Flame retardant polystyrene copolymers: preparation, thermal properties, and fire toxicities

A new phosphorous‐ and nitrogen‐containing reactive monomer, DMPMA, was first synthesized by nucleophilic substitution reaction of 2‐(6‐oxido‐6H‐dibenz[c,e][1,2]oxaphos‐phorin‐6‐yl) methanol, N‐hydroxymethyl acrylamide and methyldichlorophosphate. The copolymer of styrene (St) and DMPMA (poly(St‐co‐DMPMA)) was prepared and then characterized by Fourier transform infrared, differential scanning calorimetry, thermogravimetric analysis (TGA), microscale combustion calorimeter and steady‐state tube furnace (SSTF). The results proved that poly(St‐co‐DMPMA) was well synthesized, while the glass transition temperature of the copolymer was decreased with increasing DMPMA content. The TGA results showed that the initial degradation temperature of poly(St‐co‐DMPMA) decreased, but its char yield and decomposition temperature improved compared to that of pure polystyrene. After incorporating DMPMA, the fire performance of the copolymer was significantly improved. The results obtained from the SSTF indicated that the carbon monoxide and smoke yield density were increased due to the incomplete combustion of the copolymer.