CO2 Reduction: Part 3 of a 3-part series
Why lighter is better—with plastics

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Injection-molded truck oil pan of DuPont™ Zytel® polyamide resin by ElringKlinger for Mercedes-Benz is up to 6kgs (50%) lighter than the aluminum version
A side-impact beam for PSA Peugeot Citroën, using DuPont™ Vizilon® thermoplastic composite technology, is 40% lighter than the ultra-high-strength steel version, while absorbing more energy.


One of the most effective ways to reduce CO2 emissions is to reduce the burning of fossil fuels consumption. In motor vehicles, reducing vehicle weight with plastics is among the most effective and immediate path to achieving that goal—and the most effective way to achieve that is to replace metals with plastics.

As carbon dioxide (CO2) levels in the atmosphere rise, the bar in achieving reductions in global CO2 auto emissions is being set higher and higher. Mandatory CO2 emission reduction targets, set by European Union legislation, require all new cars to emit a maximum of 130 grams of CO2 per kilometer (g/km) by 2015 and 95g/km by 2020. These targets represent reductions of 18 and 40 percent, respectively, from the 2007 average of 158.7g/km. The progression of emissions legislation in the US, Japan and other high car density nations is similarly demanding. Every 110 kgs of weight saved on a car reduces CO2 emissions by 10g/km, and fuel consumption by nearly 5 percent.


Lighter in plastics, lower in CO2


That fact begs the question, “What is the most effective way to make a vehicle lighter?” The most practical answer is to replace metal with plastics. The lightweighting revolution in plastics is already well advanced, but there is unlimited potential for taking more weight out of cars via metals replacement, and in cutting CO2 still further to meet forthcoming limits.


DuPont is putting science to work on vehicle weight reduction to discover and develop lighter weight alternatives to metal that can withstand the intense heat, the aggressive chemicals and the high pressures in modern automotive engines. Substituting metal parts with parts made from DuPont high-performance polymers is already a proven strategy for vehicle lightweighting.


Designing for plastic


Designing for plastic—rather than using plastic in a component designed for metals—requires a different approach to ensure that all the lightweighting, strength and functional benefits are captured. This is especially true for parts exposed to high-speed impact. A successful example of this approach is a new truck oil pan of DuPont™ Zytel® polyamide resin, injection–molded by ElringKlinger for Mercedes-Benz that is up to 6kgs (50%) lighter than aluminum and resists stone chipping impacts. It also permits greater integration of parts and functions.


However, conventional metal replacement alone might not be enough to meet CO2 reduction targets. That’s why DuPont is working with automakers and Tier 1 component manufacturers on thermoplastic composites for structural or load-bearing components—such as seat structures, lift gates, cross-members, bumper beams and suspension systems—that combine the design versatility of plastics with outstanding capability to absorb energy.


Lighter by 40 percent


Working with PSA Peugeot Citroën to test a side impact beam using DuPont™ Vizilon®, a developmental thermoplastic composite technology, showed a 40 percent weight reduction compared to the ultra-high strength (UHS) steel version, while absorbing more energy than metal and short glass-fibre polymer beams. As a result, Vizilon® passed Peugeot’s crash test, making it well-suited for crash components and opening up a whole new field of plastics adoption in cars. Vizilon® also offers stiffness performance in temperatures from -40°C to +90°C, and outperforms polypropylene-based composites above 80°C.


“Can do” in plastics


Those long associated with the automotive industry will remember the doubts expressed when the first air intake manifold, cylinder head cover or oil pan in plastic was proposed. Many said “you can’t do that in plastics.” Today, the proof is that these and many more applications can be successfully achieved in lightweight plastics by combining the right material with the right design, and the right processing technology.


In the future we can expect to see several important new vehicle applications in thermoplastics. Exhaust systems are a challenging example. Although exhaust gases can reach as high as 960°C in gasoline engines—the right design, materials and processing technology can yield plastic exhaust line parts such as mufflers and tail pipes that function well and save weight.


Turbocharger housings, EGR valves and coolers are parts that are likely to be specified in thermoplastics in the near future. Thermoplastic composites of Vizilon® offer opportunities for replacing metal in structural parts and powertrain by providing all the necessary crash and energy absorbing capabilities with the added advantage of CO2-reducing lightness.