Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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coating service • In-house coating eliminates third-party mark-up • Low implementation cost, low initial capital investment with ROI of 1–5 years • UV eliminates need for large ovens freeing up plant floor space • UV processing decreases energy usage from conventional ovens • UV's speed of processing facilitates quality assurance—parts can be in- spected immediately. Risk of coating defects minimized with minimal drying time. Parts can be stacked or palletized immediately with no postcure. • Environmental savings are realized — hazardous waste disposal and shipping minimal. • 100% solids, UV-curable coatings are nonflammable; potentially de- creasing insurance costs • Dunnage remains cleaner as no uncured coating comes off on it • 100% solids, UV-curable coatings are recoverable and reusable without effecting performance or composition • 100% solids, UV-curable coatings cover more square footage efficiently and effectively THE MECHANISM OF THE UV REACTION On exposures to UV light a UV-curable composition un- dergoes the following: (1) re- action initiation, (2) reaction propagation, and (3) reaction termination. Reaction Initiation The photoinitiator component of a UV-curable formulation ab- sorbs UV light energy and gener- ates highly reactive free radicals. Each UV-curable formula- tion requires a certain thresh- old amount of UV energy to initiate the polymerization reaction. To illustrate the im- Fig. 1. A typical 2-D or flat-line curing system. This view, tak- portance of achieving this en from a conveyor belt level, shows the actual cure area il- luminated by the UV source. 175

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