After the textile has been dyed, the ability of the fabric to retain its original color can be expressed by testing different color fastnesses. Commonly used indicators for color fastness testing are wash fastness, rub fastness, light fastness, sublimation fastness, etc. of fabrics. The better the washing fastness, rub fastness, light fastness and sublimation fastness of the fabric, the better the dye fastness of the textile. The main factors affecting the above speed are two aspects: the first is the performance of the dye, and the second is the formulation of the dyeing and finishing process. The selection of dyes with excellent performance is the basis for improving color fastness, and the formulation of a reasonable dyeing and finishing process is the key to ensure color fastness. The two complement each other and cannot be neglected.
Washing fastness:
The washing fastness of the fabricf includes two aspects: fade resistance and stain resistance. In general, the worse the color fastness of textiles, the worse the stain resistance. When testing the color fastness of a particular textile, the coloration of the fiber can be assessed by checking the coloration of the fiber on the six commonly used textile fibers. These six commonly used textile fibers usually include polyester, nylon, cotton, acetate, wool or silk, and acrylic. The test of the color fastness of the six fibers is generally carried out by a qualified independent professional inspection company, and such test is relatively objective and fair.
For cellulose fiber products, the wash fastness of reactive dyes is better than that of direct dyes, and the dyeing process of insoluble azo dyes, vat dyes and sulfur dyes is more complicated than reactive dyes and direct dyes, so the last three The wash fastness of the dyeis more excellent. Therefore, in order to improve the wash fastness of cellulose fiber products, it is necessary not only to choose the right dye, but also to choose the right dyeing process. Appropriately strengthening water washing, strengthening color fixation and soaping can significantly improve the washing fastness.
For the deep color of polyester fiber, as long as the fabric is fully recovered and washed, the wash fastness of the dyed fabric can meet customer requirements. However, since polyester fabrics are usually softened by filling in cationic silicone softeners to improve the feel of the fabric, and at the same time, anionic dispersants in disperse dyes can diffuse onto the fiber surface due to thermal migration of dyes when polyester fabrics are set at a high temperature. , so deep The washing fastness of the polyester fabric with strong color and gloss may be unsuitable after setting. This is not required alreadyborrow the sublimation fastness of disperse dyes to be considered when selecting disperse dyes, but also the thermal migration resistance of disperse dyes.
There are many methods to test the wash fastness of textiles. Different conclusions will be drawn when testing the wash fastness of textiles according to different test standards. When foreign customers propose specific wash fastness indicators and specific testing standards can be proposed, it will be conducive to smooth communication between the two sides. Although strengthening washing and post-treatment can improve the washing fastness of fabrics, it will also increase the emission reduction of paint factories. Find a variety of high-efficiency detergents, rationally formulate the painting and finishing process, and strengthen the research of short process processes, which can not only improve production efficiency, but also contribute toto energy savings and emission reduction.
Sublimation speed:</strong
As far as disperse dyes are concerned. Since the dyeing principle of polyester fiber is different from other dyes, the sublimation fastness can directly express the heat resistance of dispersed dyes. For other dyes, testing the dye\'s iron fastness has the same meaning as testing the dye\'s sublimation fastness. The sublimation fastness of the dye is not good. In the dry heat state, the solid state dye is easy to detach directly from the inside of the fiber in a gas state. So in that sense, the sublimation fastness of dyes can also indirectly express the fastness to ironing of fabrics.
In order to improve the sublimation rate of dyes, we should consider the following aspects. The first is the choice of dye. The relative molecular weight is relatively large and the basic structurer of the dye is similar or similar to the fiber structure, which can improve the sublimation rate of the textile. The second is improving the painting and finishing process. Completely reduce the crystallinity of the crystalline part in the macromolecular structure of the fiber, increase the crystallinity of the non-crystalline region, ensure that the crystallinity of each region in the fiber is consistent, and let the dye enter the fiber, and the combination with the fiber is more uniform. This can not only improve the degree of dyeing, but also improve the sublimation rate of dyeing. If the crystallinity of each component in the fiber is not balanced enough, most of the dye remains in the non-crystalline region with a relatively loose structure, and after the extreme state of external conditions, the dye is also more easily detached from the non- crystalline - crystalline region in the fiber and sublimate afterto the surface of the fabric, reducing the sublimation rate of textiles.
