A complete list of factors affecting fabric color fastness - China Garment Website_China's popular garment and fashion information platform

The dye fastness of textiles (abbreviated as color fastness) refers to the way dyed or printed fabrics are subjected to external factors (squeezing, friction, washing, rain, exposure, light, seawater immersion, saliva immersion, etc.) during use or processing. The degree of fading caused by water stains, sweat stains, etc.) is an important indicator of fabrics. If the color fastness is good, the textile will not fade easily during post-processing or use; if the color fastness is poor, fading, slight discoloration, or staining will occur, causing a lot of trouble.

Textile color fastness usually includes:

Resistance to soaping, friction, light, bleaching or oxidizing agents (reducing agents), ironing resistance, perspiration resistance and perspiration-to-light color fastness, etc. Among them, soaping resistance, friction resistance, light resistance, water resistance and perspiration resistance are several color fastness indicators that most buyers pay high attention to in actual production and trade.

1. Frequently asked questions about color fastness of textiles

In daily random inspections and consumer complaints, common textile color fastness problems include the following aspects:

1) The sun fastness is unqualified. During the wearing process, the color of coats and garments will become lighter or discolored in areas exposed to more sunlight (usually the back and shoulders), while the color of areas not exposed to or exposed to less light will remain the same or change slightly, resulting in products with the same original color. The colors are different shades and can no longer be used.

2) The color fastness to washing, soaping and dry cleaning are unqualified. High-end silk clothing, wool clothing, and pure cotton clothing are prone to this problem.

3) The color fastness to rubbing is unqualified. During the use of textiles, because different parts of the product receive different degrees of friction, the degree of discoloration will be different. For example, the elbows of tops, sleeves, collars and armpits are prone to fading. In addition, the buttocks and knees of pants are also prone to fading.

4) The color fastness to perspiration is unqualified. It is mainly caused by the discoloration of summer clothes or underwear when they are soaked in sweat.

2. Factors affecting color fastness and improvement methods

Products with poor color fastness will fade during wearing, which will affect other clothes worn on the body, or contaminate other clothes when washed with other clothes, affecting the appearance and wearing performance; on the other hand, there is a direct relationship between good and bad color fastness. to human health and safety. The dye molecules and heavy metal ions on products with poor color fastness may be absorbed by the human body through the skin and harm the skin and even harm the health of the body.

The factors that affect the color fastness of textiles are divided into internal factors and external factors. Internal factors refer to the firmness of the combination of dye and fiber, and external factors refer to the external forces exerted on the product by external factors or the environmental conditions provided during the use of the product. External factors cannot be controlled, so manufacturers must work hard to improve the color fastness of the product itself. Here are a few solutions based on personal practical experience for everyone to learn from.

2.1 Selection of dyes

Regarding the color fastness of a product, the choice of dyeing materials is very important. If the dyeing materials are not selected appropriately, no matter how good the additives or the dyeing process are, it will not be possible to achieve high-quality color fastness. Only when you choose the right dye can you talk about the next step.

2.1.1 Select dyes according to fiber characteristics

Different types of dyes have different binding forms with fibers, and the strength of the binding bonds is also different. After the dye type is determined, choose a dye with high dyeing performance. For example, when dyeing wool fabrics, it is also a strong acid dye, but the domestically produced strong acid dyes do not have as good a dyeing performance as the imported strong acid dyes. Not only is the color not good, but the bonding strength is not as good as the latter; or the same domestic strong acid dyes, Different dyes have different bonding fastness to wool and different dyeing brightness. For example, the color fastness of wool yarn dyed with weak acid dyes is higher than that of strong acid dyes; for pure cotton fabrics or regenerated cellulose fiber fabrics, either direct dyes or reactive dyes can be used; in addition to silk fabrics, weak acid dyes can be used In addition to dyes and some reactive dyes, individual direct dyes can also be used.

2.1.2 Select dyes according to color depth

After determining the major categories of dyes, it is necessary to further determine which dye to use based on the color system and depth of the dyed color. First, try to choose dyes whose color light is close to the desired color. If there is a deviation, use other dyes to adjust the color; second, look at the color fastness index of the selected dye itself. The color fastness of the dye itself is poor, and the color fastness can be improved by half a level through processing. Third, it depends on whether the saturation of the dye can reach the required color depth. If you choose a dye with a very low dye pick-up rate, even if it can temporarily achieve the required high depth of color after processing, the dye will not be firmly bonded and will fall off during use or reprocessing.

2.1.3 Select dyes according to their own color fastness levels

In the introduction of each dye, the dye fastness series of the dye is introduced. When selecting dyes, be sure to select the dye according to the color fastness level required by the product, and the dye fastness of the matching color dye must beThe degree should also be similar. For example, the color fastness of the dye itself can only reach level 2 to 3, or even level 1 to 2. No matter how good the additives and dyeing processes are, it cannot produce products with a color fastness of level 4 to 5. Because the color fastness of a dye mainly depends on the bonding force between the dye and the fiber. If the bond between the two is not strong, no amount of external force can make them bond firmly, even if it improves after fixation. , and cannot withstand damage from external factors such as washing and friction.

