Impact of brominated flame retardants on the chemical recycling of polystyrene via pyrolysis

Brominated flame retardants remain a key challenge for the chemical recycling of polystyrene, particularly for expanded polystyrene used in external thermal insulation composite systems. Pyrolysis offers a viable route to recover monomer-rich oils, provided that bromine can be efficiently separated. In this study, the pyrolysis behavior of flame-retarded polystyrene containing hexabromocyclododecane and brominated butadiene-styrenecopolymer is investigated with a focus on bromine release and product composition. Thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy shows that approximately 90 wt% of bromine is released as hydrogen bromide below 350 ◦C, largely independent of composition. At elevated flame-retardant contents, stabilization effects emerge at higher temperatures due to interactions between flame-retardant decomposition intermediates and the polystyrene matrix. Pyrolysis-gas chromatography–mass spectrometry indicates that, at application-relevant loadings, the styrene-dominated product distribution remains unchanged. Heating rate variation reveals temporal separation between dehydrobromination and PS depolymerization, with rapid bromine release occurring under conditions relevant to technical pyrolysis. ... mehrThese findings demonstrate that pyrolysis can effectively direct bromine to the gas phase without compromising product quality, providing a basis for temperature-driven process design and advancing circular recycling strategies for flame-retarded polystyrene waste.