Wettability of paint to substrate

2019-08-16

Wettability of paint to substrate
The adhesion of the paint film is caused by the mutual attraction between the paint and the polar groups on the surface of the coated substrate, and the mutual attraction between the polar groups is based on the premise that the paint is well wetted on the surface of the coated substrate.Since the wet condition of the coating on the surface of the coated substrate depends on the surface tension of the paint liquid, the surface tension of the paint is lowered to improve the wetting efficiency and enhance the adhesion of the paint film to the surface of the substrate.
The wetting of the substrate by the coating is achieved by the flow of the coating.The paint liquid must have a good flow dynamics in the application, even if the powder coating must reach the flow dynamics; the coated surface can only be wetted by the flow of the paint liquid, in order to achieve the purpose of good adhesion of the paint film to the substrate.In general, the coating is not wet well, the interface contact is small, and the adhesion is poor; on the contrary, the coating is wet well, the interface contact is large, and the adhesion is good.

When low-molecular-weight substances or additives (such as stearates, plasticizers, etc.) are present in the coating, they will form a weak interfacial layer between the coating and the object to be coated, which will affect the flow of the paint to the substrate. Moisture, reducing adhesion.In addition, when the surface of the substrate is adhered with impurities such as water, dust, acid, alkali, etc., it also causes the appearance of a weak interface layer between the paint film and the substrate, hinders the wetting action of the paint liquid on the substrate, and reduces the polarity point. , resulting in a decrease in the adhesion of the paint film.

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