Thermal Stability of Fire Retardants: I, Hexabromocyclododecane (HBCD

Abstract

The decomposition kinetics of hexabromocyclododecane (HBCD), a flame retardant used in foamed polystyrene, were studied by monitoring the rate of HBr formed at temperatures between 180-240°C. Samples from five suppliers, and from two lots from three of the suppliers, were evaluated. There were significant differences in the decomposition rates, which appeared to be related to the finishing end of the manufacturing process.Samples showing the highest levels of labile bromine containing compounds (probably allylic bromides), as indicated by reactivity towards the silver nitrate, also showed the greatest rates of decomposition.

Investigation of hexabromocyclododecane thermal degradation pathways by gas chromatography/mass spectrometry

“…The degradation mechanisms in Schemes 1 and 2 were originally proposed by Larsen and Ecker 3 and found experimental confirmation in the present study via the Thus HBCD appears to decompose by a complex mechanism involving dehydrobromination reactions, 10 DielsAlder reactions and radical reactions. 11 An important feature is that the intramolecular reactions seem to prevail over intermolecular pathways, at least under the conditions studied herein.…”

“…2 Only sparse data are available on the decomposition products of aliphatic brominated flame retardants, of which hexabromocyclododecane (HBCD) is the most important from an industrial point of view. 1 The studies of Larsen and Ecker 3,4 and of Peled and co-workers 5 mainly concentrated on the thermal stability of this compound. No systematic analysis was undertaken of high molecular weight decomposition products of HBCD in inert or oxidizing atmospheres.…”

“…It is known that HBCD decomposition takes place between 240 and 270°C, if a heating rate of 10°C/min is used. 3 The identification of decomposition products was based mainly on gas chromatography/mass spectrometry (GC/MS) techniques. The use of standard samples and the analysis of fragmentation patterns allowed the identification of many products.…”

Formation of hydrogen bromide and organobrominated compounds in the thermal degradation of electronic boards

“…Most of the former studies were dedicated to shed some light on the possible formation of extremely hazardous compounds, as polybrominated dibenzo-p-dioxins (PBDD) and polybrominated dibenzofurans (PBDF), in the oxidation of BFRs [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. More recently, several investigations were dedicated to the distribution of bromine among the thermal degradation products of the more common BFRs, as tetrabromobisphenol A (TBBA) and hexabromocyclododecane (HBCD) [20][21][22][23][24][25][26][27][28][29], and of materials containing BFRs [26,[30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45]. The results obtained evidenced that, apart the formation of extremely dangerous compounds as PBDD and PBDF, hazards may derive also from the formation of relevant quantities of hydrogen bromide and high molecular weight brominated compounds.…”

Selective separation of polychlorinated naphthalene (PCNs), hexabromocyclododecanes (HBCDs) and tetrabromobisphenol A (TBBPA) in soil matrices

“…This technique is also applied to the analysis of HBCDs, but it is proved to be non-isomer-specific because the diastereomers inter-convert at temperatures over 160°C and decompose at temperatures above 240°C [16,17]. In addition, the partition of HBCDs on GC column stationary phases is poor [18].…”