ZnO nanoparticles as polymerisation photo- initiator: Levulinic acid/NaOH content variation
Résumé
Recently it was demonstrated that the well-known photo-semiconductor ZnO have the additional potential to be used as photo-initiator for the initiation of multifunctional acrylic esters in bulk. For such commercially used polymerization procedures like for food packaging or dental applications the migration and transport of molecular polymerization initiators are problematic. As analytically proven even newest commercial polymeric initiators results in possible health risks. Enlarging the size of the initiator as performed by using particles can be an alternative way to prevent contamination. In this manuscript, influences of the modification conditions using a non-chromophoric molecule on the curing potential of nanoscaled ZnO are analysed by recently developed UV-vis transmission curing measurements to demonstrate the concept of this alternative initiation system. A commercial acrylic resin containing only the modified photo semiconductor is taken as model systems for the UVcuring. An important aspect of this contribution is the brief and focused explanation of the photo-physical mechanisms for the application of bulk polymerisation which is supported by measurements of different modifications of the particles surface by organic acids or metal salts and their influences the charge transfer recombination which was monitored by fluorescence and which influence the curing potential.