Effect of Fire Residue Structure on Flame Retardancy of HIPS/Silica Nanocomposites

The nano-silica was employed to prepare HIPS/silica nanocomposites through melt blending method. The microstructure of HIPS/silica nanocomposites was observed by transmission electron microscopy technique. The flammability of the nanocomposites was evaluated by the cone calorimeter. Digital camera and scanning electron microscopy were used to examine the macro-structure, submicro-structure and micro-structure of fire residues. The results show that the addition of nano-silica significantly reduces the heat release rates (HRR) and mass loss rates (MLR) of the HIPS. Compared with the pure HIPS, the peak heat release rates (HRR) of HIPS/silica nanocomposites containing 5%, 10% and 20% nano-silica by mass are 27.52%, 46.98% and 64.76% down respectively. The addition of nano-silica also forms the fire residues with featured structures which has a vital impact on flammability reduction of the composites. The fine fire residues of HIPS/silica nanocomposites are composed as cellular structure in sub-micro scale and three-dimensional network structures in micro scale.