Factors influencing color fastness to rubbing

The color fastness to rubbing of colored products is divided into dry rubbing fastness and wet rubbing fastness. The former consists of rubbing the colored product with a dry white cloth to observe how the color adheres to the white cloth. The latter consists in rubbing. Dampen the stained product with a white cloth containing 100% water and observe the stains on the white cloth. Fabric fading from rubbing is caused by the dye falling off under the action of rubbing. In addition to exposure to external force, wet rubbing Therefore, wet rubbing fastness is generally about 1 degree lower than dry rubbing fastness.

The rub fastness of the fabric depends on the amount of floating dye, the molecular weight of the dye, and the combination of dye and fiber, the uniformity of dye penetration, and the particle state of the dye on the fabric surface.

In reactive dyes, the dyes and fibers are fully connected by covalent bonds and the fastness to rubbing is high. If insoluble Azo dyes are used for coloring. Some dyes will become insoluble if the dyeing process is not good. They are mechanically attached to the fiber surface. Their fastness to rubbing is low. If the floating paint is not cleaned, the rub fastness will be lower. The dye molecule is large (e.g. sulfur black) and the dye easily forms large dye particles floating on the surface of the fiber after dyeing.In addition, the concentration of dye is generally too high, which reduces rubbing fastness. The binding power of most dyes to fibers is more easily destroyed in PR. Therefore, wet rub fastness is lower than dry rub fastness.

Let\'s analyze the factors influencing color fastness to rubbing.

The influence of fabric surface morphology

Unfixed dye is the main cause of poor scratch resistance. In dry conditions when the surface is rough or sanded, raised fabrics, hard fabrics such as linen fabrics, denim fabrics, and pigment-printed fabrics when dry rubbing is performed It is easy to dye, LacRub off ke or other colored substances that have accumulated on the surface of the fabrics. Some colored fibers will even break and form colored particles, further reducing color fastness to dry rubbing. For sanded or napped fabrics, the fluff on the surface of the fabric and the surface of the rubbing cloth form a certain angle that is not parallel, so the frictional resistance of the rubbing head increases during the reciprocating movement, and the drying resistance of this type of cloth is increased .The color fastness by rubbing decreased.

The effect of fabric structure

On the sample surface of light and thin fabrics (usually synthetic fibers or silk fabrics), due to the relatively loose structure of the fabric when dry rubbing is performed, the Sample rubbed with the movement of the rubbing head under the action of pressure and friction. Part of the slip so that the frictional resistance increases und the friction efficiency is improved. With wet rubbing, however, the situation is different. Quite different with cellulose fibers.

Due to the extremely low hygroscopicity of the fiber or the insignificant water swelling effect and the presence of water as a lubricant, the color fastness to wet rubbing is impairedThe color fastness of this type of fabric is significantly better than dry rub fastness.

Therefore, it is not uncommon for certain fabrics to have better wet rub fastness than dry rub fastness. At this point, while the type of dye selected, the performance of the dye, the process conditions in dyeing and finishing, etc., compared to physical factors such as structure also have an impact on the color fastness to rubbing And the surface morphology of the fabric is more important. It doesn\'t seem to matter much anymore.

In most cases, these are dark productste like black, red and navy blue. Of course, for fabrics such as corduroy, twill and pigment print, color fastness to wet rubbing in wet conditions is usually Level 2 or even lower due to the dyes and printing and dyeing processes used. No better than color fastness to dry rubbing.Influence of chemical structure of reactive dyes

When tCellulose fiber fabric dyed with reactive dyes is tested for color fastness to wet rubbing. There are two main factors that cause color transfer: The water-soluble dye is transferred to the rubbing fabric when rubbed, fading original color and stains on the rubbing fabric. Second, some of the colored fibers break when rubbed, forming tiny colored fiber particles and transferred to the rubbing fabric, resulting in staining.

Factors that can affect the color of reactive dyes when wet rubbed are:

The structure and propertiesadhere to the reactive dyes themselves. The nature of the substance. Pre-treatment effect, fabric damage and surface finish, etc. Dyeing process and the effect of soaping after drying. Dye fixing effect after dyeing fabrics. Effects of finishing on dyed fabrics, etc.

Studies have shown that while there are certain differences in covalent bond strength, bond stability and adhesion between reactive dyes of different chemical structures and cellulose fibers, there is no significant difference in the Effect on color fastness when wet rubbing dyed fabrics. When the dyed fabric is wet rubbed, the covalent bond formed between the dye and the fiber is not broken, creating a levitating color. The transferred dye is usually supersaturated, does not form a covalent bond with the fiber, and relies only on the van der Waals force for absorption, ieie the so-called floating color.

Influence of the degree of dyeing of reactive dyes

The color fastness of fabrics dyed with reactive dyes to wet rubbing is closely related to the depth of dyeing, the linear relationship. Excess dyes cannot be combined with fibers, but can only accumulate on the surface of the fabric and form floating colors, significantly affecting the fabric\'s color fastness to wet rubbing.

Cotton fibers without speciesThe treatment swells in wet conditions up, friction increases and fiber strength decreases. This created good conditions for the degradation, detachment and color transfer of colored fibers. Therefore, the cellulose fiber should be properly pretreated before dyeing such as mercerizing, singeing, cellulase finishing, scouring, bleaching, washing and drying. It can improve the smoothness and capillary action of the fabric surface, friction resistancestand and reduce floating colors, effectively improving the color fastness when wet rubbing the fabric.

Effect of the softener

Improving the color fastness of reactive dye printing by soft finishing. The plasticizer has a lubricating effect that reduces the coefficient of friction and thus prevents the color from falling off. Plasticizers can also form lakes with anionic dyes, and the dyes are not easy to fall off. At the same time, the color lake reduces the solubility of the dye, which can lead to an improvement. However, plasticizers with hydraulic groups do not help to improve the wet rubbing fastness.

In production practice, the water-soluble group of the dye can be blocked by using a become color fixatives, the pH value of the finished color cloth can be controlled, the floating color can be removed, the smoothness of the fabric can be improved and the wet rub resistanceSafety of the fabric can be improved. Proper pre-baking can avoid “migration of the colorant”. Factors to consider include the amount of alkaline agent, steam duration, washing method, sufficient lathering, etc. The former two are closely related to the degree of hydrolysis of the dye, and the latter two are directly related to the degree of hydrolysis of the Dye the floating color of the dye.

The dyed fabric, especially long car upholstery dyeing, must go through sufficient washing and soaping processes to remove floating colors on the fiber surface, as well as unreacted and hydrolyzed dyes without affecting the color fastness. If you do not pay attention to the after-treatment of dyeing, it will lead to poor color fastness, and the color light will become dull at the same time.

Among the above: Mentioned factors affecting color fastness to friction of fabricsinfluence, the principles of action of each factor are very different, and the degree of influence is also different. The principle of color fastness seems simple, but the factors involved are quite complicated. In order to ensure rub fastness, it is necessary to select appropriate dyes and formulate an adequate process to ensure that the dyes can fully bond with the fibers and fully penetrate the interior of the fiber, preventing them from sticking to the surface accumulate The fiber and the floating color should be fully washed after dyeing. If necessary, the dye-fixing crosslinking agent can be added to bond the dye and fiber more firmly and reduce friction on the fabric surface. At the same time , a soft film is formed on the surface of the fiber, covering the dye, so that the dye is not easy to fall off when rubbed, and the refastness is improved.

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