The relationship between chemical degradation and thickness loss of an unpigmeted, non UV-stabilized, crosslinked amine-cured epoxy coating exposed to three UV conditions has been investigated. Samples were exposed outdoors and to two accelerated laboratory UV conditions.Chemical degradation and thickness loss were measured by transmission Fourier transform infrared spectroscopy and by laser scanning confocal microscopy (LSCM).Surface roughness and morphological changes were measured by atomic force microscopy (AFM) and LSCM.Substantial chemical degradation,thickness loss, and morphological changes have occurred in the films after exposure to the three UV environments. However, the rates of chain scission and mass loss were always greater than that of the thickness loss. Further, photodegradation of an amine-cured epoxy was not a uniform thickness reduction process; instead,nanoscale localized depressions initiated at certain sites on the surface, which then enlarged and deepened with exposure. The results of this study should help to develop better conceptual and mathematical models for predicting the service life of crosslinked amine-cured epoxy coatings.
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