Study on rheological performance and mechanism of SMA grafted TPU modified asphalt based on in-situ synthesis method

Abstract This study aimed to enhance the high- and low-temperature rheological properties of thermoplastic polyurethane (TPU)-modified asphalt through an innovative in-situ synthesis process. Styrene grafted maleic anhydride (SMA) was employed for the graft copolymerization of the TPU modifier. The asphalt’s temperature-dependent properties and the modification mechanism were comprehensively analyzed using dynamic shear rheometry (DSR), binder bending beam rheometer (BBR), Fourier-transform infrared spectroscopy (FTIR), environmental scanning electron microscopy (ESEM), and fluorescence microscopy (FM) tests. The findings revealed that the in-situ synthesized SMA-grafted TPU-modified asphalt exhibited superior rheological properties at both high and low temperatures compared to the conventional native polymerization method. The incorporation of SMA with TPU notably enhanced the asphalt’s resistance to high-temperature deformation and its temperature sensitivity while preserving its low-temperature toughness and crack resistance. Microscopic analyses indicated that TPU is synthesized internally within the asphalt matrix, ensuring excellent compatibility. The SMA grafts onto the TPU, creating a flexible network structure with rigid nodes. Optimal results were achieved with a 5% TPU modifier dosage and a TPU to SMA mass ratio of 60:40. This research contributes to the development of high-performance asphalt materials with improved thermal stability and mechanical performance.