Electrochemical and dynamic mechanical properties of polyurethane nanocomposite reinforced with functionalized TiO2-ZrO2 nanoparticles in automobile industry

Polymer coatings have been widely used in the automobile industry for the corrosion protection of metallic materials. However, the failures of the polymer materials are caused by the extensive exposure of the coated steel to the aggressive electrolytes. To enhance the protective performance of the polymer coatings, functionalized nanoparticles are added to the polymers. The 2-aminothiazole (AT) modified TiO2-ZrO2 nanoparticles examined by Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy/energy-dispersive X-ray analysis (SEM/EDX), transmission electron microscopy (TEM), and X-ray diffractometry (XRD) were added to polyurethane (PU). The synthesized PU-AT/TiO2-ZrO2-coated specimen was studied by scanning electrochemical microscopy (SECM), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) for their anti-corrosion and mechanical behaviours. EIS studies revealed excellent protection behaviour for the PU-AT/TiO2-ZrO2-coated steel in natural seawater. The coating resistance of the PU-AT/TiO2-ZrO2 nanocomposite was found to be 1970.17 k ohm.cm(2), whereas lower coating resistance was observed for the pure polyurethane-coated steel (62.17 k ohm.cm(2). It is found that the coating resistance of PU-AT/TiO2-ZrO2 nanocomposite is over 48% higher than that of the PU coating. The measured current by SECM investigation over the PU-AT/TiO2-ZrO2 nanocomposite coating was very low (1.4 nA) in comparison with the PU coating (6.1 nA). The surface morphological studies of the coated steel by SEM/EDX analysis and X-ray diffraction (XRD) analysis revealed that the TiO2-ZrO2 nanoparticles were enriched at the corrosion products which prevented corrosion initiation processes. The enhanced dynamic mechanical properties were noticed for PU-AT/TiO2-ZrO2 coating when the concentration of nanoparticles was 3 wt%. However, there was a decrease in their mechanical properties beyond 3 wt% because of the aggregation of nano-TiO2-ZrO2 particles in the PU matrix. The resulting PU-AT/TiO2-ZrO2 formulation exhibits an excellent hydrophobic behaviour (WCA: 116.9o). Therefore, it was concluded from the investigations that the newly synthesized PU-AT/TiO2-ZrO2 nanocomposite provided excellent barrier, mechanical, and hydrophobic properties due to the addition of AT/TiO2-ZrO2 nanoparticles to the polyurethane which prevented the degradation of materials and helped to prolong the life of the coated steel.