Thermal decomposition of flame-retarded high-impact polystyrene

摘要

The thermal decomposition of four high-impact polystyrene (HIPS) samples containing brominated flame retardants has been studied. Decabromodiphenyl ether (Br_(10)-DPE) and decabromodibenzyl (Br_(10)-DB) were used as flame retardants and two samples contained antimony trioxide (Sb_2O_3) 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, Sb_2O_3 reduces the thermal stability of the samples indicating that Sb_2O_3 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 Sb_2O_3. 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).