Preparation and optimization of WPU dispersion from polyether/polyester polyols for film and coating applications

Abstract

BackgroundCastor oil and polytetramethylene ether glycol (PTMG) are used as polyester and polyether polyols. The waterborne polyurethane (WPU) resin is synthesized from polyether/polyester polyols following a ketone and catalyst-free pre-polymerization process. MethodsWPU resins are prepared from PTMG/castor oil with various hydroxyl molar ratios, such as 1/0, 3/1, 1/1, 1/3, and 0/1. Significant findingsThe results indicate that the WPU dispersions has a long shelf-life, high colloidal stability, and narrow distribution of molecular size. The addition of castor oil can increase the proportion of the cross-linking density, hard segments and hydrogen bonds of the WPU molecular chain. The addition of PTMG/castor oil increases from the molar ratio 1/0 to 1/1, the tensile strength of WPU film increases from 17.1 MPa to 25.6 MPa; the T5% increases from 250°C to 262°C; the water swelling ratio at 24 h decreases from 33.2 g/g to 19.4 g/g. The results indicate the using PTMG/castor oil can improve the mechanical strength, water resistance, and thermal stability of WPU film. The WPU could be applied to wood coatings with high properties. This study provides a cleaner process for optimizing the performance of WPU resin, which can replace conventional ketone- and organotin-based films and coatings.