Aluminum pigments encapsulated with hybrid silica film with carboxyl groups and their stability and dispersibility in aqueous media

Abstract

Aluminum pigments encapsulated with hybrid SiO2 film with carboxyl (–COOH) groups were prepared through a sol‐gel process of tetraethoxysilane (TEOS) and vinyl triethoxysilane (VTES), followed by radical copolymerization of methyl methacrylate (MMA) and acrylic acid (AA) with the vinyl group of VTES. The composite aluminum pigments were characterized by means of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X‐ray photoelectron spectroscopy (XPS). Their stability in acid media as well as dispersibility in water were also evaluated. It was found that VTES and TEOS could simultaneously hydrolyze and condense with hydroxyl groups on the surface of aluminum particles to form inorganic‐organic hybrid films, and copolymerization of MMA and AA could provide the film surface with –COOH groups. This helps the composite aluminum pigments disperse better in water than raw aluminum pigments (raw Al) counterparts. Compared with the serious corrosion problem of raw Al, which generated about 113 mL H2 in acid media of pH=1 in 30 days, the composite aluminum pigments showed much better anticorrosion performance (with only about 0.5 mL H2). The waterborne coatings made with this composite aluminum pigments showed great improvements on adhesive performance and stability in 0.1 mol/L H2SO4 or NaOH media.