Bio-Based Waterborne Polyurethane Coatings with High Transparency, Antismudge and Anticorrosive Properties

Green and environment-friendly preparation are of the utmost relevance to the development of transparent antismudge coatings. To prepare a waterborne polyurethane (WPU) coating with antismudge property, it is challenging to balance the stability of dispersion and the antismudge property of coating. Herein, we prepare a transparent bio-based WPU coating grafted with a minor proportion of poly(dimethylsiloxane) (WPU-g-PDMS) using renewable castor oil, monocarbinol-terminated PDMS, hexamethylene diisocyanate trimer, and 2,2-bis(hydroxymethyl)propionic acid as raw materials. Effects of the dosage of monocarbinol-terminated PDMS, the curing temperature, and the curing time on the antismudge performance were studied. Results showed that rigorous stirring (3000 rpm) is necessary to obtain a stable WPU-g-PDMS dispersion with a storage time longer than 6 months. A high curing temperature (>160 °C) and a period of curing time (>1 h) are indispensable to obtain the excellent antismudge property because they would facilitate the grafted low-surface-tension PDMS chains to migrate from the interior to the coating surface. The facts that simulated contaminated liquids such as water, HCl solution, NaOH solution, artificial blood, and tissue fluid could slide off easily and cleanly, and marker ink lined on the coating surface could shrink, indicated that the WPU-g-PDMS coating has good antismudge properties, which could be self-compensated shortly after deterioration. Due to the high cross-linking degree caused by multifunctional polyol and isocyanate, the WPU-g-PDMS coating has high hardness and good anticorrosive performance. The antismudge functionalization and waterborne technology of bio-based polyurethane coatings proposed in this work could be a promising contribution to the green and sustainable development of functional coatings. This kind of WPU-g-PDMS coating is expected to protect and decorate electronic screens, vehicles, and buildings, especially endoscopes.