THE EFFECT OF HUMIDITY ON THE OZONE FADING OF ACID DYES

The effect of humidity on the ozone fading behavior of acid dyes on ny lon 6,6 and wool fabrics were examined. At a 0.2 ppm ozone concentrati on, high humidity (88 +/- 2%) produced significant fading in nylon 6,6 dyed with ozone-sensitive acid dyes. As the humidity level decreased, fading also decreased. Acid dyes on wool were found to have higher oz one resistance than those on nylon 6,6. Ozone fading of wool was relat ively unaffected by varying levels of humidity. Most of the ozone fadi ng of acid-dyed wool occurred during the very early stages of ozone ex posure, whereas nylon exhibited progressive fading throughout the 12-d ay exposure period. Parallel with previous studies, the ozone fading o f acid dyes was found to be governed primarily by the sensitivity of t heir chemical structure to oxidation by ozone and their ability to mig rate within the fiber. Mobility of the dye, found to be greater in nyl on than in wool, was correlated with its relative molecular size, degr ee of aggregation within the fiber, and the swelling or plasticizing e ffect of temperature and humidity on the fiber.