Hydrostatic pressure (WaterProofness abbreviated as: WP): The outdoor fabric industry customarily calls 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 value of water pressure, such as water pressure resistance of 5000mmh2o, which means that a large unit area can withstand 5m of pressure without leakage.
Commonly used test standards: American standard AATCC127; Japanese standard JISL1092B; European standard: IS0811; water pressure resistance test is divided into two methods: pre-wash and post-wash tests:
(1), Pre-wash test: Domestic outdoor brands generally test the water pressure resistance value before washing, but do not test the value after washing. Coated fabrics are washed After several times, the water pressure resistance value drops greatly, possibly by about 1000-3000mmh2o;
(2) Post-wash test: Like THENORTHFACE, there is even a method of testing the water pressure resistance after being washed 5-20 times. Due to the test after multiple washings, the water pressure resistance value drops greatly. For example, the water pressure resistance of coated fabrics requires 5 washes. After reaching 5000mmh2o, then it must be at least 7-8000mmh2o before washing; of course, this requirement will lead to higher costs!
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