UV-curable polyurethane inorganic–organic hybrid coatings

A UV-curable inorganic/organic hybrid coating was prepared from a methacrylated urethane oligomer, a reactive diluent, tetraethyl orthosilicate (TEOS) oligomers, and a free radical photoinitiator. The reactive diluent was synthesized using IPDI, HEMA, and aminopropyltetraethoxysilane (APTES), resulting in both inorganic and organic reactive groups. The photocuring kinetics was investigated using photo-DSC and real-time FTIR spectroscopy. The effect of the reactive diluent and TEOS oligomers concentration was investigated using impact resistance, pencil hardness, and adhesion. Two glass transition temperatures were observed, indicating a substantial interfacial phase generated between the inorganic and organic domains. The reactive diluent-to-reactive oligomer ratio had a larger effect on the mechanical behavior of the system than the TEOS concentration did. Adhesion improves with increasing TEOS oligomer concentration or reactive diluent concentration until maxima, after which increasing concentration has an adverse effect on adhesion.