Exploring the binary-plastic synergistic effect on waste rubber-plastic TPEs modified asphalt from multiple perspectives

The hybrid modification of asphalt binder with waste rubber and plastic can effectively balance its rheological performance across a wide temperature range. Nevertheless, the diversity of recycled plastic type results in prominent variations of rubber-plastic thermoplastic elastomers (TPEs), which are fabricated via screw extrusion under intense shear and high-temperature conditions. To integrate the characteristics of different recycled plastics, this study adopts a screw extrusion process to explore the binary blending effect of polypropylene (PP), polyethylene (PE) and ethylene-vinyl acetate (EVA). Meanwhile, microstructure analysis, macroscopic rheological experiments and molecular dynamics (MD) simulation were employed to clarify the influence mechanism of binary plastic blending. The findings showed that the PP-PE combination enabled the rubber-plastic TPEs to exhibit new vibration peaks and led to the formation of network-like structure in the corresponding modified asphalt. These positive structural features enable PP + PE binary modified asphalt to achieve comparatively favorable low-temperature, high-temperature, fatigue and storage stability performances. However, evident aggregation of EVA-based binary plastic TPEs can be observed in the asphalt matrix via micrographs, resulting to partial deterioration of mechanical properties compared with the corresponding single-phase modified asphalts. Moreover, the MD simulation results further verify that EVA molecules are susceptible to agglomeration with rubber molecules, accompanied by a weak interfacial adhesion with asphalt molecules. This study is anticipated to provide insight into the materials design of rubber-plastic TPEs modified asphalt.