Water permeability of fabric is called water permeability. The opposite performance is called waterproof or anti permeability. The characteristics of fabrics that are easily wetted with water are mainly related to the surface properties of the fabrics, so they can be called surface moisture resistance. Due to the different uses of fabrics, the surface moisture resistance requirements are also different. Fabrics used for raincoats, tents, sails, etc. need to have good water resistance, while fabrics for filtering purposes need to have good water permeability. Some outdoor garments, such as raincoats, also have certain requirements for waterproof.

What kinds of test methods or testing equipments for fabric water permeability (waterproof) properties

Fabric water-permeability (waterproof) tester is a tester which is often used in the textile industry,Different test equipment requirements for different standards and requirements,At present, fabric water permeability (waterproof) test instruments are commonly used，Hydrostatic head tester, Spray type waterproof tester (Spray rating tester), rain tester, corresponding to three kinds of water permeability test methods: hydrostatic method, spray method, rain method. These three methods will be introduced separately.

1.Hydrostatic Pressure Test method（Hydrostatic Head Tester）

The hydrostatic method refers to the water permeability of fabric under a certain water pressure,it is applicable to all kinds of fabrics, including the fabric which had been waterproof finishing fabric .Waterproof of fabric is related to the waterproof of fibers, yarns, and fabric structures. The measured results is different with water spray and rain on the fabric surface. Hydrostatic method is used to measure the waterproof of fabrics. There are hydrostatic method and dynamic pressure method.

In the AATCC 127-2003 test method experiment, take at least three samples with a size and area of 200mm×200mm along the diagonal direction of the sample to be tested. The water resistance of the two sides of the sample is different. Make a mark and test with (21±2) ℃ distilled water. The test area is 100 cm2. The test surface is in contact with water. If there are water droplets leaking from three different places on the sample, the test reaches the end. However, water droplets leaking within 3mm from the sample holder are not effective. The measured result is the average of 3 test samples under the same conditions. The larger the test value, the greater the pressure value required for water to seep out of the sample, and the better its water resistance.

2. Spray Test Method (Spray Rating Tester)

The spray method simulates the degree to which clothing gets wet when it gets drizzled. This method is applicable to all water-resistant fabrics and untreated fabrics. The measured water-resistance results have a great relationship with the treatment of fibers, yarns, fabrics, and fabric structure.

In the AATCC 22-2005 test method, the test sample is fixed with an iron ring with a diameter of 152.4mm. The sample is in a tensioned state and the surface is flat without wrinkles. 250mL of distilled water was sprayed from the standard spray head at 45°, and the sample 150mm below the spray nozzle was sprayed for 25-30 seconds. Tap the bottom of the iron ring which with sample once with a solid object, the test surface is opposite to the solid object, and then rotate the iron ring by 180° and tap it once. Water repellency of the fabric. There are 5 levels of evaluation, with 5 being the best and 1 being the worst. 

3. Rain test method(Rain Tester)

Rain test method is to simulate the waterproof of the fabric exposed to the air during heavy rain. This method is applicable to any fabric with or without water repellent finishing. Measure the impact water permeability of single layer fabric or composite fabric under the impact strength of water at different speeds. The test results are related to the waterproof of the fibers, yarns and fabric structure in the fabric.

Test with a rain tester in the experiment，AATCC 35-2006 test method is to place a 15.2 cm ×15.2 cm standard absorbent paper on the back of the sample, and weigh the standard absorbent paper,accurate to 0.1 g.On the vertical rigid surface, place the sample on the sample holder, and put the sample in the middle of the spray, 30.5cm away from the nozzle, and directly spray the water flow of (27±1) ℃ to the test horizontally for 5minutes. After spraying, carefully remove the absorbent paper and quickly weigh it and accurate to 0.1 g. Calculate the weight increase of the absorbent paper during the 5min spray time, and take the average of its test data. If it is greater than 5.0g, it is reported as + 5.0g or > 5.

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