Colour change of coatings from extended UV fluorescent lamp exposure

 
UVA-340 Fluorescent UV lamps are commonly used for accelerated weathering testing of materials. While the apparatus that use these lamps are very good at simulating the effects of real-world moisture and shortwave UV light (295 - 360 nm), it can be difficult to correlate laboratory and outdoor degradation of materials that are sensitive to longwave UV light (360 - 400 nm). A common application where longwave UV is important to consider is organic pigments used in coatings. Historically, the color change experienced by these coatings outdoors or in a xenon arc tester does not correlate to results observed from exposure to UVA-340 lamps. To address this issue, a new type of Fluorescent UV lamp was designed to deliver a broader light spectrum (295 - 450 nm). Commercially-available coatings were tested using these new lamps, and the results were compared against results obtained from standard UVA-340 Fluorescent UV, xenon-arc, and outdoor exposures. This comparison indicates that, for some materials, color change observed from the new light source matched outdoor results better than standard UVA-340 lamps. This paper will present the data collected in this study and compare the correlation of various weathering testing methods, included the new type of Fluorescent UV lamp.