Cellulosic fibres separation methods

A single-bath method can be used if desired. The dyes are dissolved separately and added to the dyebath which already contains an ethylene oxide condensate which acts as an anti-precipitant. The dyebath is adjusted to pH 5 to 5-5 with acetic acid and sodium acetate and the goods are entered at 40 to 45°C (104 to 113°F). A period of 45 minutes is taken to raise the temperature to the boil, at which it is maintained for one hour. Alternatively, the acrylic fibre may be dyed first and then the same liquor is neutralized and the cellulosic fibre is dyed. Application of a cationic fixing agent improves wet fastness of direct dyes but copper after-treatment should be avoided because this can have an adverse effect on the light fastness of the cationic dye. Very good fastness is obtained if, after the acrylic component has been dyed, the cellulosic fibre is brought to shade with vat dyes. 

Klingsberg (jf.S.D.C., 1954, 70, 563) describes a method specially designed for the chromatographic examination of vat dyes. Owing to the insolubility in virtually all solvents of the pigment form, the separation must be carried out in the leuco state. The reduced vat dyes, however, have such a marked affinity for cellulose that paper chromatography must be ruled out, but strips of material made of hydrophobic synthetic fibres, of which polyesters are the best, may be substituted. Rao, Shah, and Venka-... 

Nanofibres can be produced by a number of methods. They can be extracted from natural materials (e.g., cellulose or protein fibres) via physical separation and/or chemical extraction. They can also be produced by means of drawing, template synthesis, phase separation, self-assembly and electrospinning. The details are briefly described below. 

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