Preparation and characterization of UV/thermal dual-curable polyurethane acrylate adhesive for inertial confinement fusion experiment

A new type of polyurethane acrylate (APUE) oligomer, which contains both acrylic and epoxy group in its molecular structure, was synthesized. UV/thermal dual-curable adhesives were prepared using various contents of APUE oligomers, reactive diluent, photoinitiators and thermal-curing agent. The curing behaviors of the dual-curable adhesives were investigated using photo-DSC, on-line FT-IR spectroscopy, the determination of gel fraction and dynamic mechanical thermal analysis (DMTA). The reaction rate and extent of UV curing were studied and found to be strongly dependent on the concentration of C=C bonds in the APUE oligomers. The gel fraction was also evaluated as a function of C=C bond concentration, demonstrating that gel fraction increased with increasing C=C bond contents in the APUE oligomers. Moreover, when the dual-curable adhesive was thermally-cured, the gel fraction was largely improved, due to the thermal-curing agent initiating the unreacted epoxy groups to allow the formation of further crosslinking. The adhesion strength at −196 °C increased with increasing C=C bond content. The latent thermal-curing agent contributed to the enhancement of the adhesion strength.