Microwave-assisted functionalization of waste PET plastic with bio-oil: Enhancing compatibility with asphalt through molecular simulation and experimental analysis

With the increasing demand for resource recycling, the massive accumulation of waste polyethylene terephthalate (PET) plastic has become a significant environmental burden. However, its high polarity and poor compatibility with asphalt limit its sustainable application in asphalt materials. To address this issue, this study employs microwave technology and bio-oil to depolymerize and surface-functionalize PET plastic, thereby enhancing its compatibility with asphalt. The quantum chemical simulation was conducted to investigate the functionalization mechanism of PET plastic by bio-oil. Then, based on molecular dynamics simulations, the depolymerization behavior of PET plastic and the interaction changes between PET plastic and asphalt under microwave treatment were examined using solubility parameters, binding energy, and dynamic parameters. Finally, the compatibility enhancement effect of microwave-functionalized PET plastic with asphalt was analyzed through rheological tests and fluorescence microscopy. The results indicate that microwave irradiation can degrade the polymerization degree of PET plastic, while bio-oil molecules can undergo functional grafting reactions with the microwave-depolymerized PET products. Molecular simulation results reveal that after microwave treatment, the molecular weight of PET plastic decreases, its aggregation reduces, and its molecular diffusion rate increases, leading to significantly improved compatibility with asphalt. Furthermore, PET plastic modified with bio-oil exhibits a substantial reduction in polarity, achieving the best compatibility with asphalt. Experimental studies confirm the molecular simulation findings. With increasing microwave radiation intensity and prolonged radiation time, the depolymerization of PET plastic and the functionalization modification effect of bio-oil are significantly enhanced. Consequently, the storage stability and uniformity of PET modified asphalt are remarkably improved.