Effect of Sodium Bicarbonate in Fabrication of Carbon Black‐Filled Epoxy Porous for Conductive Application

Abstract

SummaryCarbon black‐filled epoxy porous (CBEP) was fabricated by using single emulsion technique. Mixture of epoxy, polyamide hardener, sodium bicarbonate (as blowing agent) and carbon black (as conductive filler) was dropped into a heated corn oil at 160 °C (containing free of polyunsaturated fatty acids). The epoxy‐oil system was stirred at 1000 rpm for 1 hour. Because of the immiscibility of epoxy mixture and corn oil, droplets of epoxy mixture were formed. Initial epoxy droplets were broken into small droplets due to the applied shear (from stirring). Receiving heat from oil phase, the decomposition of sodium bicarbonate and the curing reaction of epoxy and polyamide occurred simultaneously so CBEP was formed. It was found that sodium bicarbonate exhibited a significant effect on the morphology, thermal and conductivity properties of CBEP. Increase of sodium bicarbonate's content from 4 phr to 12 phr could produce larger epoxy particle size in CBEP. However, CBEP using 20 phr of sodium bicarbonate's content had the lowest particle size. The content of 20 phr could induce an early and strong decomposition reaction in the initial epoxy droplets, which broke them into smaller size; hence the smaller particle size was obtained after curing. This fact was evident from the result of bulk density, where higher sodium bicarbonate content induced lower bulk density of CBEP. Furthermore, CBEP using higher sodium bicarbonate content also exhibited better electrical conductivity.