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Driving Efficiency

High-performance plastics are finding increased relevance as a way to make cars less costly to manufacture−and fill up at the gas pump

by Alexander H. Tullo
June 12, 2006 | A version of this story appeared in Volume 84, Issue 24

Space Age
Credit: Rinspeed Photo
The zaZen, a concept car from Switzerland's Rinspeed, sports a polycarbonate roof, a holographic break light, and transparent polyurethane/polycarbonate seats.
Credit: Rinspeed Photo
The zaZen, a concept car from Switzerland's Rinspeed, sports a polycarbonate roof, a holographic break light, and transparent polyurethane/polycarbonate seats.


Driving Efficiency

A generation that grew up on $1.00-per-gal gasoline is now happy to pull into a gas station offering anything less than $3.00. People who never heard of a car sold for any attributes other than performance and convenience are now being bombarded with advertisements promising fuel economy. Times do change. And while consumers may be suffering and Detroit may not be able to unload as many sport-utility vehicles (SUVs) as it used to, one industry stands to benefit from the newfound religion on gasoline consumption: plastics.

This is because plastics help reduce vehicle weight. And every 10% reduction in vehicle weight, says an old auto industry rule of thumb, yields about a 5% increase in fuel economy.

But weight reduction isn't the only quality that automakers look for in plastics. Plastics reduce costs when they replace traditional materials like steel, a benefit that automakers can't ignore, especially now when companies like Ford Motor Co. and General Motors are struggling financially. Plastics also allow greater flexibility for car makers to differentiate themselves through design.

Over the past three decades, plastics have made steady progress in automotive applications. According to an annual survey of automotive materials compiled by the trade publication American Metal Market, the content of plastics in automobiles has increased from 168 lb, or 4.6% of the average vehicle's weight, in 1977, to 249 lb, or 7.6% of vehicle weight, in 2000.

American Metal Market no longer conducts its survey. But according to the American Chemistry Council, the combined plastics and composites content of the average North American light vehicle has increased from 286 lb, or 7.3% of vehicle weight, in 2000, to 335 lb, 8.3% of vehicle weight, in 2004.

Much of the success of automotive plastics thus far has been due to their ability to reduce costs. This isn't necessarily because a pound of plastic costs less than the 2−3 lb of steel it replaces. Deborah F. Mielewski, a plastics research technical leader at Ford, explains that it is because a single injection-molded plastic part can do the job of many metal pieces welded together. "Plastics can be molded into far more complex shapes than you can stamp steel," she says. "And many times you can mold in attachments and brackets and consolidate pieces with plastics, reducing the number of parts in the assembly process."

Maria Ciliberti, automotive regional sales manager for Ticona, the engineering plastics unit of Celanese, says the utility of plastics in an automotive application largely depends on the complexity of the part. "If the part is just a piece of sheet metal, then it is really hard to compete with," she explains. "If you have multiple pieces of metal welded together, or if you have a lot of bending and shaping and other secondary steps to be done to the metal part, then this is really where plastic's forte lies."

The desired volumes of the part come into play as well, observers say. For example, when a production run of a vehicle is fewer than 50,000 to 100,000 units annually, an injection-molded plastic part is cheaper than one made from stamped steel. The expensive tooling required for steel is only justified if it can be used to crank out a larger number of parts.

Injection-molded plastics can also provide aesthetics that are difficult to obtain with traditional materials like steel and glass. A visible example is how automotive head lamps have changed over the past 20 years. Glass headlamp lenses began to be replaced with polycarbonate ones in the 1980s, according to Clemens Kaiser, chief executive officer of Exatec, a joint venture between Bayer and GE Plastics, which is developing technology to make automotive glazing out of polycarbonate.

Initially, the polycarbonate lenses were made similar to the square and circular glass they replaced. But gradually, automakers took advantage of the new material's versatility and made more complex and attractive shapes. "If you look at today's headlamp lenses and covers, you can see the advantages that polycarbonate provides," Kaiser says. "They are all shaped differently. They become part of the face of the vehicle and part of the design, and they are extremely important to the identity and brand of the vehicle."

