Compatibility enhancement and mechanism of rubber-plastic composite modified asphalt based on POE-g-MAH flexible bridging

The application of rubber-plastic composite modified asphalt can not only improve the high-value utilization of waste tires and waste plastics, but also improve the road performance of asphalt. However, the current rubber-plastic composite modified asphalt has poor compatibility and insufficient thermal storage stability. The purpose of this investigation is to enhance the compatibility and storage stability of rubber-plastic composite asphalt by constructing a synergistic system at the rubber-plastic-asphalt three phase interface using surface grafted rubber powder and POE-g-MAH bridging. In this investigation, the silane coupling agent KH550 was firstly used to modify the surface of the rubber powder, and POE-g-MAH, LDPE and surface grafted modified rubber powder were added to the base asphalt to prepare rubber-plastic composite modified asphalt. Subsequently, the compatibility, functional group characteristics, rheological performance and molecular interaction mechanisms of CR/LDPE, ACR/LDPE and ACR/POE‑g‑MAH/LDPE modified asphalt were evaluated by segregation test, fluorescence microscopy, infrared spectroscopy, rheological tests and molecular dynamics simulations. The results illustrated that compared with CR/LDPE modified asphalt, rubber powder surface modification and the incorporation of POE‑g‑MAH reduced the segregation softening point difference of rubber‑plastic composite modified asphalt from 5.38°C to 1.42°C, and lower the phase separation coefficient from 37.5% to 28.6%. Meanwhile, the ACR/POE‑g‑MAH/LDPE modified asphalt exhibited a more uniform polymer phase distribution, and the morphological difference between the upper and lower layers of the sample after storage was greatly reduced. Molecular dynamics results further indicated that this system had stronger interfacial interactions and better molecular motion coordination. This confirmed the bridging compatibilization effect of POE-g-MAH at the molecular scale.