introduce
Consumers today are smarter than ever. They focus not only on the decoration and comfort of textiles, but also on the durability and safety of textiles. They need quality products. Market research shows that most of the time consumers buy textiles based on color. Therefore, the ability of fabric to retain its original color is one of the most important properties of textiles.
What does color fastness mean?
Colour fastness is defined as the ability to retain the colour of the original dye during the use of dyed textiles under the influence of other external factors. Or we can define colour fastness as follows: Colour fastness refers to the resistance of colour to fading or staining of dyed or printed textile materials, such as water, light, rubbing, washing, perspiration, etc. This is an important indicator to measure the quality of dyeing products.
Color fastness classification
Due to the use of chemicals in the dyeing and finishing process, such as acids, bases, oxidants, reductants, etc., and in washing, sunlight, friction, sweat, high temperature and other environments, dyed textiles may fade or fade. Become angry. Therefore, dye color fastness is various, including washing fastness, light fastness, rubbing fastness, sweat fastness, chlorine fastness, ironing fastness, etc.
The requirements for colour fastness of textiles vary with their uses and processes. For example, curtains that are not washed well require low color fastness, but require high color fastness due to long exposure to the sun. Summer clothing fabrics should have high fastness to light, washing and perspiration because they are always exposed to the sun and the human body is always sweating.
Different countries have set different standards for different color fastness requirements of different textiles. The main criteria for colour fastness are as follows
1. AATCC (American Society of Textile Chemists and Colorists) Technical Manual:
Describes 66 different colour fastness tests.
2. SDC (Association of Dyes and Dyers) :
In 1927, the SDC (Europe) established the Fastness Testing Committee.
ISO (International Organization for Standardization) :
In 1947, ISO established a Subcommittee on Color. ISO also grades color fastness:
Fastness to light: 1 ~ 8
Other fastness: 1 ~ 5
Factors affecting colour fastness characteristics
Chemical properties of fibers. For example, cellulose fibers dyed with reactive or VAT dyes will show good fastness. Protein fibers dyed with acidic mordant and reactive dyes will have good fastness and other properties. In other words, the compatibility of dye and fiber is very important.
Molecular structure of dye molecules: For example, if the dye molecule is large in size, it will be tightly bound to the interpolymer chain space of the fiber. So you get better fastness. In addition, the actual situation in the process of use will also have different degrees of influence on the color fastness of textiles.
results show that for different types of dyes, we can properly treat them during dyeing to improve the color fastness of dyes. For example, after dyeing fabrics, direct dyes react with metal salts or cationic fixatives to produce insoluble compounds, thus improving the wet fastness of direct dyes. After dyeing with disperse dyes, polyester fabrics can be reduced by reducing agents and alkaline reagents to remove floating color and improve color fastness. After dyeing with reactive dyes, textiles can be washed with soapy water to improve colour fastness to a certain extent. In addition, different uses and environmental conditions of textiles determine the key points and requirements of color fastness testing.
How is colour fastness tested?
Because the conditions and requirements for fabric processing and use vary greatly, most current testing methods are modeled according to the working environment and conditions, and therefore there is a wide range of testing methods for colour fastness. But international Standards Organization (ISO), American Society of Dyes and Chemists (AATCC), Japan (JIS), Britain (BS) and many other standards, the most commonly used test is washing resistance, light resistance, friction resistance and sweat resistance, ironing resistance, weather resistance and so on.
In practical work, the detection items are mainly determined according to the final use of products and product standards. For example, wool textile products must be tested for colour fastness to light, and of course knitted underwear must be tested for colour fastness to sweat. Outdoor textiles (e.g. umbrellas, lightbox cloth, canopy material) have been tested for weather resistance. This is an example of how to test for colour fastness to washing.
Definition and measurement of washing colour fastness
1. Color fastness to washing
It refers to the discoloration and discoloration of dye textiles during soaping. The main machine for washing colour fastness is the washing colour fastness tester. Normally, two indicators are measured in the wash colour fastness test, including the fading of the original sample and the staining of the white cloth. Fading of the original sample is the color change of the textile dyed before and after soaping. Dyeing of white cloth is the soaping of white cloth with dyed fabric.
In tests, stained samples are sewn together with one or two specified woven fabrics, placed in a soapy solution, stirred mechanically at a specified time and temperature, then rinsed and dried. At this point, the stained sample will fade and contaminate the nearby white fabric. Discoloration of stained samples and stains of adjacent fabrics were measured by gray cards. Watercolor fastness is divided into 5 grades and 9 grades, with the best grade being 5 and the worst grade being 1.
