Dispersion and Properties of Graphene Oxide and Reduced Graphene Oxide in Nanocomposites

Abstract

Reducing graphene oxide (GO) is currently seen as one of the most cost effective and scalable methods to produce graphene sheets. This method takes exfoliated graphite in the form of graphene oxide (GO) and reduces it to reduced graphene oxide (rGO). This reduction process recovers the mechanical, thermal, and electrical properties of GO,1 making it more appealing for many applications including fillers in polymers. However, the reduction of oxygen functional groups tends to lead to lower dispersion quality and activity of rGO in polymers. This remains an issue as researchers search to produce graphene based nanocomposites for different applications. This study characterizes the thermal and mechanical properties of graphene oxide and reduced graphene oxide epoxy nanocomposites to determine the overall performance in relation to dispersion quality and nanoparticle loading. For this purpose, epoxy nanocomposites of GO (C:O ratio 1:1) and rGO (C:O ratio 5:1) with various loadings (0.5, 1.0, and 2.0 wt.%) and dispersion qualities (3 different combinations of shear mixing and horn sonication) were fabricated and characterized. Transmission optical microscopy (TOM) and scanning electron microscopy (SEM) were used to qualitatively asses the level of dispersion for each dispersion technique. Flash diffusivity analysis and differential scanning calorimetry (DSC) were employed to measure the thermal diffusivity and specific heat capacity, respectively, for each sample, from which the thermal conductivity was calculated. The thermal conductivity was then correlated to the level of dispersion and filler (GO or rGO) for the composites. Nanoindentation was utilized to assess the mechanical properties of the nanocomposites with respect to dispersion, loading, and filler type.