How to solve the problem of color fastness?

According to statistics, the fastness problem is one of the most frequently asked questions among all dyeing industry.below technical experience for us maybe can help you whatever you use acid dye, direct dye, vat dye, suphur dye, basic dye etc..

Dyeing fastness has high requirements on the quality of dyed and printed fabrics. The nature or degree of variation in dyeing state can be expressed by dyeing fastness. It is related to yarn structure, fabric structure, printing and dyeing methods, type of dyes and external force. Different dyeing fastness requirements will cause great cost differences and quality differences.

there are 6 main textile fastness problem

The dyeing fastness of normal fabrics generally requires 3 to 4 levels to meet the needs of wearing. The following summarizes the six main types of textile fastness in dyeing and finishing:

1-day fastness

Sunlight fastness refers to the degree of discoloration of colored fabrics affected by sunlight. The test method can use sunlight or sunlight to compare the discoloration degree of the sample after exposure with the standard color sample. It is divided into 8 grades, 8 is the best, and 1 is the worst. Fabrics with poor fastness to sunlight should not be exposed to the sun for a long time, and it should be dried in a ventilated place.

2 rubbing fastness

The rubbing fastness refers to the degree of discoloration of dyed fabrics after rubbing, and can be divided into dry rubbing and wet rubbing. The rubbing fastness is based on the degree of staining of white cloth. It is divided into 5 levels (1 to 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 a washing solution. The gray grading sample card is usually used as the evaluation standard, that is, the judgment is based on the color difference between the original sample and the faded sample. Washing fastness is divided into 5 grades, grade 5 is the best and grade 1 is the worst. Fabrics with poor washing fastness should be dry-cleaned. If wet washing is performed, double attention should be paid to the washing conditions, such as the washing temperature should not be too high and the time should not be too long.

4 Ironing fastness

Ironing fastness refers to the degree of discoloration or discoloration of dyed fabrics during ironing. The degree of discoloration and discoloration is evaluated by the iron staining on other fabrics at the same time. Ironing fastness is divided into 1 ~ 5 grade, grade 5 is the best, grade 1 is the worst. When testing the ironing fastness of different fabrics, the temperature of the test iron should be selected.

5 Sweat fastness

Sweat fastness refers to the degree of discoloration of dyed fabrics after being soaked in sweat. Sweat fastness Due to the different ingredients of artificially formulated sweat, it is generally tested in combination with other color fastness in addition to being measured separately. The sweat 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. Sublimation fastness The gray grading sample card is used to evaluate the degree of discoloration, discoloration and staining of white cloth after dry and hot pressing. It is divided into 5 grades.

How to control various fastness?

After the textile is dyed, the ability of the fabric to maintain the original color can be expressed by testing various dyeing fastnesses. Commonly used indicators for testing dyeing fastness include fabric washing fastness, rubbing fastness, sun fastness, sublimation fastness, and the like.

The better the washing fastness, rubbing fastness, sun fastness and sublimation fastness of the fabric, the better the dyeing fastness of the textile.

The main factors affecting the above 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 fastness of various dyeings. The development of a reasonable dyeing and finishing process is the key to ensuring the fastness of each dyeing.

Wash fastness

The washing fastness of the fabric includes two aspects of fastness to discoloration and fastness to staining. Generally, the worse the color fastness of textiles is, the worse the color fastness is.
When testing the color fastness of a certain textile, you can determine the staining of the fiber by checking the staining of the six types of textile fibers (the six commonly used textile fibers usually include polyester, nylon, , Acetate, wool or silk, acrylic. The test of the six types of fiber staining fastness is generally completed by a qualified independent professional inspection company, such inspection has relative objective impartiality)
For cellulose fiber products, the washing fastness of reactive dyes is better than direct dyes. The dyeing process of insoluble azo dyes, vat dyes and sulfur dyes is more complicated than reactive dyes and direct dyes. Degree is more excellent.

Therefore, to improve the washing fastness of cellulose fiber products, we must not only choose the correct dye, but also choose the correct dyeing process. Properly strengthening the washing, fixing and soaping can significantly improve the washing fastness.

For the deep color of polyester fiber, as long as the reduction and washing are relatively sufficient, the washing fastness after dyeing the fabric can meet customer requirements. However, because polyester fabrics are mostly softened by padding cationic silicone softener to improve the feel of the fabric, and the anionic dispersant in the disperse dye may diffuse to the surface of the fiber due to the thermal migration of the dye when the polyester fabric is set at high temperature, it is deep. After washing, the polyester fabric with strong color and luster may be unqualified for washing fastness.
This requires that when selecting a disperse dye, not only the fastness to sublimation of the disperse dye, but also the heat transfer resistance of the disperse dye be considered. There are many methods for testing the washing fastness. Testing the washing fastness of textiles according to different testing standards will lead to different conclusions. When foreign customers propose specific washing fastness indicators, if they can provide specific testing standards, it will be conducive to smooth communication between the two parties. Although enhanced washing and post-treatment can improve the washing fastness of the fabric, it will also increase the emission reduction of the dyeing factory.

Finding some efficient detergents, rationally formulating the dyeing and finishing process, and strengthening the research on short-process processes can not only improve production efficiency, but also contribute to energy conservation and emission reduction.

Rubbing fastness

The rubbing fastness of the fabric is the same as the washing fastness, and it includes two aspects:

One is dry rubbing fastness and the other is wet rubbing fastness.

The physical sample cards of the dry and wet rubbing fastness of the fabric are obtained through the test of the fabric rubbing fastness test instrument. The dry rubbing fastness and wet rubbing fastness of the textile will be checked against the fabric discoloration and staining sample cards. Very convenient.

Usually when testing the rubbing fastness of deep-colored textiles, the level of dry rubbing fastness is generally about 1 level higher than that of wet rubbing fastness.

Take the direct dyeing of cotton fabric black as an example. Although it has been effectively fixed, the dry rubbing fastness and wet rubbing fastness grades will not be very high, and sometimes it will not meet customer requirements. In order to improve the rubbing fastness, reactive dyes, vat dyes and insoluble azo dyes are mostly used for dyeing. Strengthening dye selection, color fixing and soaping are effective measures to improve the rubbing fastness of textiles.

In order to improve the wet rubbing fastness of deep-colored cellulose fiber products, you can choose an additive that can improve the wet rubbing fastness of textiles. The wet rubbing fastness of the product can be significantly improved by padding special additives when finalizing the finished product degree.

For dark products of chemical fiber filaments, we can also add a small amount of fluorine-containing water-repellent agent to the finished product to improve the wet rubbing fastness of the product.

When acid dyes are used to dye deep polyamide fiber, the use of a special nylon fixing agent can significantly improve the wet rubbing fastness of the nylon fabric.

For the dark-bristled products of sanding, when testing the wet rubbing fastness, the short fiber shedding on the fabric surface of the sanding products will be more obvious than other products, so the level of wet rubbing fastness may be reduced.

Sun fastness

Sunlight has wave-particle duality. Sunlight that transfers energy in the form of photons has a strong impact on the molecular structure of dyes. When the basic structure of the color-emitting part of the dye structure is destroyed by photons, the color of the light emitted by the dye color body will change, usually the color will become lighter until it is colorless. The more obvious the color change of the dye is under the sun, the worse the sun fastness of the dye is.

In order to improve the sun fastness of dyes, dye manufacturers have taken many measures. Increasing the relative molecular mass of the dye, increasing the chance of internal complexing of the dye, increasing the coplanarity of the dye and the length of the conjugated system can all relatively improve the fastness of the dye to sunlight.

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