Disperse dyes have a high degree of association in water (especially in high-temperature water) and exist in the form of dye aggregates. However, the dye aggregate can only be adsorbed on the surface of the fiber and cannot diffuse into the interior of the polyester fiber. Only single molecules of dye in dissolved state can enter.
Therefore, the dye aggregate must be "depolymerized" to gradually release the single molecule of the dye before it can be gradually dyed.
However, the solubility of disperse dyes is extremely low, so the release rate of single dye molecules is slow. Therefore, it takes a certain amount of time to achieve the highest color balance (especially for dark colors).
If the thermal insulation dyeing time is too short, it will make the dye "depolymerization" inadequate, which not only affects the color depth, but also reduces the color fastness due to too much floating color, and even stains such as color points and stains.