聚乙烯树枝化的新模型

作者考虑到聚合物的形态结构和能带特点,应用近似的平板能带理论,说明了电子和空穴注入的不同方式和途径。同极性空间电荷的形成过程中存在着两种相互矛盾的作用,一方面它降低针尖附近介质中的电场强度,有提高树枝起始电压的趋势;另一方面注入过程中正负载流子的复合或热电子的作用,有降低树枝起始电压的倾向。模型中首次提出了在聚合物的树枝潜伏期内存在着一个低密度区的过渡阶段,并用条纹图象法证明了这个区域的存在。其他一些特殊试验支持了新模型的构思。

A NEW MODEL FOR TREEING OF POLYETHYLENE

Considering the morphology structure and energy band feature of polymer, the authors employ the flat band approximation to explain the different patterns for the injections of electrons and holes. During the formation of homogenous space charges, two contradicting factors must be considered. One of these weakens theelectrical stress in the dielectrictric near the needle tip, thus increasing the treeing initiation voltage. The other tends to decrease the treeing initiation voltage because of the recombination of positive and negative carriers or because of the effect of thermal electrons. The model for the first time shows that during the treeing period there is a transitional stage in which a low density region is formed in polym(?)r near the needle tip. the low density region has been detected by means of Schlieren technique. The new model is also supported by some other special experiments.