Resistance of polymer modified bitumen to UV radiation and oxidative aging depending on styrene–butadiene–styrene (SBS) characteristics and base binder chemical composition

Abstract This study investigates the resistance of polymer modified bitumen (PMB) to ultraviolet (UV) radiation and oxidative aging, focusing on the role of styrene–butadiene–styrene (SBS) characteristics (structure, styrene/vinyl content, molecular weight) and the chemical composition of the base binder. Twelve PMBs were produced using three 70/100 base binders with different chemical composition and four SBS types (linear vs. radial, high vs. low vinyl). Samples were subjected to three laboratory aging protocols: short-term ( R ), short-term with UV exposure (R + UV), and extended long-term (R + P, pressure aging vessel (PAV) 40 h). Aging effects were evaluated by Fourier-transform infrared (FTIR) spectroscopy and rheological tests, including multiple stress creep and recovery (MSCR), stress relaxation, and frequency sweeps. Results showed that extended long-term aging caused the most severe changes, with FTIR indices rising to 1.53–1.87, recovery decreasing more than twofold, and stress relaxation modulus increasing by up to 2 times, accompanied by a 28–34% loss in relaxation capacity. Base binder B (low saturates, high aromatics) produced the weakest unaged performance but the largest aging-induced changes, while base binder C (balanced maltenes) provided the most stable results. Radial SBS (molecular weight 118–144 kDa) was more prone to oxidative transformations than linear SBS (molecular weight 77–79 kDa). Vinyl content had only a minor effect, although high-vinyl SBS (31.3%) showed slightly lower resistance to UV aging compared with low-vinyl (7.3%) SBS. Overall, PMB durability is governed by both polymer architecture and base binder chemistry. Linear SBS combined with balanced maltene base binders offers the best resistance to UV and oxidative aging.