A series of modified waterborne polyurethane (WPU) with various epoxy contents was synthesized from poly (propylene carbonate) diol (PPCD)-based polyurethane prepolymer and ring-opening epoxy resin (RO-EP). The particle size, storage stability, and freeze-thaw resistance of the emulsions were examined. The pencil hardness and adhesion level of the films were tested. The structure of the modified waterborne polyurethane was characterized by Fourier transform infrared spectroscopy. The thermal stability of the modified waterborne polyurethane was studied by thermogravimetric analysis. The corrosion resistance of emulsion coating was tested by the salt spray test and electrochemical impedance spectroscopy (EIS). The waterborne polyurethane emulsion modified by RO-EP had excellent storage stability. When the content of the ring-opening epoxy resin was 10 wt%, the particle size of WPU was the smallest. The corresponding coating had excellent hardness and adhesion level. The salt spray and EIS test showed that the WPU coating with 10% RO-EP had superior corrosion resistance.
