Outdoor fabric hydrostatic pressure Water Proofness (WP)

Hydrostatic pressure (Water Proofness abbreviated as: WP): The outdoor fabric industry is accustomed to calling it water pressure resistance. The unit is expressed in mmh2o. It refers to the strength of water pressure per unit area. Under standard laboratory conditions, the fabric withstands the pressure of distilled water spraying upward. And record the maximum water pressure value, such as water pressure resistance of 5000mmh2o, that is, the unit area can withstand 5m of pressure without leakage.

Common test standards

Water pressure resistance: American test standard AATCC-127

Japanese standard test JIS-L 1092B, water pressure resistance is expressed in mmH2O. Most well-known foreign brands have indicators of 5000mm or above (test after washing). Domestic and foreign mid-to-low-end brands generally require within 1000-3000mm (test after washing) (Japanese standard test The straight cup method is adopted for testing, while the American Standard adopts the inverted cup method. The test value results of the two are different. It is worth noting that the testing of well-known foreign brands is done after washing 5 times or more, while the testing of domestic and foreign mid-to-low-end brands is done before washing. .The water pressure resistance test value before washing is easy to reach, but it will drop a lot after washing a few times. From a professional point of view, it is best to test 5 times or more after testing, so that the water pressure resistance is better, otherwise only repeat the test before washing According to the test, after being made into work clothes and worn on the body, the water pressure resistance drops greatly after repeated washing, the water blocking performance is poor, and it is easy to degumming or foaming). (The Japanese standard test adopts the upright cup method, and the American standard adopts the inverted cup method. The test value results of the two are different. It is worth noting that the test of well-known foreign brands is done after washing 5 times or more, and that of domestic and foreign mid- to low-end brands. Test before washing. The test value of water pressure resistance is easy to reach before washing, but it will drop a lot after washing a few times. From a professional point of view, it is best to test after 5 times or more, so that the water pressure resistance is better, otherwise Only test before washing again. After wearing it as work clothes, the water pressure resistance drops greatly after multiple washes, the water blocking performance is poor, and it is easy to degumming or foaming). (The Japanese standard test adopts the upright cup method, and the American standard adopts the inverted cup method. The test value results of the two are different. It is worth noting that the test of well-known foreign brands is done after washing 5 times or more, and that of domestic and foreign mid- to low-end brands. Test before washing. The test value of water pressure resistance is easy to reach before washing, but it will drop a lot after washing a few times. From a professional point of view, it is best to test after 5 times or more, so that the water pressure resistance is better, otherwise Only test before washing again. After wearing it as work clothes, the water pressure resistance drops greatly after multiple washes, the water repellency is poor, and it is easy to degumming or foaming).

The water pressure resistance test is divided into two methods: before washing and after washing:

(1) Pre-wash test: Domestic outdoor brands generally test the water pressure resistance value before washing, but do not test the value after washing. The water pressure resistance value of PU coated fabrics drops greatly after being washed several times, and may drop by about 1000-3000 mmH2O;

(2) Post-wash test: For example, THE NORTH FACE even adopts the method of testing the water pressure resistance after washing 5-20 times. Due to the test after multiple washings, the water pressure resistance value drops significantly. For example, the water pressure resistance of PU coated fabrics requires 5 If it reaches 5000mmh2o after washing with water, it must be at least 7-8000mmh2o before washing; of course, this requirement will lead to higher costs!

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