1 leveling mechanism
Powder paint is a solvent free uniform system, must melt can be attached to the coating above, after leveling the film coating, Ji'nan fluorocarbon spray generally need to go through three processes:
(1) from the separate powder particles, the aggregation becomes a continuous, uneven film, which is called the aggregation process.;
(2) the smooth and flat surface of the surface that flows from the continuous uneven surface, i.e., the advection process;
(3) the viscosity of the melt is continuously enhanced by crosslinking reaction and the viscosity is continuously improved. The final curing is hard film, called the curing process.
The main factors that affect the powder coatings are the melt viscosity, surface tension, particle size, coating thickness, curing temperature and time of the resin..
2 Influence of the Ji'nan fluorocarbon spray leveling factor
2.1 paint resin
The melt temperature and the glass temperature of the powder coatings determined the flow properties and storage stability of the powder coatings, which were related to the molecular weight and its distribution.. To obtain better coating, the relative molecular weight distribution of the resin is narrower.. Relative molecular mass distribution of wide implies the existence of relative molecular quality is too small or too large resin, and coating the other groups divided into good integration, in the high temperature baking under such conditions, coating melt mixing is not good, and surface tension of the coating fail to balance, the force between the particles will produce rejection or contraction of the movement, and melt flow time is limited, between them may not fully leveling time. With the curing of the coating, surface coating will shrinkage hole, orange peel and other defects. Therefore, we should choose a low melt viscosity, powder paint gelatinizing time long, horizontal flow of molten resin; but from the physical and mechanical properties of the coating, leveling time short and long curing time of mechanical properties better, the two should take into account the. Also polyester powder products in the storage process easy to agglomerate, spraying is easy to appear to flow from the hanging, orange peel, pinhole phenomenon, which is due to the polyester resin glass transition temperature (TG) is not suitable for induced. Examination of production practice, the polyester resin TG control within the range of 50 to 65 C, both to ensure full coating, good leveling, also can make the powder coating stored below 40 DEG C for 4 to 6 months, no caking, with a certain degree of stability.
2.2 leveling agent
Leveling agent is an essential ingredient in the appearance of the film.. Leveling agent distributed uniformly in the powder coating, powder electrostatic spray to the workpiece curing, it can reduce coating viscosity and surface tension, the molten coating not curing increase liquidity, and in the coating melt flow process by surface migration, gradually by intramolecular portion to migrate to the surface coating formed a single molecular layer, so that the whole surface increases the density of directed molecular structure, the coating surface is smooth, smooth, avoid membrane process in the formation of shrinkage cavity.
When the formula does not flow leveling agent or leveling agent less, the film flow flat is very poor, the film in the shrinkage hole or individual shrinkage, while consumption in more than 110% of the resin can get no shrinkage hole smooth coating. But excessive addition of leveling agent will reduce the powder coating of storage stability and flow flat agent is easy to float to the surface coating, reduce film pollution resistance and gloss, leveling agent for resin and the curing agent of the total mass of 1.0% ~ 1.3% is more appropriate.