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Analysis of common testing methods of fabric moisture permeability tester
  • 2020-08-04 17:39:39

The test of water pressure resistance of textiles is an unconventional item test, but with the increase of the market demand for waterproof and other special finishing textiles and the improvement of foreign investors' requirements for technical indexes of such commodities, the test of water pressure resistance of textiles has been paid more and more attention.

Vapor transmission method

1. Cup method

A, National standard of China :GB/ T12704-91b

B,ASTM E96 Produce B and D. ASTM E96 Produce B and D

C, Japanese Industrial standard: JIS L-1099 A2

D, Canadian standard :(CGSB)-4.2 no.49-99

E, British standard :BS 7209-1990

2. Pour cup method (also known as hygroscopic method)

ASTM E96 BW(1995 and 2000 editions)

3. Desiccant method

4. Cup method

A, Chinese National standard: GB/T 12704-91a

B, Japanese Industrial standard: JIS L-1099 A1

C, ASTM E-96 A, C, E

5. Pour the cup

A, Japanese industrial standard: JIS L-1099 B1, B2

B, American Society for Testing materials standard: ASTM E-96

C, Belgian UCB standard: UCB method

D, British standard :B.T.T.G


Sweating hot plate method, also known as skin model method

A, ISO standard: ISO 11092

B, Fire fighting fabric test: NFPA 1971

C,American Society for Testing materials Standard: ASTM F 1868-98 B

D, German standard: DIN 54 010 T01-A

Sweat dummy

Sweat dummies the sweat dummies are a bit like hot plates and are used to simulate the shape and size of a typical human body.The dummy test is of more practical significance than the sweat hot plate test, because it can consider more variables, including the surface area covered by clothing, the number of layers of textiles and the distribution of air layers on the surface of the human body, loose or tight fit, the difference in skin temperature between different parts of the human body, the position and movement of the body, etc.However, no sweating dummy has yet been able to test evaporative thermal resistance under dynamic conditions such as walking.Currently, there are no design standards or testing procedures for sweat mannequins.And because sweating dummies are more complex and expensive, they are more expensive to test than hot-plate methods.

Other methods

A, Watkins method

B, Mernander method

C, Farnworth method

D, Van Beest method

E, Ruchman law F, Gibson law

That's a lot, so let's take a look at some of the more useful ones.

Common methods:

ASTM E96 BW, American Society for Testing materials standard, Water vapor Pouring Method Since the United States has been in a high position in this industry, and the country's market is also very large, the test data of this method is relatively high, ASTM standard naturally became the common method.

Most customers now use this method for testing.

The test principle is as follows: the tested fabric is covered on a permeable cup containing distilled water, fixed and inverted, and its weight is weighed by a top loading balance with a precision of 0.001g, and placed on the position of the wind tunnel exhaust.Before the cup enters the environmental chamber with the temperature of 23℃, relative humidity of 50% and wind speed of 2.5m/s for weighing, the environmental temperature and relative humidity are recorded.The weight of each cup and the time it was weighed were recorded.The weight of 3h, 6h, 9h, 13h, 23h, 26h, 30h was recorded, WVT=24*△m/(s*t) formula was used to calculate the water vapor transfer velocity.The average value of the 6 samples is taken as the test result, and multiplied by 24 is converted into a result in g/m2*24h.It should be noted that ASTM E96 BW method has 1995 edition and 2000 edition. The testing conditions of 1995 edition are not mature and the test data are relatively high. Now, 2000 edition is basically adopted.

Methods with high test results:

JIS L-1099 B1, B2 Japanese Industrial Standard

The principle was as follows: potassium acetate was used as a desiccating agent.The PTFE film is made into a vapor permeable cup with a rubber ring around the plastic cup.Before coating the cup, put enough potassium acetate solution into a water-vapor permeable cup that fills about two-thirds of the cup's volume.Remove 3 20cm by 30cm square samples from each fabric.Each sample is placed on a test stand.All coated or laminated fabrics are secured to the support bracket with rubber rings and the coated or laminated surface facing outwards.The sample support system shall be installed in a tank capable of floating in water at 23℃.After the quality of the test cup (including sample, desiccant and film) is tested in the upward direction of the film, the test cup is quickly inverted and placed into the sample support frame.The assembly method was placed in a device with a constant temperature of 30℃±2℃.After 15min, the test cup was taken out of the thermostatic device, turned upside down and measured its weight.Water vapor permeability is calculated by WVT=24*△m/(s*t) formula.In moisture permeability tests, the Japanese desiccant pour cup method seems to be favored by manufacturers because it can be tested quickly on smaller samples, requires no control of relative humidity in the environment, and is cheaper in testing equipment and consumables.This method gives a high moisture permeability, which is preferred by manufacturers, and has a good correlation with the sweating hot plate method (which is used by many researchers).

Interesting test methods:

ISO 11092 Sweating hot plate method the hot plate method is a device used to test heat and mass transfer processes that simulate what happens close to the skin.

From the test principle, the sweat 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 (the vapor impedance refers to the difference of vapor pressure between the two sides of the fabric divided by the total evaporation heat flow per unit area in the direction of pressure gradient).The higher the evaporation resistance is, the worse the respiration of the fabric is.The lower the evaporation resistance, the better the vapor permeability, or the vapor heat transfer resistance measured by the sweating hot plate method.The Ret value of evaporation resistance is 148.7 ~ 3.9m2Pa/ W.When Ret value is less than 6, it is considered to be extremely breathable and comfortable to wear at high exercise level.It is very breathable between 6 and 13. It is generally comfortable to wear at high exercise level, but comfortable to wear at general exercise level.It is breathable between 13 and 20, uncomfortable to wear at high exercise level, but comfortable to wear at general exercise level;Between 20 and 30, for low ventilation, it is very uncomfortable to wear at high exercise level, but generally comfortable at low exercise level;Above 30, it is impermeable and uncomfortable to wear at all sports levels.The sweat hot dish method is being used by more and more manufacturers because it is more reasonable.However, the big problem in China is that there is no testing institution that can do this test, nor can Hong Kong. The Spinning extension Association in Taiwan can do this test, but it lacks the qualification of certification.Because of this, domestic fabric manufacturers do not have enough understanding of the test, unable to determine how to choose the right film and process.One sibling lost heavily this year when it failed to reach the Ret at 13.

The testing methods of fabric moisture permeability are mixed, and the results of various testing methods are not correlated and comparable, so determining the testing method is the premise of all indicators.We often see on some brands how high the waterproof moisture permeability index, but do not specify which test method to use.

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