Low density polycarbonate–graphene nanocomposite foams produced by supercritical carbon dioxide two-step foaming. Thermal stability

The thermal stability of low density polycarbonate-graphene nanocomposite foams prepared by supercritical carbon dioxide two-step foaming was investigated. Unfilled polycarbonate foams showed improved thermal stabilities when compared to the unfoamed polycarbonate, as the cellular structure of foams effectively slowed down the heat transfer process. Comparatively, polycarbonate foams with larger cells exhibited the highest delays in the early stage of thermal decomposition. Low density polycarbonate-graphene nanocomposite foams (relative densities between 0.07 and 0.28) displayed even higher thermal stabilities, with enhancements of up to 70 ºC in terms of the onset of decomposition when compared to the unfilled PC, which was attributed to a combination of a heat transfer reduction promoted by the cellular structure and the presence of the dispersed graphene nanoplatelets, which acted as a physical barrier to the release of volatile decomposition products.