Rapid FTIR method for quantification of styrene-butadiene type copolymers in bitumen

The mid-IR molar absorptivity for polystyrene (PS) and polybutadiene (PB) blocks were obtained for five styrene-butadiene-styrene (SBS) and SB copolymers, including linear, branched, and star copolymers, and their blends with bitumen. The average absorptivity for PS and PB blocks was 277 and 69 L mol−1 cm−1 and it was little affected by the S/B ratio or the copolymer architecture. In the presence of bitumen, Beer's law was obeyed but the respective PS and PB absorptivity was 242 and 68 L mol−1 cm−1, possibly because of weak interactions between the copolymer and bitumen. The absorptivity values were used to calculate the concentration of SB-type copolymers in blends with bitumen with an accuracy of 10% or better. The method can be used to probe the stability of bitumen–copolymer blends in storage at 165°C, to determine the copolymer concentration in commercial polymer modified bitumen (PMB), and to assess the resistance of PMB to weathering.