Appliance Design - October 2007 - (Page 17)

COATINGS Alliance Surface Finishing can coat plastic parts in a number of colors including ASF Metallic, blue, silver, and red. important benefit to be gained by the ability to powder coat plastics, says Robert Langlois, President and CEO of Torontobased Alliance Surface Finishing (ASF). The company is one of the most successful finishers of plastics using powder coating. “On an appliance, for example, there are usually plastic surfaces and metal surfaces,” he says. “Most of the metal surfaces have been powder coated. To coat the plastic parts with a liquid would make it very difficult to duplicate the color on the metal part.” Powder coating is also environmentally friendly. The materials contain no hazardous air pollutants (HAPs) or volatile organic compounds (VOCs); both HAPs and VOCs have negative health and environmental effects. By contrast, liquid coatings typically contain solvents that emit both HAPs and VOCs in the finishing operation, emissions that must be captured. In addition, liquid overspray creates waste material that cannot be reused. Powder coating material, on the other hand, can be reclaimed and reused. The difference between the two methods is never more evident than when establishing a new finishing line. Liquid-based finishing lines can cost more than 10 times than would a powder-based system, says Richard Peters, secondary operations leader for GE Plastics of Pittsfield, Mass. “The infrastructure needed is dramatically differwww.applianceDESIGN.com ent between the two processes, so it really benefits powder over liquid,” he says. Overcoming challenges Still, despite these advantages, powder coating plastic has its own unique challenges. With conventional powder coating, the finely granulated dry, solid powder materials are drawn to and held electrostatically by an electrically conductive metal part. Furthermore, after application, the part goes through a curing oven. The heat of the oven will first melt the powder coatings into a liquid layer for even dispersion over the surface. Then it initiates a chemical crosslinking process that cures and hardens the liquid layer into a solid film. And, therein lies the two challenges. Conventional thermoplastics plastics are non-conductive and, by nature, will deform or warp when subject to high temperature. The first challenge is addressed by making the plastic conductive, using one of two methods. One is incorporating conductive fillers in the polymer material before the part is molded. The other is to pretreat the molded part prior to coating. The second challenge is addressed by utilizing polymers that exhibit high temperature resistance, even though they are more costly. In a liquid-coating finishing application, the coating materials cure at about 180 DegF, which is not hot enough for powder coating applications. Andrew Korzen, Noryl Americas Product Manager, GE Plastics, says that: “In most cases, “powders cure from 360 DegF to 380 DegF. There are not a lot of cost-effective plastics that can withstand those temperatures and still exhibit good physical properties.” While high temperature plastic materials such as nylon can solve the warping problems, the extra material costs must be considered. Langlois says that the upfront material costs are greater, but the cost is recouped in lower environmental-related costs as well as improved quality of the finish. At ASF facilities, the company’s Alliance Powder System is used to coat millions of plastic components per month. The parts are used in the appliance, automotive, and office furniture industries. Working with its strategic partners, Nordson a coating equipment supplier in Westlake, Ohio; PPG, the Pittsburgh-based powder coatings supplier; and BASF, a supplier of nylon materials, ASF was able to develop its process for powder coating plastics over a period of two years. The ASF process does not rely on using inherently conductive plastics. Instead, the company pretreats the surface of the substrate to accept the specially formulated powders. While not revealing details, Langlois says that applianceDESIGN October 2007 17 http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - October 2007

Contents Editorial Shipments/Forecasts News Watch Applying Powder Coatings to Plastic Parts is No Longer a Pipe Dream New Technology Platform Provides the Ability for a single IC to Control Two- Motors in a Single Appliance, Simplifying Motor Control Design Advanced Motor-Control Techniques have Become More Accessible to a Wider Array of Appliances, Helping to Improve Efficiency and Reduce Noise Adding USB Host Capability to Appliances Permits In-Field Programming and Acquisition of Test Data ZigBee Modules Make it Easier to Design Wireless Connectivity into Applications New Concepts such as Rapid Tooling and Rapid Injection Molding Provide Stepping Stones Between Prototyping and Full Scale Production A Number of Factors and New Developments Affect the Decision on Whether to Build Prototypes In-House or Outsource to a Service Bureau DesignMart Advertiser’s Index Association Report: CEA

Appliance Design - October 2007

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