Flame retardancy of polymers

Transparent polycarbonate nanocomposites with improved fire behavior were prepared by incorporation of polyhedral oligomeric silsesquioxane (POSS) and resorcinol bis (diphenyl phosphate) (RDP) via melt blending. Flame retardancy performance was characterized using thermogravimetric analysis, pyrolysis combustion flow calorimeter and cone calorimeter. Simultaneous presence of RDP and POSS led to the decrease of the degradation rate and the increase of char residue due to the reaction of the additives with the decomposing polymer. This results in a significant reduction of flammability of polycarbonate. In cone calorimeter, the heat release rate as well as the smoke production rate were shown to strongly decrease due to a condensed phase mechanism that favoured the formation of a cohesive char layer. Transparency evaluation was performed in both physical and psychophysical spaces. The two approaches give various assessment of transparency. Considering the perceived optical properties, it could be concluded that flame retarded PC is translucent rather than transparent.