The plot in Fig. When a material containing a flame retardant exhibits a lower peak temperature of pyrolysis during testing (such as with a Microscale Combustion Calorimeter), it does not necessarily imply that the flame retardant is ineffective. In fact, observing a lower peak temperature might indicate that the flame retardant is functioning as intended, depending on the mechanism through which the flame retardant operates. The ability of hBN-PS composites to reduce polymer flammability is attributed to two key factors. Firstly, the hBN nanosheets, uniformly dispersed in the PS matrix, act as a physical barrier during combustion, effectively retarding the heat and mass transfer and preventing further combustion. Secondly, the presence of hBN-PS promotes char formation on the burning material's surface, reinforcing the barrier effect of the hBN nanosheets and significantly improving flame retardancy. Thus, although the hBN composite showed ignition at a somewhat lower temperature than the neat PS, this resulted from early onset char formation that ultimately resulted in improved flame resistance.