Dye refers to a class of organic compounds that can make other substances get bright and firm colors. Because the pigments used now are all synthetic, they are also called synthetic dyes. Dyes and pigments are generally compounds that have their own colors in molecular or dispersed state and can make other substances obtain bright and firm colors.

The dyeing method is simple, the chromatography is complete and the cost is low. However, its washing resistance and sun resistance are poor. If proper post-treatment is adopted, the fastness of dyed products can be improved.

Extended data:

The molecular structure analysis of dyes and the actual measurement of dyed fabrics show that dyes synthesized with carcinogenic aromatic amines as intermediates, including azo dyes and other dyes, are prohibited if they are not fully purified, even if they exist in trace amounts.

At present, about 70% of synthetic dyes on the market are mainly azo-structures, and the widely used direct dyes, acid dyes, reactive dyes, metal complex dyes, disperse dyes, cationic dyes and polycondensation dyes all contain azo-structures.

Azo dyes are not only used for printing and dyeing textiles, but also for dyeing leather, paper and food. It should be pointed out that under normal circumstances, azo dyes themselves will not have harmful effects on human body, but some azo dyes synthesized from carcinogenic aromatic amine intermediates, after long-term contact with human skin, will combine with substances released in normal metabolism of human body and undergo reduction reaction, which will break azo groups and regenerate carcinogenic aromatic compounds.

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