Synthesis of environmental-curable CO2-based polyurethane and its enhancement on properties of asphalt binder

The polyurethane (PU) modified asphalt prepared by melting method has poor thermal storage stability and the PU used is normally synthesized from non-renewable petrochemical resources. This paper aims to explore the feasibility of preparing environment-friendly PU and using it to enhance asphalt properties. Environmental-curable CO2-based PPC-PU and ordinary BDO-PU was prepared with poly propylene carbonate diol (PPC) and Butanediol (BDO), respectively. Fourier transform infrared spectroscopy and thermogravimetric analysis were used to examine their chemical compositions and thermal characteristics. Then, these two types of PU were used to modified asphalt and the chemical functional groups, microstructure, storage stability, viscosity, low temperature, and high temperature properties of various modified asphalts were tested. The findings revealed that the prepared PPC-PU and BDO-PU had good thermal stability and the decomposition temperature was above 200 °C. PPC-PU modified asphalt can be gradually cured at natural environment to form a crosslinking network, and the curing rate can reach 86.23% in 15 days. In addition to the low temperature performance, other properties of PPC-PU modified asphalt were gradually improved with the extension of curing time. Compared with BDO-PU modified asphalt, PPC-PU modified asphalt has superior storage stability, low temperature, and high temperature properties. It is concluded that the environmental-curable PPC-PU can improve performance of asphalt while consuming CO2. This research offers a fresh concept for producing of green PU modified asphalt.