Powder coating application processes

Applications of supercritical fluids for coatings and impregnation of porous and fibrous substrates (e.g., polymer fibers, wood, composite materials) with various chemicals are discussed in a number of articles (50-52). Mandel and Wang (53) reported the use of a solution of polymers diluted with SCCO2 for powder-coating applications. They reported that Ferro Corporation has developed the so-called VAMP process used in the production of powder coatings, new polymers and polymer additives, and various biomaterials, with good potential for productions of pharmaceuticals. 

In powder coating applications, one or more coating components are delivered in powdered form during the process. The powder accretes to the particle surfaces in a controlled manner as liquid coating components are applied. 

The bisphenol A terminated hardeners are produced using liquid epoxy resins and excess bisphenol A in the resin advancement process. They are essentially epoxy resins terminated with bisphenol A. They are popular in epoxy powder coating applications for rebar and pipe, providing more flexible epoxy coatings than the novolacs. 

In particular, fumed alumina and fumed silica products provide tribo-charging, free-flow, fluidization and anti-blocking in powder coating applications. Typically, fumed alumina is used for tribo coating processes and either fumed silica or hexamethyldisilazane treated fumed alumina is selected for corona coating processes (3). 

C. This is true not only for their use in plastics, such as polypropylene and polystyrene, but also for applications such as metal deco prints, which are baked at temperatures above 200°C, or powder coatings, which are processed above 200°C. 

Moreover, y-P.V.19 is also found in a variety of other media, such as powder coatings and cast resins. This includes systems based on unsaturated polyester resins whose hardening is not affected by the pigment. The list of application media includes plastics which are processed at very high temperature (such as polycarbonates), in which the pigment is thermally stable up to 320°C. PUR foams and... 

Wire is coated by being passed through a plastic extruder, but most materials are coated with solutions, emulsions, or hot powders. The classic brushing process has been replaced by roll coating, spraying, and hot powder coating. The application of polymers from water dispersions to large objects, such as automobile frames, has been improved by electrode-positon of the polymer onto the metal surface. 

A more recently introduced concept, described by Staniforth et al. (17), involves the use of electrophotographic principles (essentially those used in the photocopying process) as a basis for the application of dry powder coatings to pharmaceutical tablets. This concept is illustrated in Figure 19. 

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