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

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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.

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