Mao Jiale, Wang Shuang, Shi Qingyun, Cheng Yonghong, Chen Yu
State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, People's Republic of China.
Langmuir. 2022 Apr 5;38(13):4129-4137. doi: 10.1021/acs.langmuir.2c00228. Epub 2022 Mar 21.
Designing electrical insulation materials with excellent surface flashover strength in a vacuum environment is crucial for high-power equipment and aerospace devices. In the present paper, the effect of two types of electronegative groups, the halogen-phenyl groups and the aromatic π-conjugated naphthyl groups, is used to greatly improve the vacuum flashover characteristics of polystyrene (PS), a commonly used polymer dielectric material in high-power devices. By polymerization of the monomers containing these electronegative groups, the bulk insulation material as a whole is modified expediently. In comparison to the base polymer PS, the electron affinity of the structures containing strong electronegative groups is studied with first-principles calculations based on the density functional theory. The nanosecond pulsed vacuum flashover testing results show that the vacuum flashover strength is increased by 10% after replacing the PS pendant phenyl groups with fluorophenyl groups and increased by 44% when replaced with the naphthyl groups. Furthermore, the thermally stimulated current and secondary electron emission yield spectroscopies are measured, to study the influence of strong electronegative groups on the trapping characteristics and further the electron-emitting features of the polymer dielectrics, which are closely related to the charged particle multiplication process during the vacuum flashover. The results prove that introducing strong electronegative groups can inhibit the triggering of vacuum flashover, suppress the electron emission, delay the flashover process, and thus greatly increase the vacuum flashover voltage. The study of this paper not only puts forward two groups of easily processable polymers with excellent vacuum flashover strength but also paves ways for the future material design of special insulation polymers.
设计在真空环境中具有优异表面闪络强度的电绝缘材料对于高功率设备和航空航天装置至关重要。在本文中，利用两种吸电子基团，即卤代苯基和芳香π共轭萘基，来大幅改善聚苯乙烯（PS）的真空闪络特性，PS是高功率设备中常用的聚合物介电材料。通过使含有这些吸电子基团的单体聚合，可方便地对整体块状绝缘材料进行改性。与基础聚合物PS相比，基于密度泛函理论的第一性原理计算研究了含有强吸电子基团的结构的电子亲和能。纳秒脉冲真空闪络测试结果表明，用氟苯基取代PS侧苯基后，真空闪络强度提高了10%，用萘基取代时提高了44%。此外，还测量了热激电流和二次电子发射产额光谱，以研究强吸电子基团对俘获特性的影响，进而研究聚合物电介质的电子发射特性，这些特性与真空闪络过程中的带电粒子倍增过程密切相关。结果证明，引入强吸电子基团可以抑制真空闪络的触发，抑制电子发射，延迟闪络过程，从而大幅提高真空闪络电压。本文的研究不仅提出了两组具有优异真空闪络强度且易于加工的聚合物，还为未来特殊绝缘聚合物的材料设计铺平了道路。
