Influence of levelling agent on dyeing affinity.

Dyeing affinity depends on the structure and properties of dyes and fibers. When the structure and properties of dyes and fibers are close to each other, the two are easy to dissolve and the dyeing affinity is higher. Secondly, it is related to dyeing process conditions, especially temperature. Dyeing temperature increases, dyeing saturation value increases, while adsorption isotherm slope decreases, that is, affinity decreases with the increase of temperature. The reason is that the solubility of disperse dyes in water increases faster with the increase of temperature than in fibers. The dyeing saturation value of disperse dyes also varies with the thermal setting conditions before dyeing.
In addition, affinity is also affected by other components in the dye bath, such as dispersants, levellers and carriers. If these auxiliaries increase the solubility of dyes in the dye solution, the distribution coefficient will decrease and the affinity of dyes to fibers will decrease. In fact, it is often found that the adsorption isotherm of disperse dyes is not a straight line, which may be due to the complex state of dyes in solution. The state and true dissolution of dyes in the amorphous region of the fiber are also different: they may undergo localization adsorption, and the interaction between dye molecules may make them aggregate in the void of the fiber, resulting in the adsorption isotherm deviating from the linear characteristics.