UV-curable organic–inorganic hybrid hard coatings for metal sheets

Abstract

A new type of UV-curable organic–inorganic hybrid oligomer was synthesized from vinyltrimethoxysilane (VTMS), tetraethylorthosilicate, and colloidal silica (CS) using a sol–gel method. UV-curable hybrid hard coating formulations were then prepared by mixing the organic–inorganic hybrid oligomer and acrylic monomers, trimethylolpropane triacrylate and tetrahydrofurfuryl acrylate, with a levelling agent and a photoinitiator. The oligomer was hydrolyzed and condensed from alkoxysilane and CS to obtain the UV-cured hybrid films. The hybrid oligomer and resulting hybrid films were characterized by Fourier transform infrared spectroscopy, 29Si nuclear magnetic resonance spectroscopy, scanning electron microscopy, and ultraviolet–visible spectrophotometry to confirm the chemical functionality, oxo-silicon signal, cross-sectional morphology, and transparency, respectively. When the concentration of the CS/VTMS mixture in the organic–inorganic hybrid oligomer was 0.50 mol, remarkable pencil hardness (up to 5H) with excellent transparency was observed. The hardness and transparency of the UV-cured hybrid coating films were improved significantly by increasing the CS content in the organic–inorganic hybrid oligomer.