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Powder on MDF -- a market. (Finishing Newsfront).

According to according to
1. As stated or indicated by; on the authority of: according to historians.

2. In keeping with: according to instructions.

 ECNext, a web-based market intelligence resource firm, powder coating Powder coating is a type of dry coating, which is applied as a free-flowing, dry powder. The main difference between a conventional liquid paint and a powder coating is that the powder coating does not require a solvent to keep the binder and filler parts in a liquid suspension  material sales in the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area.  have been forecast to rise approximately 8 percent per year until 2005, when demand will reach roughly 500 million pounds, This increase in demand will continue to be driven by environmental benefits over non-compliant solvent based coatings, excellent adhesion, high resistance to both impact and scratching, and other favorable performance characteristics.

While powder coatings have become a $1 billion dollar industry in the United States, and a $3.5 billion dollar industry globally, this still represents only 5 percent of the total worldwide industrial coatings An industrial coating is a paint or coating defined by its protective, rather than its aesthetic properties, although it can provide both.
The most common use of industrial coatings is for corrosion control of steel or concrete.
 market. In an effort to provide continued growth for powder coating materials, both new and existing material suppliers are rapidly expanding the functional range of powders beyond traditional metal product finishing, into non-metallic substrates such as wood and plastics,

Of these potential substrates, engineered woods such as MDF (1) (Main Distribution Frame) A wiring rack that connects outside lines with internal lines. It is used to connect public or private lines coming into the building to internal networks.  are fast becoming an attractive market for powder coatings due to the uniform density of the substrate, smooth surface and low potential for out-gassing relative to natural woods. Specific MDF user markets that have been penetrated successfully to date are office and institutional furniture, store fixtures and displays and kitchen cabinets.

Many of the manufacturers in the aforementioned industries have been, and still are, heavy users of laminates or thermofoil. Replacement of this particular process (in addition to replacing liquid coatings on wood) represents the greatest potential for the use of powder coatings. At this point there are no powder coatings that can replace simulated woodgrain foil, however, much work has and continues to be done in the area of textured powders, speckled speck·led  
1. Dotted or covered with speckles, especially flecked with small spots of contrasting color.

2. Of a mixed character; motley.

Adj. 1.
 powders, and of course numerous colors with various levels of gloss.

UV vs. Thermoset A polymer-based liquid or powder that becomes solid when heated, placed under pressure, treated with a chemical or via radiation. The curing process creates a chemical bond that, unlike a thermoplastic, prevents the material from being remelted. See thermoplastic.  

There are two basic types of powder coatings: thermoset, which are cured with heat, and UV, which are cured by ultraviolet radiation. Both are proven technologies currently being used in the production and finishing of MDF, and the author does not endorse one type over the other.

The UV process for powder coating MDF has garnered more publicity to date, due to its shorter cycle times and reduced floor space requirements. The cycle times and equipment (gas convection ovens convection oven
An oven having a fan that shortens cooking time by circulating hot air uniformly around the food.
) utilized in the thermoset powder coating process mirror those of the powder on metal process. Because of the shorter cycle time and reduced floor space requirement for the cure oven for UV powder, the overall process requires less floor space than thermoset powders.

Typically in a UV operation, the boards to be coated are first hung on an automatic overhead conveyor Conveyor

A horizontal, inclined, declined, or vertical machine for moving or transporting bulk materials, packages, or objects in a path predetermined by the design of the device and having points of loading and discharge fixed or selective.
 and then pre-heated in a hybrid electric JR/gas convection oven. The boards are then powder coated at a line speed that is pre-determined by the amount of pre-heat and cure time required.

The boards enter a hybrid electric IR/gas convection/UV oven to cure. First, the coating melts or "flows out" for approximately 1.5 minutes. The board then continues to the UV curing stage for final curing and hardening hardening, in metallurgy, treatment of metals to increase their resistance to penetration. A metal is harder when it has small grains, which result when the metal is cooled rapidly.  of the powder. After the UV curing stage is complete, the parts cool naturally as they travel onto the unload To remove a program from memory or take a tape or disk out of its drive.  station.

With the thermoset process for powder coating MDF, boards must be preheated to about 50 degrees warmer than they do in the UV process. They are then powder coated and advance into a gas convection oven for the cure stage. Finally, the boards travel through a cooling tunnel and are unloaded.

See the table at left for specific times and temperatures needed for both processes.

Understanding the Substrate

Much has been learned to date about MDF and the process parameters required for optimum "paintability" relative to powder coatings. What has been gleaned thus far from both scientific study and "trial and error" indicates that absolute consistency must be achieved in conductivity conductivity /con·duc·tiv·i·ty/ (kon?duk-tiv´i-te) the capacity of a body to transmit a flow of electricity or heat; the conductance per unit area of the body.

