A green and solvent-free method for simultaneously producing graphene nanoplatelets, nanoscrolls, and nanodots and functionalizing their surface for epoxy nanocomposites

Graphene is an emerging class of multifunctional additives for plastic manufacturing. However, achieving the exfoliation and dispersion of graphene in polymers such as epoxy has been a significant challenge, typically requiring chemical modification or oxidation as well as organic solvents and/or surfactants, because exceptionally high-surface area graphene often stack themselves. Herein we report the preparation, exfoliation, surface modification, and dispersion of graphene nanomaterials in epoxy by a simple ball milling process. The prepared graphene nanomaterials exhibit a range of morphologies, i.e. nanoplatelets, nanoscrolls, and nanodots. These materials demonstrate high electrical conductivity, 1750 ​± ​41 ​S/cm, for a film of ∼6 μm in thickness. Furthermore, as the graphene nanomaterials' surface was functionalized with amine groups for affinity with epoxy, the nanomaterials were found to disperse readily in epoxy. At 0.25 ​vol% of graphene, the epoxy nanocomposite exhibited a 52% increment of fracture toughness and an 11% increment of Young's modulus. Notably, an electrical percolation threshold was observed at 0.52 ​vol% for the nanocomposites.