Thermal decomposition of flame-retarded high-impact polystyrene

The thermal decomposition of four high-impact polystyrene (HIPS) samples containing brominated flame retardants has been studied. Decabromodiphenyl ether (Brio-DPE) and decabromodibenzyl (Br-10-DB) were used as flame retardants and two samples contained antimony trioxide (Sb2O3) synergist besides the brominated additives. The thermal decomposition of HIPS samples was studied by thermogravimetry/mass spectrometry (TG/MS), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and pyrolysis-mass spectrometry (Py-MS). It was established that the brominated additives themselves do not change the decomposition temperature of polystyrene (PS). However, Sb2O3 reduces the thermal stability of the samples indicating that Sb2O3 initiates the decomposition of the flame retardants and PS. Water and styrene products were detected during the first stage of decomposition from HIPS samples containing Sb2O3. Nevertheless, the majority of PS decomposes at a higher temperature. The two brominated flame retardants decompose by different pathways. The scission of C-C bonds, resulting in the formation of bromotoluenes, is the most important reaction of Br-10-DB additives. In contrast, Br-10-DPE decomposes by an intermolecular ring closure pathway producing brominated dibenzofurans (DBF). (C) 2003 Elsevier Science B.V. All rights reserved.