How waterproof fabric water repellent

1 , Young's equation
Drop of liquid droplets on a solid surface , assuming ideal platform for this surface , the droplet gravity concentrated at one point, and ignore the amount of wilderness . Since the surface tension of the fiber fabric (Ys), liquid surface tension (YL) , and the interfacial tension has firmware (YLS) result of the interaction , the droplet will form a variety of shapes ( cylindrical to fully from paving ) . In addition to the night to go completely flat , the droplets on a solid surface in equilibrium , A point received scattered by gravity . [ 1 ]
Angle is called contact angle 0 , if 0 = 00, the droplets on a solid surface puping cotton , which is the solid surface is wet wild limit state ; when 0 = 1800 , the droplet is cylindrical , which is a ideal non-wetting behavior . In the water repellent finishing , the surface tension of the droplet can be considered constant. Therefore, whether wild wet the solid surface , and solid surface to have in the bank leaves late Relay tension . From the said requirements , the contact angle 0 more conducive droplets rolling loss , ie the smaller the better .

2 , fabric adhesive power
Since Ys and YLS virtually can not be measured directly, so usually the contact angle of 0 or cos0 directly assessed degree of wetting . But not wetting contact angle Yuan Ying , and actual results so some people have expressed station workman also a relationship between the interaction , and the degree of wetting parameters.
Indicates station humble workers YL and cos0 can all be measured , so style has practical meaning. Similarly, the point of the interface area of ​​the owner of the two divided bits required when the owners committee 2YL, may be called the liquid within the bow. From the above equation , the station workman increases , the contact angle decreases , really equal cohesive consensus workman , the contact angle is zero , which is a liquid on a solid surface is completely paved , as cos0 not more than 1 , so that even stations Zhuo workers than 2YL, the contact angle remains fixed . WSL = YL, then 0 to 900 . When the contact angle is 180 ° , WSL = O, shows no viscosity between liquid and solid cloud effect , however, much less since there are some points hatchback Zhuo effect, so the contact angle of 180 ° is equal to the situation never found , too much can myopia get some circumstances, such as 160 ° or larger angles.

3 , the critical surface tension of the Waterproof Fabric
Almost since the solid surface tension can not be measured , in order to understand the wettability of the solid surface , he was the critical surface tension was measured . Although not directly critical surface tension that the surface tension of the solid , but rather that the size of Ys-YLS , it makes the wetting of the solid surface is the difficulty . However, it should
Note that the determination of the critical surface tension is a rule of thumb , and the measurement range is very narrow .
In addition to cellulose , other substances are critical surface tension of the surface tension of small taxes , so they have a certain water repellency, the largest of which eleven CF3 , a CH a minimum . Obviously, the larger the contact has a smaller delivery Desks critical surface tension of the material finishing agent who can have access to better water repellent effect .