Effect of styrene-butadiene-styrene triblock copolymer structure on the rheological properties of high content SBS polymer modified asphalts

Styrene-butadiene-styrene triblock copolymer (SBS) is a thermoplastic elastomer synthesized through the anionic polymerization. The effects of SBS structure including diblock content, molecular weight and styrene content on the properties of high content SBS polymer modified asphalts (HCPMA) with 8wt% were studied. The structure of SBS was characterized by the Size Exclusion Chromatography. The rheological properties of HCPMA were analyzed by performance grading, linear amplitude sweep and zero shear viscosity. The results show that the increasing diblock content decreases the melt viscosity, and improves the workability and the thermal-cracking resistance of HCPMA. However, it reduces the high-temperature performance and fatigue resistance. Higher molecular weight of SBS improves the high-temperature properties and fatigue resistance of HCPMA, but worsens the workability and hot-storage stability. Asphalts modified by SBS with a higher styrene content show better workability and high-temperature properties, while a higher butadiene content in SBS shows better hotstorage stability and thermal-cracking resistance of HCPMA. When the styrene content of SBS is 30%, the binder represents the best fatigue resistance. The results also show that rheological tests characterize HCPMA more precisely than the conventional methods.