Coating film formation mechanism

one. Paint adhesion

1. The first step in the adhesion of plastics and coatings is the wetting of the coating on the surface of the article. The coating wets the surface of the article and replaces the air and water adsorbed on the surface. At the same time, the solvent dissolves or swells on the surface of the article. If the film is made of resin and plastic Solubility parameters are selected to make the surface of the paint film a mixed layer

two. Coating drying

1. Physical drying:

That is, the total volatilization of the solvent in the coating, and its drying rate, completely depend on the volatilization rate of the solvent in the film-forming substance;

2. Chemical drying:

If the two-component coating is formed by two-component chemical reaction (ie, cross-linking curing reaction), the film formation rate depends on the speed of the chemical reaction. However, the solidification of the chemical reaction starts from the evaporation of the solvent.

3. Drying process: (four stages)

(1) Condensation or tension:

The solvent is almost completely volatilized, the viscosity of the paint is significantly increased, and the paint film continues to be sticky and dusty;

(2) No dirt on the surface: no traces of hand touch, weak resistance to slight forces;

(3) Actual drying: no marks are left on the hand pressed film layer, and the coating film is hard and can resist mechanical action;

(4) Completely dry: The dry hardness of the entire coating film no longer increases;

(5) When the general temperature is increased or decreased by 14°C, the baking time is shortened or extended by 30 minutes.

(6) Heat distortion temperature: ABS 70~107°C PC 120~150°C

(7) Commonly used ABS coatings are mostly dry at room temperature (or forced drying type), of which 1 liquid type is solvent volatilization type, 2 liquid type is self-reactive crosslinking type