UV curing and matting of acrylate coatings reinforced by nano-silica and micro-corundum particles

For UV curable coatings, the effect of the type of photoinitiator and of the photoinitiator content on surface properties has been studied. Increasing photoinitiator concentrations yielded higher acrylate conversion but a lowering of surface hardness. Thus, curing under oxygen-free conditions with 2 wt.% photoinitiator should be applied rather than 6 wt.% photoinitiator for irradiation in air. Compared to nanocomposite materials, UV-cured polyacrylate coatings reinforced by silica nanoparticles and corundum microparticles exhibit markedly improved scratch and abrasion resistance. By using various grades of corundum, a synergetic effect between nano- and microparticles has been observed. These nano/micro-hybrid composite materials are recommended as clear coat for parquet and flooring applications.Where appropriate, matting of reinforced acrylate coatings was performed by curing with the combination of a xenon excimer lamp (172 nm photons) and a mercury arc lamp. This dual lamp set-up allows obtaining gloss levels from 1 to 20 units (at 60°) depending on the acrylate formulation and on the curing conditions.