Effects of UV absorbers and reducing agents on light fastness of cotton fabrics pre-dyed with sodium copper chlorophyllin and gardenia yellow

In this study, inorganic and organic UV absorbers, as well as reducing agents, were employed to treat cotton fabrics that were pre-dyed with two natural dyes (sodium copper chlorophyllin and gardenia yellow) to improve light fastness. The performance of UV absorbers and reducing agents was evaluated by comparing ΔE (CIELAB) of the treated samples caused by their exposure to simulated sunlight irradiation. Results show that both inorganic and organic UV absorbers present unsatisfactory effects on inhibiting the photo-fading of dyes, while the reducing agents (i.e. sodium citrate and glucose) exhibit distinctive effects on improving their light fastness. The protection was enhanced when the amount of the two reducing agents was increased from 1% to 5% o.w.f. Sodium citrate was found to be more efficient than glucose in this regard. Change in shade of gardenia yellow and sodium copper chlorophyllin pre-dyed fabrics with a treatment of 5% o.w.f. sodium citrate after 10 h exposure to simulated sunlight were ΔE 3.95 and 2.46, while for the controls were ΔE 10.34 and 8.11, respectively.