Thermal Stability of Fire Retardants:* III, Decomposition of Pentabromochlorocyclohexane and Hexabromocyclododecane under Processing Conditions

Abstract

The thermal decomposition kinetics of several aliphatic FR agents contain ing vicinal bromines were studied under temperature conditions, i.e., 200-226 °C., commonly found in extruders. The reactions were monitored by the rate of HBr evolution and by the formation of trans-stilbene in dilute (1.8-10 wt.% agent) bibenzyl solutions. The measured reaction rate constants ( kHBr) were found to include a free radical component ( kHBr1) and an ionic com ponent ( kHBr2) resulting from the homolytic cleavage of a carbon-bromine bond and from an iron or zinc induced reaction, respectively. Of the primary agents used in polystyrene, pentabromochlorocyclohexane was found to decompose at about three times the rate of hexabromocyclodo decane at any given temperature.

Thermal Stability of Fire Retardants:* V. Decomposition of Haloalkyl Phosphates under Polyurethane Processing Conditions

“…The DPE was purified by the method described in [3] and contained less than 5 ppm of iron and less than 0.01% trans-stilbene (t-S) by FID-GLC. Only single lots of the products are represented so lot to lot variations are unknown.…”

“…The decomposition procedure is given in detail in [3]. In general, the procedure consisted of dissolving a weighed amount of agent into a weighed quantity of molten DPE ( -55 ° C) and heating the solution at the desired temperature in a constant temperature bath.…”

“…WE HAVE REPORTED, previously, on the thermal stability and decomposition kinetics of a variety of FR agents, including both aliphatic and aromatic bromides, used in thermoplastics [1,2,3,4]. These studies were carried out with both neat agents and with agents dissolved in bibenzyl (1,2-diphenylethane, DPE) at temperatures normally encountered during extrusion of polymers.…”

HBCD Stereoisomer Pattern in Mirror Carps Following Dietary Exposure to Pure γ-HBCD Enantiomers

“…HBCD decomposes at temperatures above 220°C (14,15), and at temperatures between 160 and 200°C, thermal rearrangement of the HBCD isomers takes place (13,16). Recent studies have examined the isomerization of all six stereoisomers at elevated temperatures in detail (17,18).…”

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

“…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.…”