Powder Coating Processes

While there are several ways to apply powders, two are most commonly used for CPI applications. They are called electrostatic spray application and hot flocking. 

Electrostatic Spray Method. Electrostatic spray can be used to apply thin or thick films. A thin film might be as low as 1 milli-inch (25 microns). Thick films might be applied as high as 0.1 inch (2.5 mm), though typically thick films are 40-60 milli-inches (1000-1500 microns). The equipment used is depicted in Fig. 8.12. A large number of manufacturers make this t5q)e of equipment. The process starts 

An alternate approach to fluidization is with a device called a vibratory box feeder. This device fluidizes the powder directly in the box that commonly contains it during shipping. It fluidizes the powder near the pick-up tube using compressed air while the box is vibrating. Good fluidization is required to get consistent coating application. 

The powder is transported through the supply tubing to the spray gun. If the powder is passed through the gun without further interaction, it would just be sprayed into the air as a cloud. There would be no physical reason for the powder to deposit on the substrate to be coated. To make this attraction happen, a charge must be applied to the powder. This is done by two methods called corona charging and tribocharging. 

A high voltage power supply is attached to the spray gun in a corona charging system. These power supplies provide an adjustable voltage (typically 

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To prevent rejects, retouching and to reduce cost of conservatively more than enough applied powder in powder coating processes a handy measurement system allowing to determine the... 

To protect steel piping and wire we can powder coat it with a layer of nylon 11. The powder coating process consists of immersing metal heated to above the melting point of nylon II (approximately 190 °C) in a fluidized bed of the polymer powder. When the polymer powder comes into contact with the heated metal, it melts and fuses to form a continuous coating. Powder coated products include hospital bed frames, shopping trolleys, and dishwasher racks. 

See also Powder coating processes Spray coating processes discrete surface-coating methods, 7 23-24... 

Figure 19 Schematic diagram of a continuous electrostatic powder coating process.

FIGURE 4.26 Reactor coated inside by ECTFE applied by powder coating process. (Courtesy of Fisher Co. and Moore.)... 

A final remark the real development of the powder coating process was not as straightforward as in our story. It was the result of many smaller projects, with many dead ends. Even so, it did not take 700 000 years ... 

K. Abid, P. Dufour, I. Bombard, P. Laurent 2007 Model predictive control of a powder coating process an application of the MPC CB software. IEEE Chinese Control Conference, Zhangjiajie, China, 2 630-634. 

Corbett, R. P., The Influence of Powder Resistivity and Particle Size on the Electrostatic Powder Coating Process," in Elektrostatische Aufladung. Dechema-Monographien Nr. 1370-1409, DECHEMA, Frankfourt, 1974, pp. 261-271. Cotroneo, J. A. and G. M. Colver, Electrically Augmented Pneumatic Transport of Copper Spheres at Low Particle and Duct Reynolds Numbers, J. Electrostatics, 5, 1978, pp. 205-223. 

Conventional pan-coating can be applied to powder coating processes. These processes are characterized by a combination of particle wetting and powder addition to a bed of core material to accrete powder to the core. This technique has realized significant interest for drug layering applications. 

Both thermosetting and thermoplastic powders can be applied by powder coating processes. (See Table P.9.) Elaborate reclaiming systems to collect and reuse oversprayed material in electrostatic spray powder systems boost flansfer efficiency. Since the enhancement of the air quality standards this method has grown markedly. 

Introduction of or removal of hot work operations >- Introduction of powder coating processes or those that may generate dust... 

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