炭黑填充聚合物体系渗流转变过程中的介电性能

采用熔融共混的方法制备了导电炭黑填充乙烯-醋酸乙烯酯共聚物复合体系,分别通过添加填料粒子和熔融态等温处理促进粒子凝聚成网两种方法研究了体系在渗流转变过程中的电性能变化,发现在该过程中材料的导电性能和介电性能均持续上升,伏安特性和相位角分析表明粒子间始终为非欧姆接触。动态渗流测试发现,复合体系从绝缘体到导体的整个渗流转变过程中介电常数是持续增加的。因此渗流理论所预测的介电常数极大值很可能发生在临界含量的上限值,此时材料的导电机理转变为欧姆传导。

Dielectric Property of Carbon Black Filled Polymer Composites in Percolation Transition

Carbon black filled ethylene vinyl-acetate copolymer composites were prepared via melt compounding.Two methods,i.e.,randomly adding filler and isothermal annealing an unpercolated composite sample in molten state to promote the formation of percolation network by nanoparticle self-aggregation,were adopted in order to observe the evolution of dielectric property of the composites system during percolation transition.It showed that electrical conductivity and dielectric constant increased continuously during percolation transition.Current-voltage characteristics and phase angle of the composites indicated a non-ohmic contact between carbon black particles in the composites.Dynamic percolation measurement of the unpercolated sample supported that dielectric constant increased continuously during percolation transition.The results assured that the dielectric singularity predicted by percolation theory will happen at the transition from non-ohmic to ohmic contact between the conductive filler.