Do you know what fabric problems cause headaches?

Concept of color fastness: Color fastness (Color fastness) is also called color fastness and color fastness.

Dyeing fastness (Color fastness) is also called color fastness and color fastness. It refers to the resistance of the color of fabrics to various effects during finishing and use. The fastness grade is evaluated based on the discoloration of the sample and the staining of the uncolored backing fabric.

Fabric products will be subject to various external effects such as lighting, cleaning, ironing, sweat stains, friction and chemicals during their use. Some printed and dyed fabrics also undergo extraordinary finishing. Such as resin finishing, fireproof finishing, sand washing, sanding, etc., which requires the color and luster of printed and dyed fabrics to maintain a certain fastness.

Dyeing fastness refers to the product’s resistance to washing and rubbing.

The so-called color fastness (referred to as dye fastness) refers to the color fastness of the colored fabric when it is subjected to external factors (squeezing, friction, washing, rain, exposure, damage, etc.) during use or finishing. The degree of fading under the action of sunlight, seawater immersion, saliva immersion, water stains, sweat stains, etc.) is an important indicator of fabrics.

Commonly used items are washability, finish resistance, friction and sweat resistance, ironing resistance, weather resistance, etc.

In actual work, testing items are mainly determined based on the end use of the product and product standards. For example, the product standards for wool fabrics stipulate that the dyeing fastness to sunlight must be tested, and of course knitted underwear must The fastness to perspiration is tested, while outdoor fabrics (such as parasols, light box fabrics, and canopy materials) must of course be tested for weather and dye fastness.

Includes: Dye fastness to soaping (sample), Dye fastness to rubbing, Dye fastness to chlorine water, Dye fastness to non-chlorine bleaching, Dye fastness to dry cleaning , actual washing dye fastness (garments, fabrics), perspiration dye fastness, water dye fastness, full light dye fastness, sea water dye fastness, saliva dye fastness.

How to test dye fastness

1. Washing and dyeing fastness

The sample and the standard backing fabric are sewn together, cleaned, washed and dried, and washed under appropriate temperature, alkalinity, bleaching and friction conditions, so that in a short time Get test results. The friction between them is accomplished through the tumbling and impact of a small liquor ratio and an appropriate number of stainless steel beads. Gray cards are used to grade and the test results are obtained.
Different testing methods have different temperature, alkalinity, bleaching and friction conditions and sample sizes. The specific selection should be based on the testing standards and customer requirements.

Generally, colors with poor water fastness include green blue, brilliant blue, black red, navy blue, etc.

2. Dry cleaning and dyeing fastness

The dye fastness is the same as washing, except that washing is changed to dry cleaning.

3. Rubbing dyeing fastness

Put the sample on the rubbing fastness tester and rub it with a standard rubbing white cloth at a certain pressure for a certain number of times. Each group of samples needs to be tested for dry rubbing, dyeing fastness and wet rubbing. Dye fastness. The color stained on the standard rubbing white cloth is rated with a gray card, and the grade obtained is the measured rubbing fastness. Rubbing dyeing fastness requires two tests, dry rubbing and wet rubbing, and all the colors on the sample must be rubbed.

4. Sunlight dyeing fastness

Fabrics are usually exposed to the finish line during use, which can destroy the dye and cause the well-known “fading”, causing the colored fabrics to change color, usually becoming lighter or darker, and some will also The color changes completely,
Therefore, it is necessary to test the dyeing fastness. The sun dyeing fastness test is to put the sample and the blue wool standard cloth of different fastness levels together under the specified conditions for sun exposure. Compare with blue wool cloth to evaluate the dyeing fastness. The higher the grade of blue wool standard cloth, the more resistant it is to dyeing.

5. Sweat stain fastnessResistant dyes can form covalent bonds with cellulose fibers, but during coloring, if there are hydrolyzed dyes or insufficient soaping of unbonded dyes, the wet treatment fastness will also be reduced; other, and fiber Reactive dyes that have formed covalent bonds may also decompose and break bonds under acidic or alkaline conditions, and have problems such as insufficient fastness to chlorine dyeing, perspiration, and sunlight.

In order to improve the dyeing fastness of fabrics, color fixing treatment can be performed. These additives that can improve the color fastness of various types are called fixing agents.

Principle of color fixing agent

1. Generate insoluble lake on the fabric and block the soluble groups, making the dye on the fabric less likely to dissolve and fall off when exposed to water, thereby improving the wet treatment fastness. However, after these color-fixing agents are fixed, the color of the fabric may change or the light fastness may decrease.

2. Create a mesh film on the fabric to prevent the dye from falling off.

3. Use the reactive groups in the fixing agent molecules to cross-link with the reactive groups on the dye molecules and the hydroxyl groups on the cellulose molecules to improve the fixation effect of the dye on the fiber. .

4. Utilize the molecular attraction of the color-fixing agent and fiber to increase the fixing strength of the color-fixing agent, thereby improving the color fastness.

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