Ultrafast Synthesis of Nanocomposite Coatings by UV Curing of Clay- or Silica-Filled Resins
UV-radiation curing is one of the most effective processes to rapidly produce composite materials at ambient temperature. Mineral charges, such as silica particles or glass fibers, can be introduced into photocurable resins to get hard and abrasion-resistant materials that can be used as protective coatings, dental fillers, sealants, composite membranes and fiber-reinforced plastics.1-4 The abrasion and scratching resistance of UV-cured coatings was found to be greatly improved by incorporation into the polymer matrix of acrylate-functionalized colloid silica.5-7 In all of these applications, the spatial and temporal control afforded by photopolymerization, together with the short setting time, make this environment-friendly technology very attractive for rapid and inexpensive processing of polymeric composites.
In conventional composite materials, the filler and the polymer are combined on a micronic scale, which often leads to insufficient adhesion between the organic matrix and the reinforcing filler. Composite materials that exhibit a change in structure and composition over a nanometer length scale have been shown to afford remarkable property enhancements with respect to stiffness and strength, heat resistance and gas barrier properties.8 Most of the nanocomposite materials are based on linear polymers and show, therefore, insufficient chemical and heat resistance. When the mineral filler, usually layered silicate such as clay, is incorporated into the melted polymer, thermodegradation of the organoclay may occur, thus affecting the nanocomposite performance.