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4 POWDER COATING, December 2018 B Back ionization. A condition that can occur during electrostatic application of powder, in which an excessive buildup of charged powder particles limits further powder from being deposited on the sub- strate and can reverse the electrical charge of the surface layer of powder particles. Also called electrostatic rejec- tion or repelling. Bulk density. Mass per unit of volume in powder form, including the air trapped between particles. C Cloud chamber technique. A method of moving a charged or uncharged object through a charged or uncharged cloud of powder in an enclosed chamber. Compatibility. The capacity of powder coatings from different sources or of dif- ferent compositions to be combined and applied so as to yield no visible or mechanically measurable differences in the cured film or application properties. Coronacharging. The process of induc- ing a static electric charge on powder particles by passing the powder through an electrostatic field generated by a high-voltage device. Cure end point. The point either during or following the cure schedule at which the powder-coating film is determined to have developed specified properties. Cure schedule. The time/temperature relation required to properly cross link a thermosetting powder coating. Cut-through resistance. A powder coat- ing film's resistance to penetration from the combined application of sharp edges, heat, and pressure. A formalized test used by applicators of insulative powder to electrical motors. D Delivery. The process of moving the powder coating through the application equipment to the end product. Dry blending. A process of powder coat- ings' manufacture in which ma terials are blended without melting. E Edge coverage. A powder coating's capability to flow over, build, and ad here to sharp corners, angles, and edges. Electrostatic deposition. A technique of moving and charging powder so that it is deposited on a grounded substrate. Electrostatic fluidized bed tech - nique. A deposition method of charg- ing fluidized powder so that it is de - posited onto a grounded substrate. Electrostatic rejection. See Back ionization. Electrostatic spray technique. A depo- sition method of spraying and charging powder so that it is deposited onto a grounded substrate. See Corona - charging and Tribocharging. F Faraday cage effect. A condition that can exist on a substrate be cause of its geo- metric configuration, which can inhibit the electrostatic application of powder particles at that specific localized area. Film formation. The forming of a con- tinuous film by melting powder particles and coalescing them by the application of energy. For thermosetting materials, a chemical reaction, through the further ap plication of energy, also takes place. The fused and cured film has the unifor- mity, color, toughness, and other proper- ties associated with protective and deco- rative coatings. Flocking deposition technique. A deposition method of applying powder by spray to a substrate heated above the melt point of the powder material. Fluidized bed. A fixed container in which powder is suspended in a continu- ous stream of air. Preheated objects can be coated by dipping directly into a flu- idized bed. The fluidized bed can also be used to facilitate transfer of powder mate- rials to an alternate application site. Fusion. The melting and flow of individ- ual powder particles under the influence of heat to form a continuous film. G Gel time. Interval required at a given temperature for a powder to be trans- formed from a dry solid to a gel-like state. Glass plate flow. See Plate flow. Grounding. An electrical grounding of the item to be coated. I Impact fusion. The tendency of finely divided powders to combine with other particles in the application equipment during the application process. Glossary of Powder Coating Terms POWDER COATING GLOSSARY