Factors influencing the powder coating of the flowing property mainly include three aspects: one is the flow ping agent. in the formulation of powder coatings, add the appropriate flow ping agent. After the powder melting, these additives can quickly reduce the surface tension of the coating, promote the fast flow coating before curing film, eliminate or reduce the orange peel, brush marks, corrugated, surface defects such as shrinkage cavity; the second is the melt viscosity of powder coating, for thermosetting powder coating, in the melting flow process, accompanied by crosslinking curing reaction, the higher the temperature, the faster the curing reaction, the faster the system viscosity rises, the flow time is shortened, the leveling is restricted.
Therefore, the melt viscosity of powder coating can not accurately reflect the final leveling property of the coating. Powder coating powder manufacturer must consider the influence of baking process, heating rate, crosslinking curing temperature on the leveling property of the coating. The third is the baking process.
There is a heating process during baking of powder coating, and the speed of heating has a considerable influence on the leveling of coating.
The trend of dynamic viscosity changes with temperature is basically the same, that is, the viscosity decreases with the increase of temperature at the beginning, reaches the minimum value, and then increases with the increase of temperature, which is caused by the cross-linking reaction.
More importantly, the faster the heating rate, the smaller the minimum value of viscosity, and the higher the corresponding temperature is more conducive to the curing of the film, the better the leveling of the film.
The leveling property of powder coating is restricted by leveling auxiliaries, the structure of film forming resin and curing mechanism.
Using appropriate leveling additives, choosing a resin system with low melt viscosity and matching curing process (UV curing), the film with excellent leveling performance can be obtained.