Influence of Ultraviolet Radiation Exposure Time on Styrene-Ethylene-Butadiene-Styrene (SEBS) Copolymer

The effect of ultraviolet radiation on styrene-ethylene-butadiene-styrene (SEBS) has been studied at different exposures times in order to obtain a better understanding of the mechanism of ageing. The polymer materials were mechanically tested and then their surfaces were analyzed using a scanning electron microscope (SEM) and atomic force microscopy (AFM). Moreover, the optical analysis of contact angle (OCA) was used to evaluate the surface energy (γ(s)) and the yellowing index (YI) and attenuated total reflectance infrared spectroscopy (ATR–FTIR) were used to observe structural and physical changes in aging SEBS. The results obtained for the SEBS, in relation to the duration of exposure, showed superficial changes that cause a decrease in the surface energy (γ(s)) and, therefore, a decrease in surface roughness. This led to a reduction in mechanical performance, decreasing the tensile strength by about 50% for exposure times of around 200 hours.