Sustainable pavement binder application of glycolyzed waste polyethylene terephthalate to synthesize high-performance polyurethane modified bitumen

The dual challenges of accumulating polyethylene terephthalate (PET) plastic waste and the heavy reliance on petroleum-based raw materials necessitated sustainable, high-performance bitumen binder solutions. This study proposed a dual-purpose solution by chemically upcycling post-consumer PET through glycolysis to synthesize PET polyols, which partially replaced petroleum-derived Polytetramethylene ether glycol (PTMEG-2000) in the synthesis of PET-based polyurethane-modified bitumen (P-PUMB). A comprehensive evaluation of the PET polyol substitution ratios (25–75 %), curing conditions, and the PET-based polyurethane (P-PU) dosages (30–70 %) was carried out through conventional, chemical, morphological, and rheological tests. Results indicated that PET polyol substitution of 25 % and 37 % achieved an optimal balance between physical performance and waste utilization. Conventional testing, chemical and morphological analysis confirmed the optimal curing condition to be 100 ℃ for 2 h, enabling complete urethane crosslinking and formed a continuous P-PU network. Increasing the P-PU dosage for 25 % and 37 % PET polyol substitution from 30 %∼70 % resulted in the identification of a percolation threshold, where the P-PU microstructure transitioned from discrete to a continuous crosslinked network at 50 % dosage for 25 % PET polyol substitution and 60 % dosage for the 37 % PET polyol substitution. This transition led to a significant improvement in low-temperature ductility, reaching 85.7 cm for 25 % PET polyol substitution and 116 cm for the 37 % PET polyol substitution at 5 ℃, indicating enhanced low temperature performance with the addition of PET polyol. High-temperature rheological tests notably demonstrated an increased viscosity at 60 °C and a complete elastic recovery ( R = 100 %) at 64 ℃ for high P-PU dosages, indicating enhanced elasticity at elevated temperature. Moreover, the intermediate- and low-temperature rheological analysis revealed that the P-PUMB binders with high P-PU dosage (50 %∼70 %) exhibited significantly high fatigue life (N f ), and temperature-insensitive behavior due to the dominance of the crosslinked P-PU network in the P-PUMB binder. This study established a viable approach to converting plastic waste into high-performance bituminous binders for specialized applications, thereby promoting circular resource utilization and contributing to sustainable pavement infrastructure.