Effects of silane precursors on curing behavior of UV-curable hybrid coatings A photo-DSC study

摘要

This study demonstrates the effect of some commonly used silane precursors on curing behavior and photopolymerization kinetics of UV-curable hybrid coatings. Tetraethoxyorthosilane (TEOS), vinyltrimethoxysilane (VTMS), and 3-methacryloxypropyltrimethoxysilane (MPS) were polymerized under acidic conditions by the sol-gel method. The resulting structure of the tested siloxane oligomers was characterized using Si-29-NMR and H-1-NMR spectroscopy. Photo-DSC was used to evaluate photocuring enthalpy. A fully integrated model was applied to investigate propagation rate coefficients and to identify the most effective termination mechanism (monomolecular, bimolecular, or mixed). Results showed that oligomers containing MPS effectively promoted total heat of the polymerization process and consequently affected the maximum rate of polymerization and final double bond conversion. Enthalpy rating for samples containing MPS was higher than that of those containing VTMS, showing that MPS was more compatible with the acrylate systems. In addition, evaluations for photopolymerization kinetic constants proved that non-functional oligomers containing TEOS caused radical trapping and increased activity of the monomolecular termination mechanism.