Properties and classification of aluminum powder

Characteristics of aluminum metal

Aluminum is a silver-gray metal with a relative mass of 26.98, relative density of 2.55, and a melting point of 685 degrees, a boiling point of 2065 degrees and a latent heat of 323kJ /g. Aluminum is reductive, easy to oxidize and exothermal in the process of oxidation.  At rapid oxidation, the heat release is 15.5 kJ /g. Aluminum is a ductile metal and easy to work.  The oxide film on the surface of aluminum is transparent and has good chemical stability.  

The aluminum powder used for pigment refers to the aluminum powder with scaly particles and coated with treating agent on the surface, which is suitable for pigment.  Aluminum slurry is a mixture of pigment aluminum powder and solvent, its use and characteristics are roughly the same as aluminum powder, because it is easy to use, so the output and dosage is larger.  

Compared with other pigments, aluminum metal has more characteristics, which are shown in the following aspects

1. Characteristics of scaly covering Aluminum powder particles are scaly, and the ratio of the diameter to thickness is about (40:1) - (100:  1), aluminum powder dispersed to the carrier with the characteristics of parallel to the substrate, many aluminum powder connected to each other, small and large particles fill each other to form a continuous metal film, covering the substrate, and reflect the light outside the film, this is the unique hiding power of aluminum powder.  The covering power of aluminum powder depends on the size of the surface area, that is, the diameter thickness ratio.  Aluminum is extended in the process of grinding, and the diameter thickness ratio is increasing, so is the hiding power.  

2. The shielding characteristics of aluminum powder scattered in the carrier of aluminum powder floating movement, the result of its movement always makes itself parallel to the substrate coated by the carrier, the formation of a continuous aluminum powder layer, and the aluminum powder layer in the carrier film multilayer parallel arrangement.  The pores between the layers of aluminum powder are staggered each other, cutting off the carrier film hair pores, the outside water and gas can not reach the substrate through the pores, this characteristic is the good physical shielding of aluminum powder.  

3. The optical characteristics of aluminum powder aluminum powder is made of light color, high metallic luster of aluminum, its surface is smooth, can reflect visible light, ultraviolet and infrared light 60%-90%, with aluminum powder coating objects, the surface of silver bright, this is the characteristic of aluminum powder reflected light.  

4. Aluminum powder "two-color effect" characteristics of aluminum powder due to its metallic luster and parallel to the characteristics of the coating, in the carrier containing transparent pigment, aluminum powder gloss and color depth with the incident light Angle and Angle of view changes in light and color changes, this characteristic is called "two-color effect".  Aluminum powder is arranged in different layers in the film. When the incident light shines on each layer of aluminum flake, it is weakened differently through the film of different thickness, and the brightness of reflected light is obviously different.  

When light hits including transparent pigment and aluminum film, incident light through the paint particles become light, reflected by different levels of aluminum powder, can change colors and light metal, incident light and the Angle from the vertical occur gradually angular displacement, the light is through different quantity of pigment particles and different particle size of aluminum powder,  The color of the reflected light and the metallic light also change infinitely.  This characteristic of aluminum powder has been widely used in coatings, hammer paint or metal paint.  

5. Aluminum powder floating characteristics of pigment aluminum powder and aluminum slurry is a kind of floating type, it is characterized by scales floating on the surface of the coating film.  

Application of aluminum metal

Aluminum powder

Aluminum powder is commonly known as aluminum silver powder or silver powder because of its silver-white metallic luster. Its chemical composition is actually "aluminum", not "silver".  Application: powder coating, printing ink, plastic master batch, printing, imitation gold paper, imitation gold card, gold film, textiles, but in water paint and paint with acid and alkali will be oxidized black.  Not recommended for applications requiring acid and alkali resistance and combination with rain.  

Ultrafine silver powder:  

1. Ultrafine floating silver surface area is large, when it is exposed to the air, can quickly generate a layer of blunt protective film on its surface, that is, oxidation black, need to do a good job of sealing measures, floating silver is not recommended for alkali resistance occasions, if required, can consider the use of silver pearl powder;  

2. There is a certain difference between the batches of silver powder, and it is greatly affected by the process and spraying. In addition to maintaining the stability of the production process as far as possible, the production should be tested first to avoid expanding the loss.  

3. Super fine silver cover bottom add 1-2%, in the case of adding high-gloss wax AW500B 0.6%-1.5% can cover the bottom and produce a strong metallic luster, silver powder add more white, add more blue, add insufficient amount of black dots black silk, or commonly known as fly excretion, the overall black.  

4. Floating silver flake, always floating in the outer layer of the coating, so the hardness and anti-oxidation blackening performance is slightly worse, to get better hardness need to add anti-printing hardening agent AS501, plus silver powder hardening agent POL16,POL09, etc., can not add high-gloss wax, gold and silver powder arrangement agent, polyethylene wax, the longer the mixing time, the better the effect.  

Floating silver

1. The smaller the silver particle size, the stronger the metal sensation and the stronger the covering power;  It is easy to produce the phenomenon of powder spitting and blocking the head of the gun when adding too much.  When the amount is not enough, it is easy to appear black spots, flowers or fine stripes.  R18 R01, special effects, such as the new silver dispersant is the efficient dispersant with SIO2 as carrier, is different from ordinary silver dispersant, no matter how many can be evenly dispersed without adding silver black spots, and thus can be modulated by adjusting the base and reduce the dosage of silver grey black, blue and silver powder of different hue effect, add the dinky, convection ping has a good role in promoting.  It can not be directly applied, directly applied will produce grains and white spots, etc. R01 has the best effect, direct dry mixing without particles.  

2. The flake structure of floating aluminum powder will be destroyed (deformed or crushed) in the process of grinding and extrusion, resulting in gray color, so dry mixing method is generally used.  

Non-floating silver:  

1. Non-floating silver evenly, parallel distribution in the entire film, so it is wrapped by resin, so it has good oxidation resistance and wear resistance, good weather resistance and acid and alkali resistance, no fingerprints, shiny surface, and color can be adjusted from the base powder, but the amount of silver floating, metal effect is not strong, white silver floating.  

2. PCR\DIS type aluminum powder is especially suitable for outdoor products, because of the inorganic coating layer, with good water resistance, weather resistance, chemical resistance;  Although coated with silicon and other materials, but in the natural exposure environment, aluminum powder under the conditions of light and humidity, chemical and physical changes such as oxidation will soon occur, so that the metal feeling is weakened, the film gray hair dark, gray spots and so on.  In order to solve this kind of problem and be abraded and other problems, it is recommended to use transparent powder cover light.  

3. The amount added to the bottom of the cover is tested with transparent base powder, and the amount of flash silver can reach about 10% at most;  Mixing and spraying process directly affect the spraying and covering effect, please pay attention to the uniformity of mixing and spraying, the coarser the particle size, the better the flashing effect.  

4. Due to the difference between the shape, density and charge of the silver powder particles and the powder, the separation phenomenon will affect the powder.  The powder and silver powder are bonded by bonding technology, and the powder and effect are greatly improved.  

5. Aluminum powder can withstand high temperature 600 degrees does not change color.