Читать книгу Sustainable Practices in the Textile Industry - Группа авторов - Страница 21

1 Direct Dyes: Direct dye soluble in water can be taken up directly by the material. Direct dye also called substantive dyes because of their excellent substantivity for cellulosic material like cotton and viscose rayon. Turmeric, Chebulic myrobalan and Annatto used in direct dyes.

2 Vat Dyes: As the name suggests that the dye is prepared in a large container for storing and mixing liquids or wooden vessels commonly known as ‘Vat’. This is a primitive method of dye preparation.

3 Mordant Dyes: Mordant dyes are attached to textile fibers by a fixing agent “mordant” which can be organic or inorganic substance. Since chromium is used extensively hence, mordant dyes are sometimes called chrome dyes.

4 Acid Dyes: These dyes performed in acidic medium. Sulfonic or Carboxylic groups of dye molecules can form electrovalent bonds with amino groups of wool and silk.

5 Basic Dyes: These dyes form an electrovalent bond with the carboxylic group of wool and silk. Berberine has been classified as basic dye.

6 Disperse Dye: Disperse dye have low aqueous solubility and low molecular weight. These dyes require post mordanting treatment with chromium, copper or tin salt (Figure 1.3) [36].

Figure 1.3 Classification of natural dyes.