Preparation of Novel Series of UV Dual Curable Polyurethane-Modified Epoxy Monoacrylates and Their Films Properties

摘要

A new series of radical-cationic UV dual curable polyurethane-modified epoxy monoacrylates (PMEMA) was prepared. Radical-cationic UV dual curable were prepared with photosensitive resin (epoxy monoacrylates (EMA) or PMEMA), reactive diluents, radical and cationic photoinitiators. UV dual cured films of those liquid compositions were obtained by using a high pressure mercury UV lamp. FTIR spectra identified the change of C＝C and epoxy groups absorption peaks during the UV-curing process. The effect of different modified oligomers on the gel content, water absorption, mechanical and thermal properties of radical-cationic UV dual cured films was investigated. The characteristic C＝C (1635 cm~(-1), 810 cm~(-1)) and epoxide (910 cm~(-1), 772 cm~(-1)) absorption speaks were no longer detectable after UV dual cured. The gel contents of all samples using PMEMA as oligomers were beyond 97.0% and their water absorption values were about 0.80%. With the length of flexible polyurethane chain segments increased, the Young's modulus and breaking strength of UV dual cured films decreased gradually, except for the relative elongation. The volume shrinkage test indicated that the UV dual cured films exhibited lower internal stress and higher cohesive force than single radical UV cured films. The results of thermogravimetric analysis (TGA) for the UV dual cured films indicated good thermal stability with no appreciable weight loss until well above 250°C.