The development of high imitation silver plating effect metal powder coating.

Abstract: Through the analysis of experimental data, this paper discusses the key techniques of high imitation silver plating powder coating formulation and the basic principles of coating curing molding. And combined with the binding process parameters design, to achieve a beautiful mirror effect of the powder coating.
1, Introduction . Powder coatings as decorative materials, with the abundance of life, people no longer limit the powder coating single color requirements

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has a metal appearance of binding powder coating, is recognized as a powder coating field of high-end products, by home appliances, furniture and automotive and other market areas, in various fields slowly spread.
high imitation silver plating effect powder coating, due to its excellent mirror effect and beautiful appearance, much sought after.
2, high imitation silver plating powder coating research
2.1 base powder formula research
in the electroplating silver plating powder coating base powder formula selection, generally choose transparent base powder, including resin, leveling agent, breathable agent. A single transparent coating allows light to penetrate the coating and enhances the reflectivity of light.
In the experimental comparison of the selection of base powder formula, the experiment found that the base powder formula containing pigment fillers, when curing inorgable fillers in the layer irregular distribution

By table 1 data can be seen different models of resin adhesion time, horizontal flow difference is large, due to its resin itself reactive and viscosity decision, low cross-link density, slow reaction speed, there is sufficient pre-curing time, conducive to the appearance of full leveling, showing a good coating appearance.
is positive, the reaction is fast, the gel time is short, easy to produce orange peel, seriously affect the quality of products, so in the formulation design, the choice of mobile large-scale resin is more suitable.
2.2 silver powder
can be divided into two categories, floating silver and non-floating silver (or flash silver) as shown in Figure 1 below. Flash silver particle size is larger in the production process using stingric acid as a wetting medium, wetting effect is good.
the powder coating, the silver is evenly distributed in the coating film, forming a flickering effect. Floating silver after vacuum treatment, to obtain particle size is generally between 5-20 m, very thin aluminum sheet, the use of unsaturated fatty acids as a wetting medium, the use of its own and powder wetting is not good.
the curing reaction, by the surface stress, floating on the surface of the curing coating, in the coating surface to form a uniform bright silver layer, than the traditional silver pigment has a better, denser reflective effect. In the experiment, we chose floating silver with good migration effect to make high-gloss silver plating powder coating.
2.3 Choice of silver powder arranger
In the production of high-gloss silver plated silver powder coating, floating silver is mostly irregular flakes, chaotic distribution (Figure 1), floating silver and powder base powder mixed, floating silver in the base powder scattered state, irregular arrangement.
powder curing In order to achieve the ideal mirror effect, it is necessary to add a floating silver directional arrangement agent to the powder, improve the wetting between floating silver and resin, so that floating silver has a strong ability to migrate to the coating surface, and make the electroplating floating silver uniform dense distribution on the coating surface, effectively improve the powder plating effect.
can be seen from Figure 2 above, the coating contains a test sample of silver powder directional arranger, the curing coating in the electro-mirror diagram, there will be a significant layering. Without the silver powder directional arranger, there is no obvious layering.
addition of silver powder directional arrangers to the formula can also improve the overall leveling of the powder, making the mirror effect better.After repeated tests, it is concluded that the formula does not contain silver powder directional arrangers, because the density of floating silver itself is higher than the true density of powder and the characteristics of floating silver powder itself, floating silver heat will be in the coating to the upper and lower surfaces at the same time disorderly migration, will not produce a layering effect.
When the silver powder directional arranger is added, the directional arrangement agent plays an orderly arrangement effect on the aluminum powder in the powder, and makes the silver powder migrate to the upper surface in an orderly manner, to achieve a neat and orderly arrangement effect, the appearance of layering. It can be seen that the floating silver directional arranger has a decisive effect on the effect of silver plating powder coating.
3, the study of the production process
3.1 difference between dry mixing and binding
the production of high imitation silver plating powder coating, can be divided into dry mixing and binding two processes. Dry mixing is through powder and silver powder after mechanical mixing, this way is simple and economical, do not need special equipment, manual operation can be.
binding process is processed by special binding equipment, after binding float silver uniform, tight and orderly fit on the surface of the powder base powder.
Figure 3, dry mixing process made of powder coating, through the electro-mirror to see the powder, silver powder disorder, scattered stick on the surface of the powder, and some even in a separate state mixed in the powder particles. The right image uses binding process processing to see that floating silver will be dense and orderly wrapped in the surface of the powder.
theory, the addition of floating silver directional arranger, floating silver by the directional arrangement agent, when curing floating silver concentrated upward surface migration, the appearance of high-gloss plating mirror effect.
fact, however, contrary to the theory, dry mixed floating silver, although a large number of upward surface migration, after curing the surface of the coating did not appear a high-gloss mirror effect. However, after the binding process, the floating silver is evenly distributed in the layer, and the highlight mirror effect appears.
As shown in Figure 4, electroscopic spectroscopy measures the content of aluminum in the cross-section of the curing coating, and when dry mixing, a large amount of silver powder migrates up and down the surface, and a large amount of floating silver can be seen piling up on the upper and lower surfaces.
because the silver powder itself is floc-like, irregular shape, disorderly light reflection, resulting in the coating surface reflection effect gray and dark, no mirror effect.
after the binding process, floating silver in the coating dense, orderly arrangement, curing coating float silver evenly layered arrangement, and the emergence of a rule layering.
And in the layering has detected a peak of floating silver content, it can be inferred that after binding, floating silver in the powder curing by the directional arrangement agent, evenly distributed in the layer, at faults and surface evenly tiled a layer of tight arrangement, strong reflection effect of the floating silver layer, reflected by light to achieve a high-bright silver plating effect.
3.2 binding process is set
to achieve a high imitation silver plating effect powder coating, must go through the binding process. The binding machine process parameters include heating speed, binding speed and cooling speed and temperature parameter settings. By setting specific process parameters, a bright plating effect is achieved.
After experiments, the experiment proved that binding speed is the main factor affecting the effect of powder mirror, my company's binding machine speed 200-1400r/min, set the appropriate parameters,
so that floating silver and base powder in high-speed rotation; In addition, the upper limit of oxygen is controlled during binding, nitrogen is passed in, and the oxygen content of the powder is adjusted to prevent explosion.
test of the secondary performance of silver-plated silver powder with high-gloss . High imitation silver plating powder coating in the secondary performance test, because the surface of the coating tiled a layer of aluminum powder, poor chemical resistance.
NaOH (4%) by 35 degrees C drops on the coating, about 5 minutes, the coating began to corrode, a large number of bubbles emerged, diluted, the mirror effect darkened. HCL (10%) x 35 degrees C also darkens, as shown in Figure 6.
also measured high-gloss mirror coating long-term leakage in natural conditions (aging, moisture resistance, salt spray testing, etc.), surface aluminum powder easy to oxidize blackening, affecting the beauty of the coating.
in order to maintain its mirror effect with long-lasting corrosion resistance, it is common to spray a layer of transparent powder on cured surfaces for protection. This keeps the coating beautiful and durable.
5, Conclusion
The production of high imitation silver plating effect powder coating at the same time must pay attention to the following points:
(1) choose the right raw materials, it is best to choose a large viscosity, low acid value, smooth good resin.
(2) floating silver is added in a certain proportion range, otherwise the mirror effect is not ideal.
(3) binding machine production parameters should be set consistently to ensure the spray stability of the finished product produced between batches.
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