Sustainable pavement binder application of glycolyzed waste polyethylene terephthalate to synthesize high-performance polyurethane modified bitumen
Guoqiang Sun, John Mathews Kelomae, Hansong Wu, Long Cheng, Zhilong Cao, Guangchen Wang
Abstract
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.