1. The basis of surface tension

The forces on the molecules on the surface of an object are different from the forces on the molecules in the body. Since the surface molecules have no symmetrical equilibrium force, they are attracted to the unbalanced force inside the body, which is called surface tension. The presence of surface tension means that the surface molecules have a higher free energy, and the higher the surface tension, the better the leveling property of the paint, because the smooth wet paint film has a smaller contact area with the air, which helps to reduce its free energy.

Surface tension in coatings and its influence

2. Surface tension in paint

The surface tension in the paint plays a key role in pushing the wet paint film to flow in an effort to make its surface smoother. When the surface tension of the paint is low and the surface tension of the substrate is high, the wet paint film can be flattened on the surface of the substrate, thereby reducing the surface free energy of the whole system. On the contrary, if the surface tension of the paint is high and the surface tension of the substrate is low, it will lead to the retraction of the paint film, poor leveling, and even brush marks, orange peel or roll marks.

3. Molecular influence on surface tension

Surface tension is affected by molecular structure and type. For example, perfluoroalkyl (-CF3) has a low surface tension, while water has a high surface tension. The surface tension of linear aliphatic hydrocarbons increases with the extension of the chain, while the surfactants with low surface tension in the hydrophobic part can reduce the surface tension of water.

4. Dynamic surface tension

During the construction of paint, due to agitation, various molecules of different surface tension are mixed together, resulting in an unbalanced distribution of surface tension. This imbalance triggers a surface tension gradient that causes the molecules to move. This dynamic process affects the fluidity of the coating and the formation of the coating film.

Surface tension in coatings and its influence

Therefore, surface tension plays a key role in the coating, affecting the leveling, uniformity and other properties of the film. Therefore, in order to prepare a coating with good performance, it is necessary to have a deep understanding and control of the surface tension of the coating.