The coating film and the substrate can be combined through mechanical bonding, physical adsorption, formation of hydrogen bonds and chemical bonds, mutual diffusion, etc. The adhesion force generated by these effects determines the adhesion between the paint film and the substrate. This adhesion should be the sum of various binding forces (adhesion forces) between the paint film and the substrate. Adhesion is the key performance of the coating film to play the role of protection, decoration and special functions. Even if the coating itself has excellent physical and chemical properties, if it cannot be firmly bonded to the surface or coating of the substrate, it does not have much practical value, which shows the importance of adhesion in the coating performance. When the adhesion of the paint film is not good, measures such as substrate polishing, reducing the construction viscosity of the paint, increasing the construction temperature, drying, etc. can be taken to improve the mechanical bonding force and diffusion effect, so as to improve the adhesion. Adding adhesion accelerators to the coating system is also one of the most effective ways to improve adhesion.II. The four modes of action of the adhesion promoter are chemically anchored for the paint film and substrate; chemical anchoring of the paint film and physical winding of the substrate; physical winding of the paint film and chemical anchoring of the substrate; and physical winding of the paint film and substrate. Function and mechanism of action of adhesion promoter
Functional mechanism
Improve the mechanical binding force
By improving the permeability and moisture of the coating to the substrate, the coating penetrates into the holes and seams of the substrate as much as possible, and forms countless small anchors to be cured, firmly grasping the substrate, so as to improve the adhesion of the coating to the substrate. Improve the van der waals force. According to calculations, when the distance between the two planes is 1 nm, the van der waal force can reach 9.81~98.1 MPa. By improving the wetness of the paint to the substrate, the paint can be as completely moist as possible and close to the surface of the substrate before curing, so as to improve the van der waals force and finally improve the adhesion of the coating to the substrate. Provide reactive groups and create conditional hydrogen bonds for the formation of hydrogen bonds and chemical bonds. The strength of chemical bonds is much stronger than the van der waals force. Adhesion promoters such as resins and coupling agents provide reactive groups or other active groups such as amino groups, hydroxyl groups, carboxyl groups, etc., which can produce hydrogen bonds or chemical bonds with oxygen atoms or hydroxyl groups on the surface of the substrate, thus improving adhesion. Diffusion effect When the coated substrate is a polymer material, strong solvents or chlorinated polyolefin resin adhesion accelerators can be used, which can promote the mutual diffusion and dissolution of the molecules of the coating and the substrate, and eventually lead to the disappearance of the interface, thus improving the adhesion between the coating film and the substrate.