Structural and electrochemical properties of polyurethanes/polyhedral oligomeric silsesquioxanes (PU/POSS) hybrid coatings on aluminum alloys

Hybrid coatings based on polyurethanes/polyhedral oligomeric silsesquioxanes (PU/POSS) were synthesized through a sol–gel technique. Hydroxy-terminated polybutadiene (HTPB), isophoron diisocyanate (IPDI) and trans-cyclohexane diolisobuty-POSS (POSS) were used as precursors for the hybrid coatings. These hybrid films were deposited via spin coating onto an aluminum alloy in order to improve the corrosion protection. The effects induced by the POSS content on the structural, thermal properties and corrosion resistance of the coated samples were investigated. The structures of the obtained hybrid materials were characterized with gel permeation chromatograph (GPC), Fourier transform infrared (FTIR) and X-ray diffraction (XRD). The GPC, FTIR and XRD spectra suggested successful bonding of POSS silanols and polyurethane resin. The homogeneous dispersion of POSS cages in the PU matrices was evidenced by scanning electronic microscopy (SEM) and atomic force microscopy (AFM). Thermal properties of these PU/POSS hybrids have been improved over the pure polyurethane analyzed by dynamic mechanical analysis (DMA) and thermal gravimetric analysis (TGA). Potentio-dynamic and salt-spray analysis revealed that the hybrid films provided an exceptional barrier and corrosion protection in comparison with PU and untreated aluminum alloy substrates.