Photochemistry of Azo Dyes on Synthetic Fibers

Abstract

The relationship between photodegradation rates and dye concentrations were determined by extraction, reflectance, and visual methods. Polyester and cellulose ester fabrics dyed with 4-[N-(2-cyanoethyl)-N-(ethylamino)]-4'-nitroazo benzene at various concentrations were exposed to either a carbon-arc or a mercury-arc lamp, and the amount of dye de struction, as a function of time, was determined by the various methods. Correlations were found between visual lightfastness ratings on the fabrics, dye loss determined by reflectance methods, and concentration of dye in the fabric. Extraction methods were useful for determination of dye content of dyed fabrics before and after extensive photodegra dation, but they lacked the sensitivity required for determination of small dye losses resulting from photolysis. Neither the fading kinetics nor the reflectance spectra indicated extensive aggregation of dye in the fabrics.