Synthesis and performance of bio-based hyperbranched polyol in polyurethane coatings

Abstract In the present work, the bio-based hyperbranched polyol (COHBP) was prepared by using castor oil and dimethylol propionic acid (DMPA). The molecular structure of COHBP was determined by FTIR and NMR. Polyurethanes of castor oil (PU−COs) and castor oil based hyperbranched polyol (PU−COHBPs) were prepared by using various diisocyanate as cross-linking agent at NCO: OH, ratio of 1.2:1, in presence of dibutyltin dilaurate (DBTDL) as catalyst. Finally, these polyurethanes were coated on glass plate and mild steel panels. Thermal behavior of PU−COs and PU−COHBPs were studied by thermo-gravimetric analyzer (TGA). The mechanical properties of the coated panels were estimated by performing various tests such as cross-cut adhesion, scratch resistance, impact resistance, mar resistance, flexibility, and pencil hardness. Chemical resistance property of coating was evaluated by immersion method. The polyurethanes films were characterized by gel content. The corrosion rate of each coating plate was determined by electrochemical method. The surface morphology of coating films was studied by AFM and SEM, while their crystallinity was estimated by XRD analysis. The properties of PU−COHBPs were compared with PU−COs. It was found that PU−COHBPs showed excellent coating performance as compared to PU−COs.