Rubbing color fastness test

Why should we assess the color fastness to rubbing of fabrics? When people wear clothing, friction will occur between the fabric and the lining; friction will also occur at various spliced parts; friction will also occur when leaning on objects; these frictions are likely to be caused by the fabric’s color fastness to friction. Off, resulting in color transfer, thus affecting the appearance of the clothing. Therefore, it is reasonable for the color fastness to rubbing test to be listed as a basic technical requirement in GB 18401 “National Basic Safety Technical Specifications for Textiles”.

Since color fastness to rubbing is so important, we should have a deeper understanding of color fastness to rubbing so that our test results can be close to the true value of the sample.

Common standards for rubbing color fastness testing

Chinese standard: GB/T 3920

International standards: ISO 105 X12/X16

American standards: AATCC 8/AATCC 116

Japanese standard: JIS L0849 Type I /Type II

Other national standards are not often used, so the standard numbers will not be listed here. We will only popularize the standard prefixes of various countries.

EN European Union

BS UK

CAN/CGSB Canada

AS Australia

DIN Germany

NF France

Knowledge points on rubbing color fastness testing

General rules for sampling:

Each color pattern of the sample is required to be tested;

Sample size and quantity:

♦Conventional rubbing color fastness tester: The minimum sample size is 50X130mm; 2 pieces each in the longitude and latitude directions. When used in AATCC series standards, take samples at a 45-degree angle along the warp and weft yarns, and only take 2 pieces.

♦Rotary rubbing color fastness tester: sample size is not less than 25X25mm; each color and pattern must be tested.

♦Curved surface rubbing color fastness tester: The sample size is not less than 30X220mm; 2 pieces each in the longitude and latitude directions.

Note: For cutting the color fastness to rubbing sample, it is not necessary to cut it from the sample. As long as it is convenient to install the sample, the sample does not need to be cut to save testing time and improve efficiency.

Humidity conditioning of samples:

The test samples and the small white friction cloth used for testing must be conditioned for no less than 4 hours under standard atmospheric pressure (temperature: 20°C, humidity: 65%); or they must be made of raw materials with high moisture regain such as wool or cotton. , the humidity adjustment time should be increased.

The humidity of the air will affect the friction coefficient of the fabric surface, and the humidity will also change the fiber morphology in the micro state and change the stress area of the fabric surface. Humidity control is a relatively important step and should not be abandoned to save test time, especially for fabrics made from fibers with high moisture regain.

Moisture content of wet friction:

Except for the moisture content of the AATCC series standards of 65%, other standards are 95~100%.

Different moisture contents of wet friction directly affect the test results of wet friction. The moisture content must be strictly controlled. After wetting the friction cloth, the test must be completed within the specified time; otherwise, due to long-term use, the water on the friction cloth will evaporate, reducing the moisture content. Thereby affecting the test results.

Number of frictions:

♦Conventional rubbing color fastness tester: for 10 reciprocations, the frequency is 1 reciprocation/second; the stroke is 10cm.

♦Rotary friction color fastness tester: rotate the crank 20 times and the friction head 40 times.

♦Curved surface rubbing color fastness tester: Mainly used for JIS L0849 Type II, the number of times is 100 times, the stroke is 20cm.

When using a manual rubbing color fastness tester for testing, please pay attention to the starting and ending positions of the rubbing stroke. Generally, to make the rubbing cycle exactly 10 reciprocations, we can place the starting point inside the rubbing color fastness tester, so that When rubbed 10 times, it is easier to determine where the friction movement returns to the starting point.

Rating of color fastness to rubbing:

After all tests are completed, the friction cloth must be conditioned in a standard atmospheric pressure environment for at least 4 hours before it can be rated.

For rating, the fluff on the surface of the friction cloth needs to be removed with transparent tape.

When rating, raters need to use D65 light source for at least 2 minutes; the sample is placed at 45 degrees to the light.

When rating, 3 pieces of unused friction cloth need to be placed on the back of the friction cloth as the base cloth.

Factors affecting color fastness to rubbing

✔Physics:

Surface friction resistance of fabric

For different fabrics, the surface friction resistance is different; such as: cotton, linen, bamboo fiber fabrics, denim fabrics, paint-printed fabrics, etc., have rough surfaces. During dry friction tests, it is easy to remove dyes, paints or dyes accumulated on the surface of the fabrics. Other colored substances are ground off, even causing some colored fibers to break and form colored particles, which reduces the color fastness to dry rubbing.further decline. For brushed or raised fabrics, the fluff on the surface of the fabric is at a certain angle with the surface of the friction cloth and is not parallel, which increases the friction resistance of the friction head during reciprocating motion, making this type of fabric more resistant to drying. Color fastness to rubbing is reduced.

Hydrophilicity of fiber

Most chemical fibers are water-repellent fibers; while most natural fibers or natural cellulose fibers are hydrophilic fibers. For water-repellent fibers, when rubbing, in the dry state, the friction is greater than in the wet state; in the wet state, the water plays a certain lubrication effect, thereby reducing the friction resistance. Therefore, the dry rubbing color fastness of chemical fiber fabrics will be lower than the wet rubbing color fastness.

For hydrophilic fibers, the action of water will cause the fibers to absorb water and swell, thus increasing friction resistance. This is exactly the opposite of what happens with chemical fibers.

✔Chemistry:

There are many types of dyes. Among them, samples dyed with reactive dyes such as water-soluble dyes are easily transferred to the rubbing cloth when wet rubbed;

The saturation of dyes. When processing dark fabrics, an important concept is dye concentration. When the dye concentration exceeds the saturation value of the dye, a certain amount of dye will not be able to enter the interior of the fiber or be combined with the fiber surface; these excess dyes will accumulate on the surface of the fabric to form floating colors. When the color fastness to rubbing is performed, these surfaces will The floating color will be transferred to the friction cloth in large quantities and cause serious staining.

The use of additives generally follows the following principles: 1. fixing color; 2. removing floating color on the fabric surface; 3. reducing the frictional resistance on the fabric surface.

From: textiletest