Electrostatic fluidized bed

Almost all PVC powder coatings are appHed by the fluidized-bed coating process. Although some electrostatic spray-grade formulations are available, they are very erratic in their appHcation characteristics. The resistivity of plasticized PVC powders is low compared to other powder coating materials and the appHed powder quickly loses its electrostatic charge. For the same reason, PVC powders show poor appHcation characteristics in an electrostatic fluidized bed and are seldom used in this process. 

Powder coating is a solventless coating system that is not dependent upon a sacrificial medium such as a solvent, but is based on the performance constituents of solid TP or TS plastics. It can be a homogeneous blend of the plastic with fillers and additives in the form of a dry, fine-particle-size compound similar to flour. The three basic methods are the fluidized bed, electrostatic spray, and electrostatic fluidized bed processes (9). 

Electrostatic fluidized-bed coating, 7 55-56 Electrostatic forces, 9 569, 570 11 800 and adsorbent selectivity, 1 584 in adsorption, 1 583 in solvent-solute interactions, 23 91-92 Electrostatic particle forces, in depth filtration theory, 11 339 Electrostatic precipitators (ESP), 11 714 13 180 23 552 26 699-706 advantages of, 26 700 applications of, 26 701-703, 705t design considerations related to,... 

In this entry, we review basic charging concepts, corona charging, internal charging, tribocharging, and electrostatic fluidized beds. Along with these methods, some of the properties of powders needed for their application are also discussed. 

Figure 6. Schematic of an electrostatic fluidized bed coating device.

Powder coatings are used in dipping operations via fluidized bed and electrostatic fluidized beds. It is the oldest form of powder application. It was first used in Germany in 1950 and was introduced to North America in 1955 (. ... 

The three basic methods are the fluidized bed, electrostatic spray, and electrostatic fluidized bed processes. The earliest powders were applied by... 

Electrostatic fluidized-bed coating Electrostatic spray coating... 

The advantage of the electrostatic fluidized bed is that small products, such as electrical components, can be coated imiformly and quickly. The disadvantages are that the product size is limited and inside comers have low film thicknesses owing to the well-known fara-... 

In an electrostatic fluidized bed small products such as electrical components can be coated uniformly and quickly. The advantages of flnidized bed powder are uniform and reproducible film thickness on all complex-shaped product surfaces. 

Electrostatic fluidized bed powder coating. An electrostatic fluidized bed (95 to 100 percent TE) is essentially a fluidized bed with a high-voltage dc grid in-... 

A fluidized bed method is used to apply relatively thick thermoplastic powder coatings. The article to be coated is heated above the Tg of the binder resin and then suspended in a fluidized bed of coating powder. Powder particles fuse onto the object imtil the powder layer becomes sufficiently thick to act as a thermal insulator and prevent additional fusing. Since the surface may contain incompletely fused particles, the operation is completed in a separate oven. Electrostatic fluidized beds are also used, with charged powder and grounded substrates, which may or may not be preheated. 

In the continuous powder coating of wire—most often for fencing, but occasionally for insulated cable components — it is advantageous to use electrostatic fluidized bed devices. In these, electrodes arc embedded in the fluidized compound and a ground plate is mounted above the bed. This produces a cloud of charged compound particles above the actual bed, permitting the wire (also grounded) to be mn... 

Pipe, Conduit, and Fence Post Coatings These compounds typically use 5-10 phr of total filler and pigment and 20-35 phr plasticizer. This suggests the use of resins of 0.60-0.75 IV. Both electrostatic spray and electrostatic fluidized bed coatings should be free of antistats (e.g., glyceryl monostearate). Barium/cadmium liquid stabUizers have been used routinely, with ESO at 4-5 phr. In most cases, barium/zinc liquids could be substituted. Erom 2-3 phr dispersion resin is used. 

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