Development of hydrophobic coating with polymer–metal oxide nano-composites

The hydrophobicity of the nano-coating developed with TiO₂ and SiO₂–TiO₂ nanoparticles in organic binder is investigated, where polyurethane was taken as model binder. Core SiO₂ nanoparticles have been synthesized using Stober method with average particle size of 92 nm. TiO₂ and nano-core@shell have been prepared using peptization process. Particle sizes were measured as 75 nm for TiO₂ and 144 nm for core-shell nanoparticles which were prepared using peptization process. In this process, hydrophobic titania was produced at 70 °C. Here, SiO₂–TiO₂ core–shell nanoparticle was synthesized because core silica improves the mechanical strength and shell TiO₂ on core silica provides the hydrophobicity of the coating surface. Characterization of these nanoparticles was performed by UV-vis spectrophotometer, dynamic light scattering (DLS), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and XRD. The coating formulations were developed with the aforementioned nanoparticles separately and concentration of nanoparticles was varied from 1 to 6 wt%. The best performance in terms of hydrophobicity was obtained with 4 wt% of the concentration of nanoparticles in polyurethane-coating system. In this work, prepared coatings were applied on glass substrate (20 × 20 × 10 mm) using a brush, dried in oven at 80 °C for 15 min, on drying, 100-μm-thick film was obtained. Static contact angle of water droplet on these dried films was measured and obtained as 129° for PU film-containing TiO₂ nanoparticle and 133.3° for PU film with SiO₂–TiO₂ core@shell nanoparticle.