A biomass green synthesis process: aqueous jatropha oil-based polyurethane coating with high transparency, hydrophobicity and corrosion resistance

Developing waterborne bio-based coatings with both anti-corrosion and anti-fouling properties through green preparation processes was critical for environmental protection and the advancement of waterborne coatings. In this study, jatropha oil was used as a raw material, and functionalized molecular design was applied to successfully synthesize controllable jatropha oil-based polyol (o-JOL) through a catalyst-free green chemical process. This product was further polymerized with isophorone diisocyanate (IPDI) using a designed chain structure approach, resulting in a Jatropha oil-based waterborne polyurethane (JPU) coating dispersion. Subsequently, it was applied to create a high-performance coating on Q235 carbon steel surfaces. The coating exhibited a smooth surface and high density, with a transmittance of up to 90.24 %, demonstrating effective cross-linking reactivity. It maintained a high water contact angle (115°) and a low surface energy (23.51 m N/m), exhibiting excellent hydrophobic properties. Electrochemical testing revealed significant improvements in the coating's anti-corrosion performance, with a corrosion potential shift of 850 mV and a reduction in corrosion current density by five orders of magnitude. After soaking for 29 days, the impedance modulus |Z| _{f=0.01 Hz} remained at 10⁷ Ω·cm², indicating outstanding corrosion resistance, which surpassed that of similar types of bio-based polyurethane coatings. This work offers a straightforward strategy for the selection of diversified polyurethane monomers and the high-performance preparation of bio-based waterborne polyurethanes.