What are the properties of dyes?

Different types of dyes have different characteristics.

Direct dyes: Direct dyes are mostly azo dyes containing sulfonic acid groups, which are easily soluble in water. Because of its special structure, dyes have strong affinity for cellulose fibers, and can be directly connected to dyed cotton and viscose fabrics in weak alkaline or neutral dyeing baths, but the washing fastness of such dyes is not good.

Vat dye: insoluble in water, it needs to be reduced to colorless sodium salt by sodium sulfite in alkaline medium when dyeing, which is absorbed by the fiber and oxidized by air or oxidant to form a solid color on the fiber. Mainly used for cotton, sometimes dyed with vinylon.

Reactive dyes: dyes have reactive groups (called reactive groups) in the molecular structure, which can form valence bonds with hydroxyl or amino groups in fiber molecules when dyeing, and become a whole "dye-fiber", so they are also called reactive dyes. It is mainly used for dyeing cotton, hemp, silk and other fibers, and can also be used for dyeing wool and synthetic fibers.