Wetting is a phenomenon that we see every day. It may be a rain drop on a leaf or soup on a spoon. It is also seen in how an ink an ink, adhesive or coating spreads on a film. Wetting, in simple terms, is the ability of a liquid to spread across the surface of a solid to produce a uniform, continuous surface. How a solid is settled by a liquid is measured by the surface tension of the liquid relative to the surface tension of the solid. For a coating Adhesive or ink to be usable it must a) wet and adhere to the substrate, b) cure, and c) exhibit excellent enduse properties. The surface tension of a solid has important influence on these properties. A solid surface with intimate coverage of a liquid is necessary to produce a strong uniform adhesive, coating or ink bond.
Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects (e.g. water striders) to run on the water surface. This property is caused by cohesion of similar molecules, and is responsible for many of the behaviors of liquids. Surface tension has the dimension of force per unit length, or of energy per unit area. The two are equivalent—but when referring to energy per unit of area, people use the term surface energy—which is a more general term in the sense that it applies also to solids and not just liquids. FACTS OF SURFACE TENSION
|Tendency of liquids to reduce their exposed surface to the smallest possible area. A drop of water, for example, tends to assume the shape of a sphere. The phenomenon | |is attributed to cohesion, the attractive forces acting between the molecules of the liquid (see adhesion). The molecules within the liquid are attracted equally from | |all sides, but those near the surface experience unequal attractions and thus are drawn toward the center of the...