Why does the coating attach to the substrate?

Why docoatings attach to substrates? The mechanism of adhesion formation, chemical binding (chemical bond): The film-forming material in the coating has an active gene that forms a strong chemical bond with the surface matter of the coating, thus strongly binding them together- OH, -COOH, -NH—,— NHCO and other genes that can form chemical bonds with substratesII, molecular-to-molecule binding (Vanderwaals): The combination of the strong attraction produced between the coating and the subject molecule is called the inter-molecular binding, which produces dispersion forces, hoisting forces and inducing forces according to the different charge states of the moleculesThis force itself is also very powerful, the coating is the main force that causes the two to combine when diffused on the surface of the coatingthree, hydrogen bond (hydrogenbond): Generally speaking, the oxygen atom side of water molecules is "-", and the hydrogen atom side is "plus", which can form gravity between themHalogen atoms or molecular groups other than oxygen atoms with strong negative charges form a stable system after the introduction of hydrogen atoms, at which point the system can also be regarded as hydrogen bond bindingFor example, the hydrogen atoms in the coating film and the oxides on the surface of the coating can form a binding force and can become a strong bonding force4, mechanical effects: the surface of any solid material can not be absolutely smooth and defect-freeWhen the coating film is attached, it can penetrate into the tiny pits and pores on the surface of the coated object because of the fluidity of the coating before curingWhen the coating cures, it is "embedded" in the pores, like countless tiny "pins"In some alloy surfaces, acid erosion (EtchPrimer), uneven corrosion of the alloy surface, expanding and deepening its surface pores while improving the wetting of the surface, the coating penetrates its pores, and is embedded with each other, thus obtaining a certain adhesionfive, adsorption action sorption effect): adhesion is the coating and the object molecules in the interface area of each other adsorption and produce, including physical adsorption and chemical adsorption, that is, adhesion is the interaction between the molecules - subvalent forces and atomic forces - the result of the main price forceThus, when the molecules of any substance are closely closer (spacing is less than 5 E), the intermolecular forces allow the contact objects to be adsorbed together6, diffusion action (diffusion effect): when the coating and the coating compatibility, solubility parameters are similar, due to the thermal movement of the molecule, polymer chain chain cranking (or flexivity), the chain movement between the coating molecule and the surface molecule of the coating, causing the diffusion between the molecules, thus forming a "interwoven" combination between the twoFor example, ABS plastic surface spray acetate butyl acid and produce surface expansion, coatings and plastics diffuse each other, so that the interface disappears, diffusion and the formation of interwoven polymer network structures and bonded togetherSeven, static attraction electronicattraction: generally two different substances contact with each other, its interface will produce positive and negative double electric layer, this electrostatic attraction can produce adhesion forceFor different coatings, different coatings and different coating construction process, the above-mentioned effects on the specific adhesion, its role is not the same size, in the application should be specific analysis