Preparation of epoxy nanocomposites containing well-dispersed graphene nanosheets

To take full advantage of the potential of graphene nanosheets as reinforcing agents for polymer nanocomposites, good exfoliation, homogenous dispersion, and strong affinity of graphene nanosheets in a polymer matrix are needed. In this research, homogeneous dispersion of graphene nanosheets in epoxy is achieved via chemical functionalization of graphene oxide with 4-nitrobenzenediazonium salt. Optical microscopy and transmission electron microscopy demonstrate that graphene nanosheets are well-exfoliated in organic solvents and in epoxy. While only a marginal increase in Young's modulus is observed, significant improvements in tensile strength (>30%) and elongation at break (>50%) for epoxy nanocomposites with a graphene concentration of 0.8 wt.% are achieved. The thermal conductivity of an epoxy nanocomposite with modified graphene nanosheets at 5 wt.% increases to 0.56 W/mK, approximately 2.5 times that of the neat epoxy. The possible mechanisms that account for the observed improvements in tensile properties and thermal conductivity are discussed.