Nanomaterial Composite Compatibilized Rubber–Plastic Elastomer–Asphalt Interface Mechanism and Performance Evaluation

Conventional rubber–plastic modified asphalt often suffers from poor compatibility and thermal storage stability, which limits its engineering application. To address this issue, this study proposes a prefabricated nano-reinforced rubber–plastic thermoplastic elastomer (TPE) modification strategy. The specific objective was to comparatively investigate how different waste plastic matrices (HDPE, LDPE, and PP) and two representative nano-oxides (ZnO and TiO2) affect the interfacial evolution, storage stability, rutting resistance, fatigue durability, and low-temperature cracking resistance of modified asphalt. The prefabricated nano-reinforced TPE modifier was incorporated into the base asphalt, and its storage stability, interface evolution and multi-scale rheological properties were evaluated. The results show that all modified binders exhibited good thermal storage stability, with softening point differences below 2.5 °C. The enhancement mechanism was mainly governed by physical blending, swelling adsorption, and interfacial synergistic interactions rather than the formation of new chemical functional groups. A clear synergistic matching relationship between plastic type and nanoparticle type was identified. LDPE-based systems showed better phase compatibility and fatigue/low-temperature performance, whereas HDPE-based systems were more favorable with respect to improvement of high-temperature rutting resistance. In addition, ZnO contributed more significantly to storage stability, rutting resistance, and fatigue resistance, while TiO2 was more beneficial for low-temperature crack resistance. These findings provide new insight into the interfacial design of nano-reinforced rubber–plastic modified asphalt and offer guidance for performance-oriented and sustainable pavement materials.