Tentative links between thermal diffusivity and fire-retardant properties in poly(methyl methacrylate)-metal oxide nanocomposites

Possible relationships between fire-retardant properties and thermal diffusivity for poly(methyl methacrylate) (PMMA) filled by melt blending with titanium dioxide (TiO₂), alumina (Al₂O₃) and boehmite (AlOOH) were investigated for a better understanding of the mode of action of metal oxides as fire-retardants (FR) in PMMA. Fire-retardancy was measured with a cone calorimeter and thermal diffusivity (α) by Laser Flash Analysis (LFA). LFA measurements have shown that heat dispersion is higher with titanium dioxide and boehmite than with alumina despite a larger surface area. For thermal diffusivity, discrepancies between the different nanofillers were only visible from 10 wt% onwards. Thermal degradation of PMMA-oxide nanocomposites and their thermal diffusivity could be linked. Moreover, a bi-linear relationship between the peak of heat release rate (pHRR) and the average of heat release rate (AHRR) showed the occurrence of a barrier effect.