According to statistics, the issue of fastness is one of the most frequently asked questions among all dyeing questions.
Dyeing fastness has very high requirements on the quality of dyed and printed fabrics, and the nature of the variation in dyeing state or The degree can be expressed by color fastness. It is related to yarn structure, fabric organization, printing and dyeing method, dye type and external force. Different dyeing fastness requirements will cause great cost differences and quality differences.
6 main textile fastnesses
Dye fastness of normal fabrics Generally, it is required to reach level 3~4 to meet the needs of wearing. The following content summarizes the six main textile fastnesses in dyeing and finishing:
1 Sunlight fastness
Sunlight fastness refers to the degree of discoloration of colored fabrics under the action of 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, with level 8 being the best and level 1 being the worst. 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 Rubbing fastness
The rubbing fastness refers to dyed fabrics The degree of discoloration after rubbing can be divided into dry rubbing and wet rubbing. The rubbing fastness is evaluated based on the staining degree of white cloth, which 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.
3 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, with level 5 being the best and level 1 being the worst. 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.
4 Ironing fastness
Ironing fastness refers to The degree of discoloration or fading that occurs in 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 from 1 to 5, with level 5 being the best and level 1 being the worst. When testing the ironing fastness of different fabrics, the test iron temperature should be selected.
5 Perspiration fastness
Perspiration fastness refers to dyed fabrics Degree of discoloration after exposure to 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.
6 Sublimation fastness
Sublimation fastness refers to dyed fabrics The extent of sublimation phenomena that occur during storage. The sublimation fastness uses a gray grading sample card to evaluate the degree of discoloration, fading and white cloth staining of fabrics after dry heat pressing. It is divided into 5 levels, with level 1 being the worst and level 5 being the best.
How to control various fastnesses
After textile dyeing, the ability of the fabric to maintain its original color can be expressed by testing various dye fastnesses. Commonly used indicators for testing dye fastness include washing fastness, rubbing fastness, sunlight fastness, sublimation fastness, etc. of fabrics.
The better the washing fastness, rubbing fastness, sunlight fastness and sublimation fastness of the fabric, the better the dye fastness of the textile.
The main factors that affect the above-mentioned fastness include two aspects:
The first is the performance of the dye, and the second is the dyeing and finishing Process formulation. Selecting dyes with excellent performance is the basis for improving various dye fastnesses, and formulating reasonable dyeing and finishing processes is the key to ensuring various dye fastnesses. The two complement each other and cannot be neglected.
Washing fastness
The washing fastness of fabrics includes fading fastness Two aspects: strength and color fastness. Generally, the worse the fade fastness of textiles, the worse the stain fastness.
When testing the staining fastness of a certain textile, you can determine the staining of the fiber by testing the staining of the six commonly used textile fibers (these six commonly used textile fibers usually include polyester, Nylon, cotton, acetate, wool or silk, acrylic. Tests on the color fastness of the six fibers are generally completed by qualified independent professional inspection companies. Such inspections are relatively objective and fair)
For cellulose fiber products, the washing fastness of reactive dyes is better than direct dyes. The dyeing processes of insoluble azo dyes, vat dyes and sulfur dyes are more complicated than reactive dyes and direct dyes, so the latter three The washing fastness of the dye is even better.
So, to improve the washing fastness of cellulose fiber products, we must not only choose the correct dye, but also choose the correct dyeing process. Appropriate strengthening of water washing, color fixation and soaping can significantly improve the washing fastness.
For the deep color of polyester fiber, as long as it is fully restored,>
This can not only improve the leveling degree, but also improve the sublimation fastness of dyeing. If the crystallinity of each part inside the fiber is not balanced enough and most of the dye stays in the amorphous area with a relatively loose structure, then after extreme external conditions occur, the dye will be more likely to break away from the amorphous area inside the fiber and sublime to the surface of the fabric. , thereby reducing the sublimation fastness of textiles.
The scouring and mercerization of cotton fabrics, and the pre-shrinking and pre-shaping of polyester fabrics are all processing steps that balance the internal crystallinity of the fiber. The dyeing depth and dye fastness of cotton fabrics that have been scoured and mercerized, and polyester fabrics that have been preshrunk and pre-shaped can be significantly improved.
Strengthening post-processing and washing to remove more floating colors on the surface can also significantly improve the sublimation fastness of the fabric. Appropriately lowering the setting temperature during the setting process can significantly improve the sublimation fastness of the fabric. The problem of reduced fabric dimensional stability due to cooling can be compensated by appropriately reducing the setting speed. When choosing finishing agents, you should also pay attention to the impact of auxiliaries on dye fastness. For example, after using cationic softeners for soft finishing of polyester fabrics, the thermal migration of disperse dyes may cause the disperse dyes to fail the sublimation fastness test. Judging from the temperature type of disperse dyes themselves, high-temperature disperse dyes have better sublimation fastness. </p
