Powder coating has a tendency to agglomerate at a certain temperature, which is mainly caused by thermal softening of materials such as resins and leveling agents in the powder coating. The resin which is a main film-forming material is an organic polymer having a relatively low molecular weight. These resins have a physical property, and at a lower temperature, they exhibit a hard and brittle glass state. When the temperature rises to a certain extent, the resin begins to transform into a state of elasticity and adhesion, below this. At the temperature, the resin returns to the non-blocking glass state, and the temperature at which the glass state and the viscoelastic state of the resin are mutually converted 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, and the glass transition temperature of brightener (701) is about 30 degrees Celsius, while the glass of liquid leveling agent. The degree of conversion is below zero degrees Celsius. The greater the amount of material added to the low glass transition temperature in the powder coating formulation, the lower the glass transition temperature of the system. Determining the glass transition temperature requires special large-scale instruments. 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 positioned at approximately 40 degrees Celsius, which is defined as the safe temperature at which the powder coating agglomerates. Then in the production (and product storage and transportation process) as the standard, the relevant personnel should strengthen the sampling of product agglomeration when approaching and above this temperature. At present, it has entered the summer production stage. The increase in temperature will make it easier for the powder coating product to agglomerate. How to prevent the agglomeration of the powder coating during work?

First of all, we must establish a concept: the agglomeration of powder coating at a certain temperature is a natural law. To prevent the agglomeration of powder coatings, the powder coating products must be below their glass transition temperature in the whole process of milling, packaging, storage and transportation of powder coatings.

According to this point of view, there are the following solutions:

1) In the production of polyester resin, some alcohol or acid which can increase the glass transition temperature is selected, or the amount of alcohol which lowers 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 formulation design to ensure that the glass transition temperature of the powder coating system does not decrease.

3) In terms of production, the broken flakes on the steel strip should be fully cooled before entering the milling process. When grinding, the feed rate should be appropriately reduced, the air volume should be increased, and the imported air should be installed with air-conditioning to control the milling. temperature. However, if the pulverized flakes are not cooled before grinding, the latter means will not play a good role. The method of forced cooling of the crushed flakes can be considered for low temperature treatment, which is more effective than installing air conditioners.

Further, an anti-caking aid such as nano-silica (VK-SP15) or nano-aluminum oxy-aluminum (VK-L20M) micropowder may be added to prevent adhesion between powder particles, and the anti-caking agent is generally simultaneously with the crushed flakes. The grinding effect is the best.

Nano-aluminum oxide (VK-L20M), nano-silica (VK-SP15) use range:

1. Thermosetting powder coating: epoxy resin, polyester, acrylic resin. Examples of epoxy powder coatings, polyester powder coatings, acrylate powder coatings, etc.

2. Thermoplastic Powder Coatings: Thermoplastic powder coatings include: polyethylene, polypropylene, polyester, polyvinyl chloride, chlorinated polyether, polyamide, cellulose, and polyester. Examples of polyvinyl chloride powder coating, polyethylene powder coating, nylon powder coating, fluororesin powder coating, latex powder coating, etc.

Nano-aluminum oxide (VK-L20M) use characteristics:

Nano-Al2O3 (Model VK-L20M) is used in powder coatings to improve the bulkiness of powder coatings and to resist caking. It has good storage properties for powder coatings used in high temperature and high humidity environments. The addition amount is generally 0.2-0.5%, and the nano-aluminum oxide can improve the charging performance of the powder, especially when using the frictional electrification spraying, the powder powdering rate can be obviously improved and the problem of dead angle can be solved, and the gloss of the powder coating is also obtained. Degree has no effect.

The use of any single method does not effectively prevent the agglomeration of the powder coating. Excessive use of one method can cause other drawbacks to the powder coating. A scientific combination of methods can effectively prevent the agglomeration of powder coating.