Waterproof and breathable polymer film and coatings are permeable to water vapour molecules and not to permit water droplets to penetrate through them.

• 防水可呼吸性是指聚合物薄膜及涂层不允许水滴透过，同时却要保证水蒸汽分子自由透过，达到防水可呼吸的目的。