Synthesis and characterization of 1 K waterborne non-isocyanate polyurethane epoxy hybrid coating

Non-isocyanate polyurethanes (NIPU) attract more attention these days due to the increasing environmental concerns from the traditional polyurethanes that involve isocyanates in the synthesis. Herein we prepared a novel one-package (1 K) waterborne non-isocyanate polyurethane in this study. A series of 1 K waterborne epoxy hybrid coatings were synthesized from bio-based amine, cyclic carbonate, internal emulsifier, and epoxy resin. Different formulations of the 1 K waterborne NIPU epoxy hybrid coatings were designed including different ratios of soft and hard segments, different urethane contents, and different functionalities and structures of the hybridized epoxy. The chemical structure of the NIPU polymers was analyzed by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The thermal stability and mechanical property of the 1 K waterborne NIPU coatings were investigated by thermogravimetric analysis and tensile tests, respectively. One glass transition temperature studied by differential scanning calorimetry was found for each coating which demonstrated that the soft segments and the hard segments were mixed well in the 1 K waterborne NIPU coating systems. The coatings with different formulations can achieve a broad range of thermal and mechanical properties. In addition, the general coating properties, such as hardness, adhesion, and chemical resistance, were evaluated to demonstrate the practical application of the 1 K waterborne NIPU in coatings.