Tri-layer architectured epoxy composites with high electrical permittivity

Abstract

In this work, epoxy composites filled with polypyrrole (ppy) coated paddy straw micro particles exhibiting high electrical permittivity were prepared. Oxidative vapour phase polymerization was used to obtain thin ppy coating over straw particles. These single layered epoxy composites exhibited high electrical permittivity and were further used to prepare tri-layer architectured composites in which an epoxy-graphene (−ve k) composite layer was stacked in-between two epoxy-ppy-straw (+ve k) composite layers. The layered composites displayed an even higher electrical permittivities, 124.2 and 227.7 (1 kHz) and suppressed tanδ 0.055 and 0.5 at 33 wt% and 38 wt% filler concentrations respectively. The tanδ showed strong frequency dependence and their minima shifted to higher frequencies. The thickness of +ve k layers were reduced progressively and corresponding permittivities were recorded which showed a linear increase as the thickness ratio of layers (−ve k/+ve k) increased.