Fabrication of multiwalled carbon nanotube-reinforced rapeseed-oil-based polyurethane coatings for anticorrosive applications

This work describes the synthesis of a hydroxy-terminated oligomer for polyurethane preparation (HTO-PU) from rapeseed oil, salicylic acid and toluene diisocyanate. HTO-PU was further incorporated with different amounts of multiwalled carbon nanotubes (MWCNTs) to produce HTO-PU@MWCNT nanocomposites. These nanocomposites were then converted to coatings using mild steel strip as a substrate and allowed to cure at room temperature. Fourier transform infrared and NMR spectroscopic techniques were used for structural elucidation. Surface morphology was determined using scanning electron microscopy and X-ray photoelectron spectroscopy. Thermal stability (>300 °C) of these coatings was evaluated through thermogravimetric analysis and differential scanning calorimetry. Contact angle values suggest that incorporation of MWCNTs enhanced the hydrophobicity of HTO-PU coatings. Physicomechanical results reveal that these coatings are highly glossy, scratch resistant and impact resistant possessing good adhesion and excellent pencil hardness. The optimum concentration of MWCNTs was found to be 1.0 wt. %, below and above which the coating performance was observed to deteriorate. The corrosion resistance and barrier properties of these coatings were examined using electrochemical impedance spectroscopy, the results of which suggest excellent corrosion inhibition efficiency of HTO-PU@MWCNT-1.0 coatings until 28 days. This study suggests a step towards synthesis of MWCNT-incorporated green PU coatings for protective applications. © 2022 Society of Industrial Chemistry.