How Do Powder Coatings Prevent Blocking

【China Aluminum Network】 powder coating has a tendency to agglomerate at a certain temperature, which is mainly caused by the softening of the materials such as resins, leveling agents and other materials in the powder coating. The powder coatings produced by our company are all thermosetting powder coatings. That is, the main film forming resin is a low molecular weight organic polymer. These resins have a physical property. At lower temperatures, they appear as a hard and brittle state of the glass. When the temperature rises to a certain degree, the resin begins to change into a state of elasticity and blocking, which is lower than this. At the temperature, the resin is returned to the non-adhered glass state. The temperature at which the glass and viscoelastic states of the resin are converted to each other is called the glass transition temperature of the resin. Different resins have different glass transition temperatures. For example, the glass transition temperature of epoxy resin and polyester resin is about 50 degrees Celsius. The glass transition temperature of the optical enhancer (701) is about 30 degrees Celsius, and the liquid leveling agent glass The degree is below minus eight degrees Celsius. The higher the amount of material with a low glass transition temperature in a powder coating formulation, the lower the glass transition temperature of the system. To determine the glass transition temperature, special large-scale instruments are required. The general powder coating manufacturers do not have such expensive equipment. We cannot grasp the glass transition temperature of the powder system in the production process. Therefore, the powder will be produced during production. The glass transition temperature of the system is located at approximately 40 degrees Celsius, which is defined as the safe temperature for agglomeration of the powder coating. Then, in the production (and product storage and transportation process) as a standard, when the temperature is close to or higher than this temperature, related personnel must strengthen sampling inspection of product agglomeration. Now that it has entered the summer production stage, the increase in temperature will be more likely to occur in the agglomeration of powder coating products. How can we prevent the agglomeration of powder coatings during work? First of all, it is necessary to establish a concept: agglomeration of powder coatings at a certain temperature is a natural law. To prevent agglomeration of powder coatings must be in the whole process of milling, packaging, storage, transportation, etc. of powder coating production, powder coating products are below their glass transition temperature. According to this view, there are the following solutions: 1) In the production of polyester resin, some of the alcohols or acids that can increase the glass transition temperature are used, or the amount of alcohol that can lower the glass transition temperature of the resin is used to increase the glass transition temperature of the polyester resin. 2) Reduce the use of low glass transition temperature polymers, such as leveling agents and brighteners, in powder coating formulations to ensure that the glass transition temperature of the powder coating system does not decrease. 3) In production, the crushed pieces on the steel strip should be cooled sufficiently before entering the milling process. During milling, the feeding speed should be properly reduced, the amount of induced draft should be increased, and the imported wind should be installed with air-conditioning to control milling. temperature. However, if the comminuted flakes before cooling do not come under cooling, then the following means will not play a very good role, consider the method of forced cooling of broken tablets for low-temperature treatment, which is more effective than the installation of air conditioning. Further, an anti-caking aid such as nano-silica (VK-SP15) or nano-aluminum trioxide (VK-L20M) fine powder may be added to prevent the adhesion of powder particles, and the anti-caking agent and the broken tablet material are simultaneously formed at the same time. Milling effect is better. Nano-aluminum oxide (VK-L20M), nano-silica (VK-SP15) Application range: 1. Thermosetting powder coating: Epoxy resin, polyester, acrylic resin. Examples are epoxy powder coatings, polyester powder coatings, acrylic powder coatings, and the like. 2. Thermoplastic powder coatings: Thermoplastic powder coatings include: polyethylene, polypropylene, polyester, polyvinyl chloride, chlorinated polyether, polyamide, cellulose, polyester. Polyvinyl chloride powder coating, polyethylene powder coating, nylon powder coating, fluorine resin powder coating, latex powder coating and other nano aluminum oxide (VK-L20M) Uses: Nano-aluminum oxide (type VK-L20M) is used in powder coatings to increase the bulkiness of powder coatings and has a good anti-caking effect. For powder coatings used in high temperature, high humidity environments, with good storage. The addition amount is generally 0.2-0.5%. The nano-aluminum oxide can improve the charging performance of the powder, especially when the frictional electrification spraying is used, it can obviously increase the powdering rate and solve the problem of dead angle, and at the same time, the gloss of the powder coating. Degree has no effect. The use of any single method does not effectively prevent agglomeration of the powder coating, and excessive use of one method can cause other disadvantages to the powder coating. Using a variety of methods for scientific cooperation can effectively prevent agglomeration of powder coatings.

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