What are the particles that may appear during the use of powder coatings?

The function of powder coating is to perform surface treatment, and there is a headache for manufacturers during the use of powder coating, which is the appearance of particles. Once particles appear, the surface of the processed workpiece cannot achieve a smooth and flat effect, which will lead to a decrease in the value of the product. How can manufacturers prevent it?

1.1 Generation and prevention of mechanical impurity particles

Mechanical impurity particles mainly come from the material itself and its production process, equipment wear, and impurities brought in by the environment during powder coating production.

(1) The particles formed by mechanical impurities in resin may have sharp shapes due to the presence of various mechanical impurities in the raw materials or during the production process. This requires resin manufacturers to use qualified raw materials, maintain a clean production environment, strictly control production processes, and take corresponding filtering measures.

(2) Impurities in pigments and fillers. For some low-quality products such as titanium dioxide, barium, calcium, etc., they all contain a considerable amount of coarse gravel and black impurities to varying degrees. Using this pigment filler will definitely form particles in the coating. For particles, finer pigments and fillers with no residue after passing 325 mesh are less prone to particle formation; The coarser the pigment filler, the more likely particles are to appear. However, if the pigment filler is too fine, it will increase its oil absorption, which may affect the leveling of the powder coating. This requires the pigment filler to have a reasonable particle size and strictly control the presence of coarse particles.

(3) During the production process of powder coatings, metal shavings may also be generated due to wear and component detachment in the grinding chamber, and the particles formed may have a scratching sensation when touched by hand.

(4) Fabric fibers can also cause particle formation. Some powder coating manufacturers use fabric tied to the ingredient discharge port or product packaging port to receive materials. After a certain period of wear, the fibers fall off and enter the material or product, producing string like particles. Mechanical impurities particles, including dust and other impurities that may be carried by the outer packaging, can also be brought into the pre mixing position, and packaging materials (paper, plastic fibers, packaging lines, etc.) can fall into the mixer. Therefore, it is necessary to conduct inspections at all times in these sections to reduce the generation of particles.

1.2 Colloidal particles

The shape and quantity of gelatinous particles are relatively round, mainly from the extrusion process in the production of resins and powder coatings used.

(1) Colloidal particles in resin. During the resin production process, the reaction kettle may overheat locally or the stirring condition may be poor, resulting in the appearance of high molecular weight and melting point particles in the entire batch of materials. These adhesive particles cannot melt during extrusion in the production process of powder coatings, and are difficult to be crushed into too fine particles in the subsequent crushing process. If these adhesive particles are mixed in normal powder coatings, they may form particles in the coating after spraying and curing.

(2) The extrusion process in the production of powder coatings is a major factor in particle generation. On the one hand, it may be caused by the device itself; On the one hand, it may be caused by process control, either due to high temperature or extrusion material breakage and idling.

Before using powder coating, it is important to ensure a clean environment and temperature control during use. Keeping the temperature within a certain range can prevent problems such as particles, orange peel, or poor protective ability of the powder coating.