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

The purpose of this research is to improve performance of UV curable polyurethane acrylate coating by alloying with thermally curable polybenzoxazine. The hybrid polymer networks of polyurethane acrylate and polybenzoxazine were prepared by sequential cure methods i.e. UV cure method followed by thermal cure method. The effects of sequential cure methods were investigated in term of mechanical, thermal and physical properties of the resulting polymer alloy films. The experimental results revealed that the presence of the polybenzoxazine in the alloy network significantly affected the obtained properties of the PUA/BA-a alloys. The fully cured PUA/BA-a alloy films were transparent and showed only single glass transition temperature, suggesting high compatibility or no phase separation between the PUA and BA-a networks. The storage modulus in a glassy state and the glass transition temperatures (Tg) of PUA/BA-a alloys from the sequential cure method were found to substantially increase with increasing the BA-a mass fraction. Furthermore, Td at 10% weight loss of the PUA/BA-a alloy films was relatively high whereas the char yield at 800๐C was found to increase with an incorporation of the BA-a. Hardness, and water contact angle were enhanced whereas water absorption and water permeability of the alloy films were suppressed by the incorporation of the BA-a into the polymer alloys. As a consequence, thermal, mechanical and physical properties of the UV curable polyurethane acrylate networks can be positively tailored and enhanced by forming hybrid network with the BA-a. From the above results, the PUA/BA-a alloy at a 50/50 mass ratio was found to be the most suitable composition for e.g. high performance coating application.