It can be seen from the above structure that the substrate wetting agent is actually a special type of polyether modified silicone oil, and its molecular weight is usually very small. Since the rapid wetting of the substrate is a dynamic process, and in accordance with the principles of physical chemistry, the principle of the wetting agent is to quickly migrate to the surface of the system and reduce the surface tension of the system to achieve the effect of substrate wetting. . According to the theory of molecular kinematics, the migration speed of a molecule depends to a large extent on its molecular weight. The smaller the molecular weight, the faster the migration speed. Therefore, relatively small molecular weight polyether modified silicone oils are often used in aqueous systems as substrate wetting agents. From a structural point of view, polyether modified silicone oils used as substrate wetting agents usually contain only one polyether chain. That is, the value of m is usually 1, and the value of n is also very small, usually not more than 4.
With further research, polyether modified silicone oil used as a substrate wetting agent is used in aqueous systems. Due to its special structure (see Figure 6 below), the silicone segments can be fully extended, Methyl-CH3 stretches outward, which greatly reduces the surface tension of the system. Generally, the medium and high molecular weight polyether modified silicone oil can only reduce the surface tension to 25-26N · m-1 in aqueous systems, while the small molecule substrate wetting agent can usually reduce the surface tension to 22N · m-1 Below, the lowest can be between 20-21N · m-1. Because the substrate wetting agent reduces the surface tension of the aqueous system to between 20-21N · m-1, so that the aqueous coating with the substrate wetting agent can wet most substrates with low surface tension, and even Includes Teflon substrates known for their low surface tension and difficulty in wetting. At the same time, because the substrate wetting agent can reduce the surface tension of the aqueous system to a very low level, the substrate wetting agent can give the system good anti-cratering performance and atomization effect in spraying construction.