Flame retardant and smoke suppression mechanism of multi-walled carbon nanotubes on high-impact polystyrene nanocomposites

Abstract

Nanocomposites of high-impact polystyrene (HIPS) with multi-walled carbon nanotubes (MWNT) were prepared by melt blending method. The flame retardant and smoke suppression mechanism of MWNT on HIPS were intensively investigated by transmission electron microscopy (TEM), thermogravimetric (TG) analysis, cone calorimeter method, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). It was found that the addition of MWNT has no marked effect on the degradation mechanism of the nanocomposites, but it significantly reduces the smoke production rates, total smoke release, smoke factor, heat release rates and mass loss rates of the material and forms a considerable volume of residue after burning. The flame retardant and smoke suppression mechanism are due to the formation of residue with featured structure during combustion. The fine morphology of the residues for the composites showed that the residues of HIPS/MWNT nanocomposites assume a two-layer structure in sub-microscale and micro network structure in nanoscale. The two-layer structure includes a thin skin layer at the surface of the residue and an expanded cellular layer beneath the skin layer. It is the skin-cellular layer structure which considerably enlarges the thickness and volume of residue. Both the skin layer and cellular layer are constituted of MWNT, which are interconnected to form a network-like structure in nanoscale. It is a well combination of the skin-cellular layer and the nanoscale network structure that acts as a good insulation barrier to reduce flammability and smoke production of the composites.