Leather color fastness rub tester test leather color fastness experiment معدات اختبار

Product introduction

Leather is a fabric that is sensitive to color migration, and color migration not only affects the inherent color of the leather It also affects the color of objects that come into contact with it, resulting in clear

product quality defects. In practice, product quality problems and trade conflicts due to leather color migration are relatively common, and leather color migration has increasingly become the most important quality indicator for leather testing.

Essentially, color migration belongs to the category of color fastness (the ability to withstand external effects without changing color), but it has nothing to do with friction resistance, water stain resistance , heat resistance, light resistance, etc. Color migration is a more complex process than color fastness. The leather rub color fastness testthere is a test instrument for testing the color fastness color fastness of leather against rubbing. It detects the color migration of automotive leather, furniture leather and shoe upper leather, and compares and analyzes the degree of color migration. The rub fastness results were compared and the correlation between the two color fastness results was analyzed.

1. Experimental part

Instruments and materials

For polyvinyl chloride film (white), the sample test frame is the same as the test sample frame for color fastness to perspiration, where the hammer weight is 4.5kg and the bottom size is 11.5cm ×6cm. The size of the glass plate is 8 cm x 5 cm and the surface is flat. The oven is conventional and can control the temperature (50 ± 2) ℃.

The tested leather samples are divided into automotive leather, furniture leather and upper shoe leather according to their use, with 10 pieces for each category. All samples becameand placed in a standard air environment for more than 24 hours before the experiment.

Experimental method

1. Determination of leather color migration

Currently there are ISO 15701 and ASTM D5552 standards for the detection method of color migration in leather. Among them, ISO 15701 uses polyvinyl chloride film as the color bonding material, while ASTM D5552 uses white cotton liner as the color bonding material, which must be soaked in distilled water before use. In comparison, the operation of ISO 15701 is simpler and widely accepted by tanneries. This experimental operation adopts the method standard. The editing process is as follows:

Cut the sample (20mm × 30mm) with a die, and then stick the tested surface of the sample on the polyvinyl chloride film (PVC for short, 50 mm × 30 mm), place the tested side down and place the sample on two strips. Place the plate from the mbetween the plates in the apparatus and place a 4.5 kg weight on top, rotate the apparatus gently while maintaining the pressure, move the weight to keep the sample at an average pressure of 750 g/cm2 during the test. Place the device in the oven, the temperature of the oven should be within the range of (50 ± 2 )°C, and place it for 16 hours. Remove the sample from the device and place it at room temperature to cool, then separate the sample and the PVC sheet and use the gray scale to evaluate the color of the PVC sheet.

According to the requirements of GB/T 251, the rating results of tacky color are given and divided into 5 grades, of which 5 grades indicate no tacky color and no color migration , 1 Grade 1 indicates severe staining with significant color migration.

2. Determination of color fastness to wet rubbing of leather

Determination of color fastness to wet rubbing of leather is in agreementtuning with QB/T According to the requirements of 2537, the operation is as follows: fix the white felt soaked in deionized water and pressed on the test head (500g) of the rub color fastness tester, and then fix the leather sample on the test table of the instrument, slightly facing above and elongate 10% along the friction direction; put down the test head with felt, start the instrument, stop after 250 times, remove the felt and evaluate the color fastness of the felt according to the requirements of GB/T 251.

2. Results and discussion

1. Results of color migration

The measurement results of the color migration of the selected shoe uppers, furniture leathers and automotive leathers are summarized in Table 1, Table 2 and Table 3, respectively. Analysis of the data in Table 1 shows that the average color migration rate of the tested shoe uppers is 3, indicating that the color migration in the samples is clear and that the color migration ofindividual samples is severe (such as A02). The data in Table 2 shows that the average color migration grade of the tested furniture leather is between 4, indicating that the color in the sample has a slight shift. The data in Table 3 shows that the color migration degree of the automotive leather tested is essentially between 4 and 5, indicating that there is essentially no color migration in the sample.

The comparison of the data in the three tables shows that the color migration results of different applications of leather differ considerably, which is related to the processing technology and quality requirements of the product. In general, the requirements for the color fastness of automotive leather are the highest, because car manufacturers have a complete quality index system for leather fabrics, which poses a problem for the processing technology of tannery, the dyes, pigment pastes and additives used. There are strict requirements for klprevent euro migration in leather fibers and coatings. Therefore, of the three tested leathers, the degree of color migration in automotive leather is the smallest. Compared with car factories, buyers of shoe leather and furniture leather have relatively loose quality requirements, so the product quality requirements are lower than those of car leather, which also leads to relatively obvious color migration in the two types of samples tested.

2. Color Migration and Wet Rub Resistance Correlation Analysis of Fastness

In the experiment, the wet rub resistance of the selected samples was were further analyzed to analyze the correlation between color migration and color fastness to rubbing, the results are listed in Table 1, Table 2 and Table 3. When analyzing the results in the three tables, it can be seen that the average color fastness to wet rubbing of shoe uppers is between 2 and 3, the average color fastness to wet rubbing of furnitureleather is about 4, and the average color fastness to wet rubbing of automotive leather is 4. Between ~5 levels. That is, the color fastness to wet rubbing is best for automotive leather, next for furniture leather, and worst for upper leather of shoes, which corresponds to the color migration test results of the three kinds of samples. At the same time, each sample in the three tables is analyzed separately, and it can also be found that the samples with poor color fastness to rubbing (lower quality) have more significant color migration (lower quality), while the color fastness to rubbing is higher. (high level), the color migration is not clear (high level). This indicates that there is some similarity between color fastness to rubbing and color migration, i.e. samples with poor color fastness to rubbing also show clear color migration.

However, the data in the three tables also show that the results van color migration may not reflect the results of color fastness to rubbing, such as samples A03, B09 and C04, that is, color migration Remarkable sample (low content), which still has high crock fastness (high grade), also reflects that the color migration quality index differs of the color fastness, due to the color migration characteristic of the higher temperature of the coating and dyes, pigments in fiber and their extensive phenomena under the action of water, solvents and additives, etc., while the color fastness to rubbing only characterizes the situation of dyes or dyes leached by water under the action of pressure and water, and it is related to the fastness of the film in the coating. Therefore, the degree of color migration cannot reflect cake fastness.

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