What's the difference between wetting and penetration of surfactant? Drop a drop of water on a clean glass surface, and the water drops will quickly spread on the glass surface. This phenomenon shows that water can wet glass. If a layer of paraffin is coated on the surface of the glass, the water droplets can not expand on the surface of the paraffin, but exist in a spherical shape on the surface of the paraffin, indicating that water can not wet the surface of the paraffin. However, if the paraffin surface is dripped with aqueous solution containing surfactant such as powder or penetrating agent JFC, the paraffin surface will be wetted quickly. This action of wetting objects with the aid of surfactants is called wetting action. However, this phenomenon can not penetrate into the glass, because the glass has no capillary effect and can only produce wetting effect.
For textiles, if a drop of water is dropped on the grey cloth, the water drop is spherical, which also belongs to non wetting. The reason why water is difficult to wet grey cloth is not only the existence of air in the fiber, but also the existence of grease and wax in the fiber. If the grey cloth is treated by scouring and bleaching, the water droplets will quickly spread on the grey cloth and penetrate into the fiber, replacing the air with the fiber, replacing the solution fiber interface with the air fiber interface. Similarly, if a few drops of penetrant such as JFC are dropped on the unbleached grey cloth, the water drops can also spread on the grey cloth and penetrate into the interior of the grey cloth. With the help of surfactants, this kind of water penetration into the body is called osmosis. The reason why water can wet and penetrate into the fiber is that the fiber is a kind of porous material with huge surface area, which makes the solution expand rapidly along the fiber and enter into the fiber gap due to capillary action, replacing the air until it is completely wet.
There is no essential difference between wetting and permeation. The former acts on the surface of the object, while the latter acts on the interior of the object. The two can use the same surfactant, so the wetting agent can also be called penetrant.