Consulting-Specifying Engineer - August 2007 - (Page A7)

For More Information Vulcan Catalytic www.vulcancatalytic-ltd.com POWDER APPLICATION By its nature, MDF is an electrical nonconductor, unlike metal parts that are easily grounded to attract negatively charged powder particles. However, MDF has a natural water content of typically 5% to 7%. The new system uses this moisture content as a means to make the board conductive. By quickly raising the surface temperature of the MDF to 200°F during a total dwell time of 2 to 3 minutes in a catalytic preheat oven, the board becomes conductive and remains so for up to 5 minutes after leaving the oven. Board temperature at powder application is 120°F to 150°F — well below the temperature at which the powder would fuse to the MDF. This method of applying the powder to the MDF is contrary to the convection process, where the pre-heat lasts for some 15 minutes. That process dries the board and raises its temperature to 275°F, at which point the powder immediately fuses to the board. In the new process, by keeping the board conductive, the powder is easily attracted to the MDF to ensure a high degree of transfer efﬁciency. The degree of attraction is so high, that powder wraps around the board perimeter in a fashion similar to metal. Schematic shows path of MDF products for paint application, retreatment and ﬁnal curing. Preheat Oven Primer Cure Oven Prime Booth Top Coat Booth Load Unload Final Cure Oven CURING THE POWDER Once the powder is evenly deposited on the surface of the board and around the edges, it enters a catalytic cure oven. Curing is complete within 5 minutes. The catalytic heaters within the oven are arranged in such a pattern as to drive the temperature of the powder on the edges through to cure as quickly as possible. This action has a number of beneﬁts, a primary one being to seal off the edge from out-gassing. By concentrating the IR toward the edges, the face of the board also absorbs the required IR to ﬂow and cure these ﬂat areas. for a one-coat system. For many users, it is essential to achieve a homogeneous looking substrate for both the edges and the ﬂat surfaces. MDF has an end grain— and despite routing proﬁles and sanding of the edges, the differences in MDF density across the end grain are difﬁcult to hide. During the curing process, not only does out-gassing take place, but as the powder ﬂows, it will edge dive in the less dense region in the center of the board. This leaves a distinct area that telegraphs the coarser, less dense area through the ﬁnished coating. It was discovered that a second coat applied to this area blended in with the rest of the surfaces. The result was to implement two powder application booths and three ovens in a line process that would be economical and have high rates of production for quality parts. Part of the solution was to formulate a speciﬁc powder prime coat that would partially cure prior to the application of the ﬁnal top coat. tion industry. The advantages are that the building materials are pre-primed, protecting them from the elements while the owner decides on a ﬁnal color choice. The pre-primed plywood allows for easier top coat application without the high absorption rate of the typical raw wood ﬁnish, reducing labor cost and ❮GT❯ overall paint consumption. Beneﬁts of Powder Coating MDF Seamless coating that is highly water and heat resistant Can be applied to many different shapes and sized components Large color selection with solid, hammer tone, metallic or pearlescent textured ﬁnishes Front and back coated at the same time with same color and application Unlimited edge proﬁles High resistance to stains and effects of UV from direct sunlight Environmentally friendly coating, with no VOC emissions from the powder coating The process heating emits no NOx or carbon monoxide, which are harmful to the environment. POWDER COATING IN THE CONSTRUCTION INDUSTRY Factory priming is another area where catalytic technology is used to cure powder painted wood construction materials. In Australia, epoxy primed and infrared cured T-111 type plywood products are already being used by the construc- THE TWO-COAT PROCESS The process described above is the basic method of applying and curing powder A7 http://www.vulcancatalytic-ltd.com

Table of Contents Feed for the Digital Edition of Consulting-Specifying Engineer - August 2007

Contents M/E Roundtable Giants 100 Pullout Poster Giants Stand Tall: CSE Giants 100 Report Electrical Design for Tall Buildings HVAC and Fire Safety for Elevator Systems How to Beat the Codes GAS Technology Supplement Recovering Waste Heat from Boilers New Applications for Tankless Water Heating Systmes Techniques Improve for Powder Coating MDF New Tools Available for Heat Treating Steel Direct Drive Engines

Consulting-Specifying Engineer - August 2007

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