Waterborne polyurethane nanocomposite incorporated with phytic acid intercalated layered double hydroxides: A highly stable aqueous dispersion with desired corrosion protection capability

In this research, waterborne polyurethane (WPU) nanocomposites incorporated with MgAl-NO3LDH layered double hydroxide (LDH) and phytic acid intercalated LDH (PA-LDH) nanostructures were prepared as novel environmental-friendly corrosion protective coatings. Fourier-transform infrared spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis, field emission scanning electron microscope (SEM), and high-resolution transmission electron microscopy analysis confirmed the prosperous preparation of LDHs nanosheets. Moreover, structural, thermal, thermo-mechanical, and morphological investigations of prepared WPU/LDHs films were also evaluated. The SEM images exhibited that the intercalation of LDH nanosheets with PA could drastically overcome the agglomeration problem of unmodified LDH within the polyurethane matrix. Based on XRD results, WPU/LDHs films showed a lower micro-phase separation degree and crystallinity compared to pure WPU film. According to wettability analysis, WPU/PA-LDH film demonstrated the highest hydrophobicity among samples due to its lowest phase-separation degree, which causes the castor oil and poly(tetramethylene ether) glycol segments to migrate toward the surface of film from the bulk. Furthermore, the potentiodynamic polarization scanning and electrochemical impedance spectroscopy analysis revealed that the WPU/PA-LDH sample containing 1.0 wt% of PA-LDH has a superlative anti-corrosion performance for SS 304 steel with an inhibition efficiency of 99.9%. This superior anti-corrosive property benefited from the barrier property and chloride absorption capability of well-dispersed PA-LDH nanosheets, deposition of PA on the steel substrate, and improved hydrophobicity of the WPU/PA-LDH coating.

Automated summary

In this study, waterborne polyurethane nanocomposites incorporated with LDH and PA-LDH nanostructures were successfully prepared for corrosion protective coatings. The addition of PA-LDH improved the anti-corrosion performance of the films due to its excellent barrier property, chloride absorption capability, and enhanced hydrophobicity.