Classification Of Dyes Past Times Method Of Application

Classification of dyes yesteryear method of application.

The chemic classification of dyes is of involvement to the pharmacist but the dyer is concerned mainly amongst the application of dyes to fabrics. The method used for application inwards a detail representative depends on the nature of both the dye together with the fiber to hold out dyed. The dyes are ofttimes classified on the footing of the technique employed for their application.

Direct Dyes.

These tin sack hold out connected to a slice of stuff yesteryear straight immersion inwards a H2O scheme of the dye. Influenza A virus subtype H5N1 straight dye contains acidic or basic auxochrome which combines amongst the contrary polar grouping introduce inwards the chemic construction of the fiber. Wool together with silk are readily dyes yesteryear this method.

Martius Yellow, a typical dye, has the acidic auxochrome-OH which interacts amongst the basic –NH2 grouping of wool or silk.

Vat Dyes.

These dyes are insoluble inwards H2O but on reduction amongst sodium hydrosulphide inwards a vat cast a colorless soluble chemical compound which has a greater affinity for cotton fiber together with other cellulose fibers, The cloth is soaked inwards the solution of a reduced dye together with thence hung inwards the air, or treated amongst oxidants. As a result, the colorless chemical compound is oxidized back to the insoluble dye which is at ane time saltation to the fabric. Indigo is a adept representative of a vat dye.

Indigo bluish has auxochromes –OH which bind the dye fast to the cellulose fiber that contains ethereal oxygen together with OH groups, yesteryear hydrogen-bonding.

Mordant Dyes.

This class of dyes convey no natural affinity for the stuff together with are applied to it amongst the help of salts e.g., oxides of aluminum or chromium. These salts are called Mordants. Fiber such every bit cotton fiber is starting fourth dimension treated amongst a mordant together with thence amongst the dye solution. The mordant forms a soluble coordination complex betwixt the fiber together with the dye together with binds the two. The insoluble complex compounds look inwards the cast ‘lakes’ that are fast to calorie-free together with washing. Alizarin is an representative of a mordant dye.

The mordant dyeing is almost suitable for wool together with nylon.

Azoic Dyes (Ingrain Dyes).

In this method of dyeing, the water-insoluble azo dye is produced inwards the stuff itself. The cloth soaked inwards the solution of a coupling reagent-usually a phenol or naphthol. Then it is immersed inwards the solution of an appropriate diazonium salt. The dye that is developed inwards the stuff binds fast to via auxochromes. The azoic dyeing is especially suitable for cotton fiber together with other cellulosic fibers all the same may too hold out utilized for nylon.

Disperse Dyes.

These dyes are insoluble inwards the H2O all the same tin sack be scattered inwards a colloidal cast inwards water. The stuff is immersed inwards the colloidal dispersion of the dye. The fine dye particles are retained into the ‘crystal structure’ of the fabric. Disperse dyes are used amongst modern synthetic fabrics such every bit nylon, orlon, polyesters, together with cellulose acetate.