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Four test methods for water permeability and waterproofing of fabrics(3)

Water permeability and waterproofing test:

1. Rain method

The drenching method is used to test the fabric's water repellency in the air during simulated heavy rain. This method is suitable for any fabric with or without water-repellent finish.

The anti - impact permeability of single layer fabric or composite fabric was measured under different velocity water impact strength. The test results are related to the water-repellent properties of fiber, yarn and fabric structure. The principle is to wrap the test sample around the weighed absorbent paper, and then weigh the absorbent paper again after the test. The difference between the two weights is the water permeability of the sample. The quality difference of absorbent paper before and after test shall not exceed 1g; If the quality is greater than 5g, the fabric water resistance is very poor.

The test method of AATCC 35-2006 is to put a standard absorbent paper of 15.2cm 15.2cm at the back of the sample, and weigh the standard absorbent paper, accurate to 0.1g. In the vertical surface rigidity, the sample holder is put on the sample holder and sample is put in the middle of the spray position, nozzle distance of 30.5 cm.Horizontally (27 + / - 1) ℃ water spray directly to the sample, lasts for 5 min.After the spraying, carefully remove the blotting paper, and quickly weigh it(accurate to 0.1g). The weight increase of the absorbent paper in the spray time of 5min was calculated, and the average value of its test data was taken. If greater than 5.0g, the report is +5.0g or >5.0g.

2.Core suction method

The core suction method is the most commonly used and simple method to directly test the water absorption of the fabric. The test sample is usually cut into long strips. One end of the test sample is suspended on an iron frame, and the other end is in contact with the water surface (or immersed in water for a certain height). After immersion for a certain time (f), the height of water climbing through the capillary and fiber pores of the fabric (h) is measured.Fabric with good water conductivity, strong water absorption, fast water absorption speed (namely core suction speed), large climbing height per unit time, namely high water conduction height. If in the test process, due to the relationship between fabric structure, fiber, yarn and color, the climbing process of water is not obvious and cannot be observed by the naked eye, a little colorant can be added to the water.

The core suction velocity (v) depends on the physical and chemical properties of fiber and the thermal equilibrium process of liquid molecules. Macroscopically, it depends on pore morphology and direction. The core suction velocity is the height value of water rising in unit time, that is, v(cm/s)=h/t. The strength of the conductivity is related to the size of the core suction speed. Therefore and core suction can be used to test the water conductivity of the fabric.

Matters needing attention

The above various testing methods for water permeability apply to all fabrics. In practical work, different testing methods are adopted for different fabrics to better measure the water permeability or water resistance of the fabric:

1. Coating fabric because of its structure, testing its permeability can be used spray method, rain method and hydrostatic pressure method, not applicable to the core suction method.

2. In general, when the core suction method is tested, it can be found that the water absorption performance of knitted fabric is better than that of woven fabric.

3. Wet fabric in water can not be hydrostatic test, but it can be spray test.

Hangzhou Chungyo Chem Co., Ltd.

Email: chungyo@cycolorant.com

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