Development of waterborne polyurethane dispersions (WPUDs) from novel cardanol-based reactive dispersing agent

The objective of the current research work is to prepare a difunctional reactive dispersing agent derived from cardanol which can be used as an alternative for dimethylol propionic acid (DMPA) in waterborne polyurethane dispersion synthesis. The novelty of the research lies between the use of bio-based resource and utilizing the sulfonic acid group as an anionic dispersible group. The cardanol was sulfonated using oleum followed by the reaction of the hydroxyl group of phenol with the epichlorohydrin (ECH). The obtained product was then hydrolyzed to generate double functionalities which can be introduced in the PU backbone through a chemical reaction with a diisocyanate. The obtained intermediates and product were characterized using hydroxyl values, epoxy equivalent weights (EEW), CHNS analysis, FTIR and H-1-NMR analysis. The typical acetone process was used for the preparation of WPUDs, and the cured films were further analyzed for the various coating properties in which thermal properties showed significant improvements with the incorporation of HESC to the PU system along with the increased char yield and glass transition temperature (Tg), whereas the mechanical properties did not show any improvements, which could be attributed to the bulky structure of HESC and increased rigidity in the polymeric network. The detailed synthesis, characterizations and obtained results are presented and discussed here.