Polymer/carbon nanocomposites for enhanced thermal transport properties - carbon nanotubes versus graphene sheets as nanoscale fillers

Light-weight composite materials of superior thermal transport properties are important to thermal management and other applications. Carbon nanomaterials with their high thermal conductivities have been widely pursued for such a purpose. Specifically, carbon nanotubes have been shown both theoretically and experimentally to possess extraordinarily high thermal conductivities at the individual nanotube level, and thus are logically considered as ideal fillers for highly thermally conductive polymeric nanocomposites. However, the predicted dramatically enhanced thermal transport in polymers upon the incorporation of carbon nanotubes has not yet materialized. Recently, graphene research has brought new opportunities to the development of polymer/carbon nanocomposites of high thermal conductivities, with already some successful uses of exfoliated graphite sheets as nanoscale fillers. In this work poly(vinyl alcohol) (PVA) was selected as the polymer matrix for the dispersion of single-walled carbon nanotubes (seamlessly with PVA functionalization and solubilization) vs. few-layer graphene sheets as nanoscale carbon fillers for a more direct comparison on the thermal transport performance in the resulting nanocomposites. The effect of aligning the nanotubes embedded in the nanocomposite films via mechanical stretching was also evaluated. Implications of the comparison between the nanotubes and nanosheets with respect to their potentials in thermally conductive polymeric nanocomposites are discussed.