Two soaps, external reinforcement Y, color fastness is not so dry!

According to statistics, fastness is the most frequently asked question in all dyeing questions. Dyeing fastness requires high quality of dyed and printed fabrics. The nature or degree of dyeing state variation can be expressed by dyeing fastness. It is related to yarn structure, fabric structure, dyeing and printing methods, dye types and external forces. Different dyeing fastness requirements will lead to great cost and quality differences.
Fastness of six main textiles
 
1 fastness to sunlight
Solar fastness refers to the degree of discoloration of colored fabrics by sunlight. The test method can be either sunshine or sunlight machine. The fading degree of the sample after sunshine is compared with the standard color sample, which can be divided into 8 grades, 8 grades are the best and 1 grades are the worst. Fabrics with poor fastness to sunlight should not be exposed to sunlight for a long time, and should be put in a ventilated place to dry in the shade.
 
2 rubbing fastness
Friction fastness refers to the degree of discoloration of dyed fabrics after friction, which can be divided into dry friction and wet friction. The rubbing fastness is evaluated by the staining degree of white cloth, which is divided into five 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 detergent. Generally, the grey grading sample card is used as the evaluation standard, that is, the color difference between the original sample and the faded sample is used to judge. The washing fastness is divided into five grades, the best is grade 5 and the worst is grade 1. Fabrics with poor washing fastness should be dry cleaned. If wet washing is carried out, more attention should be paid to washing conditions, such as washing temperature should not be too high and 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 assessed by the staining of the irons on other fabrics at the same time. The ironing fastness is classified into 1-5 grades, 5 grades are the best and 1 grades are the worst. When testing the ironing fastness of different fabrics, the ironing temperature should be chosen well.
 
5 fastness to perspiration
Sweat fastness refers to the degree of fading of dyed fabrics after soaking in sweat. Sweat fastness is generally assessed in combination with other colour fastnesses, in addition to the determination of sweat fastness individually, due to the different components of sweat manually prepared. Sweat fastness can be divided into 1 to 5 grades, the larger the value, the better.
 
6 sublimation fastness
Sublimation fastness refers to the degree of sublimation of dyed fabrics during storage. The sublimation fastness was assessed by grey grading sample card. The degree of discoloration, fading and staining of white cloth after dry hot pressing was divided into five grades, the first grade was the worst and the fifth grade was the best. The dyeing fastness of normal fabrics is generally required to reach grade 3 to 4 in order to meet the wearing requirements.
How to control various fastness
After textile dyeing, the ability of the fabric to retain its original color can be expressed by testing various dyeing fastnesses. Commonly used indicators of dyeing fastness include washing fastness, rubbing fastness, sunshine fastness, sublimation fastness and so on.
 
The better washing fastness, rubbing fastness, sunshine fastness and sublimation fastness of fabrics, the better dyeing fastness of textiles.
 
The main factors affecting the above fastness include two aspects:
 
The first is the properties of dyes.
The second is the formulation of dyeing and finishing processes.
 
Selective dyes with excellent dyeing properties are the basis for improving dyeing fastness. The key to ensure dyeing fastness is to formulate a reasonable dyeing and finishing process. They complement each other and can not be neglected.
 
Washing fastness
The washing fastness of fabrics includes fading fastness and staining fastness. Generally, the worse the fading fastness of textiles is, the worse the staining fastness is.
 
When testing the staining fastness of a textile, the staining fastness of the fibers can be determined by examining the staining condition of the fibers to the six commonly used textile fibers (these six commonly used textile fibers usually include polyester, nylon, cotton, acetate, wool or silk, acrylic). The test of staining fastness of six kinds of fibers is usually carried out by qualified independent professional inspection companies, which is relatively objective and impartial.
 
For cellulose fiber products, 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 complex than that of reactive dyes and direct dyes, so the washing fastness of the latter three dyes is better.
 
Therefore, in order to improve the washing fastness of cellulose fibre products, we should not only choose the right dyes, but also choose the right dyeing process. Proper strengthening of washing, fixing and soaping can obviously improve the washing fastness.
 
As far as the deep color of polyester fibers is concerned, the washing fastness after dyeing can meet the customer's requirements as long as the fabric is cleaned by reduction. However, most of the polyester fabrics are softened by dipping and rolling cationic organosilicon softeners to improve the handle of the fabrics. At the same time, anionic dispersants in disperse dyes may diffuse on the surface of the fabrics due to the thermal migration of dyes during high temperature setting. Therefore, the washing fastness of deep-colored polyester fabrics after setting is good. May not be qualified. This requires that not only the sublimation fastness of disperse dyes, but also the thermal migration of disperse dyes should be considered when selecting disperse dyes.
There are many ways to test the washing fastness of textiles. According to different testing standards, the washing fastness of textiles can be tested.We will come to the conclusion that Division J does not work. When customers in foreign countries put forward specific water fastness indicators, if specific testing standards can be put forward, it will be conducive to smooth communication between the two sides. Strengthen washing and post-treatment can improve the washing fastness of fabrics, but it will also increase the emission reduction of dyeing plants.
 
