What is disperse dyes? Characteristics of disperse dyes.

Disperse dyes

Disperse dyes are small polar molecules, usually containing anthraquinones or azo groups that do not charge the cationic or anionic groups within the structure. It should be dissolved in a small amount of water and spread on the dye with the help of a surfactant. As a small amount of dissolved dye is scattered in the fiber, the excess dye dispersed in the solution dissolves until the dye is almost completely exhausted in the dyed fiber. The lightfastness and wash fastness of these dyes are generally good but there has been a problem with fume fading from some of the dispersed dyes.

It is non-ionic, water-insoluble, and does not react chemically with nylon. Dyeing occurs regardless of the −COOH or −NH2 group, but the dyes are held by the van der Wales balls and H-bonds by the fan.

Disperse dyes are supplied as a powder and liquid form products. Powder dyes contain 40-60% dispersing agents but liquid formulas contain between 10-30%. Formaldehyde concentration products and lignin sulfonates are widely used for this purpose. Some dispersed dyes contain organic halogen, but they are not expected to be found in equal amounts after treatment with unclean water due to their active composition.

Characteristics of disperse dyes

i. Disperse dyes are molecularly dispersed in the liquor at the time of dyeing.

ii. It is very less soluble in water which makes fine dispersion.

iii. It crystalline material with a high melting point (>150°C).

iv. The saturation level of pure disperse dyes in the fiber is relatively high.

v. It has fair to good lightfastness and a lightfastness rating of 4-5.

vi. Washing fastness is moderate to good, rating of 3-4.

vii. Its good sublimation power due to its stable electron arrangement.

viii. Disperse dyes are non-ionic in nature.

ix. The color will fade due to heat application on dispersed dye.

x. In the presence of nitrous oxide, textile material dyed with certain blue and violet disperse dyes with anthraquinone dye structure will be faded.

xi. It is used for dyeing hydrophobic thermoplastic fibers including nylon, polyester, acrylic, and other synthetics.

xii. The general structure of dispersed dyes is small and planar, and it contains polar functional groups like hydroxyalkyl, –NO2, and –CN.

xiii. It is characterized by the absence of solubilizing groups and low molecular weight.

xiv. The good migration properties of disperse dyes result in problem-free level dyeing.

xv. The zeta potential of commonly used disperse dyes ranges from − 30 to -80 mV.

xvi. These dyes have a bulk density of 0.4–0.6, a pH value of 7.0–9.0 (10 g/L water)

xvii. It is usually containing anthraquinone or azo groups which do not have charged cationic or anionic groups within the structure.

xviii. It is unsuitable for human skin because of the allergic effect.

xix. It is known that this kind of sensitive dispersed dye is still used in items such as stockings and tights, socks, leggings, blouses, and underwear.

xx. It does not require any specific fixing agent because the dyes become substantive to the fibers through phase changes initiated by temperature.