In water-based paints, emulsions, thickeners, dispersants, solvents, leveling agents can reduce the surface tension of the paint, and when these reductions are not enough, you can choose a substrate wetting agent.
Please note that a good choice of substrate wetting agent can improve the leveling property of waterborne paint, so many substrate wetting agents are leveling agents.
The types of substrate wetting agents are: anionic surfactants, nonionic surfactants, polyether-modified polysiloxanes, acetylene diols, etc. The basic requirements for substrate wetting agents are high efficiency in reducing surface tension, good system compatibility (especially for high-gloss water-based paint), usually soluble in water, low bubble and not stable bubble, low sensitivity to water, and will not cause recoating problems and adhesion loss.
Commonly used substrate wetting agents are ethylene oxide adducts (for example, polyoxyethylene-nonylphenol type), polyorganosilicon type and non-ionic fluorocarbon polymer type compounds and other types, of which fluorocarbon polymer type wetting agent to reduce surface tension is the most significant effect.
A misconception, influenced by advertising, is that the effect of reducing surface tension alone is determined when it is the spreading ability of the coating on the substrate that is more important, and this property is also related to the compatibility of the system and the proper surface tension.
The spreading ability of a wetting agent can be determined by measuring the spreading area of a given volume (0.05 ml) of paint on a pre-coated substrate after adding a given concentration of substrate wetting agent to the paint. Wetting agents.
In many cases, the value of static surface tension cannot correspond to the wetting ability of the paint during construction, because the paint is in the stress field during construction, and the lower the dynamic surface tension at this time, the more beneficial to wetting. Fluorocarbon surfactants mainly reduce static surface tension, which is one of the reasons why the application of fluorocarbon surfactants is far less extensive than that of silicones.
Selecting the appropriate solvent can also have a good substrate wetting effect. Because the solvent is compatible with the system, the dynamic surface tension is low.
Special attention: if the substrate wetting agent is not chosen properly, it will form a single molecular layer on the substrate, thus the compatibility with the coating system is not good anymore, which will affect the adhesion.
Several different wetting agents can be mixed to solve more complex substrate wetting.
Post time: Aug-05-2022