The Effect of Ultraviolet Radiation on Dyed Man-Made Textile Fibers Using UV-Vis Microspectrophotometry (MSP): Technical Aspects on Spectral Alterations in Time

Abstract

Little is known about changes in dyed man-made fibers caused by environmental conditions, especially exposure to ultraviolet (UV) radiation over long periods of time. Even less known are the deviations of the spectral curves collected from these samples using UV-visible microspectrophotometry (UV-Vis MSP) from the spectral curves collected from unexposed fiber samples. Spectral alterations, however, may derive from undesired causes inherent to the operation of the instrument or the samples themselves. Hence, the primary goal of this research was to study the effect of UV radiation on various combinations of man-made fiber types, color, and dye types. A UV radiation box was constructed as a controlled (indoor) environment and was compared to a dedicated (outdoor) natural exposure facility in Buckeye, AZ. In both settings, the fiber samples were exposed up to 32 weeks and collected and analyzed at intervals of 8 weeks. The undesired causes of UV exposure of induced photobleaching inherent to the xenon source of the spectrophotometer and the latent polarization of the selected fiber samples as a function of their orientation on the stage of the microscope were also evaluated. Although issues due to latent polarization from the samples were not identified, induced photobleaching was observed within 8 seconds of exposure to the xenon source in a few instances. In this study, different types of spectral alterations were observed, which occurred both in the visible and the UV spectral regions. These alterations were the same as observed in the indoor setting, the outdoor setting, and the instrument-induced photobleaching study, although their times of occurrence differed. This study focused on technical aspects related to the proper use of UV-Vis MSP to the analysis of textile fibers exposed to UV radiation. It has led to the formulation of recommended measures that aim at minimizing the risks of spectral alterations resulting from causes other than the environmental UV exposure of interest.