Update:In water-based coatings, which coating additives can eliminate cratering?
The wettability of the coating to ...
The wettability of the coating to the substrate is an important factor that determines the quality of the coating. How to improve the wettability during application? Which additive is suitable for a particular problem? What is the mechanism behind it? We are often asked these and similar questions, and they reflect how important the issue of wetting is considered by paint manufacturers.
Not surprisingly, in the application or drying process, if the wetting is not sufficient, then defects may be expected, for example, it is impossible to form a uniform, airtight coating film.
None of the above questions have answers; each question is considered individually. A more detailed method requires consideration of both the material surface and the coating film. The function of painting is to combine the surface of the material with the paint in a good way. The wetting phenomenon only occurs at an interface. The few molecules between the substrate and the polymer determine whether the material is properly protected and whether the coating film has defects. The success or failure of paint manufacturers and paint users depends on these few elements.
The interfacial tension of the liquid at the air interface is called surface tension.
This is the energy required to bring an elementary particle from the liquid to the air interface. The surface of the liquid is enlarged, and the attractive force acts between the molecules of the liquid. Inside the liquid, these forces cancel each other out because they act in concert in all directions. At the interface, these forces are directed towards the inside of the liquid; the liquid tries to reduce its surface area. Liquids all use ideal graphics, because for a specific volume this is the surface or interface area of the bottom. Generally speaking, this is the surface that acts on the surface (interfacial tension).
The work required to expand an interface area A by one unit is named interface energy W. It is proportional to the size of the additional unit and can be expressed by a differential formula: Y=DW/DA quotient Y is defined as the surface tension of the interface. The symbol o is also used in the case of a liquid/air interface. Its size is the energy per unit area (j/m2), which is the work required to obtain a new surface. The sl unit of surface tension is N/M.
Because the liquid phases are deformable, their surface tension can be directly measured. The surface tension of the curved solvent used for the coating ranges from 14 to 73 nm/m. When the surface tension of pure water is 73nm/'m, the high-volatility low-aliphatic solvent shows a low value. The surface tension of a type of coating depends not only on the solvent used, but also on other ingredients. Nevertheless, surface tension is still an important parameter