Compatibility investigation of waste plastics in bitumen via a molecular dynamics method

The compatibility between waste plastic polymers and bitumen is the most challenging issue hindering the improvement of modified bitumen performance. The current practice of recycled waste plastics includes the use of polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), etc. This study was designed to investigate the compatibility of different waste plastic polymers with bitumen binders by conducting molecular dynamics (MD) simulations at different temperatures. The molecular models of these materials were constructed in this study for the compatibility analysis, and they include the base bitumen, polymers (PVC, PP, and PE), polymer- bitumen blending systems. Using the output and related calculations of these MD models, the properties of these blending systems were measured at different temperatures through the calculation of the solubility parameter (δ) and interaction energies. The compatibility analysis is discussed in the context of these simulation results. The simulation results for the solubility parameters and interaction energies show consistent trends. The results showed that PVC and PP had better compatibility with bitumen at 433.15 K and that PE and bitumen had good compatibility at 393.15 K. Moreover, it can be deduced that the order of compatibility of the three polymers with bitumen is as follows: PVC > PE > PP. In addition, these research results can be referenced for the industry and research development of modified bitumen.