2.1.4 Dyeing rate of dyes on fibers

Different dyes will show different dyeing rates, and under different dyeing conditions, the dyeing rates of the same dye are also different. Therefore, when selecting dyes, the dyeing rate must be considered, otherwise there will be a dyeing competition phenomenon between dyes, that is, one of the dyes occupies the dyeing position of the fiber in advance, causing the other dyes to only dye on the surface of the fiber and not evenly. It forms a strong bond with the fiber and is thus first destroyed in subsequent processes or daily use. This is why some colors fade to reveal a completely different shade than their original color. Therefore, when choosing dyes, you must choose dyes that have a similar fiber dyeing rate under the same conditions, which is also very beneficial to the next step of formulating the process.

2.1.5 The dyes must have good compatibility

Different dyes in the same type of dye have different compatibility. The greater the compatibility value, the better the ability of the dyes to match each other’s colors. There must be good compatibility between dyes that match colors. For colors that are difficult to match, use the three primary colors. The three primary colors are the three dyes with good compatibility among each type of dye, and they are also the three dyes that can be matched with complete and accurate colors. Therefore, for some strange colors that are difficult to dye, it is best to use the three primary colors to match the color. Try not to use other dyes to match the color, which is prone to competing dyeing and dyeing.

2.1.6 Minimize the number of dyes required

When choosing dyes, you should first choose a dye with a color that is similar to the desired color, and then use one or two dyes to supplement the color that the main dye lacks. Moreover, you should choose dyes with a color that is in the same color system, so that the color produced Pure, smooth, gorgeous and full. Try not to use four or five dyes for coloring. This is not only difficult to adjust the color, but also difficult to operate in large quantities. Moreover, although the color is correct, the dyed color is not bright and full, and the dye cannot fully combine with the fiber, resulting in poor color fastness.

Color fastness to soaping

1. Comparison of test methods for color fastness to soaping

Color fastness to soaping is one of the common color fastness assessment items. Color fastness to soaping refers to the degree of fading of colored fabrics after soaping under specified conditions. It includes two evaluation contents: original fading and white cloth staining.

Original fading refers to the fading of colored fabrics before and after soaping; white cloth staining refers to the situation where white cloth and colored fabrics are sewn together in a certain way, and after soaping, the white cloth is stained due to the fading of the colored fabrics. The degree of fading or staining should be tested under the specified light source and rated with a standard gray card. The results are divided into 5 levels, with level 5 being good and level 1 being poor.

2. The relationship between dye structure, dyeing and post-treatment technology and soaping color fastness

In daily tests, a considerable number of textiles, including cotton, wool, polyester, nylon and their blended fabrics, as well as elastic fabrics containing spandex, stained nylon and acetate fiber linings at level 3 or below.

Although the dyes and printing and dyeing processes used in different fiber materials are different, the problems that arise are quite similar. This is mainly related to the floating color on the cloth surface and the transfer of some colored fiber particles, and is therefore related to the type of dye used, the dyeing process and the post-processing process.

3. The color fastness of reactive dye dyeing products to soaping depends on the unfixed dye

Taking reactive dyes as an example, theoretically speaking, due to the covalent bonding between dyes and fibers, washing with water cannot easily cause dye desorption, fading and bleeding. Therefore, the soaping color fastness of reactive dye dyeing products is determined by The amount of unfixed dye (hydrolyzed dye and a small amount of unreacted dye). If the hydrolyzed dye cannot be completely removed by soaping, the color will continue to fade after subsequent washing. Soaping fastness is also related to the bonding stability of bonded dyes, and bond-broken dyes will also fade when washed.

Therefore, the most important factors that affect the color fastness to soaping are the dye structure and properties, followed by dyeing and post-dye treatment processes. Reactive dyes have a high fixation rate or a slow hydrolysis rate, resulting in a small amount of hydrolyzed dye and a small amount of dye that needs to be removed by washing. Unfixed dyes and hydrolyzed dyes have low directness, good water solubility, are not easy to stain, and are easy to wash off. However, if the dye concentration is high and the amount of residual dye is large, it is difficult to wash off.

4. Soaping fastness is also closely related to the dyeing process

In addition, soaping fastness is also closely related to the dyeing process. The dye adsorption and diffusion are sufficient, the color fixation rate is high, the residual dye and hydrolyzed dye are less, and it is easy to wash off. The dyeing process is reasonable,The covalent bond between the dye and the fiber is not easily broken during dyeing and post-processing, and the color fastness to soaping is good.

Color fastness to rubbing

1. Comparison of test methods for color fastness to rubbing

The rubbing color fastness test refers to a test in which a colored sample is rubbed with a dry rubbing cloth and a wet rubbing cloth respectively, and then the staining degree of the rubbing cloth is evaluated. The test results are divided into 5 levels, with level 5 being good and level 1 being poor. Although the test process is simple, it is the basic color fastness assessment index of textile products. It is almost one of the items that buyers from all over the world must assess when placing orders. The technical conditions of rubbing fastness testing standards in various countries are very similar, but there are also some differences.

