Surface Modification of Oxide Nanparticies for Polyacrylate Reinforcement

Reinforced clear coats were prepared using nanosized silica and alumina particles in UV/EB curable acrylate formulations. For a firm embedding of the oxide nanofillers via covalent bonds to the network acrylates their surfaces were modified by polymerization-active trialkoxysilanes, e.g., methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane. The cured nanocomposite clear coats showed improved scratch and abrasion resistance. However, oxide modifications accomplished by silanes having polymerization-inactive methyl, n-propyl, and isobutyl functionalities yield coatings with similar scratch and abrasion resistance. To explain these findings, infrared and multinuclear MAS NMR experiments, MALDI-TOF and ESI-MS mass spectroscopy, and atomic force microscopy results were used to reveal the structure of surface-anchored organosilanes and their interaction with the acrylate matrix. Ladder-like polysiloxane chains chemically grafted onto the filler particles have been proposed. These ladder-like structures build a short range interpenetrating network with the polyacrylates. This results in a durable link between the organic and inorganic phase.