New Fluorescent Probes for Monitoring Polymerization Reactions: Photocuring of Acrylic Adhesives, 2

Abstract

The results of following the fluorescence of selected probes during the entire range of curing of acrylic-based adhesives are presented in this work. The change of fluorescence parameters has been continuously measured during the photocrosslinking reactions of acrylic adhesive systems under UV-irradiation. Real-time FT-IR (RT-FT-IR) has been used to measure the conversion reached at different irradiation times. Intensity ratio, maximum emission wavelength and the first moment of fluorescence have been used as parameters to correlate with the double bond conversion degree. Two-slope plots have been obtained during UV-curing, which correspond to the different stages of the crosslinking reaction. Also, the size of fluorescent probe appears to be a parameter that influences the sensing time in which the probe can detect the changes in viscosity/polarity occurring along the UV-curing process. The results are compared with those of commercial probes such as dansylamide and prodan. The use of the fluorescence technique allowed us to understand the mechanism taking place and the role of the binder matrix, depending on the photoinitiator used. This information is not obtained when the reaction is followed by the conventional RT-FT-IR technique.