Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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FUTURE PERSPECTIVES In addition to the on going demand from end users for products that continue to perform better, the enactment of the Clean Air Act Amendments in 1990 and oth- er related environmental legislation highlighted the need for more environmentally friendly systems. In order to comply with these regulations, VOC reduction has be- come the most important goal for all coating manufacturers. Urethane-based coatings, due to the flexibility and versatility of urethane chemistry and the de- velopment of new generations of isocyanate adducts and derivatives, allow coating formulators greater freedom in designing new high-solid systems for two-com- ponent or one-component coatings and VOC-free waterborne or powder coat- ings. Urethane-based coatings also allow the coating formulators to tailor-make coat- ing formulations for specific applications. Today, many of these emerging ure- thane coatings are either already in use or are under development for various ap- plications. For the automotive industry, the superior weathering and acid rain etching re- sistance of polyurethane-based topcoats and clearcoats has been widely recognized; therefore, despite their premium prices, polyurethane coatings continue to pen- etrate large segments of the European automotive topcoat market. In the Unit- ed States, about a quarter of new cars currently use polyurethane topcoat, primarily for high-end models. With the changing attitudes of today's car-buying cus- tomers, who increasingly demand better performance, such as excellent surface appearance and acid rain etching protection for their purchases, more American models will certainly use urethane topcoats in the near future. Recently, one-component heat-curable OEM coatings were developed for clear coat applications using blocked polyisocyanates. These coating formulations not only perform as well as two-component systems, but they also do not re- quire on-site mixing, have long pot life, and have the benefit of reducing the paint-line cleaning and preparation time. Furthermore, these one-component coat- ings also eliminate handling of curing agents containing free isocyanate groups in the paint lines.With these benefits, the one-component automotive OEM coatings systems based on blocked polyisocyanates are expected to grow rapid- ly at the expense of conventional acrylic melamine systems. Recently, newer blocked polyisocyanates are becoming available that not only offer lower un- blocking temperatures and faster heat cure time, but also offer additional per- formance benefits such as better yellowing resistance at overbake conditions, and no VOC increase. In addition to the emerging applications of urethane coatings for the auto- motive clear topcoats, anticorrosive electrodeposition primers for automobiles have relied on polyurethane systems for quite some time. With the need to reduce VOC, the development of waterborne polyurethane systems for this application has already made good inroads. In the past several years, heat-cured waterborne chip-resistant coatings have also been reported. Some of the newly developed wa- terborne polyurethane coatings are two-component polyurethanes that improve performance by allowing further crosslinking to occur during the droplet coa- lescence stage. The development of these systems in many respects is made pos- sible by the development of low-viscosity polyisocyanates. For automotive refinish applications, two-component polyurethane coatings have prevailed for many years as the best coatings in terms of performance and productivity. The trend toward using more plastic automotive OEM body pan- els, which are easy to coat with polyurethanes, will only further enhance the 95

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