Color fastness is also called color fastness and dye fastness. It refers to the resistance of the color of textiles to various effects during processing and use. The fastness grade is evaluated according to the discoloration of the sample and the staining of the undyed lining fabric.
During its use, textiles will be exposed to various external effects such as light, washing, ironing, perspiration, friction and chemical agents. Some printed and dyed textiles are also subjected to special finishing processes, such as resin finishing, flame retardant finishing, sand washing, and grinding. This requires that the color of printed and dyed textiles relatively maintain a certain fastness.
Factors affecting color fastness:
The so-called color fastness (abbreviated as color fastness) means that the dyed fabric is subjected to external factors (extrusion, friction, washing, rain, exposure, light, seawater 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 most commonly used items are washing resistance, light resistance, friction resistance, perspiration resistance, ironing resistance, and weather resistance.
In actual work, the test items are mainly determined according to the end use of the product and product standards. 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, while the outdoor textiles (Such as parasols, light box cloth, canopy materials), of course, the color fastness to weather resistance must be tested.
Including: color fastness to soaping (sample), color fastness to rubbing, color fastness to chlorine water, color fastness to non-chlorine bleaching, color fastness to dry cleaning, color fastness to actual washing (clothing, fabric), perspiration resistance Color fastness, color fastness to water, color fastness to light, color fastness to sea water, color fastness to saliva.
How to test the color fastness?
1. Color fastness to washing
The sample and the standard lining fabric are stitched together, washed, cleaned and dried, and washed under suitable temperature, alkalinity, bleaching and friction conditions, so that the test results can be obtained in a relatively 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 rating 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 the test standards and customer requirements. Generally, the colors with poor color fastness to washing are turquoise blue, brilliant blue, black scarlet, navy blue and so on.
2. Color fastness to dry cleaning
The color fastness is the same as washing, except that washing is changed to dry cleaning.
3. Color fastness to rubbing
Place the sample on the rubbing fastness tester and rub it with a standard rubbing white cloth for a certain number of times under a certain pressure. Each group of samples must be tested for dry rubbing fastness and wet rubbing 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. Color fastness to rubbing requires two tests, dry rubbing and wet rubbing, and all colors on the sample must be rubbed.
4. Color fastness to sunlight
Textiles are usually exposed to light when they are in use. Light can destroy dyes and cause the well-known "fading", which makes colored textiles lighter and darker, and some of them will also change color. Therefore, it is necessary to color fast The test of color fastness to light is to put the sample and blue wool standard cloth of different fastness grades together under the specified conditions for sunlight exposure, compare the sample with the blue wool cloth, and evaluate the light fastness For color fastness, the higher the grade of blue wool standard cloth, the better it is to light.
5. Color fastness to perspiration
The sample and the standard lining fabric are stitched together, treated in a sweat solution, clamped on the perspiration fastness tester, placed in an oven at a constant temperature, then dried, and graded with a gray card to obtain the test results. Different test methods have different perspiration liquid ratios, different sample sizes, and different test temperatures and times.
6. Color fastness to water stains
The water treatment sample is tested as above.
Color fastness to chlorine bleaching: After the fabric is washed in a chlorine bleaching solution under certain conditions, the degree of color change is evaluated. This is the color fastness to chlorine bleaching.
7. Color fastness to non-chlorine bleaching
After the fabric is washed under washing conditions with non-chlorine bleach, the degree of color change is evaluated, which is the non-chlorine bleach color fastness.
8. Color fastness to pressing
After the dry sample is covered with a cotton lining fabric, it is pressed for a certain period of time in a heating device with a specified temperature and pressure, and then the gray scale is used 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.
Types of color fastness test and analysis of fastness:
The nature or degree of the variation of the dyeing state can be expressed by the color fastness.
The dye fastness of the fabric is related to the type of fiber, yarn structure, fabric structure, printing and dyeing method, dye type and external force.
The color fastness test generally includes light fastness, weather fastness, washing fastness, rubbing fastness, perspiration fastness, etc. Sometimes there are some according to different textiles or different use environments. Color fastness for special requirements.
Generally, the color fastness test is the degree of discoloration of the dyed material and the degree of staining to the lining. The color fastness is rated, except for the light fastness of eight, the rest are all five. The higher the grade, the better the color fastness.
1. Light fastness
Light fastness refers to the degree of discoloration of colored fabrics by sunlight. The test method is to compare the fading degree of the sample after simulating sunlight with the standard color sample, which is divided into 8 grades, 8 is the best result, and 1 is the worst. Fabrics with poor light fastness should not be exposed to the sun for a long time and should be dried in the shade in a ventilated place.
2. Washing fastness
Washing or soaping fastness refers to the degree of color change of dyed fabrics after washing with washing liquid. Usually, the gray graded sample card is used as the evaluation standard, that is, the color difference between the original sample and the faded sample is used for judgment. 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.
3. Friction fastness
Friction fastness refers to the degree of fading of dyed fabrics after friction, which can be dry friction and wet friction. The rubbing fastness is evaluated based on the degree of white cloth staining, and it is divided into 5 levels. The larger the value, the better the rubbing fastness.
4. Perspiration fastness
Perspiration fastness refers to the degree of discoloration of dyed fabrics after a small amount of perspiration.
5. Ironing fastness
It refers to the degree of discoloration or fading of dyed fabrics during ironing.
6. Sublimation fastness
It refers to the degree of sublimation of dyed fabrics during storage. The dye fastness of normal fabrics generally requires 3-4 grades to meet the needs of wearing.