Product physical properties and indicators
Appearance: white – end
Active ingredient: 98%
Relative density: 1.03~1.05g/ml
ph value: 5.0-6.0
If the heating speed is too fast, the solidification temperature is high, and the solidification speed is fast, the melt viscosity rises quickly, shortening the time available for flow and leveling, and it is easy to form orange peel. The heat capacity of small powder particles is lower than that of large particles, and the melting time is shorter than that of large particles, so it can coalesce into a film and level, and the appearance of the formed coating film is better than that of large particles; while the melting time of large powder particles Longer than small particles, the formed coating film may produce orange peel. The thickness of the first coating of powder coating should be 60~75um. If the film thickness is too low, the orange peel effect will increase; if the film thickness is too high, the coating film The adhesive force of the product is reduced, and it is not conducive to the escape of bubbles and easy to produce pinholes.
The power of leveling when the powder coating is formed into a film comes from the ability to homogenize the surface tension of the system, and the resistance comes from the melt viscosity. To make the coating film have good leveling properties, obviously, the surface tension leveling ability should be as high as possible, and the melt viscosity should be as low as possible. However, a too low melt viscosity will cause vertical sagging and edge shrinkage. Therefore, the system melt viscosity Should be controlled within an appropriate range. In addition, micronized amide wax the change of melt viscosity leads to the change of surface tension, and the cross-linking reaction speed and cross-linking density of each part of the system are different, which makes the surface tension of the coating film unbalanced, resulting in a Bernard vortex, leading to orange peel. Therefore, helping the coating film to achieve surface tension uniformity as soon as possible is an effective method to improve the leveling performance.
The role of anti-crater and leveling agent in powder coatings
Adding anti-shrinkage and leveling agents to the powder coating formulation can improve the appearance of the coating film and eliminate surface defects such as orange peel, shrinkage, pinholes, and edge shrinkage. Anti-shrinkage and leveling agents prevent shrinkage by reducing the surface tension of the system and increasing the wettability of the substrate, and help to form a smooth and smooth surface by promoting the uniformity of the surface tension of the coating film. Good anti-cratering and leveling agents can also reduce the melt viscosity of the coating, improve the flow and leveling of the coating, and facilitate the release of air, thereby eliminating surface defects.
The effects of anti-cratering and leveling agents on the surface tension of powder coatings during melting and curing are shown in Table 8-7. In the table, A represents epoxy-polyester powder coatings without leveling agents, and B represents Contains 0.55% polyacrylate leveling agent Moda flow 2000 in A.
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