, moisture content and board density in order to achieve a hard, durable, and uniform finish that is consistent in both gloss and color.

Adequate grounding is essential. This is achieved and maintained by hanging the board with clean metal hangers hangers

used for hanging x-ray films to dry. There is a clip type, with a clip at each corner, and a channel type in which the film sits in channels in the sides of the frame.
 on a conveyor that is tied to an earth ground. Once the board is grounded, preheating the board drives moisture content to the outer surface, achieving optimum conductivity. Studies have shown that optimum controlled moisture content prior to pre-heating is 6 percent to 9 percent.

In order for the board to be uniformly pre-heated, and therefore uniformly conductive conductive

having the quality of readily conducting electric current.

conductive flooring
flooring or floor covering made specially conductive to electrical current, usually by the inclusion of copper wiring that is earthed
, the board must possess uniform density of the fibers and resins that it is constructed from. One method of illustrating this is to pre-heat and powder coat a kitchen cabinet door that is designed with a decorative routing on the face of the door. The dimensional differences in the thickness will only serve to magnify mag·ni·fy
To increase the apparent size of, especially with a lens.
 the differences in density and moisture content between the routed (thin) area of the door and the rest (thicker section) of the door. The thinner area tends to lose its moisture content quicker than the thicker area. This can be overcome, however, through precision control of the powder gun's electrostatic charge Noun 1. electrostatic charge - the electric charge at rest on the surface of an insulated body (which establishes and adjacent electrostatic field)
electric charge, charge - the quantity of unbalanced electricity in a body (either positive or negative) and
 and powder flow rate.

Process Benefits

There are three critical market drivers behind the favorable economics of powder coating on MDF:

* Operational cost reductions: A well-known economic benefit of powder coating is the ability to reclaim and re-use powder to achieve overall system efficiencies over 97 percent. Waste disposal costs are further reduced because waste powder requires no special handling for disposal and can be landfilled.

* New design opportunities: High-end office furniture manufacturers are moving away from the "classic" shapes (squares and rectangles) for office furniture. While less complex shapes are amenable to an edgebanding process to hide the exposed edges of laminated laminated /lam·i·nat·ed/ (-nat?ed) having, composed of, or arranged in layers or laminae.


made up of laminae or thin layers.
 workpieces, new configurations require: curved edges, including interior circles and ellipses Ellipses is the plural form of either of two words in the English language:
  • Ellipse
  • Ellipsis
 for computer cord drop-through; seamless desktop coatings; and a broad variety of unconventional colors and effects. All are strengths of the powder coating process.

* Streamlined manufacturing: Reduced labor and material handling costs provide two key manufacturing benefits. Throughput is increased because powder coating is a continuous coating process, and because powder is a single-coat process that does not require a long time to dry. Powder coating also reduces the amount of sanding and handling of parts needed, and eliminates edgebanding costs.


Finally, to ensure that the powder coating on MDF process meets your specific product performance requirements, it is necessary to:

* Open lines of communication "Lines of Communication" is an episode from the fourth season of the science-fiction television series Babylon 5. Synopsis
Franklin and Marcus attempt to persuade the Mars resistance to assist Sheridan in opposing President Clark.
 with major powder material and powder equipment suppliers relative to finishing MDF;

* Test a variety of engineered woods from a variety of suppliers; and

* Develop a better understanding of the different processes, their capabilities, and their associated costs (or cost savings).

Proven technology and process development have helped to make the overall powder on MDF process a viable one for those finishers that are interested in achieving greater throughput, reduced process time, and an attractive, durable finish.
omparison of cycle times and heat levels needed for UV and thermoset
powder coatings on MDF

                             UV-CURED         THERMAL-CURED

Cycle Time              90 second pre-heat  15 minute pre-heat
                          90 second cure      5 minute cure

Board Temperature
 After preheat                 225F                275F
 At spray guns                 150F                200F
 At melt and flow oven         250F            not required
 At cure oven exit             200F                300F

Note: All times and temperatures and averages for a 3/4-in. board.
Process specifics vary depending on substrate and coating material.

John Binder binder: see combine.

An earlier Microsoft Office workbook file that let users combine related documents from different Office applications. The documents could be viewed, saved, opened, e-mailed and printed as a group.
 is marketing manager for Nordson Corp.'s Powder Systems Group. This article was excerpted from notes for Binder's presentation at the Powder Coating 2002 show in Indianapolis, IN.
COPYRIGHT 2003 Vance Publishing Corp.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2003, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Title Annotation:powder coatings on medium density fiberboard, US
Author:Binder, John
Publication:Wood & Wood Products
Geographic Code:1USA
Date:Apr 1, 2003
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