Experimental Investigation of the Compatibility and Performance of Asphalt Modified with Maleic Anhydride–Grafted Polypropylene

The increasing population and economic development have led to a rapid rise in the production and consumption of plastic products, including polypropylene (PP) and polyethylene (PE), resulting in significant amounts of plastic solid waste. Using PP as a modifier for asphalt presents an economically and environmentally friendly approach for recycling PP waste. However, like most polymers, the compatibility of PP with asphalt can be poor, limiting its application in asphalt modification. To improve the compatibility of PP with asphalt and enhance the overall performance of modified asphalt, PP was grafted with maleic anhydride using melt blending methods and a twin-screw extruder. The study analyzed the compatibility strengthening mechanisms of PP using Fourier transform infrared (FTIR) spectroscopy. Additionally, the compatibility of maleic anhydride–grafted PP (MPP) with asphalt was studied through appearance comparison and fluorescence microscope analysis. The high- and low-temperature properties, as well as the anti-fatigue performance of MPP-modified asphalt, were characterized using conventional performance tests, temperature scanning, the multiple stress creep recovery test, bending beam rheology tests, and the linear amplitude sweep test. The modification mechanisms were preliminarily analyzed using FTIR spectroscopy and four-component tests. Increased compatibility of MPP significantly improves the high-temperature and fatigue resistance of asphalt, due to the formation of strong bonds between chemical bonds and functional groups (e.g., C═O, C─ H, sulfoxide, and C─ C) and the asphalt binder. In conclusion, using MPP in asphalt modification benefits both environmental protection and pavement durability.