Impact of molecular structure of SBS on thermomechanical properties of polymer modified bitumen

This article presents an investigation of 6 different triblock SBS (styrene-butadien-styrene) polymers with different structure (radial and linear) and different butadien:styrene ratio, used for modifying bitumen (70/100) with 5 and 16% polymer content. The behaviour of the polymer and the polymer modified bitumen (PmB) is characterized by dynamical shear rheometer (DSR), differential scanning calorimetry (DSC) and fluorescence microscopy (FM). The conditions for the formation of a polymer network within PmB and its effect on the mechanical performance of PmB were investigated. Based on the obtained results the number of styrene end blocks was identified as the key parameter for the formation of a polymer network. The polystyrene content controlled the coalescence and hence the distribution of polymer within the PmB. An increased poly butadiene content, on the other hand, lead to a more pronounced swelling of polymer within PmB by the adsorption of the maltene phase from bitumen, resulting in an increase of the polybutadiene particle size.