Halogen-modified impact polystyrenes: Quantification of preflame phenomena

A novel flash thermolysis technique was developed and used to elucidate factors which control preflame phenomena in halogen‐modified impact polystyrenes. The interrelation between the flux of fuel from impact polystyrene, the flux of flame quenching agents from decabromodiphenyl oxide and metal oxides, and the formation of char was quantified in flash thermolysis experiments at >500°C. The results were correlated with the performance of materials in a standard flammability rating test. In contrast to existing theories of flame retardancy via aromatic halide–antimony trioxide systems, it was found that polymeric free radicals generated during the burning process participate in the halogen release mechanism. The temperature for the halogen release is proportional to the bond strengths of the matrix resin. The specific role of polybutadiene in halogen‐modified impact polystyrene was recognized to include impact modification, halogen release synergism, and the reduction of dripping tendencies during burning.