Thin Pongee Fabric

Thin Pongee Fabric

Grs Factory Recycled Polyester Pongee 400t Ultra Thin Down Proof Waterproof Jacket Fabric

How to repel water

1. Young's formula

A drop of liquid drops on a solid surface. Assuming that the surface is perfectly flat, the droplet's gravity is concentrated at one point, and the amount of field is ignored. Due to 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 firmware, the droplets will form a variety of different shapes (from cylindrical to fully flattened) ). Except for the complete de-leveling at night, when the liquid droplet is in equilibrium on the solid surface, point A receives the action of dispersive force. [1] 

Angle 0 is called the contact angle. When 0=00, the liquid droplet is spread on the solid surface, which is the limit state of the solid surface being wetted by the wild; when 0=1800, the liquid droplet is cylindrical, which is a kind of Ideal non-wetting behavior. In the water-repellent finishing, the surface tension of the droplets can be regarded as a constant. Therefore, whether the wild land can wet the solid surface, go to the relay tension of the lotus leaf in the bank with the solid surface. From what is said to be a requirement, the larger the contact angle 0, the more conducive to the rolling loss of water droplets, that is to say, the smaller the better.

2. Fabric adhesion

Since Ys and YLS can hardly be measured directly in practice, contact angle 0 or cos0 is usually used to directly assess the degree of wetting. However, the contact angle is not the cause of wetting, and the actual result is that some people have the adhesion work to express the relationship between the interaction and the parameter of the degree of wetting.

Both YL and cos0, which represent the work of adhesion, can be measured, so the formula has practical significance. In the same way, the work required to divide the liquid bead per unit area on the interface into two beads is 2YL, which can be called the cohesive work of the liquid. It can be seen from the formula that when the adhesion work increases, the contact angle decreases. When the adhesion work is equal to the cohesive work, the contact angle is zero. More than 2YL, the contact angle remains unchanged. WSL=YL, then 0 is 900. When the contact angle is 180°, WSL=O, indicating that there is no viscous effect between the liquid and the solid. However, due to some adhesion between the two compartments, the contact angle equal to 180° has never been found, and only some can be obtained at most Approximate situation, such as an angle of 160° or greater.

3. The critical surface tension of the fabric

Since the surface tension of a solid is almost impossible to measure, in order to understand the wettability of a solid surface, someone measures its critical surface tension. Although the critical surface tension cannot directly indicate the surface tension of the solid, but the size of Ys-YLS, it can explain the difficulty of the solid surface to be wetted. But should

Note that the determination of critical surface tension is an empirical method, and the measurement range is also very narrow.

It can be seen from Table 10-1 that, except for cellulose, the critical surface tension of other materials is low, so they all have a certain degree of water repellency. Among them, CF3 is the largest, and CH is the smallest. Obviously, whoever has a finishing agent for a material with a larger contact surface and a smaller critical surface tension can obtain a better water repellent effect.

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