2. Main factors affecting color fastness to rubbing and their control measures

During the friction process between textiles and other objects, the color of the textiles falls off or the degree of staining of the rubbed objects is affected by many factors.

There are two ways for color to peel off and stain:

First, the dyes on the textiles fall off or fade and are stained on the surface of the friction object;

Second, the dyed fibers fall off and adhere to the surface of the friction object.

3. In practice, dye shedding is the main cause of staining

Although there are certain differences in the covalent bond strength and adhesion between reactive dyes with different chemical structures and cellulose fibers, their effects on the wet rubbing fastness of dyed fabrics are basically the same.

When dyed fabrics are wet rubbed, the covalent bonds formed between the dye and the fiber will not break and cause floating color. The transferred dye usually does not form a covalent bond with the fiber, but only relies on van der Waals forces to produce adsorption, that is, floating color.

Light fastness

1. Comparison of test methods for light fastness

The light fastness test refers to placing a textile sample and a set of blue wool standard samples under artificial light sources and exposing them under specified conditions, and then comparing the discoloration of the two to evaluate the color fastness.

2. Ways to improve light fastness

The photofading mechanism of dyes is very complex, but the main reason is that the dye is excited after absorbing photons, and a series of photochemical reactions occur to destroy the structure, resulting in discoloration and fading. The light fastness of textiles mainly depends on the chemical structure of the dye, as well as its aggregation state, combination state and mixed color matching. Therefore, the rational selection of dyes is very important.

3. Select dyes according to fiber properties and textile uses

For cellulose fiber textiles, dyes with better oxidation resistance should be selected; for protein fibers, dyes with better resistance to reduction or containing weak oxidizing additives should be used; for other fibers, dyes should be selected based on their impact on fading. In order to enhance the photooxidation stability of the azo group in the dye molecular structure, during the dye synthesis process, some strong electron-withdrawing groups are usually introduced at the ortho-position of the azo group, thereby reducing the electron cloud density of the azo gas atom.

In addition, hydroxyl groups can also be introduced into the two ortho-positions of the azo group, and their coordination ability can be used to complex with heavy metals, thereby reducing the electron cloud density of the hydrogen atoms of the azo group and shielding the azo group, ultimately increasing the Color fastness of dye to light.

4. The dye should be selected according to the color depth

A large number of tests have proven that the light fastness of reactive dyes on cellulose fibers is directly proportional to the depth of the dye, that is, the darker the color, the better the light fastness. This is because the higher the concentration of the dye on the fiber, the greater the aggregation of the dye molecules, the smaller the surface area of the same amount of dye exposed to air, moisture and light, and the lower the chance of the dye being photo-oxidized.

On the contrary, the lighter the color, the dye is mostly highly dispersed on the fiber, and the probability of being exposed to light is higher, resulting in a significant decrease in light fastness. Therefore, when dyeing light-colored varieties, dyes with higher light fastness should be used. In addition, many finishing agents such as softeners and anti-wrinkle finishing agents are added to the fabric, which will also reduce the light fastness of the product. Therefore, dyes that are not sensitive to these finishing agents should be selected.

5. Color matching dyes with good light stability and compatibility should be selected

Different dyes have different fading properties and even different photofading mechanisms. Sometimes, the presence of one dye can sensitize the fading of another dye. When color matching, you should choose dyes that will not sensitize each other and can even improve light stability. This is especially important when dyeing dark colors such as black.

If one of the three primary colors of dye fades too quickly, it will quickly cause the dyed fiber or fabric to discolor, and the faded dye residue will also affect the light stability of the other two dyes that have not faded. Reasonably control the dyeing process to fully combine the dye with the fiber and try to avoid hydrolyzed dye and unfixed dye.The dye residue on the fiber is an important way to obtain higher light fastness.

Color fastness to water/sweat

1. Comparison of test methods for color fastness to water and perspiration

The color fastness to water reflects the discoloration of the textile itself and the staining of the adjacent fabric under the combined action of a certain amount of moisture, pressure and temperature. During the test, after the sample and the backing fabric are fully soaked, they are placed in an oven at a certain temperature for a certain period of time under a certain pressure, then taken out to dry, and the discoloration and staining levels are evaluated. The discoloration and staining grades are divided into 5 levels, with level 5 being good and level 1 being poor.

The color fastness to perspiration reflects the discoloration of the textile itself and the staining of the adjacent fabric under the combined action of pressure and temperature in different test solutions containing histidine. Use a gray card to evaluate the discoloration of the sample and the staining of the backing fabric. The results are divided into 5 levels, with level 5 being good and level 1 being poor.

2. Ways to improve color fastness to water and perspiration

The main way to improve the color fastness of fabrics to water and sweat resistance is to rationally select dyes, especially dyes with high color fixation rate and good stability. Properly formulate and control the dyeing process, strengthen the fixation conditions, and form highly stable covalent bonds, which can fully fix the dye. For example, when dyeing less reactive dyes, a catalyst can be used, an appropriate fixing agent can be used, or the color can be fixed at a higher temperature.

From Zhejiang China Textile Label/Fabric 114