Coating surface tension and its effects

1. The basis of surface tension

The force on molecules on the surface of an object is different from the force on molecules in the body. Since surface molecules do not have a symmetrical equilibrate force, they are subjected to an unbalanced force that attracts into the body, called surface tension. The presence of surface tension means that surface molecules have higher free energy, and the higher the surface tension, the better the leveling of Coating, because a smooth wet paint film has a smaller contact area with air, which helps reduce its free energy.

2. Coating surface tension

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

3. Molecular effects on surface tension

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

4. Dynamic surface tension

During the construction of Coating, due to agitation, various molecules of different surface tensions are mixed together, resulting in an unbalanced distribution of surface tension. This imbalance will trigger the surface tension layer and cause the molecules to move. This dynamic process affects the flowability of Coating and the formation of film.

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