The security risks of powder coating is lower than ordinary paint, compared with the air mixture, the ignition energy initiator of the air mixture is 50-100 times than powder.
However, all flammable powder or dust will form an explosive mixture with air, it is a potential source of danger. Take appropriate measures in advance can securely transport, store and process. For safety reasons, the concentration of previously mentioned various powders should be no more than10g/m3.
Compared with non-pigmented resin powder, when the coating added 5-6% aluminum powder, the so-called Dust Comstant (explosive metric) and the maximum explosion pressure will be increased 10%. Aluminum powder content continues to be increased, the explosive power will increase. When the aluminum content greater than 25%, it will reach the explosive power of pure metal powder. But, whatever the dispersion method, pure resin powder is lower than the minimum trigger combustion energy. If aluminum powder pigment content more than 10% and use small particle size and without coating treated aluminum powder, the lowest combustion initiation energy may be reduced.
Containing aluminum powder coatings, which the same as the ordinary pigmented powder coatings, as long as do not exceed the prescribed limit, there is no fire and explosion hazard. In order to ensure the safety of the spraying process, there must be avoided aluminum powder separated, accumulated and concentrated in the factory. These basic requirements also apply in solvent-based coatings which containing copper alloy powder. However, the explosion risk directly caused by copper-zinc alloy powder is smaller than aluminum powder.
Powder equipment, the most important is that all the parts and the operators must have a good ground connection. Indoor dust concentration should be controlled at the lowest level, use exhaust system according to the requirements. In any case, avoid open flames, sparks and hot surfaces.
Aluminum powder production and processing methods are mainly have three kinds: Melt extrusion method, this method is heating extrude the metallic paint and the rest ingredients of the powder coating (resins) from the screw extruder. Although metallic paint and powder coating can be fully mixed, but the metal pigment in the high melt viscosity is less orientation. In addition, in the following crushing process, pigment sheet structure will inevitably be undermined. Use this method to produce metal powders, the metal effect with grey. Therefore, this method can only be used to malleolar stria powder production.
Dry mix method, which is add the metallic pigment powder to crushed coatings powder then mixing with mechanical mixers. Dry mixing method has the advantage of metallic pigments and powder coatings mixing is not very intense, thus preventing the deformation of sheet metal pigments, metal effect will not be affected. In addition, loose pigment/resin mixture is also very beneficial to the metallic pigment orientation, improved flash effect. The disadvantage of this method is that while using automatic powder spray equipment treating and recycling powders, due to the metal pigment and the resin powder particle shape, density and electric charge are very different resulting in separation phenomenon.
Bonding-Process, which is dry-mixing metal paint and powder coating, and heating at the same time, make the temperatures just above the softening point resins, can be fixed metallic pigments in bonding with adhesive resin powder surface at this time, thereby preventing the segregation of metallic pigments and resin powder at the time of construction and after construction recycling. This is the popular binding methods currently.
Article Source:http://www.mhcmp.com
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