Disperse dye is non-ionic dye. They are insoluble in water. Effect of Temperature & pH on disperse dye plays an important role. While dyeing with Disperse dye, the dyeing parameters are a crucial factor. If the dyeing parameters are not maintained properly, uneven dyeing can take place. In some case, no dyeing may occur. This content is all about the effect of temperature and pH on disperse dye. this dye is particularly used with a dispersing agent for polyester dyeing. With Disperse dye, polyester can be dyed in three methods. Polyester can be dyed in carrier method with dye carriers, high temperature high pressure method and pad-thermosol method.
Effect of Temperature:
While dyeing with Disperse dye, temperature is an important factor. Polyester is a hydrophobic fiber which is dyed with disperse dye. In normal room temperature, the dye can’t get into the fiber polymer. So, either carrier is used or high temperature is required for this purpose. For the swelling of fiber high temperature is needed. At room temperature they are insoluble in water but only has limited solubility at higher temperature. But with carrier, the dyeing of disperse dye is carried out at only 85-90℃. In case of, thermosol method, temperature is kept again higher. Here, 180-220℃ temperature is maintained but the fabric must be kept for a little time. Otherwise, dye sublimation and fabric strength loss can take place. The solubility of Disperse dye increases with increasing temperature.
Effect of pH:
For dyeing with disperse dye acidic medium is required. Many disperse dyes undergo degradation if pH is uncontrolled. Some disperse dyes have hydrolysable groups in their molecules, such as ester group which makes them particularly sensitive to hydrolysis, especially in alkaline medium. The hydrolyzed form of dye could be of different shade and in some cases of different affinity for fibers compared to un-hydrolyzed dye. In order to minimize dye hydrolysis dyeing is carried out at 5-6.
Disperse dye is an important dye class for synthetic fibers. Dyeing parameters should be crucially controlled for dyeing with disperse dye.