Functional soybean oil-based polyols as sustainable feedstocks for polyurethane coatings

The development of renewable and viable alternatives to petroleum-based polymeric materials is a major challenge to the long-term environmental and waste management issues of the polymer industry. In this study, a technology platform composed of a series of efficient and quantitative thiol-ene reactions for preparing functional and sustainable polyols is proposed. First, a soybean oil (SO)-based polyol with two hydroxyl groups (MSO) was synthesized through a controlled thiol-ene click reaction between SO and 2-mercaptoethanol. Second, other functional groups, such as silane, fluorine or ethylene oxide units, were introduced to the MSO through another thiol-ene reaction between the MSO and thiol-terminated intermediates to afford SO -based functionalized polyols. The thiol-terminated intermediates were obtained using a Michael addition reaction between dithiol- and methacrylate-terminated compounds. Employing silane-modified MSO (SiMSO) as a representative functionalized polyol, preparation of polyurethane (PU) coatings was demonstrated. For comparison, PU coatings with commercially available poly(propylene glycol) (PPG) and MSO were also prepared. The thermal, physico-mechanical and anticorrosion properties of the PU coatings clearly demonstrated that coatings made with the silane groups had a better performance. PU coatings with SiMSO exhibited higher hardness, T-g, and adhesion strength than the PU coatings with MSO and PPG. Notably, incorporation of SiMSO improved the anticorrosion properties of the PU coating in a 3.5 wt% aqueous NaCl solution, probably due to the improved blocking and adhesion properties of the coating on mild steel panel. The present study demonstrates SO -based functional polyols as promising alternatives to conventional polyols to afford PU coatings with desirable properties.