Insufficient dye fastness is a fatal flaw for cotton, polyester-cotton and other fabrics. Different dye fastness requirements will cause great cost differences. Therefore, many fabric manufacturers often require dyeing factories to use lower-cost dyes when dyeing. Domestic dyes are used to reduce dyeing costs, which often brings about a series of problems in dye fastness.
General concepts of color fastness
Dye fastness is a quality requirement for dyed and printed fabrics. Because dyed fabrics may become discolored or discolored due to light, sweat, friction, washing, ironing, etc. during wearing and storage, thus affecting the appearance of the fabric or clothing. The nature or degree of variation in dyeing state can be expressed by dye fastness. The dye fastness of fabric is related to yarn structure, fabric structure, printing and dyeing method, dye type and external force. It can be divided into light fastness, washing or soaping fastness, rubbing fastness, perspiration fastness, ironing fastness and sublimation fastness, etc.
1. Sunlight fastness
Sunlight fastness refers to the degree to which colored fabrics change color due to sunlight. The test method can be either sunlight exposure or insolation machine exposure. The fading degree of the sample after exposure is compared with the standard color sample. It is divided into 8 levels, 8 is good, and 1 is poor. Fabrics with poor sun fastness should not be exposed to the sun for a long time and should be placed in a ventilated place to dry in the shade.
2. Washing fastness
Washing or soaping fastness refers to the degree of color change of dyed fabrics after being washed with detergent. The gray graded sample card is usually used as the evaluation standard, that is, the color difference between the original sample and the sample after fading is used for evaluation. Washing fastness is divided into 5 levels, level 5 is good and level 1 is poor. Fabrics with poor washing fastness should be dry cleaned. If wet cleaning is performed, extra 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.
3. Rubbing fastness
Rubbing fastness refers to the degree of color fading of dyed fabrics after rubbing, and can be divided into dry rubbing and wet rubbing. The rubbing fastness is evaluated based on the staining degree of white cloth, and is divided into 5 levels (1~5). The larger the value, the better the rubbing fastness. Fabrics with poor rubbing fastness have a limited service life.
4. Perspiration fastness
Perspiration fastness refers to the degree of color fading of dyed fabrics after being immersed in sweat. Since the composition of artificially prepared sweat is different, the perspiration fastness is generally not only measured separately, but also combined with other color fastnesses for assessment. The perspiration fastness is divided into levels from 1 to 5, with the higher the value, the better.
5. 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 levels 1 to 5, with level 5 being good and level 1 being poor. When testing the ironing fastness of different fabrics, the test iron temperature should be selected.
6． Sublimation fastness
Sublimation fastness refers to the degree of sublimation phenomenon that occurs in dyed fabrics during storage. The sublimation fastness uses a gray grading sample card to evaluate the degree of discoloration, fading and white cloth staining of the fabric after dry heat pressing. It is divided into 5 levels, 1 level is poor, and 5 level is good.
The dye fastness of normal fabrics generally needs to reach level 3 to 4 to meet the needs of wearing.
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