Facilitating Supercritical CO2 Assisted Exfoliation of Graphene Nanoplatelets with the Polymer Matrix

Abstract The currently mass-produced graphene materials are typically graphene nanoplatelets (GnPs) with multiple-layer structures the properties of which are not comparable to those of mono-layer or few-layer graphene. In this work, high concentrations of commercial GnPs (15 wt% with potential to be higher) were effectively exfoliated in polypropylene (PP)/GnP nanocomposites using supercritical CO2 (sc-CO2) in a foaming process. It was shown that the exfoliation of GnPs was increased with an increased expansion ratio in the foaming window of PP/GnP (159-163°C). However, a high degree of GnP exfoliation can be maintained at elevated temperatures (e.g., 200°C) with minimized expansion ratios (