Synthesis and characterization of sequential interpenetrating polymer networks of polyurethane acrylate and polybenzoxazine

High-performance ultraviolet (UV) curable polyurethane acrylate (PUA) coating alloyed with thermally curable polybenzoxazine (PBA) is developed. The hybrid polymer networks of PUA and PBA-a were prepared by sequential cure methods, i.e., UV cure of the PUA followed by thermal cure of the PBA fraction. The effects of sequential cure were investigated in terms of mechanical, thermal, and physical properties of the resulting polymer alloys. The fully cured PUA/PBA-a alloy films showed only single glass transition temperature (T-g) suggesting high compatibility between the two polymer networks, possibly of an interpenetrating polymer network type. The storage modulus in a glassy state and T-g of PUA/PBA-a alloys were found to substantially increase with increasing PBA-a content. Furthermore, degradation temperature at 10% weight loss of the PUA/PBA-a alloy films was relatively high whereas the char yield at 800 degrees C was found to increase with a PBA-a component. Hardness was enhanced, whereas water absorption and water vapor permeation rate of the alloy were suppressed by the incorporation of the PBA-a into the polymer alloys. As a consequence, the properties of UV curable PUA networks can be positively tailored and enhanced by forming hybrid network with PBA-a. POLYM. ENG. SCI., 54:1151-1161, 2014. (c) 2013 Society of Plastics Engineers