The Impact of Disperse Dye Thermal Migration on the Color Fastness of Polyester Fibers and Improvement Methods

Polyester fibers, when dyed with disperse dyes using a high-temperature and high-pressure method, undergo varying degrees of color fastness changes after being heat-treated at temperatures above 140°C.

Polyester fibers, when dyed with disperse dyes using a high-temperature and high-pressure method, undergo varying degrees of color fastness changes after being heat-treated at temperatures above 140°C. The color fastness of the dyed fabric can change due to the alteration in the smoothness of the fabric surface and the color shade after heat treatment.

Polyester fiber is a thermoplastic fiber, which means that below its glass transition temperature, it is resistant to deformation under external forces, making it suitable for normal use. The softening point temperature of polyester fibers is between 230°C and 240°C. When the temperature exceeds this range, the fiber begins to lose its orientation, resulting in irreversible deformation. During dyeing and finishing processes, the heat-setting temperature in dyeing and printing factories typically ranges from 180°C to 240°C.

The minimal water solubility of disperse dyes is crucial because only dissolved dye molecules can penetrate the microvoids of polyester fibers and diffuse within them. The tightly packed molecular structure of polyester fibers makes dyeing at room temperature difficult, necessitating dyeing under high-temperature and high-pressure conditions. The process of disperse dye dyeing is illustrated in the following stages:

1. Dispersed state of the dye;  

2. Single molecule dispersal and soluble phase of the dye;  

3. Adsorption of the dye onto the fiber;  

4. Diffusion of dye molecules;  

5. Equilibrium state of dyeing;  

6. Recrystallization of the dye.

The thermal migration phenomenon of disperse dyes after dyeing polyester fibers is the key issue that causes the above-mentioned problems. Thermal migration refers to the movement of disperse dye molecules within the fiber towards the fiber surface when the dyed fabric undergoes high-temperature heat-setting in the post-finishing process. This is influenced by exposure to dry or moist heat, causing the dye to redistribute on the surface of the polyester fiber. As a result, the color fastness of the polyester fabric decreases after heat treatment, leading to changes in color shade and potential staining of other fibers.

I. Factors Affecting Disperse Dye Thermal Migration

1. Depth of shade on polyester fibers

2. Heat-setting temperature

3. Heat-setting time

4. Thermal sublimation properties of the dye

5. Surfactants in auxiliary agents

6. Post-finishing auxiliaries

7. Heat-setting process

II. Improvement Methods

1. Enhance the pre-treatment of polyester fabrics

2. Select disperse dyes with good thermal sublimation fastness and compatible properties

3. Adjust the depth of shade and dye compatibility for additive effects

4. Strengthen the reduction cleaning after dyeing

5. Consider the impact of post-finishing auxiliaries and chemicals on color fastness

6. Apply fixation treatments after dyeing

7. Use a heat-setting process with relatively lower temperatures during post-finishing.

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