Kinetic studies of UV-waterborne nanocomposite formulations with nanoalumina and nanosilica

UV-waterborne coatings are gaining in popularity because of their environment friendly advantages. Most of the mechanical properties of such coatings are lower in comparison with high solids content UV coatings. For these reasons a nanocomposite-based approach was followed and seems promising in order to promote the use of UV-waterborne coatings in the wood products industry. The kinetic study of coatings gives interesting information regarding the curing process and photodifferential scanning calorimetry (photo-DSC) has proved its efficiency. The aim of this work was to study the photopolymerization kinetics by photo-DSC of a typical UV-waterborne coating formulation containing different amounts of nanoparticles. Formulations were mainly based on a polyurethane–acrylate (PUA) resin and a photoinitiator. Nanoalumina and functionalized nanosilica were added to the formulation at three concentrations: 1, 3 and 5 wt%. UV-waterborne formulations were dried during 10 min at 80 °C before curing under a UV source (47 mW/cm2). DSC-exothermic curves demonstrated that photopolymerization was less efficient when nanoparticles were introduced but the UV-curing of coatings based on functionalized nanosilica were better than those containing nanoalumina. Finally the kinetic profile of UV-waterborne coating formulations were characterized using an autocatalytic model and kinetic parameters k, m and n were determined.