Chemiluminescence and fluorescence for monitoring the photooxidation of an UV-cured aliphatic polyurethane-acrylate based adhesive

The photooxidation of an UV-cured polyurethane-acrylate adhesive, has been monitored through the use of chemiluminescence and fluorescence techniques. Chemiluminescence analysis shows early stages of photooxidation in the adhesive when there is neither loss or change in the physical and chemical properties of the material. Moreover, fluorescent probes incorporated into the adhesive formulation have been found to be very useful to detect the first oxidation species. Quenching of fluorescence follows the same kinetics as the chemiluminescence increase during UV-exposure. Two fluorescent probes, p-dimethylamino salicylic acid and 2',7'-difluorfluorescein, were sensitive to the formation of oxidation products. Therefore, good correlations between fluorescence and chemiluminescence were established. We conclude that the fluorescence emission from extrinsic probes can be used as a valuable method to analyse photooxidation from the initial stages. (C) 2002 Elsevier Science Ltd. All rights reserved.