Color fastness (dyeing fastness)

Update: 10-05-2019
Abst: The so-called color fastness (referred to as color fastness) means that the dyed fabric is subjected to external factors (extruding, friction, wash...

The so-called color fastness (referred to as color fastness) means that the dyed fabric is subjected to external factors (extruding, friction, washing, rain, exposure, light, sea water immersion, saliva immersion, water stains, sweat stains) during use or processing. Etc.) The degree of fade under the action is an important indicator of the fabric.

The color fastness is good or bad, directly related to the health and safety of the human body. During the wearing process, the product with poor color fastness will cause the pigment on the fabric to fall off and fade when it encounters rain or sweat. The dye molecules and heavy metal ions are all It may be absorbed by the human body through the skin and endanger the health of the human skin. On the other hand, it may also affect other clothing worn on the body to be stained, or stain other clothing when washed with other clothing.

However, looking at the International Standards Organization (ISO), the American Society of Dyeers and Chemists (AATCC), Japan (JIS), the United Kingdom (BS) and many other standards, the most commonly used are washing resistance, light resistance, abrasion resistance, perspiration resistance, and Ironing, weather resistance, etc.

In actual work, the test items are mainly determined according to the end use of the product and the product standard. For example, the wool textile product standard stipulates that the color fastness to sunlight must be tested. Of course, the perspiration fastness of knitted underwear must be tested. Textiles (such as parasols, light box cloth, canopy materials) must of course be tested for color fastness to weather.

The dye fastness of normal fabrics generally requires 3-4 grades to meet the needs of wearing.

Washing color fastness: The sample is sewn together with the standard lining fabric, washed, washed and dried, and washed under suitable temperature, alkalinity, bleaching and friction conditions, so that the test results can be obtained in a short time . The friction during the process is accomplished by rolling and impacting with a small bath ratio and an appropriate number of stainless steel beads. The gray card is used for grading and the test results are obtained. Different test methods have different temperature, alkalinity, bleaching and friction conditions and sample size, and the specific ones should be selected according to test standards and customer requirements. Generally, the colors with poor color fastness to washing are turquoise blue, brilliant blue, black, scarlet, navy blue, etc.

Color fastness to dry cleaning: Same as color fastness to washing, except that washing is changed to dry cleaning.

The washing fastness is divided into 5 grades, grade 5 is the best and grade 1 is the worst. The fabrics with poor washing fastness should be dry-cleaned. If they are wet-washed, the washing conditions should be paid extra attention, such as the washing temperature should not be too high and the time should not be too long.

Color fastness to rubbing: Put the sample on the rubbing fastness tester, rub it with a standard white cloth under a certain pressure for a certain number of times. Each group of samples needs to do dry rubbing color fastness and wet rubbing color fastness. The color stained on the standard rubbing white cloth is graded with a gray card, and the grade obtained is the measured rubbing color fastness. The color fastness to rubbing needs to be tested for dry rubbing and wet rubbing. All the colors on the sample must be rubbed.

Light fastness: Textiles are usually exposed to light when they are in use. Light can destroy dyes and cause the well-known "fading", which causes colored textiles to become lighter and darker. In some cases, the color and light will change. , It is necessary to test the color fastness. The light fastness test is to put the sample and blue wool standard cloth of different fastness grades together under the specified conditions for sunlight exposure, and the sample and the blue wool The cloth is compared to evaluate the light fastness. The higher the blue wool standard cloth, the better the light fastness.

Color fastness to perspiration: sew the sample together with the standard lining fabric, put it in a sweat solution, and place it on the perspiration fastness tester, put it in an oven at a constant temperature, then dry, and use a gray card for rating. Get the test result. Different test methods have different perspiration liquid ratios, different sample sizes, and different test temperatures and times.

Color fastness to water stains: Test as above with water-treated samples.

Color fastness to chlorine bleaching: After washing the fabric in a chlorine bleaching solution under certain conditions, evaluate the degree of color change. This is the color fastness to chlorine bleaching.

Color fastness to non-chlorine bleaching: After washing the fabric under washing conditions with non-chlorine bleaching, evaluate the degree of color change, which is the color fastness to non-chlorine bleaching.

Pressing color fastness: After covering the dry sample with a cotton lining fabric, press it for a certain period of time in a heating device at a specified temperature and pressure, and then use a gray scale to evaluate the color change of the sample and the staining of the lining fabric. The color fastness of hot pressing includes dry pressing, wet pressing, and wet pressing. The specific test method should be selected according to different customer requirements and test standards.

Color fastness to saliva: attach the sample to the specified lining fabric, treat it in artificial saliva, remove the test solution, place it between two plates in the test device and apply the specified pressure, and then place the sample Dry the lining fabric separately, and use a gray card to evaluate the discoloration of the sample and the staining of the lining fabric.

For the color fastness rating, except for the light fastness of eight grades, the rest are all five grades. The higher the grade, the better the color fastness.