Effect of Wet Oxidation on the Dispersion and Electrical Properties of Multi-Walled Carbon Nanotubes/Epoxy Nanocomposites

Abstract

Carbon nanotubes (CNTs) have excellent mechanical and electrical properties than conventional materials (carbon black and glass fibers), and are promising candidates as reinforcement material for composites. Formation of electrical conductive with effective dispersion of filler remains a main challenge in the polymer matrix and fillers in order to achieve a good electrical conductivity. Therefore, one of the solutions is to functionalize through wet oxidation of the CNTs besides adding surfactants or assisted liquids. Functionalization of CNTs involves the generation of chemical moieties on their surface that can improve the solubility and processibility. Any functionalization that is undertaken must preferably not influence other key properties such as strength and electrical conductivity of the nano-composite. The matrix used in this study was epoxy and reinforcement filler was multi-walled carbon nanotubes (MWCNTs). MWCNTs were treated with sulfuric acid and nitric acid at 3:1 (v/v) ratio. The present of functional groups on CNTS were investigated using Fourier Transform Infrared (FT-IR). Different weight percentages of MWCNTs (functionalized and as produced) / epoxy composite were prepared. The electrical conductivity of functionalized MWCNTs nanocomposites and as produced MWCNTs nanocomposites were measured by the four point probe. Dispersion state of CNTs in epoxy matrix was observed on fractured surface by scanning electron microscopic. Functionalized CNTs gave better dispersion stability in solvents than non-functionalized CNTs. As expected, non- functionalized CNTs (as produced MWCNTs) are not dispersed at all in all the solvents. However, functionalized CNTs composites give low electrical conductivity. Defects from acid treatment are assumed will damage the original chirality of as produced CNTs and give unbalance polarization on the CNTs, which are the reasons for no formation of conductive pathway networks of acid treated CNTs under electric field.