Development of bio‐based anticorrosive polyurethane nanocomposite coatings from mahua oil polyol and silver‐doped eggshell hydroxyapatite nanoparticles

Abstract Price variations, limited availability, non‐biodegradability and environmental importance have led to an increased demand for renewable alternatives to petroleum‐based counterparts. In line with the requirements, the present study focused on the preparation of mahua‐oil‐derived polyols for the formulation of nanocomposite polyurethane (PU) coatings. The polyol was characterized using 1 H NMR and FTIR spectroscopy, gel permeation chromatography and end group analysis. Silver‐doped hydroxyapatite nanoparticles (Ag‐HAPs) were also synthesized from waste chicken eggshell as another renewable alternative. These nanoparticles were incorporated into the PU matrix in varying amounts (0.4–3.2 wt%) to improve the performance of the PU coatings. The surface morphology of Ag‐HAPs and their PU composites was studied by optical microscopy and SEM. The resulting nanocomposite PU coatings showed enhanced mechanical and protective properties such as pencil hardness, flexibility, adhesion, chemical resistance and corrosion protection compared with pristine PU coatings. In addition, the incorporation of Ag‐HAPs increased the hydrophobicity of the composite film evidenced by higher contact angles. X‐ray Diffraction (XRD) and TGA confirmed the amorphous nature of the PU matrix and that it exhibited better thermal stability with increasing nanoparticle content. Overall, the developed nanocomposite coatings offer a promising sustainable substitute to petroleum origin materials and demonstrate excellent thermal stability and anticorrosion performance. © 2026 Society of Chemical Industry.