Fabrication of azobenzene non-covalent bonding grafting graphene composite and its application in weathering and corrosion resistant polyurethane coating

The azobenzene non-covalent bonding grafting graphene composite (GN-Py-AZO) is fabricated by π-π interaction between Py-AZO (with a pyrene ring, a hydrophilic group and azobenzene structure) and graphene, which is confirmed by FT-IR, 1 HNMR, XRD, UV–vis and XPS. The impact resistance, hardness and hydrophobic properties of the composite polyurethane coating (PU) are significantly increased after adding GN-Py-AZO in PU. Electrochemical impedance spectroscopy and Tafel polarization curves show that GN-Py-AZO improves effectively the anti-corrosion performance of the composite polyurethane coating and 0.5% GN-Py-AZO/PU composite coatings have best anti-corrosion performance. FT-IR and SEM are applied to investigate the weather-resistance of PU films which showed that 0.5% GN-Py-AZO/PU films had the weakest changes and can maintain the basic planar morphology without defects such as wrinkles, big cracks and protrusions after UV aging for 650 h with the best UV-aging resistance. In conclusion, 0.5% GN-Py-AZO/PU showed excellent overall performances in weathering resistance and anti-corrosion. The weathering-resistance and anti-corrosion mechanism of GN-Py-AZO/PU composite coating is also discussed.