Fabric definition waterproofBreathable fabricThe main functions are: waterproof, moisture permeable, breathable, insulating, windproof and warm.Technically speaking, the technical requirements of waterproof and breathable fabrics are much higher than that of ordinary waterproof fabrics. At the same time, from the perspective of quality, waterproof and breathable fabrics also have other functional characteristics that other waterproof fabrics do not possess.Waterproof and breathable fabrics enhance their fabric tightness and water tightness, and their unique steam permeability can quickly discharge water vapor inside the structure, avoid the structure of mold, and keep the body dry. It perfectly solves the problems of air permeability, wind protection, water proofing and thermal insulation. It is a healthy and environment-friendly new fabric. The real waterproof fabric is in a humid climate for a long time, and it also can withstand the pressure of water seepage.For example, long time walking in the rain and rain, kneeling or sitting on wet ground will not seep.
Working principle Under the condition of water vapor, water particles are very small. According to the principle of capillary movement, they can smoothly infiltrate the capillary to the other side, resulting in vapor transmission.When water vapor condenses into water droplets, the particles become larger. Due to the effect of the surface tension of water droplets, the water molecules can not escape smoothly from the water droplets to the other side, that is, to prevent water penetration and make the permeable membrane have waterproof power.
How to resist water 1. Yang's formula A drop of liquid drops on the surface of the solid, assuming that the surface is perfectly flat, the droplet gravity is concentrated at one point, and the amount of wild land is ignored.As the surface tension (Ys), the surface tension (YL) of the fabric, and the interfacial tension (YLS) of the firmware are also interacted, the droplets will form various shapes (from cylindrical to fully paved).The A point receives the effect of scattered gravity when the surface is completely out of balance and the droplet is in equilibrium state on the solid surface. Angle 0 is called contact angle. When 0=00, the droplet is on the solid surface, which is the limit state of wetting the solid surface. When 0=1800, the droplet is cylindrical, which is an ideal non wetting state.In water repellent finishing, the surface tension of droplets can be regarded as constants.Therefore, whether the wilderness can moisten the solid surface and go along with the solid surface of the lotus leaf in the bank has the late relay tension.According to the requirement, the greater the contact angle 0, the better the rolling loss of water droplets, that is, the smaller the better.
2. Fabric adhesion work Because Ys and YLS can hardly be measured directly, the contact angle 0 or cos0 is usually used to directly assess the wetting degree.However, contact angle is not the cause of wetting, and the actual result is that there is also an interaction between personnel and adhesive work, and the parameters of wetting degree. YL and cos0, which indicate adhesive work, can be measured, so the formula has practical significance.In the same way, the work required to separate the liquid sphere of the unit area into two liquid beads is 2YL, which can be called the cohesive work of the liquid.According to the formula, the contact angle decreases when the adhesion work increases. When the adhesive work is equal to the cohesive work, the contact angle is zero. This is the liquid completely paving on the solid surface. Since the cos0 can not exceed 1, even if the adhesive power is greater than 2YL, the contact angle remains unchanged.WSL=YL, 0 is 900.When the contact angle is 180 degrees, WSL=O shows that there is no turbidity between the liquid and the solid. However, due to the adhesive effect of the reduction of the hatchback, the contact angle is equal to 180 degrees, and no case can be found at most, such as 160 degree or greater angle.
3. Critical surface tension of fabrics Because the surface tension of a solid can hardly be measured, the critical surface tension is measured in order to understand the wettability of the solid surface.Although the critical surface tension can not directly indicate the surface tension of the solid, it represents the size of Ys-YLS, but it can explain the difficulty of wetting the solid surface.But it should be It is noted that the determination of critical surface tension is an empirical method, and the range of measurement is also very narrow. As can be seen from table 10-1, except for cellulose, the critical surface tension of other substances is small in tax surface tension, so they all have a certain water repellency. Among them, one CF3 is the largest and one CH is the smallest.Obviously, a material carrier with larger contact with less critical surface tension can get better water repellent effect.