Experimental and molecular simulation study on compatibility and interaction in hybrid plastic–rubber modified asphalt

The application of plastics in asphalt pavements has attracted considerable attention due to its potential environmental and engineering benefits. However, the type and properties of hybrid plastics are critical to the compatibility of modified asphalt. In this study, Rubber–plastic-based thermoplastic elastomer (TPE) modifiers were prepared by twin-screw melt extrusion and subsequently incorporated into asphalt. Experimental tests and molecular dynamics simulation were employed to investigate the compatibility and interaction mechanisms of modified asphalt. The results showed that TPE-modified asphalt exhibited improved storage stability of modified asphalt by reducing the softening point difference, the rutting-factor segregation rate (RS), and the difference in initial decomposition temperature between the upper and lower parts of the binder. Fluorescence microscopy observations revealed a more uniform distribution and finer morphology of the polymer-rich phase in the TPE-modified binders. Fourier transform infrared (FTIR) spectroscopy results were consistent with a proposed compatibilizing role of maleic anhydride-grafted styrene–ethylene/butylene–styrene (SEBS-g-MAH) at the mixed-plastic/rubber/asphalt interfaces. Molecular dynamics (MD) results indicated closer thermodynamic matching between the TPE modifiers and the light asphalt fractions, while the hybrid-plastic composition affected molecular diffusion behavior.