Heteroatom-Doped Graphitic Carbon Nitrides for Reducing the Fire Hazard of Polystyrene

High fire hazard, including heat release and toxic volatile production, has been the bottleneck in expanding the application of polystyrene (PS). Here, a heteroatom doping strategy is adopted to strengthen the flame-retardant effect of graphitic carbon nitride (g-C₃N₄) on PS. It is observed that the doped g-C₃N₄ fillers (PCN-1, PCN-2, PCN-3, BCN-1, BCN-2, BCN-3, PBCN-1, PBCN-2, and PBCN-3) show nanosheet-like morphologies, while common g-C₃N₄ presents bulky morphology. Also, the doped g-C₃N₄ fillers show higher thermal stability than common g-C₃N₄. Consequently, the doped g-C₃N₄ fillers show a better dispersion state in the PS matrix, benefiting the generation of an efficient barrier network. Cone results reveal that using the doped g-C₃N₄ fillers endows the polymer with a lower peak heat release rate, a peak smoke production rate, and a peak CO yield (PCOY). Typically, adding CN results in corresponding reductions of 7.2, 3.74, and 12.4%, respectively. By contrast, incorporating PCN-2 leads to decreases of 39.9, 23.0, and 53.2%, respectively. Thermogravimetric analysis/infrared spectrometry analysis indicates that the use of these additives contributes to the inhibition of the release of decomposed volatiles. Thus, it is firmly believed that utilizing heteroatom-doped g-C₃N₄ impairs the fire hazard of the polymer.