In recent years, with the heat of the domestic auto market heating up, China's auto industry has developed rapidly, which also makes people put forward higher requirements for the appearance, safety, and energy saving and environmental protection of the car. The use of lightweight plastic materials can not only reduce the quality of the car, save energy, make the car more safe and comfortable, it is also more resistant to atmospheric corrosion than gasoline, resistant to gasoline, easy processing and molding to reduce production costs, and therefore has become more and more widely usage of. Although the application of plastic parts has many advantages, the plastic parts themselves also face many problems, such as poor resistance to ultraviolet light and aging. Therefore, in order to improve the texture of plastic products, improve their protective and decorative effects, and extend the life of plastic parts, plastic products must be surface-coated. Most plastics have the characteristics of small polarity, large crystal, low surface tension, poor wettability, smooth surface, etc., resulting in poor adhesion of plastic parts. Therefore, how to improve the adhesion of the plastic coating is one of the key issues that need to be solved in plastic coating. In order to solve the problem of coating adhesion of automotive plastic parts, it is necessary to understand the process flow of automobile plastic parts coating. According to the author's finishing collection, the process flow of automobile plastic parts can be roughly divided into the following parts: The blanks are polished by a chemical treatment, a dust-removal primer, a paint (or a metallic flash paint), a light, a baking, a inspection, a qualified product, and a defective product for rework or paint stripping. It is understood that in this many process links, the most important link to improve the adhesion of plastic coating is pre-painting. The purpose of automotive pre-paint pre-painting is to improve the adhesion of paints to plastics through a series of physical and chemical methods, reduce various defects of the coating, and thus improve the quality of plastic coatings. Plastic pre-paint pretreatment include conventional treatment, acid treatment, flame treatment, surfactant treatment, thermal solvent treatment, ultraviolet treatment and plasma treatment. 1, conventional processing method The so-called conventional treatment, that is, dust, static electricity, degreasing. Plastics are poor conductors, and are prone to static electricity. Adsorption of dust or debris from the product during storage and transportation will seriously affect the adhesion of the coating and the hardness of the coating. To clean the surface of the product, chemical solutions can be used to clean it, and dust and static electricity can also be removed. 2, acid treatment In this method, the plastic surface is treated with an acidic substance to introduce a hydrophilic functional group into the surface to improve the surface wettability, and the surface is etched into a porous structure to improve the adhesion of the paint on the plastic. 3, flame treatment The flame treatment is to spray the flame onto the plastic surface so that the surface temperature reaches 1000-2800°C, but the treatment time is extremely short (in seconds) to avoid plastic damage and melting. This allows local oxidation of the plastic surface molecules to improve wetting and adhesion. 4. Interface active agent treatment The surfactant treatment method is to add a surfactant to the plastic to form a monolayer on the surface of the plastic to obtain a high-energy surface and improve the adhesion of the coating film. In addition, surfactants can simultaneously impart antistatic properties, wettability, and adhesion to plastics. 5, hot melt processing method Thermal solvent treatment means that the plastic is treated with a specific solvent for a short time at a high temperature. During the treatment, the plastic surface undergoes intense expansion, or coarse surfaces containing the corroded amorphous portion and the less affected crystalline portion appear to improve the adhesion of the coating. 6, UV treatment The UV treatment method uses ultraviolet light to irradiate plastics, and uses the oxygen in the air to generate polar groups on the plastic surface, increase the surface tension, reduce the contact angle of the paint, and increase the adhesion of the coating film. 7, plasma treatment The plasma equipment consists of a plasma generator, a gas delivery system, and a plasma jet. The working principle of the method is as follows: a high-frequency high-frequency energy is generated by a plasma generator, a low-temperature plasma is generated by glow discharge, and the plasma is sprayed onto the surface of the plastic part by means of compressed air to eliminate static electricity on the surface of the plastic part and remove the surface of the plastic part. Hydrocarbon dirt (for example, additives such as grease and plastic materials). In addition, in order to improve the adhesion of the coating, the surface treatment and construction environment of the plastic parts prior to painting should also be strictly controlled during the construction process to ensure the coating quality. When using new plastic materials, attention should be paid to improving the surface tension. And polarity, if necessary, change the pre-treatment process and the primer variety. Ningbo Metal Sharing Supply Chain Management Co., Ltd , https://www.zenlesf.com
May 03, 2023