Flexible decorative wood veneer with high strength, wearability and moisture penetrability enabled by infiltrating castor oil-based waterborne polyurethanes

In this study, a simple vacuum impregnation process was proposed to infiltrate castor oil-based waterborne polyurethane (PUDs) into three types of rift cut wood veneers for developing flexible decorative wood veneers (FDWVs). The effect of PUDs with different emulsifier, hydroxyl/isocyanate molar ratio, and solid content on the flexibility, mechanical properties, micromorphology, wearability, water resistance, and thermomechanical properties of the FDWVs from cationic PUDs were investigated systematically. It is found that the cationic waterborne PUDs demonstrated easier impregnation and better improvement in flexibility than anionic waterborne PUDs. FDWVs impregnated with cationic PUDs has better flexibility and strength. The flexibility of FDWVs improved about 16–24 time, the flexible basswood veneers (FBW) can be rolled with 0.5 mm diameter steel bars without cracking, which was much better than the market requirements for the decorative wood veneers. In addition, the incorporation of cationic PUDs improved the tensile strength of FDWVs by 4–6 time in transverse and by 2–3 time in longitudinal direction. The resulting FDWVs demonstrated excellent water resistance and good breathability characteristics for surface decorative materials, which allow wood-based panels to adjust indoor humidity through moisture absorption and desorption. In brief, environmentally friendly flexible decorative wood veneers with enhanced flexibility and strength, good water resistance, excellent wearability, and good breathability were produced through a simple and energy-efficient method without hot-pressing and pretreatment processes, which provides a novel process for preparing FDWVs and enriches the variety of decorative materials.