Accelerating the photodegradation of commerical polymeric materials has great practical importance in the weathering community. However, questions exist as to whether high radiant flux exposure results cn be extrapolated to in-service exposure levels. Based on the reciprocity law, the photoresponse of a material is dependent only on the total energy to which the specimen is exposed and is independent of the exposure time and the intensity of the radiation taken separately. An experiment to validate the applicability of the reciprocity law for polymeric coatings has been carried out using the NIST integrating sphere-based ultraviolet (UV) weathering device. A non-pigmented, non-UV stabilized acrylic-melamine coating was exposed to six different UV radiation intensities ranging from 36 W/m^2 to 322 W/m^2, in the spectral region between 290nm and 400nm. Chemical changes in the coating due to UV exposure were measured with transmission Fourier transform infrared (FTIR) spectroscopy and UV-visible spectroscopy. Using two dose-damage models, the reciprocity law photoresponse for this polymeric system was verified for different photodegradation mechanismns, including chain scission, oxidation and mass loss.
Conference Dates: October 27-29, 2004
Conference Title: Proceedings of the 82nd Annual Meeting Program of the FSCT
Pub Type: Conferences
acrylic-melamine, photodegradation, reciprocity law, Schwarzschild Law, ultraviolet radiation