其接枝到PE分子链上，制备得到了极性基团均匀分布的抗氧剂接枝改性PE绝缘材料，测试了接枝改性PE的空间电荷分布，发现受阻胺抗氧剂接枝改性具有更加优异的抑制空间电荷积聚的效果，较少的抗氧剂用量即可得到较优异的直流介电性能。通过热刺激电流谱以及第一性原理计算研究了改性PE的电荷行为和陷阱分布特性，揭示了抗氧剂接枝改性抑制空间电荷积聚、改善直流电导特性、提高直流击穿强度的机理。受阻胺抗氧剂接枝改性PE绝缘材料具有优异的直流介电性能的同时，接枝抗氧剂仍保持有良好的抗氧化效果并具有抗迁出性，不需要添加额外的抗氧剂。本研究为探讨全有机XLPE绝缘材料抑制空间电荷积聚，改善直流介电性能机理奠定坚实工作基础，为高压直流电缆XLPE绝缘材料的研发提供新的思路。