Li Peng, Wang Xuan, Jin Jin, Zhang Hui, Han Wei
Key Laboratory of Engineering Dielectrics and Its Application of Ministry of Education, Harbin University of Science and Technology, Harbin 150080, China.
Materials (Basel). 2023 Oct 12;16(20):6659. doi: 10.3390/ma16206659.
To enhance the direct current (DC) dielectric properties of cross-linked polyethylene (XLPE) for high-voltage (HV) cable insulation, the polyethylene molecular chain is modified by grafting bismaleimide ethane (BMIE), which creates carrier deep traps within the polymer material. Compared to the traditional modified molecule maleic anhydride (MAH), BMIE has a significantly higher boiling point than the production temperature of XLPE. Additionally, it does not release bubbles during the production process and, thus, preserves the dielectric properties. It was proved by infrared spectroscopy and a gel content test that BMIE was successfully grafted onto the polyethylene molecular chain and had no effect on the crosslinking degree of the polymer while reducing the amount of crosslinker, thereby reducing the influence of the by-products of the decomposition of dicumene peroxide (DCP) on the electrical resistance of polymers. The analysis of DC breakdown field strength, current density, and space charge distribution at various temperatures demonstrates that grafting BMIE can greatly enhance the dielectric properties of insulation. Polar groups in the BMIE molecule create deep trap energy levels in XLPE-g-BMIE, and these trap energy levels contribute to the formation of a charged layer near the electrode, which is shielded by Coulomb potential. As a result, the charge injection barrier increases. Additionally, the presence of these polar groups reduces the mobility of charge carriers through trap-carrier scattering, effectively suppressing the accumulation of space charge within the material. First-principle calculations also confirm that bound states can be introduced as carrier traps by grafting BMIE onto polyethylene molecules. The agreement between experimental results and simulation calculations indicates that grafting BMIE to enhance the dielectric properties of polyethylene is a new and feasible research direction in the exploitation of materials for HVDC cables.
为提高用于高压（HV）电缆绝缘的交联聚乙烯（XLPE）的直流（DC）介电性能，通过接枝双马来酰亚胺乙烷（BMIE）对聚乙烯分子链进行改性，这在聚合物材料中产生了载流子深陷阱。与传统改性分子马来酸酐（MAH）相比，BMIE的沸点显著高于XLPE的生产温度。此外，它在生产过程中不会释放气泡，因此保留了介电性能。通过红外光谱和凝胶含量测试证明，BMIE成功接枝到聚乙烯分子链上，在减少交联剂用量的同时对聚合物的交联度没有影响，从而降低了过氧化二异丙苯（DCP）分解副产物对聚合物电阻的影响。对不同温度下的直流击穿场强、电流密度和空间电荷分布的分析表明，接枝BMIE可以大大提高绝缘的介电性能。BMIE分子中的极性基团在XLPE-g-BMIE中产生深陷阱能级，这些陷阱能级有助于在电极附近形成带电层，该带电层被库仑势屏蔽。结果，电荷注入势垒增加。此外，这些极性基团的存在通过陷阱-载流子散射降低了载流子的迁移率，有效抑制了材料内部空间电荷的积累。第一性原理计算也证实，通过将BMIE接枝到聚乙烯分子上可以引入束缚态作为载流子陷阱。实验结果与模拟计算之间的一致性表明，接枝BMIE以提高聚乙烯的介电性能是高压直流（HVDC）电缆材料开发中的一个新的可行研究方向。
