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The effect of preparation process on PVDF powder coating //
01 preparation method on PVDF powder coating
PVDF powder coating preparation method is many, there are many melting extrusion mixed frozen crush grading method, solvent dissolving dispersed grinding drying grading method, mixed Bonding high temperature pinching crush grading method, emulsion co-precipitation method, dispersion spray drying method in solvents, etc. Below we will introduce the first three PVDF fluorocarbon powder coating preparation methods, the advantages and disadvantages of the corresponding preparation methods compared to Table 4 below.Table
4 Comparison of the three PVDF fluorocarbon powder preparation methods
According to the comparison of the three preparation methods for PVDF fluorocarbon powder coatings in Table 4, we consider the third method to be an ideal preparation method
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) from the aspects of environmental protection, energy conservation, product quality control effect, etc.
we also selected the powder coating obtained by the above three preparation methods for electron microscope analysis, the results of which are as follows Figure 1, Figure 2, Figure 3.
the above three methods visually reflect that different preparation methods not only have an effect on the shape of the powder particles, but also have an effect on the wetting dispersion of the material in the powder. Figure 1 and Figure 3 particle surface is also relatively smooth, particle angle is less, Figure 3 particles are closer to the spout, in contrast, Figure 2 powder particle surface is very rough, and the particle shape is not regular, indicating that the material in the formula in the powder dispersion is poor.
02 particle size on PVDF powder coating effect
particle size D50 in 30 to 35 m of conventional powder coating can not achieve the flatness of the liquid coating, so the thickness of the powder coating is often more than twice the liquid coating, otherwise it is difficult to form a flat and uniform coating, and because the PVDF powder melting viscosity is large, melting fluid leveling required baking process is more demanding, making the coating flatness of the problem more difficult to highlight. Below we will use the same formula to prepare powder coatings of different particle sizes to explore the effects of different particle size distributions on the performance of PVDF coatings, the results of which are shown in Tables 5 and 4.
Table 5 Effect of different particle sizes on PVDF coating performance
Figure 4 Effect of different particle sizes on the appearance of PVDF powder coating
From Tables 5 and 4, it can be seen that the D50 is about 13 m of powder 1 coating is the best flatness and good adhesion, D50 is 25 sm and 34 m, respectively The coating flatness of the powders 2 and 3 is gradually decreasing, and the orange peel phenomenon begins to appear to varying degrees, and its adhesion performance also decreases, which is due to the large powder particle size, uneven heat, the powder is relatively uneven, resulting in a less uneven coating, while the fine powder particle size is small, the heat is uniform, the powder is relatively uniform, the coating is relatively flat. At present, although ultra-fine powder technology can solve the PVDF powder coating flatness and adhesion and other problems, but the particle size is too small on the powder electrostitive spraying of the charge effect and powder rate, etc. have an impact on the recycling of powder coating re-use also put forward new problems, need to be sprayed equipment, such as electrostectronic spray gun structure, recycling equipment also need to be adapted and improved to meet the requirements.