What Are the Different Uses of Aluminum Powder?

Aluminum powder, commonly known as "silver powder", is a silver metallic pigment. Pure aluminum foil is added with a small amount of lubricant, crushed and crushed into scaly powder, and then polished. Aluminum powder is light, has high floating power, strong hiding power, and has good light and heat reflection properties. After treatment, it can also become non-floating aluminum powder. Aluminum powder can be used to identify fingerprints and can also be used for fireworks. Aluminum powder is a large class of metallic pigments due to its wide use, large demand and many varieties.

Aluminum powder processing method

1. Melt extrusion method
In this method, the metal pigment and the remaining components of the powder coating (resin, etc.) are heated and extruded through a screw extruder. Although metal pigments and powder coatings can be mixed well, metal pigments are insufficiently oriented in high-viscosity melts. In addition, in the next pulverization process, the flake structure of the pigment will inevitably be destroyed. When the metal powder produced by this method is applied, the metal effect is gray. Therefore, this method is only used for making hammer grain powder.
2.Dry blending method
In this method, a dry metallic pigment is added to the pulverized powder coating and mixed by a mechanical mixer. The advantage of the dry-blending method is that the metallic pigment and the powder coating are not mixed fiercely, thereby preventing deformation of the flake metallic pigment, and thus the metal effect is not affected. In addition, the loose pigment / resin mixture is also very beneficial to the orientation of metal pigments, improving the glitter effect. The disadvantage of this method is that when automatic spray equipment is used to process the recovered powder, the metal pigment and resin powder particles have a large difference in shape, density, and electrical charge, which results in separation.
3. Bonding-Process
In this method, the metal pigment and powder coating are dry-mixed and heated at the same time, so that the temperature just exceeds the softening point of the resin. At this time, the metal pigment can be fixed and bonded to the surface of the resin powder with stickiness, thereby preventing the powder from being applied during Neutralize the separation of metal pigments and resin powders during recovery after construction. Is the popular Bonding Law.
4, jet crushing method
This method is based on the principle of supersonic airflow pulverization. Because aluminum powder is susceptible to oxidation, JZDB series nitrogen-protected airflow pulverization classifiers are generally used to produce ultrafine aluminum powder.

Aluminum powder safety matters

Powder coatings have a lower safety risk than ordinary paints. Compared to solvent / air mixtures, the ignition energy of powder / air mixtures is 50-100 times. However, all flammable powders or dusts can form explosive mixtures with air and are a potential source of danger. However, if appropriate measures are taken in advance, safe transportation, storage and processing can be carried out. For the sake of safety, the powder concentration of the aforementioned powders should not exceed 10 g / m 3 . In spraying areas, this concentration is often exceeded. Since there is always sufficient oxygen content, sparks exceeding this minimum energy must be avoided.
PTB (Federal Institute for Physical Technology) BAM (Federal Laboratory for Materials Testing) has determined explosion data for various pigmented powder coatings. The results prove that there is no difference between extruded and dry-blended materials in terms of "maximum explosion pressure" and "maximum increase pressure".
Compared with resin powders without pigments, when 5-6% aluminum powder is added, the so-called powder constant (a measure of explosive force) and the maximum explosion pressure increase by 10%. As the content of aluminum powder continues to increase, the explosive force will also increase. When the content of aluminum powder is greater than 25%, the explosive force of pure metal powder will be reached. However, this dependence on aluminum powder pigments is not intended to be used for minimum ignition energy. No matter what kind of dispersion method is used, pure resin powder cannot reach the minimum ignition energy. If the aluminum powder pigment content is> 10% and the fine particle size and uncoated aluminum powder is used, the lowest ignition energy may be reduced.
Powder coatings containing aluminum powder are the same as ordinary pigmented powder coatings, as long as they do not exceed the specified limits, there is no danger of fire and explosion.
In order to ensure the safety of the entire spraying process, the separation, accumulation and concentration of aluminum powder in the factory must be avoided. These basic requirements also apply to solvent-based coatings containing copper and gold powder. However, the explosion hazard caused directly by copper-zinc alloy powder is smaller than aluminum powder.
The most important thing for powder equipment is that all parts and operators must be well grounded. The indoor dust concentration should be controlled to a minimum level, and an exhaust system should be used according to local regulations. In any case, avoid open flames, Mars and hot surfaces. [3]


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