Finding some efficient detergents, reasonably formulating dyeing and finishing process and strengthening the research of short process technology can not only improve production efficiency, but also contribute to energy saving and emission reduction.
 
Rubbing fastness
The rubbing fastness of fabrics is the same as the washing fastness, which includes two aspects:
One is dry rubbing fastness, the other is wet rubbing fastness.
 
The physical sample card of dry and wet rubbing fastness of fabrics can be obtained by testing the fabric rubbing fastness tester. It will be very convenient to test the dry and wet rubbing fastness of textiles by comparing the color change sample card with the stained sample card.
 
Usually, when testing the rubbing fastness of textiles with deep color, the dry rubbing fastness of textiles is about one grade higher than the wet rubbing fastness.
 
Taking cotton fabric dyed with direct dyes as an example, although it has been effectively fixed, the grade of dry and wet rubbing fastness is not very high, and sometimes it 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 soaping are effective measures to improve the rubbing fastness of textiles.
 
In order to improve the wet rubbing fastness of cellulose fibre products with deep colour, special additives can be selected to improve the wet rubbing fastness of textiles, and the wet rubbing fastness of products can be obviously improved by dipping and rolling special additives during the finalization of finished products.
 
The wet rubbing fastness of dark chemical filament products can also be improved by adding a small amount of fluorine-containing waterproofing agent to the final product.
 
When acid dyes are used to dye polyamide fibers with deep colour, the wet rubbing fastness of polyamide fabrics with deep colour can be obviously improved by using special fixing agent for polyamide fibers.
 
For dark-coloured abrasive products, the wet rubbing fastness may be reduced because the shedding phenomenon of short fibers on the surface of abrasive fabrics is more obvious than that of other products when testing their wet rubbing fastness.
 
Light
Solar light has wave-particle duality. Solar light, which transmits energy in the form of photons, has a strong impact on the molecular structure of dyes. 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 chromophore will change, usually the color will become lighter until colorless. The more obvious the color change of dyes under sunshine, the worse the fastness to sunlight of dyes.
 
In order to improve the sun fastness of dyes, dye manufacturers have adopted many methods. Increasing the relative molecular weight of dyes, increasing the chances of complexation within dyes, increasing the coplanarity of dyes and the length of conjugated system can improve the light fastness of dyes.
 
For phthalocyanine dyes with 8-grade fastness to sunlight, the brightness and fastness of dyes can be significantly improved by adding appropriate metal ions to the dyeing and finishing process to form complexes within the dye molecules. For textiles, the choice of dyes with better fastness to sunlight is the key to improve the product's fastness to sunlight. The effect of improving the fastness to sunlight of textiles by changing the dyeing and finishing process is not obvious.
 
Sublimation fastness
As far as disperse dyes are concerned, because the dyeing principle of polyester fibers is different from other dyes, sublimation fastness can directly express the heat resistance of disperse dyes. For other dyes, testing the ironing fastness of dyes has the same significance as testing the sublimation fastness of dyes. The sublimation fastness of dyes is not good. Under dry and hot conditions, the dyes in solid state can easily be separated from the fibers directly in gas state. So in this sense, the sublimation fastness of dyes can also indirectly express the ironing fastness of fabrics. Comprehensive arrangement of Dyers without boundaries
 
In order to improve the sublimation fastness of dyes, the following aspects should be taken into consideration:
 
The first is the choice of dyes.
The sublimation fastness of textiles can be improved by the relative molecular weight, the basic structure of dyes and the structure of fibers are similar or similar.
 
Second is to improve the dyeing and finishing process.
The crystallinity of the crystalline part of the macromolecule structure of the fibers is reduced sufficiently, and the crystallinity of the amorphous region is increased, so that the crystallinity of the various regions within the fibers tends to be the same, so that the dyes can enter the fibers and bond with the fibers more evenly.
 
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 and most of the dyes remain in the amorphous region with relatively loose structure, it will be easier for the dyes to separate from the amorphous region inside the fiber and sublimate to the surface of the fabric after the extremity conditions occur, thus reducing the sublimation fastness of the textiles.
 
The scouring and mercerizing of cotton fabrics and the pre-shrinking and pre-setting of polyester fabrics are all processes for balancing the internal crystallinity of fibers. Cotton fabrics scoured and mercerized, polyester fabrics pre-shrinked and predefinedThe dyeing depth and fastness can be improved obviously.
 
The sublimation fastness of fabrics can also be improved by strengthening post-treatment and washing and removing more surface float. The sublimation fastness of fabrics can be obviously improved by lowering the setting temperature properly during the setting process. The problem of decreasing dimensional stability of fabrics caused by cooling can be remedied by properly reducing the setting speed. In the selection of finishing agents, attention should also be paid to the effect of auxiliaries on dyeing fastness. For example, when cationic softeners are used in the softening of polyester fabrics, the sublimation fastness test of disperse dyes may be unqualified due to the thermal migration of disperse dyes. Viewed from the temperature type of disperse dyes themselvesThe sublimation fastness of high temperature disperse dyes is better.