Transparent UV curable antistatic hybrid coatings on polycarbonate prepared by the sol–gel method

Abstract

UV curable, hard, and transparent organic–inorganic hybrid coatings with covalent links between the inorganic and the organic networks were prepared by the sol–gel method. These hybrid coating materials were synthesised using a commercially available, acrylate end-capped polyurethane oligomeric resin, hexanedioldiacrylate (HDDA) as a reactive solvent, 3-(trimethoxysilyl)propoxymethacrylate (MPTMS) as a coupling agent between the organic and inorganic phase, and a metal alkoxide, tetraethylorthosilicate (TEOS). The materials were applied onto polycarbonate sheets and UV cured, followed by a thermal treatment to give a transparent coating with a good adhesion and abrasion resistance. The high transmission and the thermogravimetric behaviour indicate the presence of a nanoscale hybrid composition. In a taber abrasion test, uncoated polycarbonate sheets exhibit a 48% decrease in light transmittance at 633 nm after 300 wear cycles, whereas the hybrid coating system containing 10 wt% silica shows only 10% decrease in light transmittance. For obtaining antistatic coatings, an intrinsically conductive polymer (ICP) was added to the optimised coating formulation. It is shown that the surface resistivity of the organic–inorganic hybrid coating can be reduced from 10 16 to 10 6 Ω for a high concentration of ICP in the coating formulation.