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16 Powder and Bulk Engineering April 1988

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Glossary of term

~ ~~ ~~ The Powder Coating InstitUte Alexandria, Va.

Cloud chamber ttxhniqup, A method of moving a charged or un- charged object through a charged or uncharged cloud of powder Powder coating is often referred to as a “dry painting process.” in an enclosed chamber. Though the technology has been amnd since the mid-l95Os, in the last 5 years it has made a major impact on the indus- try. Today powder coatings are used on metal, , and products. Because oftheir superior quality, powder coated fihes [email protected] capacity of powder coatings from either Mer- are fast replacing as the fihof choice in major mar- ent sources or of different compositions to be combined and ap plied so to yield no visible or mechanically measmble differ- kets such as automobiles and appliances. as ences in the cured or application properties. As the powder coating industry has matured, a number of terms fii and defiions peculiar to the technology of powder coatings have been born. While some are unique to the powder coating industry, others are aberrations of terminology associated with the Gmna charge.The process of inducing a static electric charge on and coating industries. As a result, these borrowed terms powder particles by passing the powder through an electrostatic have, in many instances, acquired different meanings than might field generated by a high-voltage device. be seen elsewhere. This glossary is meant to clarify terms used by equipment and materials suppliers. In all instances, the simplest and least cumbersome defionhas been offered. Cure endpoint. The point either during or following the cure schedule at which the powdercoating film is determined to have developed specified properties.

Back ionization. A condition that can occur during electrostatic application of powder, in which an excessive buildup of charged Cure schedule. The timeltemperature relationship required to powder particles limits further powder to be deposited on the properly crosslink a thermosetting powder coating. substrate and can reverse the electrical charge of the surface of powder particles. Also called electrostatic rejection or repelling. Cut-through resistance. A powdercoating film‘s resistance to pen- etration, resulting fiom the combined application of sharp edges, Bulk &m@. Mass per unit of volume in powder form, including heat, and pressure. A formalized test used by applicators of insu- the air trapped between particles. lative powders to electrical motors. 0 0 73 Powder and Bulk Engineering, April 1988 17 ra2. 5 d 0 Deliwty. The process of moving the powder coating through the In@maa'heswn. A powder coating's ability to adhere to previ- cn application equipment to the end product. ously applied films. 0 -0 S Dty bknding. A process for powder coatings' manufacture where Lower explosive hit (LEL). The lower point for a range of con- E-. materials are blended without melting. centrations of organic particles suspended in air that can be ig- cns nited by a sufficient energy source. Also referred to as minimum 3 explosive concenlration (MEC). ca Edge cowrage A powder coating's ability to flow over, build, and -0 adhere to sharp corners, angles, and edges. 0 A d M& miring. predominant process for the manufacture of pow- Q der coatings involving the continuous compounding of the pig- % EktmsttatiC deposition.A technique of moving and charging pow- ments, fiers, catalysts, and resins at elevated temperatures. P, der so that it is deposited on a grounded substrate. 3 Q Meupoint. The temperature at which a finely divided powder will m Electrostatic fluidized bed technique. A deposition method of begin to melt and flow r_ 7i charging fluidized powder so that it is deposited on a grounded rn substrate. 3 MicrOn/mil. A common unit of measurement of coating thick- E. ness: 25 microns (micrometers) equals 1 mil (one thousandth of 3 an inch). (D

