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Normally, the surface tension of water is very high at around 72 dynes. The surface tension of most of our substrates, whether they are metal, plastic, cement, etc., is lower than, or even much lower than, the surface tension of water. Just like when we drop a drop of water onto a substrate, the wetting process is usually difficult to occur.

Its contact angle is usually greater than 90 °, which is not suitable for its moisture transport and spreading processes. When we add moisture, its spreading process can only proceed normally, and it can be wetted. Normally, water-based coatings require the addition of substrate cloud agents to form a continuous coating, but we also have some, such as latex paint,

It faces substrates such as cement substrates and putty layers, and its surface probability may also be relatively high. In the formula of latex paint, we also add some propylene glycol and some dispersants, which have the effect of reducing surface tension.

So sometimes, there are some formulas that do not require the addition of this substrate wetting agent, but conventional water-based paints, especially water-based industrial paints, require the addition of substrate wetting agents. For water-soluble coatings, there are also some solvents inside, which play a role in reducing surface tension.

For some substrates with relatively high surface tension, it is not necessary to add substrate wetting agents. However, the vast majority of water-soluble coatings also require the addition of substrate wetting agents to assist in the wetting process.

Do solvent based coatings also require the addition of substrate wetting agents?

Generally speaking, due to the surface tension of solvents, whether they are alcohol based, ester based, or benzene based solvents, the surface tension of similar solvents is relatively low. Generally, it can wet various substrates, so solvent based coatings and substrate wetting agents can be omitted. And in our solvent based coatings, some leveling agents are added, which also have the function of reducing surface tension and transporting stone substrates. However, container based coatings are designed for certain special situations, such as the primer of some wood coatings, in order to improve the penetration of the coating and the filling ability of the conduit. We add a substrate wetting agent inside, which will greatly help improve its milk communication. In this case, we can suggest adding a small amount of muscle wetting agent.