EPR Imaging Determination of High Molecular Weight Nitroxide Radicals in the UV Degradation of Polycarbonate-Poly(acrylonitrile-butadiene-styrene) Polymers

The determination of nitroxide concentrations and distributions across plaques of polycarbonate/acrylonitrile-butadiene-styrene copolymer blend (PC/ABS) containing a high molecular weight hindered amine stabilizer (HALS) exposed to thermal and photochemical degradation treatments by EPR and EPR imaging (EPRI) is reported. Three different polymer compositions were examined: PC/ABS blends not-pigmented and white pre-pigmented with titanium dioxide; neat polycarbonate (PC); neat acrylonitrile-butadiene-styrene copolymer (ABS). The distribution profiles of the nitroxide radical in the various samples show large differences in the radical concentration across the plaques, these differences depending on the nature of the polymer and on the degradation treatment (thermal or photochemical). The experimental information provides important details on the mechanism of degradation of a complex polymeric matrix such as PC/ABS.