The use of acid dyes on nylon to produce dyeings of good washing fastness invariably involves the risk of barré because dyes of poor migration do not evenly dye filaments with chemical and physical variations. This risk is almost absent when using disperse dyes. The consequence of their good migration during dyeing, however, is poor to moderate wet fastness, especially in heavy shades. The dyeing of nylon with disperse dyes is therefore limited mainly to pale shades for lingerie fabrics and sheer hose that do not require repeated or severe washing. Disperse dyes on nylon are also more sensitive to fading by ozone and nitrogen dioxide. They are, however, economical and easy to apply.
Most nylon filaments are oriented by drawing but both undrawn and partially oriented yarns can be dyed with disperse dyes. With increasing draw ratio, the increased polymer chain orientation decreases the rate of dyeing (decreased fibre accessibility) but not the extent of dye absorption at equilibrium (unchanged fibre availability). It is only at the very high draw ratios typical of strong industrial yarns that the equilibrium dye absorption decreases. Uniform drawing of filaments is essential. Accessibility differences in dyeing can be minimised provided that the selected dyes and conditions are conducive to levelling. Disperse dyes on nylon are much better in this respect than acid dyes.
Dyeing of nylon involve with two steps
Preparation of nylon for dyeing
Application of disperse dyes to nylon
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