The effects of silica nanoparticles on the photocuring behaviors of UV-curable polyester acrylate-based coating systems

The photocuring behaviors of UV-curable PEA-based coating systems with and without silica nanoparticles have been studied by photo-DSC, UV-visible spectroscopy, and FTIR spectroscopy. Photo-DSC analysis revealed that as the concentration of silica nanoparticles was increased up to 5 wt%, the exotherm, ultimate percentage conversion, and cure rate increased gradually, whereas they decreased above 10 wt%. This result was confirmed by FTIR spectroscopy analysis and indicated that the presence of silica nanoparticles at below 10 wt% accelerated the cure reaction and cure rate of the UV-curable PEA-based systems due to the synergistic effect of silica nanoparticles as an effective flow or diffusion-aid agent during the photopolymerization process and by lengthening the path of the UV light by partial scattering or reflection. However, a decrease in photopolymerization reactivity occurred when the silica content was increased above 10 wt%, which is attributable to aggregation of silica nanoparticles due to their high surface energy.