Sanding and mercerizing cotton fabrics, pre-shrinkage and pre-curing full polyester fabrics are all processing steps to balance the crystallinity in the fibers. The paint depth and color fastness of the sanded and mercerized cotton fabric and the pre-shrunk and pre-set polyester fabric can be clearly improved. Strengthening post-treatment and washing to remove more floating color on the surface can also greatly improve the sublimation rate of the fabric. Properly lowering the curing temperature during the curing process can significantly improve the sublimation rate of the fabric. The problem of reduced dimensional stability of fabrics due to cooling. This can be compensated for by appropriately reducing the speed of the stereotyped vehicle. When choosing finishing means shouldwe also pay attention to the influence of additives on color fastness. For example, after using a cationic fabric softener in softening polyester fabrics, the sublimation fastness of disperse dyes may fail due to thermal migration of disperse dyes. From the perspective of the temperature type of the disperse dye itself, the high temperature sublimation resistance of the disperse dye is better.
Sunlight fastness:
Sunlight has a wave-particle duality, and sunlight transmitting energy in the form of photons has a strong influence on the molecular structure of dyes . When the basic structure of the chromogenic part of the dye structure is destroyed by photons, the color of the light emitted from the dye chromophore will change, usually the color will lighten until it is colorless. The clearer the color change of the dyeunder sunlight, the worse the lightfastness of the dye.
To improve the lightfastness of dyes, dye manufacturers have adopted many methods. Increase the relative molecular weight of the dye, increase the probability of internal complexing of the dye, and increase the co-leveling of the dyeSurface and conjugate system length can relatively improve the lightfastness of dyes. For phthalocyanine dyes that can achieve grade 8 lightfastness, adding appropriate metal ions during the dyeing and finishing process to form complexes in the dye molecules can greatly improve the clarity and lightfastness of the dyes. For textiles, choosing dyes with better lightfastness is the key to improving the lightfastness of the product. The effect of improving the lightfastness of textiles by changing the dyeing and finishing process is not obvious.
Abrasion resistance:
The rub resistance of the fabric is the same as the washing resistance, and also includes two aspects, one is dry rub resistance and the other is wet rub resistance. Obtain the physical sample map of the dry rub resistance and wet rub resistance of the fabric through the detection of the fabric rub resistance test instrument, and check the dry rub resistance and wet rub resistance of the textile by comparing the fabric color change sample map and the color sample map Very convenient. Usually, when testing the rub resistance of deep-colored textiles, the dry rub resistance degree is generally about 1 degree higher than the wet rub resistance degree. For example, take the direct dyeing of cotton fabric black. Although it is effectively fixed, its dry rub resistance and wet rub resistance are not very high, and it sometimes cannot meet customer requirements. To improve the rub resistance, reactive dyes, vadyes and insoluble azo dyes used for dyeing. Strengthening dye selection, strengthening color fixation treatment and soaping are effective measures to improve the rub resistance of textiles.
In order to improve the wet rub resistance of deep-colored cellulose fiber products, special additives can be selected that can improve the wet rub resistance of textiles, and the product can be greatly improved by filling the special additives when the finished product is formed wet rub resistance. For dark-colored chemical fiber filament products, the wet rub resistance of the product can also be improved by adding a small amount of fluorine-containing water repellent when the final product is formed. When acid dyes are used to dye deep colored polyamide fibers, the wet rub resistance of deep colored nylon fabrics can be significantly improved by using aspecial fixing agent for nylon. For sanded dark-colored products, when testing their wet rub resistance, the level of wet rub resistance can be lowered because the shedding of short fibers on the fabric surface of sanded products is more apparent than for other products.
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