For heavy color clothes, it is also very possible that the dye on the dyed clothes will undergo photolysis and aging after repeated washing and long-term sun exposure, which will lead to the discoloration of the clothes
this phenomenon occurs step by step, and its process is relatively complex
when the sun shines on the dyed clothes, the light energy stimulates the dye molecular activity. Active dye molecules can react with chemical active substances. First of all, they must react with oxygen in the air. The presence of water will promote the intensity of chemical reaction. Due to the oxidation or reduction reaction of dye molecules, the dyed clothes will fade. For example, the fading of cotton fabric dyed with azo dyes in the sun is the result of oxidation, while the fading of protein fabric dyed with the same dyes in the sun is the result of reduction< 1n addition, the fading of dyed clothes is also related to the structure of dye molecules. Among the dye molecules, the stability is poor, and the fading of dyed clothes is also related to the structure of dye molecules. Among the dye molecules, the hydrogen atom with poor stability and strong reaction ability can promote the oxidation process. For example, when the dye molecular structure contains more amino (- NH2) or hydroxyl (- OH) and other color groups, it is easy to oxidize and reduce the light fastness. When the dye molecules contain groups that can form hydrogen bonds, or hydroxyl (- COOH), sulfo (- SO3H), nitro (- NO2) and other groups, the light resistance of the dye will be improved