Scratch resistance of nano-silica reinforced acrylic coatings

Organic–inorganic hybrid coatings were obtained by a dual-curing process combining the sol–gel reaction with the UV-induced polymerization technique by starting from bisphenol A ethoxylate (15 EO/phenol) dimethacrylate (BEMA, as organic network former), methacryloyloxypropyl-trimethoxysilane (MEMO, as coupling agent) and tetraethoxysilane (TEOS, as inorganic silica network precursor). For comparison, TEOS was also substituted with preformed silica nanoparticles. Scratch test was carried out in order to study the scratch resistance of that silica reinforced acrylic resins. Excellent scratch resistant coatings were obtained by UV and sol–gel dual curing process. On the contrary, coatings with very poor scratch resistance were obtained by dispersing preformed nano-silica into the acrylic resin indicating the key role played by the morphology of the inorganic filler and its interaction with the organic matrix.