A kinetic investigation into the effect of silica properties on the photo-oxidation of a water based silica coating

Films prepared from a copolymer methyl methacrylate/butylacrylate system co ntaining silica as a matting agent, have been the subject of an accelerated photo-oxidation study. An intensive FT-IR experiment was designed in which 13 different silica samples were carefully chosen in order that the effect s of key silica properties on the rate of photo-oxidation could be determin ed. The properties where those effects were anticipated included metal ion content, coated or uncoated silica, particle size, pH, pore volume and sili ca type (fumed or gelled). To complete the study the effect of silica loadi ng was also investigated. The rate of photo-oxidation was followed using re flectance FT-IR spectroscopy to monitor the change in concentration of key functional groups and also by measuring changes in the cured film propertie s. This study found that silica can influence the rate of photo-oxidation, the extent of which is dependent on key silica properties such as metal ion content and the contact area of the silica surface with the lacquer formul ation. (C) 1999 Elsevier Science Ltd. All rights reserved.