“…[1][2][3][4][5][6] As a significant characteristic of PUs, phase separation has been studied extensively through the application of differential scanning calorimetry, dynamic mechanical analysis (DMA), infrared spectroscopy, small angle X-ray scattering, transmission electronic microscope, scanning electronic microscope, and atomic force microscope. Therefore, water resistance (hydrophobicity, always defined by water absorption ratio and water contact angle [28][29][30] ) is one of the most important properties of WPUs which strongly affect the performance of WPU materials. [15][16][17][18] Waterborne PUs (WPUs) are one of the most prosperous branches of polymer materials because of their adjustable molecular structures, excellent properties such as low-temperature resistance, high tensile strength, and high flexibility, and environmentally friendly characteristic compared with solvent-borne PUs.…”