. Six main textile fastness

1. Light fastness

Light fastness refers to the degree of discoloration of colored fabrics by sunlight. The test method can be sun exposure or daylight 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 the best, and 1 is the worst. Fabrics with poor light 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

Rubbing fastness refers to the degree of discoloration of dyed fabrics after rubbing, which can be divided into dry rubbing and wet rubbing. The rubbing fastness is evaluated based on the degree of white cloth staining, and it is divided into 5 levels (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. Usually, the gray graded sample card is used as the evaluation standard, that is, the color difference between the original sample and the faded sample is used for judgment. The washing fastness is divided into 5 grades, grade 5 is the best and grade 1 is the worst. The fabrics with poor washing fastness should be dry-cleaned. If they are wet-washed, the washing conditions should be paid more attention to, 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 fading of dyed fabrics during ironing. The degree of discoloration and fading is evaluated by the iron’s staining of other fabrics at the same time. Ironing fastness is divided into grades 1 to 5, with grade 5 being the best and grade 1 being the worst. When testing the ironing fastness of different fabrics, the temperature of the iron used for the test should be selected.

5. Perspiration fastness

Perspiration fastness refers to the degree of discoloration of dyed fabrics after being immersed in sweat. The perspiration fastness is not the same as the artificially prepared sweat composition, so it is generally evaluated in combination with other color fastnesses in addition to a separate measurement. The perspiration fastness is divided into 1~5 grades, the larger the value, the better.

6. Sublimation fastness

Sublimation fastness refers to the degree of sublimation of dyed fabrics in storage. The sublimation fastness is evaluated by the gray graded sample card for the degree of discoloration, fading and staining of the white cloth after the dry hot pressing treatment. There are 5 grades, 1 is the worst, and 5 is the best. The dye fastness of normal fabrics is generally required to reach level 3~4 to meet the requirements of wearing.

, How to control various fastness

The ability of a textile to retain its original color after dyeing can be demonstrated by testing for various color fastness. Commonly used indicators to test dyeing fastness include fabric washing fastness, rubbing fastness, sun fastness, sublimation fastness and so on. The better the fastness to washing, rubbing, sun and sublimation of the fabric, the better the dye fastness of the fabric.

There are two main factors affecting the above fastness:

The first is the properties of the dye

The second is the formulation of dyeing and finishing process

The selection of dyes with good properties is the basis to improve the dyeing fastness, and the formulation of reasonable dyeing and finishing technology is the key to ensure the dyeing fastness. The two complement each other and cannot be balanced.

Washing fastness

The washing fastness of fabric includes two aspects: fading fastness and staining fastness. Generally, the worse the fading fastness of a textile, the worse the staining fastness.

When testing the color fastness of a textile, you can determine the color staining of the fiber by testing the color staining of the fiber on the six commonly used textile fibers (the six commonly used textile fibers usually include polyester, nylon, cotton, acetate, wool or silk, acrylic fiber. About six fibers stained color fastness test generally by a qualified independent professional inspection company to complete, this test has a relatively objective impartiality) for cellulose fibre products, washing fastness of reactive dyes is better than the direct dye, insoluble azo dyes and VAT dye and sulfur dye dyeing process relative to the reactive dyes and direct dyes is more complex, so the back three more excellent washing fastness of dye. Therefore, to improve the wash fastness of cellulose fiber products, it is not only necessary to choose the right dye, but also to choose the right dyeing process. Appropriate strengthening of washing, fixing and soaping can obviously improve the wash fastness.

As for the deep concentrated color of polyester fiber, as long as the fabric is fully reduced and cleaned, the washing fastness after dyeing can meet the customer’s requirements. But because most of polyester fabric by pad cationic organic silicon softener complete finishing to improve the fabric feel soft, at the same time, the anion sex in disperse dye dispersants for dyes in polyester fabric with high temperature to finalize the design that may heat transfer and diffusion in the fiber surface, so the deep colour polyester fabric shape after washing fastness could be unqualified. This requires that the selection of disperse dyes should not only consider the sublimation fastness of the disperse dyes, but also consider the heat transfer of the disperse dyes. There are many ways to test the wash fastness of textiles, according to different testing standards to test the wash fastness of textiles, we will get the conclusion of the department.

When foreign customers put forward specific washing fastness indexes, if they can put forward specific testing standards, it will be conducive to smooth communication between the two sides. Enhanced washing and post-treatment can improve the wash fastness of fabric, but also increase the reduction rate of dyeing factory. Finding some efficient detergents, reasonably formulating the dyeing and finishing process, and strengthening the research on short-flow process can not only improve production efficiency, but also contribute to energy saving and emission reduction.

