Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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Page 179 of 331

weight acrylates, which incorporate physical properties from materials such as ure-thanes, polyesters, silicones, etc. 3.Pigments, Fillers, and Additives—Control and impart color, adhesion, surface properties such as gloss, slip, marring, filling properties of porous substrates, and so on. UV coatings require a minimal dwell time (time between application and cure) on parts. Minimal dwell time minimizes the potential for incompatibilities to manifest between the coating and substrate. Truly zero-VOC, UV-curable coatings require no flash-off, and UV processing can immediately follow appli- cation of the coating. Once cured, the coating is extremely durable and stable im- mediately making parts ready for packing, shipping, and invoicing. UV-cured coat- ings tend to be chemically stable and resistant to chemical attack, but even strip- pable coatings can be produced through formula design. Formulators enjoy a growing arsenal of raw materials from which to design coatings. The formulation latitude for coating properties is impressively broad allowing for lock-and-key fit of the coating to its application. Where circum- stances dictate the need to custom engineer a coating product it is critical to establish a firm and unchanging checklist of desired coating properties and test methods by which both parties may verify such properties. Though formulators are capable of engineering coatings to meet the cus- tomer's needs, purchasing off-the-shelf coatings avoids the additional expense of custom formulation/development. Communication between the coating end user and coating supplier is critical during the development of a new coat- ing. Once a satisfactory coating product is tested, it should be implemented with any additional enhancements carried out as product development. The coat- ing supplier should be able to provide information from their experience with their product that will enable reputable UV-equipment vendors to recommend and quote suitable UV equipment or systems. UV EQUIPMENT Recommended Lamp Type and Configuration UV-coating formulators know exactly what wavelengths their formulation react to. These frequencies may, however, be considered proprietary resulting not in a frequency recommendation, but the recommendation of a lamp type, i.e., mer- cury bulb, gallium bulb, "H" bulb, or other. The availability of UV equipment to a formulator is vital to successfully devel- oping and testing a viable coating product. The availability of UV equipment is the only way a coating supplier can recommend, with any confidence, what lamp type, dosage, and lamp configuration are required to properly cure the coating. Do not hesitate to request from your coating supplier a diagram showing: 1.Recommended lamp positioning and distances relative to the part (angled, cantered, etc.) 2.Recommended lamp types, i.e., mercury, "D" bulb, iron lamp, gallium lamp, etc. If there are multiple lamp types recommended is there a rec- ommended lamp sequence? Lamp sequencing serves to differentially ef- fect surface cure versus through cure or sequence. What part of the 178

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