Sodium bicarbonate as a blowing agent on morphology and properties of conductive carbon black-filled epoxy porous prepared by emulsion system

Abstract

This study reported a single emulsion method to produce conductive epoxy porous (CEP), which worked as a conductive additive. The CEP was fabricated to overcome the high content of conductive filler using in composite and provide better filler dispersion. Conductive epoxy porous (CEP) had been fabricated from the mixture of epoxy, polyamide hardener, carbon black filler and sodium bicarbonate. Carbon black filler worked as conductive additive while sodium bicarbonate worked as blowing agent. Sodium bicarbonate was selected because of cost effectiveness and non-toxic gases formation. Epoxy mixture was dropped into a heated corn oil with different temperature. Because of the immiscibility of epoxy and corn oil, epoxy droplets were formed. Initial epoxy droplets were broken into smaller droplets due to the applied stirring shear. In addition, the decomposed gas (carbonic gas and water vapour) from sodium bicarbonate also caused an internal expanding pressure to further break the epoxy droplet into many fine droplets. Curing reaction of epoxy and polyamide occurred simultaneously and formed CEPs. Through this, carbon black was dispersed throughout the porous. The results showed that emulsion temperature at 160 °C was selected as the optimum temperature to provide the large packing group of epoxy porous particles. On the other hand, the effect of carbon black content on morphology, thermal properties and electrical properties of conductive epoxy porous was studied. It was found that epoxy particle in CEP became smaller with the high carbon black content. The use 20 phr carbon black content was optimum content exhibited highest electrical conduction by adding of 20 wt% CEP into epoxy-polyamine as binder. The advantageous of CEP versus direct carbon black filled epoxy-polyamine composite is proven form the higher conducting. As expected, the highest sodium bicarbonate content (20 phr in CEP) exhibited promoted better electrical conductivity which is 3.7409x10⁻⁶ S/m.