Green synthesis of polyurethane with reversible oxime-urethane bond to enhance the self-healing properties of asphalt binder at room temperature

The oxime-urethane group can undergo dynamic reversible reaction at room temperature, which can endow polyurethane (PU) with self-healing ability at ambient temperatures. This study prepared CO2-based PU containing oxime-urethane groups and introduced it into asphalt to enhance the self-healing performance of asphalt at room temperature. Firstly, the chemical structure, self-healing performance, and thermal stability of the prepared PU and ordinary PU were characterized. Then, the two types of PU were sheared in asphalt to prepare PU modified asphalts, the chemical characteristics and microstructure of the modified asphalts were characterized. Finally, the healing performance of different asphalts at room temperature was characterized. The results indicated that the prepared self-healing PU had good thermal stability and exhibited rapid self-healing performance at room temperature. After 6 h of healing, the maximum tensile strength can recover to 88.78% of its initial value. Self-healing (S-PU) was successfully introduced into asphalt system without decomposition, but due to the role of intermolecular hydrogen bond and dynamic covalent bond of PU, its dispersion in asphalt was poor. The addition of S-PU can significantly enhance the self-healing capability of asphalt at room temperature. This study provides a new idea for the preparation of green PU modified asphalt containing dynamic covalent bond.