Bio-Based Polyurethane Asphalt Binder with Continuous Polymer-Phase Structure: Critical Role of Isocyanate Index in Governing Thermomechanical Performance and Phase Morphology
Polyurethane asphalt (PUA) has attracted considerable attention in the field of pavement engineering. However, traditional PUA systems typically exhibit low concentrations of polyurethane (PU), leading to a continuous bitumen-dominated phase that adversely affects mechanical properties. Furthermore,...
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2025-06-01
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| author | Haocheng Yang Suzhou Cao Chengwei Wu Zhonghua Xi Jun Cai Zuanru Yuan Junsheng Zhang Hongfeng Xie |
| author_facet | Haocheng Yang Suzhou Cao Chengwei Wu Zhonghua Xi Jun Cai Zuanru Yuan Junsheng Zhang Hongfeng Xie |
| author_sort | Haocheng Yang |
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| description | Polyurethane asphalt (PUA) has attracted considerable attention in the field of pavement engineering. However, traditional PUA systems typically exhibit low concentrations of polyurethane (PU), leading to a continuous bitumen-dominated phase that adversely affects mechanical properties. Furthermore, the non-renewable nature of raw materials raises environmental concerns. To address these limitations, this study developed an eco-friendly and cost-efficient bio-based PUA binder (PUAB) featuring a continuous high-biomass PU matrix (over 70% biomass) and a high bitumen content (60 wt%). The effects of the isocyanate index (NCO/OH ratio) on the cure kinetics, rheological behavior (rotational viscosity over time), viscoelasticity, damping capacity, phase morphology, thermal stability, and mechanical performance were systematically investigated using Fourier-transform infrared spectroscopy, dynamic mechanical analysis, laser-scanning confocal microscopy, and tensile testing. Key findings revealed that while the rotational viscosity of PUABs increased with a higher isocyanate index, all formulations maintained a longer allowable construction time. Specifically, the time to reach 1 Pa·s for all PUABs at 120 °C exceeded 60 min. During curing, higher isocyanate indices reduced final conversions but enhanced the storage modulus and glass transition temperatures, indicating improved rigidity and thermal resistance. Phase structure analysis demonstrated that increasing NCO/OH ratios reduced bitumen domain size while improving dispersion uniformity. Notably, the PUAB with the NCO/OH ratio of 1.3 achieved a tensile strength of 1.27 MPa and an elongation at break of 238%, representing a 49% improvement in toughness compared to the counterpart with an NCO/OH ratio = 1.1. These results demonstrate the viability of bio-based PUAB as a sustainable pavement material, offering a promising solution for environmentally friendly infrastructure development. |
| format | Article |
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| institution | Kabale University |
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| language | English |
| publishDate | 2025-06-01 |
| publisher | MDPI AG |
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| series | Molecules |
| spelling | doaj-art-0eaff0bdf1704d728387f7d8a0e913422025-08-20T03:46:38ZengMDPI AGMolecules1420-30492025-06-013011246610.3390/molecules30112466Bio-Based Polyurethane Asphalt Binder with Continuous Polymer-Phase Structure: Critical Role of Isocyanate Index in Governing Thermomechanical Performance and Phase MorphologyHaocheng Yang0Suzhou Cao1Chengwei Wu2Zhonghua Xi3Jun Cai4Zuanru Yuan5Junsheng Zhang6Hongfeng Xie7MOE Key Laboratory of High Performance Polymer Materials and Technology, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, ChinaMOE Key Laboratory of High Performance Polymer Materials and Technology, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, ChinaMOE Key Laboratory of High Performance Polymer Materials and Technology, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, ChinaExperimental Chemistry Teaching Center, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, ChinaPublic Instrument Center, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, ChinaModern Analysis Center, Nanjing University, Nanjing 210023, ChinaMOE Key Laboratory of High Performance Polymer Materials and Technology, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, ChinaMOE Key Laboratory of High Performance Polymer Materials and Technology, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, ChinaPolyurethane asphalt (PUA) has attracted considerable attention in the field of pavement engineering. However, traditional PUA systems typically exhibit low concentrations of polyurethane (PU), leading to a continuous bitumen-dominated phase that adversely affects mechanical properties. Furthermore, the non-renewable nature of raw materials raises environmental concerns. To address these limitations, this study developed an eco-friendly and cost-efficient bio-based PUA binder (PUAB) featuring a continuous high-biomass PU matrix (over 70% biomass) and a high bitumen content (60 wt%). The effects of the isocyanate index (NCO/OH ratio) on the cure kinetics, rheological behavior (rotational viscosity over time), viscoelasticity, damping capacity, phase morphology, thermal stability, and mechanical performance were systematically investigated using Fourier-transform infrared spectroscopy, dynamic mechanical analysis, laser-scanning confocal microscopy, and tensile testing. Key findings revealed that while the rotational viscosity of PUABs increased with a higher isocyanate index, all formulations maintained a longer allowable construction time. Specifically, the time to reach 1 Pa·s for all PUABs at 120 °C exceeded 60 min. During curing, higher isocyanate indices reduced final conversions but enhanced the storage modulus and glass transition temperatures, indicating improved rigidity and thermal resistance. Phase structure analysis demonstrated that increasing NCO/OH ratios reduced bitumen domain size while improving dispersion uniformity. Notably, the PUAB with the NCO/OH ratio of 1.3 achieved a tensile strength of 1.27 MPa and an elongation at break of 238%, representing a 49% improvement in toughness compared to the counterpart with an NCO/OH ratio = 1.1. These results demonstrate the viability of bio-based PUAB as a sustainable pavement material, offering a promising solution for environmentally friendly infrastructure development.https://www.mdpi.com/1420-3049/30/11/2466polyurethane asphaltbio-based polyurethaneisocyanate indexglass transition temperaturephase separationmechanical properties |
| spellingShingle | Haocheng Yang Suzhou Cao Chengwei Wu Zhonghua Xi Jun Cai Zuanru Yuan Junsheng Zhang Hongfeng Xie Bio-Based Polyurethane Asphalt Binder with Continuous Polymer-Phase Structure: Critical Role of Isocyanate Index in Governing Thermomechanical Performance and Phase Morphology Molecules polyurethane asphalt bio-based polyurethane isocyanate index glass transition temperature phase separation mechanical properties |
| title | Bio-Based Polyurethane Asphalt Binder with Continuous Polymer-Phase Structure: Critical Role of Isocyanate Index in Governing Thermomechanical Performance and Phase Morphology |
| title_full | Bio-Based Polyurethane Asphalt Binder with Continuous Polymer-Phase Structure: Critical Role of Isocyanate Index in Governing Thermomechanical Performance and Phase Morphology |
| title_fullStr | Bio-Based Polyurethane Asphalt Binder with Continuous Polymer-Phase Structure: Critical Role of Isocyanate Index in Governing Thermomechanical Performance and Phase Morphology |
| title_full_unstemmed | Bio-Based Polyurethane Asphalt Binder with Continuous Polymer-Phase Structure: Critical Role of Isocyanate Index in Governing Thermomechanical Performance and Phase Morphology |
| title_short | Bio-Based Polyurethane Asphalt Binder with Continuous Polymer-Phase Structure: Critical Role of Isocyanate Index in Governing Thermomechanical Performance and Phase Morphology |
| title_sort | bio based polyurethane asphalt binder with continuous polymer phase structure critical role of isocyanate index in governing thermomechanical performance and phase morphology |
| topic | polyurethane asphalt bio-based polyurethane isocyanate index glass transition temperature phase separation mechanical properties |
| url | https://www.mdpi.com/1420-3049/30/11/2466 |
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