Multi-walled carbon nanotubes (MWCNTs) have received considerable attention as fillers in multifunctional polymer composites due to their high tensile strength, stiffness, and thermal conductivity as well as their low coefficient of thermal expansion and tunable electrical conductivity. However, the realization of these excellent properties in a composite material can only be achieved when the MWCNT and polymer matrix interact favorably. A proven method of enhancing the nanotube-polymer interface involves functionalizing the MWCNTs through oxidation by strong acids. While effective at laboratory scales, this technique is not well-suited for large scale operations due to long processing times, poor yield, safety hazards, and environmental concerns. The advent of commercial MWCNT production in recent years has not been matched by the development of scalable functionalization methods. As a result, alternative oxidation strategies are needed for MWCNTs to find widespread application in polymer composites. Our research aims to identify and optimize new methods for the oxidation of MWCNTs that are rapid, dry, and cost-effective. We are currently developing flash heating, plasma, ultraviolet, and fluidized ozone reactions to endow MWCNTs with oxygen-bearing functional groups, which will act as platforms for further functionalization using amine and epoxy-capped silane coupling agents. These f-MWCNTs should disperse relatively easily in an epoxy resin and will be able to react with epoxy or amine groups as the resin cures, facilitating a strong bond between the epoxy matrix and the MWCNTs.
Danny Vennerberg, Rafael Quirino, Michael Kessler