Heraeus Vulcan is a worldwide leader in the development of pre-heating and curing systems for successful application of powder on MDF. We have been at the forefront of New Developments in MDF Coatings. Using unique catalytic oven designs with our high efficiency heaters, together with the latest in low bake powder technology, the process has become more predicable and consistent.
Powder coating has now evolved to offer many advantages over liquid paint application. Advances in technology continue to increase the efficiency and cost effectiveness of the process. As part of our ongoing research, Heraeus Vulcan has found significant opportunities in powder coating, but the most exciting of these existed in the wood industry, and in particular, M.D.F.
MDF (Medium Density Fiberboard) is well known for its versatility, particularly in the furniture and construction industries, with new applications being developed continually. Although the material itself is relatively inexpensive, much of the production cost of mass produced products is associated with the finishing of the product’s surface, either by conventional wet paint spraying, vacuum coating or membrane pressing. The method adopted is dependent on the type of board, production requirements, the finish and of course the cost.
While long established and proven systems, they do have intrinsic drawbacks. Our research indicates a significant potential for an effective finishing process giving the benefits of wet paint without the distinct disadvantages. Heraeus Vulcan has spent considerable time developing and refining the process of applying powder to MDF. resulting in an extremely reliable and efficient system for a two coating process that enhances the sealing and protective properties of the MDF. To understand the significance of powder for MDF, we must look at the established methods of finishing MDF.
Wet Paint applied using a spray gun there has an ongoing cost of over sprayed paint, maintenance of the paint booths and the disposal of the residual material. Of greater concern is that virtually all‑usable wet systems have the major problem of V.O.C. (Volatile Organic Compounds) emissions. Ever increasing environmental legislation has prompted the search for an 'environmentally friendly' alternative to wet paint.
The common alternative to wet painting is Membrane Pressing. This process involves the application of glue to the substrate, and the subsequent pressing of a vinyl onto the surface. While application of vinyls gives a very good finish, the major problems include the time taken to apply the glue and the timing between the application of the glue and the pressing of the vinyl. Also, differing conditions from day to day can effect the glues and their subsequent performance. A further drawback can be found in the pressing process. Sharp corners, acute angles, and thick boards can result in stretching, bubbles and the bucking up of the vinyl, producing rejects, a large proportion of which can not be re worked and have to be disposed of.
With the application of powder coating, liquid paint problems can easily be overcome. As powder is a dry film when applied solvents are not required, thus alleviating the major hurdles imposed by legislation on VOC emissions. Also, because powder is a dry film and subsequently heated to melt and cure the film, the over-sprayed powder can be potentially collected and re‑used, thus minimizing waste. The design and shape of the MDF. board can utilize unusual shapes, which would be impossible for membrane pressing. Finally, powder coating is easily automated, not only the application but also the recovery and introduction of fresh virgin powders into the system.
A simple online pre‑conditioning of the board, again using I.R., has overcome the problem of coating consistency from one batch of MDF. to another or due to the shaping of the surface. Preconditioning is in fact an essential part of the process whether using I.R. and U.V., or simply in the final cure. This draws moisture and resins to the surface of the MDF. facilitating uniform attraction of the charged powder particles to the substrate. Preconditioning may be achieved using I.R. or hot air circulating ovens or a combination of the two. The ultra low bake system is a proven and highly utilized system which has now been put to use in an application which previously would have been inconceivable! Capital investment is lower, therefore pay back times for the investment are shorter.
The requirements for the final cure of ultra low bake powders will vary depending upon a number of factors, the MDF. board and of course the conveyor speed, whether IR or hot air re-circulating ovens are to be used, or a combination of the two. These factors may be determined during trials at Eurotec headquarters.
A great deal of excitement and interest is now being generated by the fact that this is now a proven production process using standard powder coating application equipment and virtually standard format coating powders. This means of course that manufacturers can now mass‑produce a variety of products finished with all the advantages of powder coating.
Heraeus Vulcan will, of course, be at the forefront of new technology development in this area.
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