Electrostatic powder deposition

Continuous Processes Based on Electrostatic Powder Deposition... 

For electrostatic deposition or electrostatic powdering, the scheme is slightly different ... 

Dosed treatment of a powder layer deposited on the substrate with a Cl aerosol turned out to be highly convenient for the introduction of liquid inhibitors into polymer coatings. Polymer particles can be treated by a liquid Cl directly during jet deposition (Fig. 3.32) or during electrostatic powder application. In the latter case, the properties of the electrically deposited layer are altered. 

Thermoplastic coatings are often fabricated from powders. To coat a metallic object it is either dipped into a fluidized bed from which the powder deposits or one uses a spray gun to project the powder onto the metal surface. In electrostatic powder coating the polymer powder is projected in the presence of an electric field. This permits coating of recesses and hidden faces that are not in line of sight with the spray gun. After application of the powder, the object is annealed, and the powder transforms into a compact polymer coating. 

Miscellaneous Methods. Powdered metals such as aluminum, chromium, nickel, and copper, along with various aHoys, can be appHed to parts by electrostatic deposition. The metal strip containing the attached powdered metal must be further processed by cold rolling and sintering to compact and bond the metal powder. 

The use of nylon-11 for powder coatings or dry coatings (qv) has been developed in response to a growing concern for the environment (44) (see Coating PROCESSES, powder technology). Electrostatic deposition allows thin films to be appHed to metal substrates. Once the powder is appHed, it must be melted and coalesced into a continuous plastic film. Eorced draft or irradiant ovens are used for fusion, and because no polymerization or cross-linkage are required for curing, coated objects can be processed quickly and air-cooled (45). 

The potential for liquid aerosols or finely divided powders to be inhaled will be determined by their particle size. Deposition patterns for dusts will depend not only on the particle size of the dust but also the hygroscopicity, electrostatic properties and shape of the particles, and the respiratory dynamics of the individual. Thus, it is only possible to make very general statements about sites of... 

The coating zone is defined by the needs of an individual tablet, and the quantity of coating applied is controlled by the magnitude of the electrical field that is created and the electrostatic properties of the powder that is to be deposited. 

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