The working principle of waterproof and breathable membrane

In the state of water vapor, the water particles are very small. According to the principle of capillary movement, they can smoothly penetrate the capillary to the other side, thus causing vapor transmission. When the water vapor condenses and turns into water droplets, the particles become larger. Due to the surface tension of the water droplets (the water molecules "pull against each other"), the water molecules cannot smoothly escape from the water droplets and penetrate to the other side, which is to prevent The permeation of water occurs, giving the vapor permeable membrane a waterproof function.

The technology of waterproof and breathable membrane was first introduced from European and American countries. However, the production technology of domestic products is varied, and the quality of products from various manufacturers is uneven, and a unified quality standard has not been formed. In fact, the waterproof breathable membrane mainly consists of three layers: PP spunbond non-woven fabric, PE polymer breathable membrane, and PP spunbonded non-woven fabric. The function of spunbond non-woven fabric is mainly to enhance the tension and hydrostatic pressure and to protect the middle layer (breathable membrane). The real breathability mainly depends on the middle layer of PE polymer breathable membrane.