Preparation, high-temperature and low-temperature performance evaluation of bio-based polyurethane modified asphalt

To achieve sustainable and environmentally friendly development of pavement materials, it is essential to identify alternative materials to reduce dependence on petroleum resources. This study aims to functionalize castor oil (CO) with isocyanates to prepare bio-based polyurethane-modified asphalt (Bio-PUMA), determine its optimal preparation parameters, and evaluate the effects of Bio-PU content and isocyanate index (R) on the high- and low-temperature performance of Bio-PUMA. The orthogonal experimental design (OED), grey correlation grade analysis (GCGA), penetration, softening point, ductility, and viscosity were conducted to determine the preparation process and evaluate the performances of Bio-PUMA. The results show that the preparation factors affecting the performance of Bio-PUMA are ranked as follows: stirring temperature > stirring time > stirring rate. The optimal preparation parameters were the temperature of 155 °C, 30 min for T1 and 50 min for T2, 300 r/min for S1, and 600 r/min for S2. The temperature sensitivity of Bio-PUMA decreases gradually with the increase in Bio-PU content. As the R value increases, the temperature sensitivity decreases and then increases, with the lowest temperature sensitivity observed at R= 1.2. Increasing the Bio-PU content or the R value improves the high-temperature performance of Bio-PUMA but has a slightly negative impact on its low-temperature performance. It is recommended that the isocyanate index R in the Bio-PUMA formula should not exceed 1.5, and the content should not be less than 6 %.