1·Causes affecting the rubbing fastness of dyed fabrics
Color fastness to rubbing is one of the color fastness tests of textiles, and is also one of the common inspection items in the trade process of textiles. It refers to the degree of color fading of dyed fabrics after friction, and is an assessment of the resistance of dyes to mechanical friction. , divided into dry friction and wet friction. The principle is to fix the textile sample of specified size on the friction tester platform with a clamping device, and then rub it with a dry friction cloth and a wet friction cloth respectively, and then The staining degree of white cloth is used as the basis for evaluation, and compared with the standard gray sample card, it is divided into 5 levels. The higher the level, the better the rubbing fastness. Fabrics with poor rubbing fastness will seriously affect their use. There are many factors that affect the color fastness of fabrics to rubbing. Several of them are analyzed below.
1.1 Influence of fabric surface morphology
Since unfixed dyes are the main cause of poor color fastness to rubbing, under dry conditions, fabrics with rough surfaces, brushed or raised fabrics, hard fabrics such as linen, denim fabrics and paint-printed fabrics are easily susceptible to dry rubbing. The dyes, paints or other colored substances accumulated on the surface of the fabric are rubbed off, which may even cause some colored fibers to break and form colored particles, further reducing the color fastness to dry rubbing. For brushed or raised fabrics, the fluff on the surface of the fabric is at a certain angle with the surface of the friction cloth and is not parallel, which increases the friction resistance of the friction head during reciprocating motion, making this type of fabric more resistant to drying. Color fastness to rubbing is reduced.
1.2 Influence of fabric structure
Not much attention has been paid to the influence of fabric structure and surface morphology on color fastness to rubbing. On the sample surface of light and thin fabrics (usually synthetic fiber or silk fabrics), due to the relatively loose structure of the fabric, when dry rubbing is performed, the sample will undergo friction with the movement of the friction head under the action of pressure and friction. Partial slippage increases friction resistance and improves friction efficiency. But when it comes to wet rubbing, the situation is completely different with cellulose fibers. Since the fiber has extremely low hygroscopicity or the water swelling effect is not obvious, and the presence of water acts as a lubricant, the color fastness to wet rubbing of this type of fabric is significantly better than the color fastness to dry rubbing, which is consistent with people It is generally believed that the color fastness to dry rubbing of textile products should be better than the color fastness to wet rubbing, which creates a clear contrast and often causes people’s confusion.
Therefore, it is not uncommon for certain fabrics to have better color fastness to wet rubbing than to dry rubbing. At this time, although the type of dye selected, the performance of the dye, the process conditions of dyeing and finishing, etc. will also have an impact on the color fastness to rubbing, compared with the physical factors such as the tissue structure and surface morphology of the fabric, it is It doesn’t seem very important anymore. Statistics show that most of these situations occur with dark-colored products, such as black, red, and navy blue. Of course, for fabrics such as corduroy, twill and pigment printing, under wet conditions, due to the dyes and printing and dyeing processes used, the color fastness to wet rubbing is usually level 2, or even lower, and No better than its color fastness to dry rubbing.
1.3 Influence of chemical structure of reactive dyes
When the cellulose fiber fabric dyed with reactive dyes is tested for color fastness to wet rubbing, there are two main factors that cause color transfer: First, the water-soluble dye is transferred to the rubbing fabric during rubbing, causing the original color to fade and make the fabric fade. The friction cloth is stained; secondly, the partially dyed fibers break during friction, forming tiny colored fiber particles and being transferred to the friction fabric, causing staining. Therefore, the factors that may affect the color fastness of reactive dyes to wet rubbing include: the structure and characteristics of the reactive dye itself; the properties of the fabric; the pre-treatment effect, fabric surface damage and surface finish, etc.; the dyeing process and the effect of soaping after dyeing; the fabric The effect of color fixation after dyeing; the influence of finishing of dyed fabrics, etc.
Research shows that although there are certain differences in the covalent bond strength, bond stability and adhesion between reactive dyes with different chemical structures and cellulose fibers, there is no obvious difference in their effects on the color fastness to wet rubbing of dyed fabrics. . When dyed fabrics are wet rubbed, the covalent bonds formed between the dye and the fiber will not break and cause floating color. The dyes that are transferred are usually supersaturated dyes that do not form covalent bonds with the fiber and only rely on van der Waals forces to produce adsorption, which is the so-called floating color
1.4 Influence of dyeing degree
Research has also proven that the color fastness to wet rubbing of fabrics dyed with reactive dyes is closely related to the depth of dyeing. That is, when wet rubbing is performed, the amount of color transfer and the dyeing depth have an almost linear relationship. Among them, the process of dyeing during dyeing Saturation is an important factor. When dyeing dark colors, the concentration of dye used is higher, but it cannot greatly exceed the saturation value, because excess dye cannot combine with the fiber, but can only accumulate on the surface of the fabric to form floating colors, seriously affecting the fabric. Color fastness to wet rubbing. In addition, cotton fibers without special treatment will swell under wet conditions, increase friction, and weaken the fiber.The force decreases, which creates good conditions for the breakage, shedding and color transfer of colored fibers. Therefore, proper pre-treatment of cellulose fibers before dyeing, such as mercerization, singeing, cellulase polishing treatment, scouring, bleaching, washing, and drying, can improve the surface finish and wool effect of the fabric and reduce friction resistance. , Reduce floating color, thereby effectively improving the fabric’s color fastness to wet rubbing.
1.5 The influence of softener
Improve the color fastness of reactive dye printing through soft finishing. Softeners have a lubricating effect and reduce the coefficient of friction, thus preventing the dye from coming off. Cationic softeners can also form lakes with anionic dyes, making the dyes less likely to fall off. At the same time, the lake reduces the solubility of the dye and improves the wet rubbing fastness. However, softeners with hydrophilic groups are not conducive to improving wet rubbing fastness. In the production process, fixatives can be used to block the water-soluble groups of dyes, control the pH value of the finished cloth, remove floating colors, improve the smoothness of the fabric, and thereby improve the wet rubbing fastness of the fabric. Proper pre-baking can avoid dye “migration”. Factors that need attention include the amount of alkali agent, steaming time, washing method, sufficient soaping, etc. The first two are closely related to the degree of hydrolysis of the dye, and the latter two are directly related to the floating color of the dye.
Dyed fabrics, especially long-car pad dyeing, must undergo sufficient water washing, soaping and other processes to remove floating color and unreacted and hydrolyzed dyes on the fiber surface, so as not to affect the color fastness. If you do not pay attention to the post-processing of dyeing, it will It will cause poor color fastness and the color will become dull.
2·Conclusion
Among the above-mentioned factors that affect the color fastness of fabrics to rubbing, the working principles of each factor are very different, and the degree of influence is also different. The color fastness issue seems simple, but the factors involved are quite complex. Over the years, whether in the field of dye research and production or in the field of textile dyeing and finishing, people have invested a lot of manpower and material resources in trying to solve the color fastness problem of textile products, and have made great progress. Various new Dyes, new processes and new additives are constantly emerging, but there are still many problems that need to be solved.
Extended reading: https://www.alltextile.cn/product/product-60-599 .html
Extended reading: https://www.alltextile.cn/product/ product-8-274.html
Extended reading: https:/ /www.yingjietex.com/product/400D-Polyester-coating-Oxford-fabric.html
Extended reading:https://www.brandfabric.net/full-dull-nylon-dobby-checked-taffeta-fabric/
Extended reading:https://www.alltextile.cn/product/product-48-945.htm
