表层氟化聚乙烯中的空间电荷

本文试图简要地汇集近年来与近期我们所取得的关于表面氟化对聚乙烯(PE) 空间电荷行为影响的研究结果, 总结与探讨PE中的空间电荷积累与其氟化层特性和特征间的关联. 这些结果显示在氟化反应气中没有氧存在时一个非常薄的氟化层能产生有效的电荷抑制, 而当氧存在时为达到有效的电荷阻挡、需要一个具有高氟化度的非常厚的氟化层. 在影响空间电荷的诸电学因素中, 氟化层的电荷传导特性比其电荷俘获特性和介电常数或极性对阻止电荷注入材料内部更为重要, 尽管氟化层的高介电常数和被俘获的电荷会降低界面电场、因此减少电荷的电极注入. 氟化层的电荷传导特性密切关联于其自由体积, 反应混合气中存在的氧对减小自由体积、因此对电荷的抑制具有强的负面影响.

Space charge in surface fluorinated polyethylene

Direct fluorination, as one of the most effective approaches to chemical modification of polymer surfaces, has been widely developed from fundamental researches to industrial applications for about forty years in chemical industry field. However, today, its investigations and applications in adjusting and controlling the electrical properties of polymers are still deficient. The present paper attempts to briefly bring together our study results obtained in recent years and recently, related to the influence of surface fluorination on space charge behavior in polyethylene (PE), and to give a concluding discussion on the correlation between space charge accumulation in PE and its fluorinated layer properties and characteristics. The results show that a very thin fluorinated layer can yield effective charge suppression in the absence of oxygen in the reactive gas mixtures, whereas a very thick fluorinated layer with a high degree of fluorination is needed to achieve the effective charge blocking in the presence of oxygen. Among the electrical factors influencing space charge, charge transport properties of the fluorinated layer are more important than its charge trapping properties and permittivity or polarity to prevent charge injection into the bulk material, although high permittivity and deeply trapped charges in the surface layer would reduce the interface electric field and thus decrease charge injection from the electrodes. The charge transport properties of the fluorinated layer are closely related to its free volume, and oxygen in the reactive gas mixtures has a strong negative influence on the decrease of free volume and thus on the suppression of space charge.