2.3 ra EkctnwttatiCspray technique, A deposition method of spraying and Minimum qhiwconcentmtiOn. See Lower qhsiwlimit. cha@ng powder so that it is deposited on a grounded substrate. See Corona charge and Tnbdmging. Noneledrostatic deposition. A technique of depositing powder onto a substrate, which may be heated above the melt point ofthe powder material. Some methods are flocking and fluidized bed. Famday cage effed. A condition that can exist on a substrate due to its geometric conf&ration, which may inhibit the electrostatic application of powder particles at that specific localized area. Rartick size The average diameter of an object having irregular boundaries, which can be determined through various test meth- ods. Filmfirmation. The forming of a continuous film by melting powder particles and coalescing them by the application of en- ergy. For thermosetting materials, a chemical reaction, through Phma deposition technique, A method of applying powder using the further application of energy, also takes place. This fused and compressed gas and melting the powder in a flame before the cured film has the udormity, color, toughness, and other prop powder impinges on the surface. erties associated with protective and decorative coatings. Plateflow. The distance a powder coating flows in the molten Flocking depositwn technique. A deposition method of applying state prior to gel. Also called inclined plateflow glass plateflow powder by spray to a substrate heated above the melt point of the and pillflow powder material. &umbil$v. The ability ofa dry powder to flow uniformly or to be Eluidized bed A fmed in which powder is suspended in continuously poured !?om a container at a steady state. a continuous stream of air. Preheated objects may be coated by dipping directly into a fluidized bed. The fluidized bed may also &w&r coatings. Coatings that are protective, decorative, or both, be used to facilitate transfer of powder materials to an alternate which are formed by applying a coating powder to a substrate and application site. which are fused into continuous films by the application of heat or radiant energy. Coating powders are finely divided particles of organic that generally contain pigments, fillers, and ad- hwn.The melting and flow of individual powder particles un- ditives, and which remain finely divided during storage under der the influence of heat to form a continuous film. suitable conditions.

Gel tim The interval required at a given temperature for a pow- Reclaim. A process to recycle nondeposited powder through the der to be transformed from a dry to a gel-like state. delivery system for reuse.

Grounding. An electrical grounding of the item to be coated. Rmvev. The process of removing nondeposited powder from the air prior to recirculatingthe powder through the delivery sys- tem. Irnpacrjkwn. The tendency of finely divided powders to com- bine with other particles in the application equipment during the application process. wing.See Back ionidit. 0 0 73 18 Powder and Bulk Engineering, April 1988 ra2. 5 d 0 Sintering. The tendency of some powders and powder-coating Bansportabil$v. A powder coating’s ability to be carried in an air cn materials to agglomerate during storage. stream and be passed through tubing and ducts designed to trans- 0 fer the powder. -0 S Spray/reclaim booth. A specially designed enclosure in which E-. coating powders are introduced, contained, and recovered dur- Tnbocha&ng. The process of creating a static electric charge on cn powder particles by ffiction against a nonconductive material. s ing the coating process. ca3 -0 Storage stabil$v. The ability of powder coatings to maintain uni- ViVgnpowder.Unsprayed powder as opposed to sprayed or re- 0 claimed powder. d form physical and chemical properties after being subjected to Q the manufacturer’s specified storage conditions. % volatilecontent. The quantity, expressed as a weight percent of the P, powder, which is lost under specified conditions of temperature 3 Surjike appmnce Generally refers to the smoothness and gloss Q ofpowdercoatingfiis and the presence or degree of surface de- and time. m r_ fects. 7i Ww.A characteristic of powder coatings in electrostatic appli- rn cation to seek out and adhere to parts ofthe substrate not in direct 3 Thermopbtb. A powder coating that will repeatedly melt when line of sight of the delivery system end point. PBE E. subjected to heat and solidify when cooled. Typical examples are 3 (D vinyl (PVC), nylon, and polyolefin. Glossary wus ahptedfiom a Technical Brief titled “PowderCoat- 2.3 ing Terms & Defniti0ns”prepared by The Powder WingInsti- ra Thermosetting. A powder coating designed to undergo an irre- tute. PCI represents with specifc interests in the manu- versible chemical change during the cure schedule. Typical ex- companies facturing, handling, application, recycling, and disposal of dry amples are acrylic, , and polyester. powderedpaint.For additional information onpowdercoatingtech- nology or PCI membership contact Gregory J. Bocchi, PCI, 1800 Tmfire#2zhcy. The ratio of the powder deposited compared Diagonal Rod, Suite 600, Alexandria, VA 22314. El: (703) 684- to the amount directed at the part to be coated. 4409.