Photo-Curing of off-set Printing Inks by Functionalized ZnO Nanoparticles

Abstract

Abstract ZnO nanoparticles surface functionalized with α -oxo-carboxylic acids have been used as photo-initiators for the curing of UV off-set printing inks. Other than commercial molecular photo-initiators ZnO nanoparticles do not migrate in the cured resins, they do not leach out and therefore, even if in contact with food, there is no danger of contamination. ESR and in-situ Raman-spectroscopy have been applied to analyze the kinetics of this free radical bulk photo-polymerization process. Upon UV irradiation the Photo-Kolbe-reaction (decarboxylation of carbonic acids by the photo generated electron hole) takes place as could be confirmed by ESR and GC-MS measurements.