Temperature-tuned dimensional transition of graphitic nanoparticles and its effect on the fire safety of epoxy nanocomposites

The one- and two-dimensional (1D and 2D) carbon-based nanomaterials are extensively studied as flame retardants in the last decade, widely believed with better performances than other counterparts. However, the research for the systematic comparison between the two with similar elemental composition is rare. Meanwhile, the considered factors which influence the performances are mainly restricted to aspect ratio and specific surface area of the carbon-based nanomaterials, regardless of the crystallinity, nanostructure and others. Hence, we compared the flame retardant efficiency of graphitic nanotubes and nanosheets in the epoxy nanocomposites. The products with different dimensions were prepared by tuning the pyrolysis temperature. Interestingly, the nanosheets imparted lower peak of heat release rate to the nanocomposites, while the nanotubes endowed lower total heat release and smoke production amount. The high aspect ratio of the nanosheets provided strong physical barrier effect, while the broad inner cavities of the nanotubes facilitated the formation of graphitic char layers. This work is expected to uncover the flame retardant effects of 1D and 2D graphitic nanomaterials on polymer nanocomposites.