Powder Coated Tough - Spring 2008 - (Page 26) Should Early Powder Technologies Be Reconsidered for Today’s Market? BY GORDON COLE, GCA ASSOCIATES Since the early 1970s, a number of alternate powder coating technologies have been considered or developed but have never been commercialized. industrial finishes. While this powder offered good exterior durability, grinding was a major problem. Cellulose Acetate Butyrate (CAB), commercialized early for fluidized bed coating of transformer lids and select decorative products, was later replaced by the first epoxy powders marking the sucPhoto courtesy Nordson Corporation Considerable effort was also devoted to powder coating cans at liquid coating speeds. The Weld-Arm system, shown in the photo above, was designed to ES powder coat the interior of 3-piece tin-plated steel cans but required more powder material and equipment development to meet the very low coating weights and application cost requirements. Powder Coated Tough T he following represents a review of some of these early promoted powder coating technologies, which have been broken down into powder coating materials, application and recovery equipment, and manufacturing processes. A few of these might suggest merit for reconsideration in today’s market. Powder Coating Materials The first development of electrostatic spray (ES) powder coating materials was based on thermoplastic resins such as vinyl chloride and nylon 11, which are still used for fluidized bed thick film and ES protective-functional coating applications. These thermoplastic powders, though, generally required a primer, suffered from poor thermal stability, and could not be cryogenically ground to small enough uniform particle size for thin film coating applications. Eliminating the need for a primer, a major effort was made to develop a vinyl chloridemaleate copolymer powder coating to replace liquid alkyd melamine-type 26
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