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Abstract: In this first of two papers, the thermal decomposition of bisphenol A bis(diphenyl phosphate)-flame retarded polycarbonate (PC) blends with different impact modifiers was studied. The impact modifiers were an acrylonitrile–butadiene–styrene (ABS), a poly(n-butyl acrylate) (PBA) rubber with a poly(methyl methacrylate) (PMMA) shell and two silicone–acrylate rubbers consisting of PBA with different amounts of polydimethylsiloxane (PDMS) and different shells (PMMA and styrene–acrylonitrile, SAN). The focus of this work was to study the impact of the acrylate and silicon–acrylate rubbers with respect to pyrolysis and flame retardancy in comparison to common ABS. Thermogravimetry (TG) was performed to investigate the pyrolysis behaviour and reaction kinetics. TG in combination with FTIR identified the pyrolysis gases. Solid residues were investigated by FTIR-ATR. PC/ABS shows two-step decomposition, with PC decomposing independently from ABS at higher temperatures. Pure acrylate rubber destabilises PC due to interactions between the rubber and PC, which leads to earlier decomposition of PC. Using silicone–acrylate rubbers led to similar results as PC/ABS with respect to pyrolysis, reaction kinetics and analysis of the solid residue; hence the exchange of ABS for the silicone–acrylate rubbers is possible. [Copyright &y& Elsevier]

Abstract: In this second of a series of two papers, the fire behaviour of halogen-free flame retarded polycarbonate (PC) blends with different impact modifiers was studied. The impact modifiers were acrylonitrile–butadiene–styrene (ABS), a poly(n-butyl acrylate) rubber (PBA) with a poly(methyl methacrylate) (PMMA) shell and two silicone–acrylate rubbers consisting of PBA with different amounts of polydimethylsiloxane (PDMS) and different shell materials (PMMA and styrene–acrylonitrile, SAN). The flame retardant was bisphenol A bis(diphenyl phosphate) (BDP). Flammability was determined by LOI and UL 94. The burning behaviour under forced flaming conditions was studied by cone calorimeter under different external irradiations and by pyrolysis combustion flow calorimeter measurements. The exchange of ABS with the pure acrylate rubber worsened flammability, while similar results were obtained in cone calorimeter measurements. The exchange of ABS with the silicone–acrylate rubbers is promising, particularly with higher amounts of PDMS. In flammability tests strongly enhanced LOI values were obtained and therefore silicone–acrylate rubbers look like promising alternatives for ABS. [Copyright &y& Elsevier]

The pyrolysis of polycarbonate (PC) and PC/acrylonitrile-butadiene-styrene (PC/ABS) with and without arylphosphates (triphenylphosphate TPP, resorcinol-bis(diphenyl phosphate) RDP and bisphenol A bis(diphenyl phosphate) BDP) is investigated by thermal analysis as key to understanding the flame retardancy mechanisms and corresponding structure–property relationships. The correspondence between the decomposition temperature range of arylphosphates and PC is pointed out as prerequisite for the occurrence of the reaction between arylphosphate and structures that are typical for the beginning of PC decomposition. Resulting cross-linking enhances charring in the condensed phase and competes with the alternative release of phosphate in the gas phase and thus flame inhibition. Flame inhibition was identified as the main flame retardancy mechanism. The additional condensed phase mechanisms optimise the performance. [ABSTRACT FROM AUTHOR]