Chemical effect of photo-irradiation in expanded polystyrene studied by XPS

The evolution of chemical states in expanded polystyrene irradiated electromagnetically in the near ultraviolet region, 295–365 nm, was analyzed in this work. The study was done with the purpose to quantitatively measure the changes in the chemical structure of EPS due to UV incidence at the light of the environmental exposure. The analysis was performed by X-ray photoelectron spectroscopy and IR spectroscopy. The results indicated that 13 carbon chemical states were identified during the irradiation with percentages depending on the irradiation time and on the depth profile in the polymer. The main modification showed an increase in oxidation (9.7%) and in a decrease in hydrogenation (6.4%) on the surface that received the incident beam, with only little changes at 90 nm depth. It was considered that the oxidation percentage could represent the degradation percentage of the material since it has the main effect of photo-irradiation.