Why does indigo denim clothing turn yellow easily?

What are the reasons for the yellowing?

(1) Determined by the characteristics of the dye itself

Indigo denim is woven from warp yarns dyed with indigo dye and weft yarns that are not dyed. Indigo dye dyeing requires sodium hydroxide and caustic soda to be reduced to leuco dyed fibers, which are then oxidized by air to form insoluble dye particles fixed on the fibers. Therefore, the structure of indigo dye itself is easily affected by the reducing and oxidizing environment.

(2) Chemical residues have an impact

The processing of denim clothing is actually a process in which the color is partially or completely faded through mechanical, chemical and biological methods. The processing uses such as potassium permanganate, bleaching water, sodium bisulfite, sodium metabisulfite, oxalic acid, etc. Oxidizers and reducing agents, if these chemical substances remain on the fabric, they will easily continue to interact with the dyes on the fabric during the air placement process, and these substances themselves will turn yellow when placed in the air.

(3) Yellowing of softener is the main cause

Generally, denim garments have to be softened at the end, and softeners are the only chemicals that are expected to remain on the fabric. The current softener generally adopts cationic type, which is very easy to oxidize and cause yellowing in the air. The stronger the ionicity, the more serious the yellowing.

(4) Improper packaging and storage are external factors

The phenolic substances contained in various packages contaminate the clothing, and the sun exposure and humid environment can also easily lead to yellowing of the fabric.