Sophia Dashevsky

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 bis(diphenyl phosphate) (RDP), and PC—acrylonitrile–butadiene–styrene (PC–ABS) blend containing RDP was studied by thermogravimetry. Volatile and solid products of thermal decomposition were collected at different steps of thermal decomposition and characterized either by gas chromatography–mass spectrometry or infrared and chemical analysis. It was found that phosphorus accumulates in the condensed phase. Upon combustion of the fire-retardant mixture PC–ABS + RDP, accumulation of phosphorus is observed in the charred layer, at the surface of the burning specimens. It is suggested that PC undergoes a Fries-type rearrangement upon thermal decomposition, and RDP reacts with the formed phenolic groups through a trans-esterification mechanism. Kinetic analysis of the thermal decomposition of PC containing RDP supports the proposed mechanism.

Synergistic action between aryl phosphates and phenolic resin in PBT

Abstract Fire retardant efficiency of aryl phosphates in combination with phenol-formaldehyde novolac type resin was studied in poly(butylene terephthalate) (PBT). It was shown that resorcinol bis(diphenyl phosphate) or bisphenol A bis(diphenyl phosphate) in combination with novolac is an efficient fire retardant in non-glass reinforced PBT. Co-addition of triphenyl phosphate was required for glass-reinforced PBT to reach similar fire retardant performance. Apparently aryl phosphates/novolac prevent exudation of aryl phosphates to the surface and facilitate crystallization of PBT. Although the aryl phosphates/novolac are compatible with PBT and do not decompose polymer during compounding, PBT exhibited some reduction of Izod impact strength and heat distortion temperature. These phenomena were attributed to changes in the crystalline morphology, and probably also in the amorphous regions of the polymer.