What are the types of drying of paint? What is its mechanism?

There are mainly physical mechanism drying and chemical mechanism drying. (1) Physical mechanism drying Physical mechanism drying is just a coating drying film-forming mechanism that relies on the evaporation of liquid (solvent or dispersed phase) in the coating to obtain a dry hard coating film. (2) Chemical mechanism of drying Chemical mechanism The film-forming process of drying is mainly chemical effects such as condensation and polymerization. We can formulate coatings from linear or lightly branched polymers or even simple low molecular compounds. After the paint is applied, a cross-linking reaction occurs and becomes a polymer compound with a solid network structure. The formed coating film can no longer be dissolved by solvents or melted by heat. Therefore, this type of coating is also called thermosetting coating.

According to the curing mechanism, coatings can be divided into volatile drying coatings and curing drying coatings. The former is generally called volatile paint, while the latter includes air-drying paint, baking paint and radiation-curing paint, etc., which are also called non-volatile paint. Volatile paint: It refers to paints that dry to form a film after the solvent in the coating has evaporated, such as nitrocellulose paint, insect carving paint, etc. commonly used in wood products. air drying paint: It refers to paints whose coating needs to react with oxygen or moisture in the air to solidify into a film. It also generally refers to paints that can naturally solidify into a film without special heating or radiation. It is also called self-drying paint, such as phenolic paint, alkyd paint, etc. Radiation curable paint: The coating requires infrared or ultraviolet radiation to cure into a film, such as photosensitive paint. Drying film forming mechanism of paint: The non-conversion type generally refers to the physical film formation method, which mainly relies on the volatilization of solvents or other dispersion media in the coating film, and the viscosity of the coating film gradually increases to form a solid coating film. For example: Conversion types such as acrylic paint, chlorinated rubber paint, asphalt paint, and vinyl paint generally refer to the chemical reaction that occurs during the film-forming process, and the paint mainly relies on chemical reactions to form films. This kind of film formation is the process in which the film-forming substances in the paint polymerize into a coating film called a polymer after construction. It can be said to be a special polymer synthesis method, which completely follows the polymer synthesis reaction mechanism. For example: Alkyd coatings, epoxy coatings, polyurethane coatings, phenolic coatings, etc. However, most modern coatings do not form films in a single way, but rely on multiple methods to finally form films.

According to the curing mechanism, coatings can be divided into volatile drying coatings and curing drying coatings. The former is generally called volatile paint, while the latter includes air-drying paint, baking paint and radiation-curing paint, etc., which are also called non-volatile paint. Volatile paint: It refers to paints that dry to form a film after the solvent in the coating has evaporated, such as nitrocellulose paint, insect carving paint, etc. commonly used in wood products. air drying paint: It refers to paints whose coating needs to react with oxygen or moisture in the air to solidify into a film. It also generally refers to paints that can naturally solidify into a film without special heating or radiation. It is also called self-drying paint, such as phenolic paint, alkyd paint, etc. Radiation curable paint: Paints that require infrared or ultraviolet radiation to cure into a film, such as photosensitive paint

Different film-forming methods require different drying conditions, and drying conditions directly affect the film-forming effect and coating anti-corrosion performance. The drying and film-forming methods of coatings are mainly divided into: Natural drying and heated drying (such as convection, radiation and electric induction, etc.). No matter which drying method is used, in order to ensure the quality of the coating, the following conditions should be met for drying the paint film. 1) The surrounding environment should be kept clean and dust-free, and the air should be clean. 2) The temperature should meet the technical requirements of the coating. If it is too high or too low, it will affect the drying efficiency and coating quality. 3) The air must flow, because air flow is conducive to the volatilization of the solvent and is conducive to drying and film formation. 4) Generally, the second layer of paint must be applied after the previous layer of paint is fully dry. Otherwise, paint film defects such as bottom bite and bleeding may easily occur and the drying effect will be affected. However, some coatings, such as epoxy resin paints, have a certain recoating period. If it is too late, the film will not form, and if it is too late, the adhesion between layers will be poor.