CHAIN-SCISSION AND YELLOWING IN HIGH-IMPACT POLYSTYRENE

Different grades of impact-modified polystyrene were studied by viscom etry, tensile impact test and colour change upon exposure to polychrom atic irradiation at 55 degrees C in air. The samples underwent extensi ve reduction in intrinsic viscosity [eta] and tensile impact strength, and yellowed upon polychromatic irradiation (lambda greater than or e qual to 290 nm). Chain-scission during photo-oxidative degradation was also studied under conditions where evolution of volatiles was neglig ible. Tri-stimulus values were calculated for unirradiated and irradia ted samples. The rate of oxidative degradation was maximum in the samp le possessing higher unsaturation content.