Friction fastness

The rub fastness of the fabric is the same as the wash fastness, which also includes two aspects:

One is dry rub fastness and the other is wet rub fastness. It is very convenient to check the dry rubbing fastness and wet rubbing fastness of textile by comparing with the color changing sample card and the color staining sample card. Generally, the grade of dry rub fastness is about one grade higher than that of wet rub fastness when inspecting the rub fastness of textiles of deep concentrated color. Direct dye dyed cotton fabric black as an example, although through effective color fixation treatment, but dry rubbing fastness and wet rubbing fastness grade is not very high, sometimes can 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 screening, fixing treatment and soap-washing are effective measures to improve the rubbing fastness of textiles. In order to improve the wet rubbing fastness of deep concentrated color cellulose fiber products, special auxiliaries can be selected to improve the wet rubbing fastness of textile products, and the wet rubbing fastness of the products can be obviously improved by dipping the special auxiliaries in the finished products.

For the dark products of chemical fiber filament, the wet rubbing fastness of the products can be improved by adding a small amount of fluorine waterproofing agent when the finished product is finalized. When polyamide fiber is dyed with acid dye, the wet rubbing fastness of polyamide fabric can be improved by using special fixing agent of nylon fiber. The wet rubbing fastness grade may be reduced in the test of the wet rubbing fastness of the dark finished product because the short fibers on the surface of the fabric of the finished product will be shed more obviously than that of other products.

Sunlight fastness

Sunlight has wave-particle duality and it has strong impact on the molecular structure of dyestuff by transferring energy in the form of photon.

When the basic structure of the chromogenic part of the dye structure is destroyed by photons, the color of the light emitted by the dye chromogenic body will change, usually the color becomes lighter, until colorless. The color change of dye is more obvious under sunshine condition, and the fastness to sunlight of dye is worse. In order to improve the fastness to sunlight of dye, dye manufacturers have adopted many methods. Increasing the relative molecular weight of the dye, increasing the chance of complexation inside the dye, increasing the co-planarity of the dye and the length of the conjugate system can improve the light fastness of the dye.

For phthalocyanine dyes, which can reach grade 8 light fastness, the brightness and light fastness of dyes can be improved obviously by adding appropriate metal ions in the dyeing and finishing process to form complex molecules inside the dyes. For textiles, the choice of dyes with better sun fastness is the key to improve the sun fastness grade of products. It is not obvious to improve the sun fastness of textiles by changing the dyeing and finishing process.

Sublimation fastness

As for disperse dyes, the dyeing principle of polyester fibers is different from other dyes, so the sublimation fastness can directly describe the heat resistance of disperse dyes.

For other dyes, testing the ironing fastness of dyes and testing the sublimation fastness of dyes has the same significance. The dye resistance to sublimation fastness is not good, in the dry hot state, solid state of the dye is easy to be directly separated from the interior of the fiber in a gas state. So in this sense, dye sublimation fastness can also indirectly describe the fabric ironing fastness.

In order to improve the dye sublimation fastness, we must start from the following aspects:

1, the first is the choice of dyes

The relative molecular weight is larger, and the basic structure of the dye is similar to or similar to the fiber structure, which can improve the sublimation fastness of the textile.

2, the second is to improve the dyeing and finishing process

Fully reduce the crystallinity of the crystalline part of the macromolecular structure of the fiber, improve the crystallinity of the amorphous region, so that the crystallinity between the interior of the fiber tends to be the same, so that the dye into the interior of the fiber, and the combination between the fiber is more uniform. This can not only improve the leveling degree, but also improve the sublimation fastness of dyeing. If the crystallinity of each part of the fiber is not balanced enough, most of the dye remains in the relatively loose structure of the amorphous region, then in the extreme state of external conditions, the dye is also more likely to be separated from the amorphous region of the fiber interior, sublimation to the surface of the fabric, thereby reducing the textile sublimation fastness.

The scouring and mercerizing of cotton fabrics and the pre-shrinkage and preshaping of all polyester fabrics are all processes to balance the internal crystallinity of the fibers. After scouring and mercerizing the cotton fabric, after pre-shrinkage and predetermined polyester fabric, its dyeing depth and dyeing fastness can be improved significantly. dye

The sublimation fastness of the fabric can be improved obviously by strengthening post-treatment and washing and removing more surface floating color. The sublimation fastness of the fabric can be improved obviously by lowering the setting temperature properly. The problem of decreasing the dimensional stability of fabric caused by cooling can be compensated by decreasing the setting speed appropriately. Attention should also be paid to the effect of additives on dyeing fastness when finishing agent is selected. For example, when cationic softeners are used in the soft finishing of polyester fabrics, the thermal migration of disperse dyes may lead to the sublimation fastness test of disperse dyes failing. From the point of view of the temperature type of disperse dye itself, the high temperature disperse dye has better sublimation fastness.