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 .