How to improve the color fastness of fabrics?

What is color fastness?
Color fastness is also known as dyeing fastness and dyeing fastness. It refers to the resistance of the color of textiles to various functions in the process of processing and use. The fastness grade is evaluated according to the discoloration of the sample and the staining of the non-dyed lining fabric. Textile color fastness test is a routine item in textile intrinsic quality test.
It is an important index to measure the quality of dyes. The main contents of the evaluation are light fastness, washing fastness, friction fastness, perspiration fastness, saliva fastness, ironing fastness, etc.
Usually, the color fastness test is the degree of discoloration of the dyes and the staining degree of the lining. The color fastness rating is five except the light fastness grade 8. The higher the series, the better the color fastness.
Light fastness (sun fastness)
Sunlight fastness refers to the ability of printing and dyeing fabrics to maintain their original color under illumination, that is, the ability of non-fading and non-fading under illumination.
There are eight levels of light fastness, the first level is the largest and the eighth level is the smallest.
There are three methods to test the color fastness to sunlight: sunlight test, xenon arc lamp test and carbon arc lamp test.
The general test procedure for the color fastness to sunlight is as follows:
The textile sample and the reference standard sample (blue standard wool) agreed by both sides were exposed to artificial light source in accordance with the specified conditions, then the discoloration degree of the two samples was compared, and the light fastness grade of the sample was determined by the standard sample of the light fastness of the blue wool exposed at the same time.
The relative comparison method is used in all the test standards of sunshine color fastness, and the test results are not provided directly by the sunshine equipment. The performance of the equipment depends mainly on the control of the parameters affecting the test environment.It includes spectrum, illumination intensity, temperature, relative humidity and so on.
Colour fastness to perspiration
The color fastness to perspiration is a reflection of textiles'self-discoloration and pornography on the lining fabric under the combined action of pressure and temperature in different test solutions containing histidine. The grey card was used to evaluate the discoloration of the sample and the staining of the lining fabrics. The results were classified into 5 grades, 5 grades were the best and 1 grades was the worst.
Test methods:
The samples were stitched together with standard lining fabrics, treated in perspiration solution, clamped on the perspiration fastness tester, placed in the oven at constant temperature, then dried, graded with gray card, and the test results were obtained. Different testing methods have different proportion of sweat stain, different sample size, different testing temperature and time.
Colour fastness to rubbing
The textile sample is rubbed with a dry friction cloth and a wet friction cloth respectively to determine the staining degree of the friction cloth.
Test methods:
The samples were placed on a friction fastness tester and rubbed with standard white cloth for a certain number of times at a certain pressure. The dry and wet color fastness of each group of samples were required. The color stained on the standard friction white cloth is graded by gray card, and the series obtained is the measured color fastness to friction. Friction colour fastness requires dry and wet rubbing tests, and all colours on the sample are rubbed to.
colour fastness to washing
Textile color fastness test is a routine item in textile intrinsic quality test. When testing, the fastness grade is evaluated according to the discoloration of the sample and the staining of the non-dyed lining fabric. The color fastness to Washing of fabrics is one of the most important properties of textiles. It refers to the degree of color change of non-ferrous fabrics and the degree of staining of many kinds of fiber fabrics after washing for a certain time in a certain temperature and bath ratio solution.
Test methods:
Water-washing color fastness test is the most important and common item in textile inspection. It is to sew white cloth on the sample, put it into a certain temperature of washing liquid, soak and wash it in accordance with the prescribed time under mechanical stirring, and evaluate the grade of discoloration and staining with grey card after drying. Due to the variety of washing methods and detergents, the test results are an index with strict conditional value. Specific steps are as follows: stitching sample according to standard & rarr; allocating soap solution & rarr according to standard method; washing & rarr according to standard method; cleaning & rarr; drying & rarr; grading with gray sample card or instrument.
Some dyes can dye brighter colors, but because of the water-soluble groups on the dyes, the fastness to wet treatment is poor, and the fading and staining phenomena are serious, which not only make the appearance of the textiles obsolete, but also stain the white or other colored fibers when the dyes fall off. It produces staining and matching phenomenon.
In addition, although reactive dyes can form covalent bonds with cellulose fibers, the fastness to wet treatment will also be reduced if hydrolytic dyes or inadequate soaping of unbounded dyes are present in dyeing process. In addition, reactive dyes with covalent bonds with fibers may break bonds in acidic or alkaline conditions, and The color fastness to chlorine, perspiration and sunshine is insufficient.
In order to improve the color fastness of fabrics, fixing treatment can be carried out. These auxiliaries which can improve various kinds of dyeing fastness are called fixing agents.
Fixing Principle of Fixing Agent
1. Insoluble colour lakes are formed on the fabrics and soluble groups are sealed so that the dyes on the fabrics are not easy to dissolve and fall off when they are exposed to water, so as to improve the fastness to wet treatment. But after fixing with these fixing agents, the color and light of the fabrics will change or the fastness to sunlight will decrease.
2. To prevent the dye from falling off, a network film is formed on the fabric.
3. Reactive groups in the fixing agent molecule, reactive groups on the dye molecule and hydroxyl groups on the cellulose molecule are used to cross-link to improve the fixation effect of dyes on fibers.
4. Using the molecular attraction between fixing agent and fibers, the fixation strength of fixing agent is increased, and the dyeing fastness is improved.