Effect of heating rate on the pyrolysis of high-impact polystyrene containing brominated flame retardants: fate of brominated flame retardants

In the case of plastics containing brominated flame retardants, various brominated organic compounds, including polybrominated dibenzodioxins and dibenzofurans, are yielded when they are degraded. In order to reduce the hazard that might be generated during after-live treatment, the behaviour of flame retarded high-impact polystyrene containing decabromo diphenylether and antimony oxide (Sb₂O₃), was investigated using several heating programs. It was found that the separation of the thermal process into two steps divided at 330 °C makes it possible to obtain an oil fraction rich in brominated compounds at low temperatures and an oil fraction depleted in brominated compounds at high temperatures. The low temperature oil contained a high concentration of SbBr₃ and dibromodibenzofurans. Various brominated compounds with a low volatility and 1-bromo-1-phenylethane from the reaction of HBr with styrene were among the substances in the high temperature oil. The concentration of brominated compounds was reduced from 6 wt% for degradation in a single step to below 1 wt% in the high temperature oil in the two step process.