For friends who buy digital printers, many people are most concerned about color fastness. So what exactly is color fastness? In fact, color fastness belongs to a branch of the color characteristics of printed fabrics. Today, SUBLISTAR will introduce to you in detail what is color fastness for digital printing?
Color fastness
Fabric printing is a surface treatment material. Except for thin fabrics, general printing dyes rarely penetrate into the deep fabric structure. Washing or dry cleaning and subsequent drying, as well as daily wear and tear caused by abrasion, will always cause the fabric surface of the fiber to fall off. Lighten the surface of the fabric or expose uncolored fibers, causing the fabric to fade.
Sublimation is a phase change process from solid phase to gas phase without entering the liquid phase.
In addition to light fastness, sublimation printing fastness may be the most important requirement for dyed polyester. The migration behavior and wet fastness of disperse dyes on polyester are closely related to their reaction to heat treatment.
Adequate high-temperature fastness is essential so that the dyed material will be able to withstand the conditions encountered at high temperatures.
1. Heat setting
2. Durable pleating
3. Ironing or compacting the goods during the garment process.
4. The finishing process involving high temperature.
5. Thermal fixing of printed matter.
Poor sublimation fastness causes the following problems
1. Change the original shadow
2. The contrasting color fabric is dyed on adjacent fibers.
3. In the thermal fixing of printed products, the color printing volume and fixing rate are low.
4. Dyeing of polyester sewing thread dyed after sewing and embroidery of contrasting color sewing and embroidery products.
5. Cross staining during storage.
How to avoid problems caused by poor sublimation printing fastness?
Since the problem of poor sublimation is related to the polarity of the substation group in the dye molecule, it is recommended to take the following steps to avoid this problem:
1. Preheat and set most fabrics before dyeing.
2. Choose the dyes carefully so that the yarns of all components have satisfactory fastness in the color/contrast color design, and the fabric is heat-set.
3. Choose dark high sublimation dyes, dark medium/low sublimation dyes.
4. The sublimation fastness is affected by the dyeing conditions and the dyeing cycle, so the dyeing cycle must be optimized to obtain the best sublimation fastness.
How to test the sublimation fastness of disperse dyes?
The sublimation fastness of disperse dyes is usually tested for dyeing and color change, at 180℃/210℃ for 30 seconds, and graded with a gray scale of 1-5.
Disperse dyes become molten or sublimated rather than decomposed when heated to 150-230 degrees, that is, they are easily vaporized from the solid state in heated dry air. The sublimation properties are related to the polarity of the substituents. For the preparation of dyes, disperse dyes with different sublimation fastnesses for different purposes can be prepared according to various requirements. Polyester fibers and acetate fibers dyed with disperse dyes may have color fastness problems during the heat setting process or other finishing processes. This is due to poor sublimation color fastness or dry heat color fastness. Due to poor sublimation fastness, polyester fiber or acetate fiber garments dyed with disperse dyes may show original color change or discoloration. The dyeing or printing process setting of polyester fiber is closely related to the sublimation fastness of disperse dyes, because the thermal fixation temperature directly affects the coloring rate and fixation rate. For the application of dyes, items and equipment must have sublimation fastness. The sublimation fastness of disperse dyes is also related to the type of textile. In order to prevent the fibers of the colored woven fabric from contaminating each other during the heat setting process, dyes with high sublimation fastness must be selected. The sublimation fastness can also be expressed by the temperature at which the dye sublimates, so the application range of the dye at different heat setting temperatures can be distinguished. Dyes with high sublimation fastness do not respond to color depth; try to use dyes with lower sublimation fastness in light or medium shades to ensure that it has no effect on heat setting. BASF uses the contact heat value to indicate the heat setting fastness of disperse dyes. If the contact heat value is less than 40, the dye is not suitable for heat setting; if the contact heat value is between 40 and 50, the dye has a medium heat fixation fastness If the contact heat value is higher than 50, the dye has a higher color fastness to heat fixation.
