Waterproof textile which breaths may be defined asintelligent waterproof fabric, which is permeable to water vapour i.e.perspiration at a rate of 2000-2500 g/m2/day for light applications and4000-5000 g/m2/day for heavy applications. By 1998 it was common to see claimsof 10000 g/m2/day.
Waterproof fabric completely prevents the penetration andabsorption of liquid water in, in contrast to water-repellent fabric, whichonly delays the penetration of water. Traditionally, fabric was made waterproofby coating it with a continuous layer of impervious flexible material. Thefirst coating materials used were animal fat, wax and hardened vegetable oils.Nowadays synthetic polymers such as polyvinylchloride (PVC) and polyurethaneare used. Conventional polymers coatings are considered to be moreuncomfortable to wear than water-repellent fabric, as they are relatively stiffand do not allow the escape of perspiration vapour. Consequently they are nowused for emergency rainwear. Water-repellent fabric is more comfortable towear but its water-resistant properties are short lived.
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