Preparation of waterborne polyurethane with high solid content and elasticity

s Herein, we demonstrated the preparation of waterborne polyurethane (WPU) resulting in reducing volatile organic compounds (VOCs) emissions. The prepolymer was first synthesized based on the step-growth addition polymerization of 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-cyclohexane (isophorone diisocyanate) with long-chain diols of polycaprolactone (PCL) and polytetrahydrofuran (PTMG). Subsequently, 3-hydroxy-2-(hydroxymethyl)-2-methyl-propanoic acid (2,2-dimethylolpropionic acid, DMPA) and 2-ethyl-2-(hydroxymethyl)-1,3-propanediol (trimethylolpropane, TMP) were used as chain extension, and then the polymerization system was diluted by a small quantity of acetone. After DMPA was neutralized by N, N-diethyl-ethanamine (triethylamine) acetone solution and acetone was removed by vacuum evaporation, the WPU with high solid content to 60% was obtained. Note that the radius of polyurethane particles was about 80 and 60 nm measured by dynamic light scattering (DLS) and scanning electron microscope (SEM), respectively. Moreover, the particles could stably disperse in aqueous solution in terms of Zeta potential at around −30 mV detected by Zeta potential meter. In addition, the composition of the polyurethane was analyzed by Fourier transform infrared spectroscopy (FTIR). Furthermore, WPU was dried at 80 °C and room temperature to provide polyurethane film. Its property was tested by the micro-mechanical stretching machine and atomic force microscope (AFM), indicating high elasticity.