Sorbitol-based aqueous cyclic carbonate dispersion for waterborne nonisocyanate polyurethane coatings via an environment-friendly route

The cyclic carbonate derivatives carrying carboxyl groups were prepared via the reaction of the sorbitol-based cyclic carbonate (SC) with anhydrides including succinic anhydride, o-phthalic anhydride, and maleic anhydride. (Succinic anhydride-, o-phthalic anhydride-, and maleic anhydride-based cyclic carbonates were named SSC, PSC, and MSC, respectively.) The structures of SC, SSC, PSC, and MSC were characterized by ¹H NMR and FTIR. Then, the novel sorbitol-based aqueous cyclic carbonate dispersion was prepared. It was found that SSC dispersion possessed excellent stability and its particle sizes ranged from 63 to 174 nm with −73.3 to −48.2 mV for the zeta potentials. A series of novel waterborne nonisocyanate polyurethanes coatings (WNIPU) were successfully prepared by sorbitol-based cyclic carbonate reacted with diamines. The effects of diamine categories and the molar ratios of isophorone diamine (IPDA) and hexamethylene diamine (HMDA) on the properties of WNIPU were studied. The results showed that the pencil and pendulum hardness of WNIPU coatings were all relatively decreased with the increase in HMDA contents. The WNIPU coatings exhibited excellent flexibility, adhesion, gloss, and impact resistance with the molar ratios of IPDA/HMDA ranging from 1:1 to 1:3. Moreover, cured films display good thermal stabilities with only 5% weight loss (T_5%) in temperatures ranging from 246 to 272°C.