How does the water repellency principle of canvas arise?

The editor first summarizes the working principle of the canvas: in the state of water vapor, the water particles are very small. According to the principle of capillary motion, it can smoothly penetrate into the capillary to the other side, thereby causing the phenomenon of vapor permeation. When the water vapor condenses into water droplets, the particles become larger. Due to the surface tension of the water droplets (the water molecules 'pull and compete with each other'), the water molecules cannot smoothly escape from the water droplets and penetrate to the other side, which also prevents the water Osmosis occurs, making the vapor-permeable membrane waterproof. A drop of liquid is dropped on a solid surface. Assuming that this surface is ideally flat, the gravity of the droplet is concentrated at one point, and the amount of field is ignored. As a result of the interaction of the surface tension (Ys) of the fibers in the fabric, the surface tension of the liquid (YL), and the interfacial tension (YLS) of the fasteners, the droplets can form a variety of shapes (from cylindrical to flat). In addition to the nighttime ** levelling, when the droplet is in equilibrium on the solid surface, the point A receives the action of decentralization. The angle 0 is called the contact angle. When 0=00, the droplet is flat on the solid surface, which is the limit state of the solid surface being wetted by the field; when 0=1800, the droplet is cylindrical, which is a kind of Ideal non-wetting behavior. In water repellent finishing, the surface tension of the droplets can be considered as a constant. Therefore, whether the field can wet the solid surface, go to the relay tension of the late lotus leaf in the bank with the solid surface. According to the said requirements, the larger the contact angle 0, the more conducive to the rolling loss of water droplets, that is to say, the smaller the better.