What are the influencing factors of color fastness to rubbing?

Influence of fabric surface morphology

Since the unfixed dyestuff is the main reason for the poor color fastness to rubbing, under dry conditions, for rough surface or brushed, raised fabrics, hard such as hemp fabrics, denim fabrics and pigment printed fabrics, it is very easy to do some dry rubbing. The dyes, coatings or other colored substances accumulated on the surface of the fabric are ground down, and even some colored fibers are broken and colored particles are formed, which further reduces the color fastness to dry rubbing. For sanded or raised fabrics, the fluff on the surface of the fabric is at a certain angle with the surface of the friction cloth, which is not parallel, so that the frictional resistance of the friction head during reciprocating motion increases, and the drying resistance of such fabrics is increased. The color fastness to rubbing decreased.

Influence of fabric structure

The surface of the sample of light and thin fabrics (usually synthetic fibers or silk fabrics), due to the relatively loose fabric structure, during dry friction, the sample will occur with the movement of the friction head under the action of pressure and friction. Part of the slippage, thereby increasing the frictional resistance and improving the frictional efficiency. But with wet rubbing, the situation is completely different with cellulose fibers.

Due to the extremely low hygroscopicity of the fibers or the insignificant effect of water swelling, and the presence of water acts as a lubricant, the color fastness to wet rubbing of such fabrics is significantly better than the color fastness to dry rubbing.

Therefore, for some specific fabrics, it is not uncommon for the color fastness to wet rubbing to be better than the color fastness to dry rubbing. At this time, although the selected dye varieties, dye properties, dyeing and post-finishing process conditions, etc. will also affect the color fastness to rubbing, compared with physical factors such as the structure and surface morphology of the fabric, the It doesn't seem to be very important.

Most of these cases are still dark products, such as black, red and navy blue. Of course, for fabrics such as corduroy, twill and pigment printing, under wet conditions, the color fastness to wet rubbing is usually level 2 or even lower due to the dyes and printing processes used by them. Not better than its color fastness to dry rubbing.

Influence of chemical structure of reactive dyes

There are two main factors that cause color transfer when cellulose deposits dyed with reactive dyes are tested for wet rubbing fastness:

1] The water-soluble dye is transferred to the friction object when rubbing, so that the original color fades and the rubbing cloth is stained;

2] The partially dyed fibers are broken during friction, forming tiny colored fiber particles and being transferred to the friction object, resulting in staining.

Factors that may affect the wet rubbing fastness of reactive dyes are:

1) The structure and characteristics of the reactive dyes themselves; the properties of the fabric; the pretreatment effect, the damage of the cloth surface and the surface finish, etc.;

2) Dyeing process and the effect of soaping after dyeing; the effect of color-fixing treatment of fabrics after dyeing; the effect of finishing of dyed fabrics, etc.

Studies have shown 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 significant difference in the effect on the color fastness to wet rubbing of dyed fabrics. . When the dyed fabric is wet rubbed, the covalent bond formed between the dye and the fiber will not break and cause floating color. The transferred dyes are usually supersaturated dyes that do not form covalent bonds with fibers, and only rely on van der Waals forces to produce adsorption, which is the so-called floating color.

Influence of dyeing degree of reactive dyes

Influence of dyeing degree of reactive dyes The wet rubbing fastness of reactive dyeing fabrics is closely related to the depth of dyeing, that is, when wet rubbing is performed, the amount of color transfer and dyeing depth are almost in a good linear relationship. Excessive dyes cannot be combined with fibers, but can only accumulate on the surface of the fabric to form floating color, which seriously affects the color fastness of the fabric to wet rubbing.

Cotton fibers without special treatment will swell under wet conditions, increase friction, and decrease fiber strength, all of which create good conditions for colored fibers to break, fall off and color transfer. Therefore, proper pretreatment of cellulose fibers before dyeing, such as mercerizing, singeing, cellulase finishing, scouring, bleaching, washing, and drying, can improve the surface finish and wool effect of the fabric and reduce frictional resistance. , Reduce floating color, thereby effectively improving the color fastness to wet rubbing of the fabric.

The effect of softeners

The effect of softeners improves the color fastness of reactive dye prints by softening finishes. Softeners have a lubricating effect and reduce the coefficient of friction, thereby preventing dye shedding. Cationic softeners can also form lakes with anionic dyes, and the dyes are not easy 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 the improvement of wet rubbing fastness. In the production practice process, the water-soluble group of the dye can be blocked by using a fixing agent, the pH value of the finished colored cloth can be controlled, the floating color can be removed, the smoothness of the fabric can be improved, and the wet rubbing fastness of the fabric can be improved. A proper prebake can avoid dye "migration". Factors that need to be paid attention to are 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.

The dyed fabrics, especially long-car pad dyeing, should undergo sufficient washing, soaping and other processes to remove the floating color and unreacted and hydrolyzed dyes on the fiber surface, so as not to affect the color fastness. It will result in poor color fastness, and the color light will also become dull.