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Design News, January 2013

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Materials & Assembly 2 percent. Generally, replacing a metal component with a plastic one results in a 50 percent weight reduction, so the math is attractive to designers striving to reach Corporate Average Fuel Economy (CAFE) targets. In addition, better fuel economy means lower greenhouse gas emissions, which rose again globally by 2 percent in 2012 to a record high of 2.4 million pounds per second, according to the Associated Press. Running a close second on this list is the additional design freedom that today's advanced plastics afford. In other words, advances in polymer formulation technology are enabling more design freedom than ever before. Rather than welding, fastening, and bending — all of which require secondary operations and therefore more cost — most automotive plastic parts are produced to net shape in one automated operation. Geometry is yet another freedom. Plastic part design has become a sophisticated science, enabling parts to be designed to exact contours to save space under the hood. Additionally, bumpers and fascia can be more aerodynamic and stylish, and interior components can bend to the designer's will for greater differentiation. Finally, all of these factors combined allow multiple metal parts to be redesigned and replaced by plastics and consolidated into a single unit for reduced after-sale maintenance and production process improvement. Automotive HVAC units that switch from TPVs to TPEs not only perform better, but can be manufactured more efficiently. Polymer Options Abound polymers. Rather than looking for materials that can replace a metal part using the identical geometry, designers are now capitalizing on the additional freedom to form plastics into net shapes. The substitutions aren't limited to metal either. Designers are also replacing thermoplastic vulcanizates (TPVs) with easily recyclable and colorable thermoplastic elastomers for a host of benefits. Let's take a look at some reasons and examples. Today's automotive designers are looking for system optimization, greater design freedom, process improvement, and the ability to adapt to regulatory changes. Polymers are providing answers to these challenges, and the palette of choices keeps growing. Long-fiber and carbon-fiber composites are making their way into structural and semi-structural applications such as exterior panels, stiffeners, mechanical components, seat components, accessories, underhood components, brackets, and fixtures. Thermally and electrically conductive plastics now sport 10 to 100 times more conductivity than conventional plastics, a level equivalent to stainless steel. They're making their way into heat sinks, EMI/RFI shields, and a range of components for hybrid electric and electric vehicles, such as connectors, power electronics, and infotainment modules. Why Replace Traditional Materials? Proof in Production Today, there are four compelling factors driving metal replacement in automotive applications — weight reduction, design freedom, part geometry, and part consolidation. Reducing weight is at the top of the list. Studies by the EPA and other organizations show that every 5 percent of vehicle weight removed can improve fuel economy by One recent success story underscores the fact that not all materials replacement in vehicles involves metal to plastic conversion. Designers at DENSO, a leading technology, systems, and components supplier to major automakers worldwide, were seeking an alternative to a TPV seal used in the HVAC unit of a new car model, looking to enhance Source: PolyOne Replacing painted metal with metallic-filled polymers for engine covers offers greater design freedom while reducing VOC emissions and production cost. Design News | jaNuary 2013 | www.d esign n ews.com –52–

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