How To Improve The Leveling Of Powder Coatings

How to improve the leveling of powder coatings? Powder coatings are a new type of solvent-free 100% solid powder coating. Powder coatings are made of resins, pigments, fillers, curing agents and other additives, mixed in a certain proportion, and then prepared by hot extrusion and crushing and screening. At room temperature, it is stable in storage. After electrostatic spraying or fluidized bed dipping, heating and baking to melt and solidify, a flat and bright permanent coating film is formed to achieve the purpose of decoration and corrosion protection.

Leveling refers to the flat and smooth state of the coating after the coating is applied. The surface with good leveling should not have irregular shapes such as orange peel, brush marks, ripples, shrinkage holes, etc.

The factors that affect the leveling of powder coatings mainly include three aspects:
1. Leveling aids: Add appropriate leveling aids to the formula of powder coatings, such as Tianshi TWAX-988 powder coating wax powder, which has high melting point, smooth feel, good fluidity, easy dispersion, and ultra-fine particle size; small addition amount, cost reduction and efficiency improvement; improve the powdering rate of silver powder.
2. Melt viscosity of powder coatings: For thermosetting powder coatings, during the melting flow process, accompanied by cross-linking and curing reactions, the higher the temperature, the faster the curing reaction, the faster the system viscosity rises, the flow time is shortened, and the leveling is restricted. Therefore, the melt viscosity of powder coatings cannot accurately reflect the final leveling of the coating film, and the effects of baking process, heating rate, cross-linking and curing temperature on the leveling of the coating film must be considered at the same time.
3. Baking process: There is a heating process when the powder coating is baked after coating. The speed of the heating rate has a considerable influence on the leveling of the coating. Under different heating rates, the trend of dynamic viscosity changing with temperature is basically the same, that is, the viscosity decreases with the increase of temperature at the beginning and reaches the minimum value, and then the viscosity increases with the increase of temperature. This is caused by the cross-linking reaction. More importantly, the faster the heating rate, the smaller the minimum value of the viscosity, and the higher the corresponding temperature, the more conducive to the curing of the coating film and the better the leveling of the coating film.

The leveling of powder coating is restricted by the structure and curing mechanism of leveling agents and film-forming resins. The use of appropriate leveling agents, the selection of low melt viscosity resin systems and matching curing processes can obtain coatings with excellent leveling performance. Wax powder is used in powder coatings, and it can also play a bonding effect. Ultrafine wax powder does not dissolve at the bonding temperature and can be coated on the powder coating particles to prevent the powder coating particles from sticking. Compared with inorganic materials, wax powder as a bonding release agent will not have an adverse effect on the leveling of powder coatings.