Affecting Factors of Color Fastness to Rubbing

 

The color fastness to rubbing of dyed products is divided into dry rubbing fastness and wet rubbing fastness. The former is to rub the dyed product with a dry white cloth to observe the color sticking to the white cloth. The latter is to rub the dyed product with a white cloth containing 100% water and observe the staining of the white cloth. The friction fading of the fabric is caused by the dye falling off under the action of friction. In addition to the action of external force, wet rubbing also has the action of water. Therefore, wet rubbing is generally about 1 grade lower than dry rubbing fastness.

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

  • For reactive dyes, the dyes and fibers are fully combined by covalent bonds, and the rubbing fastness is high.

  • If insoluble azo dyes are used for dyeing, some dyes will become insoluble when the dyeing process is not good. They are mechanically attached to the fiber surface. Its rubbing fastness is low. If the floating color is not cleaned, the rubbing fastness will be lower.

  • The dye molecule is large (such as sulfur black), and dye easily forms large particles of dye floating color on the surface of the fiber after dyeing. In addition, the concentration of the dye is generally too high, which reduces the fastness to rubbing.

  • The binding force of most dyes to fibers is more easily destroyed in the presence of moisture. Therefore, the wet rubbing fastness is lower than the dry rubbing fastness.

Let’s analyze the influencing factors of color fastness to rubbing.

The influence of fabric surface morphology

Unfixed dye is the main cause of poor crocking fastness. Under dry conditions, if the surface is rough or sanded, raised fabrics, hard such as linen fabrics, denim fabrics and pigment printed fabrics, if dry rubbing is performed, it is easy to rub off the dyes, paints or other colored substances accumulated on the surface of the fabrics. Even causing some colored fibers to break and form colored particles, further reducing the color fastness to dry rubbing. For sanded or piled fabrics, the fluff on the surface of the fabric and the surface of the friction cloth form a certain angle, which is not parallel, so that the friction resistance of the friction head increases during the reciprocating motion, and the dry resistance of this type of fabric is increased. Rubbing color fastness 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 performing dry friction, the sample will be rubbed with the movement of the friction head under the action of pressure and friction. Part of the slip, so that the friction resistance increases, and the friction efficiency improves. But when it comes to wet rubbing, the situation is completely different with cellulose fibers.
Due to the extremely low hygroscopicity of the fiber or the insignificant water swelling effect, 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.

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 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 physical factors such as the structure and surface morphology of the fabric, it is more important. It doesn’t seem very important anymore.

Most of these cases are dark 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.

Three other influencing factors affecting rubbing fastness can be found here.

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