Commonly used fabric testing methods

Commonly used fabric testing methods Commonly used methods: ASTM E96 BW, American Society for Testing and Materials standards, water vapor cup method. Since the United States has always been in the leading posi…

Commonly used fabric testing methods

Commonly used methods: ASTM E96 BW, American Society for Testing and Materials standards, water vapor cup method.
Since the United States has always been in the leading position in this industry, and the country’s market is also very large, the data tested by this method is also relatively high, and the ASTM standard has naturally become a commonly used method. Most customers now use this method for testing.
The test principle is as follows: Cover the fabric to be tested on a moisture-permeable cup filled with distilled water, fix it and turn it upside down, weigh it using a top-loading balance with an accuracy of 0.001g, and place it in the position of the wind tunnel row. Before the cup enters an environmental chamber with a temperature of 23°C, a relative humidity of 50%, and a wind speed of 2.5m/s for weighing, record the temperature and relative humidity of the environment. The weight of each cup and the time it took to weigh it were recorded. Record the weight at 3h, 6h, 9h, 13h, 23h, 26h, and 30h, and use the formula WVT=24*△m/(s*t) to calculate the water vapor transfer rate. The average value of 6 samples is used as the test result. The average value is multiplied by 24 and converted to the result in g/m2*24h.
It should be particularly pointed out that the ASTM E96 BW method has 1995 and 2000 editions. The test conditions of the 95 edition are immature and the relative test data is relatively high. Now the 2000 edition is basically used.
2. Methods with high test results: JIS L-1099 B1, B2 Japanese Industrial Standard
The test principle is as follows: Use potassium acetate as a desiccant. Hoop the PTFE film around the plastic cup with a rubber ring to create a water vapor-permeable cup. Before wrapping the film on the cup, put enough potassium acetate solution into the water vapor-permeable cup to fill about 2/3 of the cup. Take 3 samples of 20cm*30cm square from each fabric. Each sample is placed on a test support frame. All coated or laminated fabrics are secured to the support frame with rubber rings, with the coated or laminated side facing outward. The installation of the sample support system shall be subject to being able to float in a water tank with a water temperature of 23°C. After testing the quality of the test cup (including sample, desiccant and film) with the film facing upwards, quickly turn the test cup upside down and place it into the sample holder. This assembly method is placed in a constant temperature device of 30℃±2℃. After 15 minutes, take the test cup out of the thermostatic device, turn it upside down and measure its weight. Water vapor permeability is calculated according to the formula WVT=24*△m/(s*t).
In the moisture permeability test, Japan’s desiccant pouring cup method seems to be more favored by manufacturers because it can be quickly tested on smaller samples, does not require control of the relative humidity in the environment, and the test device and Consumables are relatively cheap. This method gives high moisture vapor transmission values, which is preferred by manufacturers, and correlates well with the perspiration hot plate method (used by many researchers).
3. Testing method of concern: ISO 11092 Sweating hot plate method
The hot plate test method is a device used to test and simulate the heat and mass transfer process that occurs close to the skin. From the testing principle, the sweating hot plate test method belongs to the evaporative heat transfer impedance method, which is used to measure the resistance of different types of fabrics to water vapor (water vapor impedance refers to the vapor pressure difference on both sides of the fabric divided by the direction of the pressure gradient. Total evaporation heat flow per unit area). The higher the evaporation resistance, the worse the breathability of the fabric; the lower the evaporation resistance, the better the water vapor permeability, or the sweat hot plate method tests the vapor heat transfer resistance. The evaporation resistance test value (Ret value) range is generally 148.7~3.9m2Pa/w.
When the Ret value is less than 6, it is considered extremely breathable and comfortable to wear at high exercise levels; when it is between 6 and 13, it is very breathable, with average wearing comfort at high exercise levels, but comfortable to wear at ordinary exercise levels; Between 13 and 20, it is breathable, which is uncomfortable to wear at high exercise levels, but comfortable to wear at normal exercise levels; between 20 and 30, it is low breathability, very uncomfortable to wear at high exercise levels, but comfortable to wear at normal exercise levels. Generally comfortable at low activity levels; above 30 it is non-breathable and uncomfortable at all activity levels.
The sweating hot plate method is being adopted by more and more businesses because it is more reasonable. However, the big problem facing China is that there is currently no testing agency that can do this test, and Hong Kong can’t do it either. Taiwan’s Textile Association can do it, but it doesn’t have the qualifications for certification. Because of this, domestic fabric manufacturers do not know enough about this test and are unable to determine how to choose the correct film and process. This year, a brother company suffered heavy losses because it could not reach a Ret value of 13.
Methods for testing fabric moisture permeability are mixed, and the results of various test methods are not relevant or comparable. Therefore, determining the test method is the prerequisite for all indicators. We often see how high the waterproof and moisture permeability indicators are on some brands, but they do not indicate which testing method to use.


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