For printing and dyeing factories, it is necessary to meet the rubbing fastness indicators specified by customers, but sometimes, they just cannot meet the requirements! Keep the technicians in the dyeing workshop busy! Having said that, let’s first understand what color fastness indicators are and their types. The mandatory national standard GB18401-2003 “National Basic Safety Technical Specifications for Textile Products” stipulates that the various color fastness indicators of qualified products must be greater than or equal to level 3. Color fastness ratings are: Level 1, Level 1-2, Level 2, Level 2-3, Level 3, Level 3-4, Level 4, Level 4-5, Level 5. Level 5 is 9 levels, level 1 is the worst and level 5 is the best (no fading). Level 3 can only be a basic level, an intermediate level.
The color fastness of textiles usually includes: resistance to soaping, rubbing, light resistance, bleaching or oxidizing agents (reducing agents), ironing resistance, perspiration resistance and perspiration resistance Light color fastness, etc.
Color fastness to rubbing
Color fastness to rubbing: Rub the textile sample with a dry rubbing cloth and a wet rubbing cloth respectively to determine the staining degree of the rubbing cloth. From the above concept, we can know that there are two types of color fastness to rubbing: dry rubbing and wet rubbing; what is evaluated is the staining of the rubbing cloth, not the discoloration of the sample.
Color fastness to rubbing standards
Commonly used standards for color fastness to rubbing include GB/T 3920-2008, AATCC 8-2007, AATCC 116-2010 and JIS L 0849-2004. Let’s take a look at the similarities and differences of these four standards in the table below.
▲As can be seen from the table, 4 standards exist in terms of sample size, number of frictions, moisture content of friction cloth, gray card for rating, etc. If the difference is large, the results of testing according to different standards will be different.
AATCC 116-2010 (rotary friction method) is suitable for yarns or fabrics made of various fibers, especially suitable for printed fabrics. It can test better than AATCC 8-2007 A smaller area is required to clearly reflect the rubbing fastness of various colors of multi-color fabrics, which helps to quickly find out the reasons for the poor rubbing fastness of multi-color fabrics, so that measures can be taken to improve the rubbing fastness.
In the test of color fastness to rubbing, due to irregular weaving or uneven dyeing of the fabric, it is easy to cause inconsistent results after repeated rubbing, which is accidental and needs to be measured several times. Method, obtain highly reproducible results and produce a specific report.
Influencing factors of color fastness to rubbing
1. Influence of fabric surface morphology. Since unfixed dyes are the main cause of poor color fastness to rubbing, under dry conditions, for fabrics with rough or brushed or raised surfaces, hard fabrics such as linen, denim fabrics and For pigment-printed fabrics, dry rubbing can easily remove the dyes, coatings or other colored substances accumulated on the surface of the fabric, and 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.
2. Influence of fabric structure. The surface of the sample of light and thin fabrics (usually synthetic fiber or silk fabrics) is relatively loose due to the relatively loose structure of the fabric. During dry friction, the sample will be affected by pressure and Under the action of friction force, partial slip will occur with the movement of the friction head, thereby increasing the friction resistance and improving the friction efficiency. But when it comes to wet rubbing, the situation is completely different with cellulose fibers.
Because 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 requires Significantly better than dry rubbing color fastness.
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.
Most of this happens 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. Not superior to its color fastness to dry rubbing.
3. Influence of chemical structure of reactive dyes
Research shows that although the strength and stability of the covalent bonds formed by reactive dyes with different chemical structures and cellulose fibers There are certain differences in properties and adhesion, but there is no obvious difference in the impact 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 produce Floating color. The transferred dye is usually a supersaturated dye that does not form a covalent bond with the fiber and only relies on van der Waals force to produce adsorption, which is the so-called floating color.
4. The influence of the degree of dyeing with reactive dyes. 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 is almost the same as the dyeing depth. A good linear relationship is formed. Excess dye cannot be combined with the fiber, but can only accumulate on the surface of the fabric to form a floating color, seriously affecting the color fastness of the fabric to wet rubbing.
Cotton fibers that have not been specially treated will swell under wet conditions, increase friction, and decrease fiber strength. These create good conditions for the breakage, shedding, and color transfer of colored fibers. Therefore, before dyeing, Proper pre-treatment of cellulose fibers, such as mercerization, singeing, cellulase polishing treatment, scouring, bleaching, washing, and drying, can improve the smoothness and wool effect of the fabric surface, reduce friction resistance, and reduce floating color. Thereby effectively improving the fabric’s color fastness to wet rubbing.
5. The influence of softeners improves reactive dye printing through soft finishing Color fastness. Softeners have a lubricating effect and can reduce the coefficient of friction, thereby preventing dyes from falling off. Cationic softeners can also form lakes with anionic dyes, which prevent dyes from falling off. At the same time, lakes reduce the solubility of dyes and can improve wetness. Rubbing fastness. However, softeners with hydrophilic groups are not conducive to the improvement of wet rubbing fastness. In the production practice, the water-soluble groups of dyes can be blocked by using color-fixing agents to control the texture of finished colored cloths. Surface pH value, remove floating color, improve the smoothness of the fabric, thereby improving the wet rubbing fastness of the fabric. Proper pre-drying can avoid dye “migration”. Factors that need attention include the amount of alkali agent, steaming time, water 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.
Dyeed fabrics, especially Long lathe pad dyeing requires 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-dying treatment, it will cause poor color. Fastness, and the color will also become dull.
Afterwords
In the above Among the factors that affect the color fastness to rubbing of fabrics, 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. </p
