Polyurethane coatings reinforced with 3-(triethoxysilyl)propyl isocyanate functionalized graphene oxide nanosheets: Mechanical and anti-corrosion properties

In the present study, graphene oxide (GO) nanosheets were synthesized and then functionalized with 3-(triethoxysilyl)propyl isocyanate (TEPIC) reactive precursor to study the effect of surface functionality of GO on the mechanical and anti-corrosion properties of polyurethane (PU) based coatings cured with polyisocyanate. FTIR, TGA, XRD, UV-vis and FE-SEM analyses were employed to compare the surface and bulk properties of the pristine and TEPIC-functionalized GO (fGO) nanosheets. Reactive TEPIC groups were found to be covalently bonded to GO surface by the aid of hydroxyl and carboxyl groups of GO nanosheets. Then, pristine and fGO nanosheets were incorporated into PU/isocyanate system, cured and analyzed using FT-IR, EIS and pull-off measurements. Incorporation of GO into PU led to ca. 4% fall in strain at break of nanocomposite coating with respect to the blank PU, while fGO addition was responsible for ca. 31% rise in elongation at break. Likewise, energy at break of PU remained almost unaffected by GO addition, whereas a two-fold rise was the case for PU/fGO sample. Log vertical bar Z vertical bar recorded from Bode diagram at 10 mHz for PU decreased from ca. 10 to 8 Omega cm(2) over 14 days, but for PU/fGO it remained almost constant at 9 Omega cm(2). Moreover, phase degree at 10 kHz dropped steadily for PU over 14 days, while it increased for PU/fGO system. In agreement with anti-corrosion properties, DFT calculation revealed low binding energy of -11.44 kcal/mol for TEPIC attachment to GO through -OH groups.