Exploring in situ integration of pongamia oil to improve barrier properties of polyurethane coatings

Polyurethane coatings have been the focus of continuous innovation, such as bio-based coatings and self-healing coatings. This study investigates the route achieving superior coatings by in situ integration of pongamia oil during the curing process. Stronger urethane and carbonyl bonds for these oil-modified coatings are observed using Fourier transform infra-red spectroscopy. Thermogravimetric analysis reveals an increase in their thermal stability. A sustained high coating resistance and an increased Bode impedance (by ∼10² Ω cm²) for the oil-modified coatings is observed using electrochemical impedance spectroscopy, which is corroborated by the cyclic corrosion test. Scanning electron microscopy depicts a roughened coating morphology with an increased water contact angle due to the integrated oil-polyurethane polymer chains. Further, a preliminary computational fluid dynamics confirms this inhibited electrolyte mass flow through an oil-modified coating with denser regions as compared to a clear coating. A consolidated schematic model incorporating the experimental and simulation results is proposed.