Self-stratifying and orientation of exfoliated few-layer graphene nanoplatelets in epoxy composites

A deep morphological study was carried out in graphene/epoxy composites reinforced with two types of nanoparticles: chemically exfoliated graphene and non-treated graphene nanoplatelets. Different morphological features, such as exfoliation, distribution, dispersion and orientation were analyzed. Composites with exfoliated graphene nanoparticles presented stratification, where few-layer graphene particles occupy top positions while thicker nanoplatelets fell down at the bottom. In order to solve this heterogeneity, a rotating mould was designed. Rotating the reinforced probes during curing treatment, up gelation, the stratification of graphene nanoplatelets could be avoided. It was also corroborated that the graphene/epoxy composites show preferential orientation, where most of graphene particles lies parallel to the sample surface, leading anisotropy in materials. This effect was specially marked in composites with thicker graphene nanoplatelets reinforcement regard to those with exfoliated nanosheets. (C) 2013 Elsevier Ltd. All rights reserved.