Production Principles of Powder Coatings

Powder coating is a powdery coating composed of synthetic resins, fillers, pigments, curing agents, and additives. Powder coating, as a new type of environmentally friendly coating, has the advantages of low environmental pollution, low resource and energy consumption, low production cost, and high production efficiency. With the increasing production of powder coatings, their application fields are also gradually expanding. Powder coatings are gradually replacing other solvent based coatings and becoming a more promising coating in modern society.

The production principle of powder coatings

The production principle of powder coatings: Solid materials such as synthetic resins, fillers, pigments, curing agents, and additives are added to a mixer in a certain proportion and formula for pre mixing. The pre mixing process should be operated under anhydrous or other solvent conditions. The materials passing through the mixer are melted at high temperature by the extruder, and then enter the cooling Tablet press for cooling and pressing into thin sheets after complete mixing. The flakes enter the cyclone separator after being crushed. The separated coarse powder gets the finished powder coating after sieving, and the fine powder is recycled. The production process of powder coatings does not involve any chemical reactions and is a purely physical process.

Factors Influencing the Quality of Two Powder Coatings

1. Quality of raw materials

The quality of raw materials plays a decisive role in the quality and performance of powder coatings. Therefore, each raw material should be selected appropriately. The structure and performance of synthetic resins are the main factors determining the quality of powder coatings. The synthetic resin used in powder coating raw materials must meet the following conditions: the synthetic resin should contain active functional groups; The temperature difference between the melting temperature and the decomposition temperature should be large. The melting viscosity of synthetic resin is low, the melting range is narrow, and when the temperature reaches above the melting point, the melting viscosity should quickly decrease; Synthetic resin should have good physical and chemical stability, high melting point and glass transition temperature; Synthetic resin should be non-toxic and have a light color.

Pigments and fillers, as important components of powder coatings, must have stable chemical properties. During the production and storage process of powder coatings, they must not react with other components and should also have good thermal and light stability. In addition, pigments and fillers are required to be evenly dispersed in the synthetic resin. The main function of fillers in powder coatings is to increase the capacity of components and reduce production costs. If the filler is used properly, it can also play a modifying role in meeting the basic properties of powder coating film, such as the smoothness and glossiness of the film.

Curing agents have a significant impact on the film performance of powder coatings and are an important measure for modifying synthetic resins. The curing agent needs to meet the following conditions: solid at room temperature; During production and storage, there is no chemical reaction with synthetic resins and other components; Less irritating odor and toxicity; Colorless, etc.

In order to improve the leveling, glossiness, or create patterned surfaces of powder coatings, additives are often added. Special attention should be paid to the amount of additives added. For example, when the dosage of viscous additives or solid additives exceeds 2%. The stability of powder coatings may deteriorate during storage and are prone to agglomeration.

Choose suitable raw materials to ensure the quality of the materials, and do not use them as a filling or improper selection of materials.

2. Formulation of formulas

In the formulation and selection process of powder coatings, special consideration should be given to the internal relationships of each component. The excellent miscibility between each component is the foundation for ensuring the quality of powder coatings. Ignoring this makes it difficult to achieve the desired coating effect. The synthetic resin in the powder coating components determines the basic performance of the coating. Therefore, the first consideration in the selection and formulation of formulas is to choose a suitable synthetic resin. Secondly, based on this, select other components and their dosage and ratio. The formula of powder coatings should have stability and continuity. Formula is an important factor determining the quality and market competitiveness of powder coatings. An excellent formula is the lifeline of powder coating enterprises, and the confidentiality of the formula should be well maintained.

3. Selection of production equipment

The production of powder coatings is a physical process. Production equipment has a significant impact on the stability of formulas and the quality of powder coatings. The selection of powder coating production equipment largely depends on the type of product to be produced, quality requirements, and production batch. Pre mixing is the previous process in powder coating production, which mixes and disperses all components to create a good uniform system for melting and mixing. Therefore, the pre mixer is required to have good homogenization and dispersion capacity, high Shear stress, no dead corner in the mixing area, and good airtightness. Melt mixing extrusion is a key process in the production of powder coatings. It involves heating and melting the mixed materials during the extrusion process, and under the action of high shear force, melting the materials into a suitable viscosity to ensure the production of high shear force during extrusion, which is conducive to the high dispersion of materials and the formation of a uniform system of each component. It is also necessary to control the appropriate extrusion temperature while using the * * extruder. The extruder should meet the following requirements: it can evenly disperse additives throughout the entire material; Able to accurately adjust and control temperature; The material has no dead corners inside the barrel; Easy to disassemble and clean. The crushing process involves crushing the crushed material particles into a particle size suitable for high-pressure spraying. The size of powder coating particles directly affects the film performance of the coating. The pulverizer should meet the following requirements: timely discharge of crushing heat generated by particle motion; Not only should it have crushing ability, but it should also have accurate particle size grading ability, which can accurately adjust the particle size of the crushed product.

Testing Technology for the Quality of Three Powder Coatings

At present, powder coatings have been widely used both domestically and internationally. Its main use is as a decorative coating and metal protection, by electrical insulation and corrosion prevention, and a small amount is also used for other functional purposes. According to the different uses of powder coatings, there are different testing performance items and requirements. However, the testing of powder coatings is generally divided into two categories: one is to test the performance of powder coatings before film formation, which mainly reflects the performance related to production processes, packaging, storage, and other aspects. Another type is to test the performance of powder coatings after film formation, which mainly reflects the physical and mechanical properties, corrosion resistance, etc. related to usage requirements. In order to make the detection structure comparable and facilitate communication and trade, many countries have developed unified detection methods and standards. For example, ANSI/ASTM standards of the United States, IEC455-2 standards of the International Electrotechnical Commission, and GB6554-86 standards for powder coatings in China. The testing of powder coatings is an effective guarantee of their quality. Mastering the testing technology of powder coatings is extremely important for departments engaged in research, production, and application of powder coatings. Only by understanding the testing technology of powder coatings can we better select and adjust raw materials and formulas, reasonably control and adjust production processes, and better stabilize and improve the quality of powder coatings.

Four concluding remarks

Powder coating, as a new type of environmentally friendly coating, has promising development prospects. The powder coating production process is simple and easy to automate, greatly saving resources and energy, ensuring the health of operators, and improving labor productivity. The development of powder coatings has undoubtedly made outstanding contributions to society.