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Various textile dyeing fastness and control
According to statistics, the fastness problem is the most frequently asked question in all dyeing questions. Dyeing fastness has high requirements on the quality of dyed and printed fabrics, and the nature or degree of dyeing state variation can be expressed by dyeing fastness. It is related to yarn structure, fabric structure, printing and dyeing method, dye type and external force. Different color fastness requirements will cause great differences in cost and quality. 1. 6 main textile fastnesses 1. Light fastness Light fastness refers to the degree to which colored fabrics are discolored by sunlight. The test method can use sunlight exposure or sunlight exposure. The fading degree of the samples after exposure is compared with the standard color sample, and it is divided into 8 grades, 8 grades are the best, and 1 grades are the worst. Fabrics with poor light fastness should not be exposed to the sun for a long time, and should be dried in a ventilated place. 2. Rubbing fastness Rubbing fastness refers to the degree of fading of dyed fabrics after rubbing, which can be divided into dry rubbing and wet rubbing. The rubbing fastness is based on the staining degree of white cloth as the evaluation principle, which is divided into 5 grades (1~5). The larger the value, the better the rubbing fastness. The service life of fabrics with poor rubbing fastness is limited. 3. Washing fastness Washing or soaping fastness refers to the degree of color change of dyed fabrics after washing with washing liquid. The gray grading sample card is usually used as the evaluation standard, that is, the evaluation is based on the color difference between the original sample and the faded sample. The washing fastness is divided into 5 grades, 5 is the best and 1 is the worst. Fabrics with poor washing fastness should be dry cleaned. If wet cleaning is carried out, more attention should be paid to the washing conditions, such as the washing temperature should not be too high, and the washing time should not be too long. 4. Ironing Fastness Ironing fastness refers to the degree of discoloration or fading of dyed fabrics when ironed. The degree of discoloration and fading is evaluated by the staining of other fabrics by the iron at the same time. Ironing fastness is divided into 1 to 5 grades, 5 is the best and 1 is the worst. When testing the ironing fastness of different fabrics, the temperature of the test iron should be selected. 5. Perspiration fastness Perspiration fastness refers to the degree of color fading after dyed fabrics are soaked in sweat. The perspiration fastness is not the same as the artificially prepared perspiration components, so it is generally not only measured separately, but also evaluated in combination with other color fastnesses. Perspiration fastness is divided into 1 to 5 grades, the larger the value, the better. 6. Sublimation fastness Sublimation fastness refers to the degree of sublimation that occurs in dyed fabrics during storage. The sublimation fastness is graded by gray scale sample card to evaluate the discoloration, fading and white cloth staining of the fabric after dry hot pressing. The dyeing fastness of normal fabrics generally requires grades 3 to 4 to meet the needs of wearing. 2. How to control various fastnesses After dyeing of textiles, the ability of fabrics to maintain the original color can be expressed by testing various dyeing fastnesses. Commonly used indicators for detecting dyeing fastness include washing fastness, rubbing fastness, light fastness, sublimation fastness and so on. The better the washing fastness, rubbing fastness, light fastness and sublimation fastness of the fabric, the better the dyeing fastness of the textile. The main factors affecting the above-mentioned fastness include 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 the dyeing fastness, and the formulation of a reasonable dyeing and finishing process is the guarantee The key to each color fastness, the two complement each other and cannot be neglected. Washing fastness The washing fastness of the fabric includes two aspects: fading fastness and staining fastness. Generally, the worse the color fastness of textiles, the worse the color fastness. When testing the staining fastness of a certain textile, the staining of the fiber can be determined by examining the staining of the fiber to the six commonly used textile fibers (the six commonly used textile fibers usually include polyester, nylon, cotton, etc.). , acetate, wool or silk, acrylic. The color fastness test of the six fibers is generally completed by a qualified independent professional inspection company, and this test is relatively objective and fair.) For cellulose fiber products It is said that the washing fastness of reactive dyes is better than that of direct dyes. The dyeing process of insoluble azo dyes, vat dyes and sulfur dyes is more complicated than that of reactive dyes and direct dyes, so the washing fastness of the latter three dyes is better. Therefore, to improve the washing fastness of cellulose fiber products, it is necessary not only to choose the correct dye, but also to choose the correct dyeing process. Appropriate strengthening of washing, strengthening of color fixing and soaping can significantly improve the washing fastness. For polyester fiber with deep color and luster, as long as it is fully restored and cleaned, the washing fastness of the fabric after dyeing can meet customer requirements. However, since polyester fabrics are mostly softened by padding cationic silicone softeners to improve the fabric feel,At the same time, the anionic dispersants in disperse dyes may diffuse to the surface of the fibers due to the thermal migration of the dyes when the polyester fabrics are set at high temperature, so the washing fastness of the polyester fabrics with dark colors may be unqualified after setting. This requires that not only the sublimation fastness of disperse dyes, but also the thermal migration resistance of disperse dyes should be considered when selecting disperse dyes. There are many ways to test the washing fastness. According to different testing standards, the washing fastness of textiles will be tested, and the conclusion will be drawn.
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