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Green Matter: Plastics drive automotive weight loss

At the annual international VDI “Plastics in Automotive Engineering” conference held in Mannheim, Germany this week, it was very clear that the role played by plastics in this industry has not only undergone a fundamental change over the past several years, but that it will continue to gain significance in the years to come. 

At the annual international VDI “Plastics in Automotive Engineering” conference held in Mannheim, Germany this week, it was very clear that the role played by plastics in this industry has not only undergone a fundamental change over the past several years, but that it will continue to gain significance in the years to come. 

The theme generating the most discussion was that of weight; or rather, how to get rid of it. A huge amount of carmakers’ time, money and effort goes into figuring out how to do so safely, and in a way that will not affect performance, function and enjoyment of the driving experience.

 You might say that in cars, less is more: less weight means a lower fuel consumption and better longitudinal dynamics, lighter wheels mean better acceleration due to the reduction of rotational mass, easier braking and cornering capabilities. Less weight means a smaller engine and lower CO2 emission levels—not unimportant, as EU legislation requires that by 2015, CO2 emissions from all new cars registered in the EU should not exceed 130g/km. The target will be gradually phased in: in 2012 65% of each manufacturer's newly registered cars must comply, rising to 75% in 2013, 80% in 2014 and 100% by 2015. Manufacturers whose fleet average exceeds the limit from 2012 will have to pay a penalty for each car registered. 

Low weight is, moreover, essential in electric vehicles, now and in the future, to maximize the range and speed achieved on a single battery charge.

Across the board, carmakers agree that plastics—in the interior, the exterior, under the hood, or used in lightweight structural components—were the key to building the cleaner, leaner cars of the future. Manufacturers of plastics materials could not agree more. 

BASF Sr. VP Engineering Plastics Europe, Dr. Willy Hoven-Nievelstein, argued that materials producers played a guiding role in the growing use of plastics in the auto industry.  “We offer solutions,” he said. “We need to, as otherwise, carmakers would never stop thinking in metal.”

BASF sees multi-material systems—composites—as the way forward. At the VDI conference, the company was showing off the seat pan developed for the new Opel Astra OPC, which for the first time was produced from a thermoplastic laminate with continuous (glass) fiber reinforcement (organo sheet), using two different grades of Ultramid. The seat pan is 45% lighter than its predecessor. End-of-life issues surrounding the use of glass-fiber reinforced materials are not seen as a problem by the company, who feels that the benefits of using multi-material systems far outweigh any recycling concerns, and strongly advocates the use of thermal recycling.

Lenzing, an Austrian-based manufacturer of manmade cellulosic fibers is also betting on composites. Offering consistent mechanical properties, Tencel FCP fibers are made from dissolved cellulose pulp, and are a mere 10 microns in diameter. Special milling and surface treatment allow a far more even dispersion of these than is normally achieved with natural-fiber reinforcements, and make processing on large machines possible. Tencel-reinforced PP offers properties—higher tensile strength, good impact-energy absorption—that look extremely promising for automotive applications. At Volkswagen, for example, the potential of natural fibers is recognized but because of the often very narrow processing window and less than stable quality, other fillers are more frequently chosen. This remains an area for opportunity for manufacturers of natural-fiber composite materials.

Even Audi Technology Networking’s Heinrich Timm, designer of the famed aluminum “space frame,” which, in its time, yielded a 40% weight reduction compared to the steel used until then, sees the potential offered by fiber-reinforced plastics for lightweight construction that is also economically feasible. Composites can provide integrated solutions, precisely tailored to the function of the component. He is especially enthusiastic about carbon-reinforced polymer materials, which he called a “valuable addition to the portfolio of lightweight materials.” Development of a technology enabling the economic manufacture of parts in CRP in large series, i.e. much shorter cycle times and a 90% reduction in processing costs compared to 2010 levels is, however, a prerequisite.

Besides composites, foams and polycarbonate were also named as major weight-savers. Calling it a “transparent breakthrough”, Gerard Liraut of Renault explained that polycarbonate offers a lower mass density than glass, less complexity and reduced costs due to part integration, better insulation properties in sun roofs, thereby helping to avoid the “sizzling head effect,” truly spectacular design freedom, scratch resistance and a better LCA than glass (21% reduction in CO2; 23% reduction in energy). According to Sabic, who has worked closely with Renault to advance this technology, the material can be employed, "wherever you need performance.”  

I came away from the VDI conference feeling that the heroic efforts of the automobile industry in this area, whether made under pressure of customer demand or legislation, are wholly to be applauded. One thought, however, continued to niggle at my mind: what about the drivers? In view of today’s escalating global epidemic of obesity, might the increasing number of excessively heavy humans in cars not work to cancel out the positive effects of the efforts of the car industry?

Unfortunately, that’s not a problem plastics can fix.

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