(628c) Photopolymerization Kinetics of Epoxide Systems Containing ZnO Nanoparticles

Epoxide monomers are used in a variety of applications such as adhesives, coatings, and electronics. Using light, rather than heat, to drive the polymerization eliminates as much as 90% of the energy requirements. In addition, the long life time of active centers of growing epoxide polymers provides potential applications in thick coatings and curing of three-dimensional objects where light cannot reach. Unfortunately, the inherent brittleness of cured epoxide thermosets is a problem that limits further application of these systems. In this study, zinc oxide nanoparticles (ZnO NPs) were introduced to cationic photopolymerization systems to impart high impact resistance and toughness to epoxide polymer matrix. However, little is known about how the cationic photopolymerization of epoxides is affected by the presence of ZnO NPs. To address this isuue, the UV absorbance of ZnO NPs was characterized using UV-Vis spectroscopy. Raman spectroscopy was also used to monitor cationic photopolymerization as a function of UV light intensity and photoinitiator concentration. The experimental results revealed that the presence of the nanoparticles reduced the rate of photopolymerization in a manner that was consistent with the competitive absorption of the initiating light. Effective photopolymerization of nanoparticle-filled epoxides required incident light intensities above 1 W/cm2 and photoinitiator concentrations above 32 millimolar.