2. Wash color fastness test
(1) Laboratory equipment and materials
Color fastness to washing tester (FIG. 1), gray card for evaluation of discoloration, gray card for evaluation of staining, beaker, anhydrous sodium carbonate (CP), standard soap paper, standard multi-fiber repair cloth (made of wool, polyacrylonitrile fiber, polyester, polyamide fiber, cotton) (vinegar fiber) or single fiber repair cloth, to be tested samples.
Figure 1 Washing colour fastness tester
1 Drain water pump 2 Heater protector 3 Passive gear 4 Motor 5 Reducer 6 Motor vise 7 Drainage port
8- Drive Gear 9- Rotary frame 10- Test cup 11- Studio temperature controller 12- Time relay 13- Buzzer
14- Preheating room temperature controller 15- Drain switch 16- Door cover 17- Power switch 18- Insulation
19- Temperature sensor 20- Tubular heater 21- drain pipe 22- Drain pipe connection 23- Water pipe 24 rounds
(2) Test method
A) Sample preparation
① Fabric sample. Take a 40mm * 100mm sample, then sew its positive pole and 40mm * 100mm multi-fiber patch cloth together along the short side to form a composite sample; Or place the sample in two 40mm * 100mm single fiber patch cloths, the first single fiber patch cloth made from the same fiber as the sample, and the second from the corresponding fiber of the first woven fabric in Table 1. Is a mixed textile or wound fabric, the first piece is made of the fibers of the primary component, the second piece is made of the fibers of the secondary component.
② Sample of yarn or scattered fiber. Insert approximately half of the total mass of adjacent fabrics into 40mm * 100mm multi-fiber adjacent fabrics
A piece of non-dyeable 40mm * 100mm fabric (e.g. polypropylene fibre) sewn along four edges to form a composite sample. Either a filling yarn or approximately half the total mass of adjacent fabrics are inserted between two adjacent 40mm * 100mm single-fiber fabrics, sewn along four edges to form a composite sample. If the sample is yarn, it can be woven into a woven fabric and tested according to the textile testing method.
Table 1 Selection of adjacent fabrics for testing colour fastness to washing
|
first part |
second thing |
|
first part |
second thing |
|
|
|
40℃/ 50℃ |
60℃/ 95℃ |
|
40℃/ 50℃ |
60℃/ 95℃ |
|
cotton |
wool |
Viscous fiber |
Vinegar fibers |
Viscous fiber |
Viscous fiber |
|
wool |
cotton |
--- |
Polyamide fibre |
mao/cotton |
cotton |
|
silk |
cotton |
--- |
Polyester fiber |
mao/cotton |
cotton |
|
linen |
wool |
Viscous fiber |
Polyacrylonitrile fiber |
mao/cotton |
cotton |
|
Viscous fiber |
wool |
cotton |
--- |
--- |
--- |
B) Operating procedures
① According to product types and requirements, parameters of color fastness to washing are shown in Table 2. If the fabric material is silk, viscose fiber, wool, nylon, method 1 can be used. If the raw material is cotton, polyester or nitrile, method 3 can be used.
Table 2 Test parameters of color fastness to washing
|
Set conditions |
Temperature (℃) |
Time (minutes) |
Soap composition (bath ratio) |
|
Steel ball |
|
|
|
|
Standard soap paper (g/L) |
Anhydrous sodium carbonate (g/L) |
|
|
Method 1 |
40 2± |
30 |
5 |
--- |
--- |
|
Method 2 |
50 2± |
45 |
5 |
--- |
--- |
|
Method 3 |
60 2± |
30 |
5 |
2 |
|
|
Method 4 |
95 2± |
30 |
5 |
2 |
10 |
|
0Method 5 |
95 2± |
240 |
5 |
2 |
10 |
② Place the prepared mixture sample into a container and pour the soapy liquid preheated to a specific temperature into it.
③ Turn on the washing colour fastness tester.
(4) Take out the combined sample within a certain time and wash it twice with grade 3 water. It is then rinsed under running cold water and squeezed to remove excess water. Finally separated, the sample was attached to the adjacent fabric by short-side stitching, hung and dried in air not exceeding 60℃.
Grey cards were used to assess the discoloration of the original sample and the staining of adjacent fabrics.