Fire-retardant action of resorcinol bis(diphenyl phosphate) in PC-ABS blend. II. Reactions in the condensed phase

The thermal decomposition of polycarbonate (PC), PC containing resorcinol b is(diphenyl phosphate) (RDP), and PC-acrylonitrile-butadiene-styrene (PC-AB S) blend containing RDP was studied by thermogravimetry. Volatile and solid products of thermal decomposition were collected at different steps of the rmal decomposition and characterized either by gas chromatography-mass spec trometry or infrared and chemical analysis. It was found that phosphorus ac cumulates in the condensed phase. Upon combustion of the fire-retardant mix ture PC-ABS + RDP, accumulation of phosphorus is observed in the charred la yer, at the surface of the burning specimens. It is suggested that PC under goes a Fries-type rearrangement upon thermal decomposition, and RDP reacts with the formed phenolic groups through a trans-esterification mechanism. K inetic analysis of the thermal decomposition of PC containing RDP supports the proposed mechanism. (C) 1999 John Wiley & Sons, Inc.