Synthesis, Characterization, and Evaluation of Siloxane-Containing Modifiers for Photocurable Epoxy Coating Formulations

Abstract

Reactive modifiers for photocurable epoxide coatings were synthesized by reacting caprolactone polyols with tetraethyl orthosilicate (TEOS). The structures of the TEOS functionalized polyols were characterized using IR, 1H-NMR, and ESI-FTMS spectroscopy. The resulting siloxane functionalized polyols were used as reactive modifiers for UV-curable cycloaliphatic diepoxide coatings. The crosslinking reactions were monitored using IR and 29Si-NMR spectroscopy. Based on the curing behavior and spectroscopic data, possible crosslinking reactions were postulated. The coatings were evaluated with respect to curing rate, gel content, and adhesion to aluminum substrate. Tensile properties of the cured films were measured. The modified polyols functioned effectively as adhesion promoters without affecting the coating properties of polyol-epoxide coatings, when used as partial replacements of the polyols at the level of 10 wt % of the parent polyol.