Color fastness is one of the important quality indicators of textiles. The so-called color fastness refers to the degree to which the color of dyed textiles remains fast under physical and chemical effects. That is, the color fastness of dyed textiles is affected by external influences and becomes dye fastness. The color fastness is expressed by the color change of the sample after the test and the evaluation grade of the staining degree of the white cloth.
Among various color fastness items, the most commonly used color fastnesses are color fastness to rubbing, color fastness to perspiration, color fastness to washing, color fastness to light, color fastness to water immersion, color fastness to washing, Items such as weather resistance and color fastness.
concept
Color fastness to rubbing is one of the color fastness tests of textiles and one of the most common testing items in the trade process of textiles. It refers to the ability of the color of textiles to withstand rubbing and is divided into dry rubbing and wet rubbing.
The principle is to fix the textile sample of the 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. Finally, the degree of staining of the white cloth is used as the basis for evaluation and compared with the standard. The gray sample card is divided into 5 levels. The higher the level, the better the rubbing fastness. Fabrics with poor rubbing fastness will seriously affect its use.
Dry friction test
Place a piece of (50×50) mm friction cloth (standard white cotton cloth) flat on the friction head after adjusting the humidity (more than 4 hours) in a standard atmosphere (temperature 20℃±2℃, humidity 65%±4%) on the sample, make the direction of the friction cloth consistent with the allowed direction of the friction head, the running speed is one reciprocating friction cycle per second, and a total of 10 friction cycles. The friction stroke on the sample is (104±3) mm, and the applied direction The down force is (9 ± 0.2) N. After completing the entire 10 cycles, remove the friction cloth, adjust the humidity (more than 4 hours), and remove any excess fibers on the friction cloth that may affect the rating. As shown in the picture:
Wet friction test
Completely immerse the weighed piece of friction cloth in distilled water, take it out, and reweigh the friction cloth to ensure that the moisture content of the friction cloth reaches 95%-100%. Then the operation method is the same as dry rubbing.
Rating
Finally, we need to take the friction cloth that has been adjusted and moistened after rubbing to the grading room in the standard light source box, and use the gray sample card for staining evaluation to evaluate the staining grade of the friction cloth. (Note: The staining grade of each friction cloth is evaluated. Place three layers of friction cloth on the back) as shown:
Commonly used 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.
It can be seen from this table that different testing standards have different requirements for the size of the sample cloth. When the customer prepares the sample cloth, if the sample to be tested is a fabric or carpet: prepare two sets of samples with a size of not less than 50 mm × 140 mm, each Group two pieces each. (When sampling, one piece of fabric is parallel to the warp yarn, and the other piece of fabric is parallel to the weft yarn.) Another sampling method is to sample at a certain angle between the length direction of the sample and the warp and weft direction of the fabric.
If it is a pile fabric and the pile is easy to identify, the direction of the pile should be consistent with the length of the fabric when cutting the sample. Generally speaking, the national standard and the European standard adopt the method of taking one piece each in the longitude and latitude directions, while the American standard adopts the method of tilting at an angle of 45 degrees.
If the fabric to be tested is yarn: it needs to be woven into a fabric with a sample size of not less than 50 mm layer.
Factors affecting color fastness to rubbing
1
Effect 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 orSeparate washing, soaping and other processes are required to remove floating colors and unreacted and hydrolyzed dyes on the fiber surface to avoid affecting the color fastness. If you do not pay attention to the post-dyeing treatment, it will cause poor color fastness and the color light will also be affected. Become dim.
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 efforts 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.
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