Analysis Of Water Repellent Principle Of Waterproof And Moisture Permeable Fabric

Waterproof and moisture permeability Fabric The principle of water repellency mainly lies in the following aspects:

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, the contact angle is not a wet baby, and the actual result is that there is a relationship between human interaction and the degree of wetting.

It means that both YL and cos0 of station workers can be measured, so the formula has practical significance. Similarly, the work committee 2YL, which is divided into two owners, whose interface is point area, can be called the internal bow of liquid. From the formula we can see that the contact angle decreases when the station worker increases. When the real work is equal to the cohesion consensus, 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 station is more than 2YL, the contact angle will remain 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 fact that there are some standing Zhuo functions in the reduction of the hatchback, the contact angle is equal to 180 degrees, which has never been found. Only a few degrees of nearsightedness can be obtained, such as 160 degrees or larger angles.

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. However, it should be noted that the measurement of critical surface tension is an empirical method, and the scope of measurement is also very narrow.

As can be seen from table 10-1, fibre 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.