Dyes having high photostability on hydrophobic fibers
The need for photostable (lightfast) dyes for hydrophobic fibers, especially polyester, stems from their use in automobile interiors, where stability to prolonged and repeated exposures to sunlight in combination with heat and humidity is paramount. Our research in this area began in 1985, with funding from a consortium of companies in the supply chain leading to fabric and carpet for automobile interiors and, subsequently, from NSF to characterize the contribution of heat and humidity to the dye fading process (cf. Fig 1). At the heart of this work was to determine the mechanisms of fading associated with prototype synthetic dyes used in this area of technology and to use the resulting information to design dyes immune to the observed mechanisms. This research led to a family of lightfast disperse dyes containing a built-in photostabilizer (e.g. 1-2). In this regard, it was found that the nature and location of the built-in stabilizer played a key role in the viability of the dyes obtained.
Fig. 1. Dyed PET films before (left) and after (right) sunlight exposure.
In closely related studies, we are investigating the influence of the host fiber on the photodegradation of adsorbed dyes and preliminary results indicate that the photostability of dyes on polyester is adversely influenced by the host fiber unless a photostabilizer is present. This also suggests that stabilization of the excited polymer molecules is critical to the life of the adsorbed dye.