Color fastness refers to the performance that the dyes on the textile are subjected to various factors to maintain the original color to varying degrees during the use or subsequent processing of dyed products. The dyeing fastness of fabric is related to fiber type, yarn structure, fabric structure, printing and dyeing method, dye type and external conditions. There are many kinds of color fastness, mainly including sun fastness, washing fastness, rubbing fastness, perspiration fastness, ironing fastness, etc.
Fastness to sunlight
Sun fastness refers to the degree of discoloration of colored fabrics under the action of sunlight. The test method can be either sunlight or heliometer. The fading degree of the sample after sunlight is compared with the standard color sample to determine the result. The sun fastness is divided into 8 grades, with grade 1 being the lowest and grade 8 being the highest.
Color fastness to washing
Color fastness to washing refers to the fastness of dyes to washing in soap and other solutions. The color fastness to washing includes the fastness to fading as is and staining of white cloth. Fading as is refers to the fading of the fabric before and after soaping. Staining of white cloth refers to the staining of white cloth soaped at the same time as the dyed fabric due to the fading of the dyed fabric. The fading and staining grades of color fastness to washing shall be evaluated according to gray sample card and staining sample card respectively. The sample card is divided into 5 levels, level 1 is the worst and level 5 is the best.
Rubbing fastness
Rubbing fastness refers to the fading degree of dyed fabric after rubbing, which can be divided into dry rubbing fastness and wet rubbing fastness. Dry rubbing fastness refers to the staining of white cloth when it is rubbed with dry white cloth under certain pressure. Wet rubbing fastness refers to the staining of white cloth with 100% moisture content under the same rubbing conditions. Therefore, wet rubbing fastness is generally worse than dry rubbing fastness. The test method of rubbing fastness is gb3920-2008. During the test, the white cloth is rubbed with the sample under the specified conditions, and the grade is evaluated by comparing the fading and staining of the original white cloth with the fading and staining gray sample card respectively. The rubbing fastness is also divided into 5 levels, with level 1 being the worst and level 5 being the best.
Fastness to mercerizing finish
In order to improve the added value of cotton dyes, it is necessary to carry out post mercerization and further fix the hydrolyzed dyes at the same time. There are many kinds of color fixing agents for reactive dyes, each of which has its own characteristics and shortcomings. It is difficult to solve all the problems of color fastness and other properties through a single color fixing agent. According to the synergistic effect, using the mixture of different color fixing agents is an effective way.
Ironing fastness
Ironing fastness refers to the degree of discoloration or fading of dyed fabrics during ironing. This discoloration and fading degree is evaluated by the staining of other fabrics by the iron at the same time. Ironing fastness is divided into 5 levels, 5 is the best and 1 is the worst. When testing the ironing fastness of different fabrics, the iron temperature for the test should be selected.
Sublimation fastness
Sublimation fastness refers to the degree of sublimation of dyed fabrics during storage. The degree of discoloration, fading and white cloth staining of the fabric after dry hot pressing is evaluated by gray grading sample card. It is divided into 5 levels, of which level 1 is the worst and level 5 is the best.
Fastness to chlorine
Because active chlorine exists in tap water, the worse the water quality is, the more chlorine is introduced. Reactive chlorine can change and fade the dyed fabric, which first occurs on the fiber surface. It is considered that the mechanism is that the positively charged chlorine attacks the dye on the surface of the fiber, oxidizes and decomposes the dye molecules, resulting in the breaking of its chemical bond and the fading of the dyed fabric. Therefore, higher requirements are put forward for the chlorine fastness of reactive dyes.
