The waterproof nylon fabric https://www.wanshiyitex.com/product/nylon-fabric/ refers to the ability of fabric to be completely impervious to water under the condition of applying water pressure, to be permeable to water vapor in daily use, and to maintain this characteristic throughout its service life. The essence is that there is a huge difference between the volume of water vapor molecules and water droplets. In order to improve the waterproofness, it is usually required that the outer surface of this fabric is not easily wetted. The American Association of Textile Chemists and Dyers (AATCC) and the American Society for Testing Materials (ASTM) define repellency as the ability of fabric to resist permeation or both.
There are two ways for liquid water to enter the inside of the garment through the fabric of the garment:
