Preparation and Characterization of a Novel Self-Healing Polyurethane-Modified Asphalt Based on Dynamic Disulfide Bond

Asphalt pavement will crack under the action of traffic load and harsh environment, and the cracks can be repaired by the self-healing properties of asphalt itself, but the healing efficiency is lower. This study developed a novel self-healing asphalt based on disulfide-crosslinked polyurethane elastomer. A low-cost crosslinking agent (CY-OA) was synthesized from cystamine dihydrochloride as raw material, and then a disulfide-crosslinked polyurethane prepolymer (PU-SS) was synthesized using a stepwise copolymerization method for modification of asphalt to obtain a self-healing polyurethane-modified asphalt. The chemical properties, microscopic morphology, and self-healing capability of disulfide-crosslinked polyurethane elastomer and polyurethane-modified asphalt were evaluated in this study. Infrared spectroscopy confirms the introduction of CY-OA into the polyurethane main chain. Thermal gravimetric analysis shows excellent thermal stability of PU-SS. Healing tests demonstrate that disulfide bonds enhance the self-healing ability between polyurethane elastomer and asphalt binder. PU-SS exhibits a healing efficiency as high as 96.33% within 12 h at 60°C. With an increase in PU-SS content and repair time in the modified asphalt, the repair efficiency increases, with a maximum fatigue recovery index of 80%. The objective of this study is to introduce dynamic covalent bonds to enhance the self-healing performance of asphalt and improve the long-term crack resistance of asphalt pavement.