Design flexibility can have practical benefits as well. Mark Minnichelli, director of commercial technology for engineering plastics at BASF, says the nylon oil pans that BASF is developing can be molded into "unorthodox geometries," unlike rectangular metal pans. This flexibility eliminates a problem for auto designers looking for places to cram components underneath the hood. "Most people, when they think of design flexibility, they think of pretty design," Minnichelli says. "This type of design flexibility is purely functional."

Weight reduction was previously a favorable side effect of using plastics to reduce costs or give a car a sharp look. But because of concerns over high gas prices, weight is now becoming a more conscious consideration for car designers when they decide to go with plastics.

Americans are becoming aware of fuel efficiency in a way they haven't in years. SUVs are falling out of favor after ruling Detroit's automakers for nearly a decade. The automotive market consulting firm Autodata, for example, says U.S. sales of such light trucks slipped by 1.9% in the first four months of this year compared with 2005, while passenger car sales increased by 1.6%. Additionally, the Department of Transportation is reining in SUVs through new corporate average fuel economy (CAFE) standards. By 2011, pickup trucks, minivans, and SUVs will be required to average 24 mpg versus the 21.6 mpg required today.

Plastics makers have to adjust to the decreased demand for SUVs. Chad Waldschmidt, North American director for engineering plastics at Rhodia, has noticed this trend trickle down to engineering plastics suppliers. He has seen his sales to the tier-one suppliers-the parts firms in the supply chain closest to the car company's assembly line-move away from products destined for larger SUVs. "Overall, we are seeing a trend away from some of these vehicles and into smaller vehicles," he says.

But plastics makers also see opportunity in the new attention to fuel efficiency. George Hamilton, president of Dow Automotive, says the car industry is becoming more interested in the potential of plastics to trim vehicle weight. "Until gas got to be about $2.50 per gal, there was more interest in productivity and cost reductions," he says. "But since gas has gone beyond the $2.50-per-gal mark, we find more and more people interested in having discussions about how to lightweight the vehicle and make it more fuel efficient."

Ford's Mielewski confirms that car companies are increasingly looking to plastics. "We are at the point in time when automotive companies will be increasingly pressured to find lightweight technologies that will support improved fuel economy," she says. "Plastic materials for various applications are one way to achieve these improvements."

Howard Cox, lab group manager for composites processes and materials at General Motors, agrees that plastics play a part in car companies' fuel efficiency strategy. "But," he adds, "there is an opportunity for other materials as well, such as advanced high-strength steel, aluminum, magnesium, and composites."

Big Red
Credit: General Motors Photo
The Hummer H3 has front and rear fenders made from Noryl GTX resin.
Credit: General Motors Photo
The Hummer H3 has front and rear fenders made from Noryl GTX resin.

For example, Cox points out that carbon-fiber-based composites can lower the weight of car components such as structural pillars by as much as 60%. GM has traditionally used glass-fiber composites in the body panels of the Chevrolet Corvette. Now the company is rolling out composites for other vehicles as well, such as the Cadillac XLR, which has a body made from composites silmilar to those of the Corvette.

Although weight reduction is a growing consideration, Christopher S. Murphy, automotive director for DuPont Automotive Performance Materials, argues that it is still second to cost reduction for original equipment manufacturers (OEMs). "Weight saving in and of itself still does not drive new programs," he says. "At a given time, the OEM has more potential cost-savings projects than there are resources to work on those projects. If a project also offers weight reduction, chances of that project getting attention are higher than they were even a year or two ago, when gas prices were lower."

James R. Best, president of the Toledo, Ohio, automotive plastics consultancy Market Search Inc., also doubts the primacy of weight. "There's never been a plastics application where weight has made a difference in whether plastics have been used," he says. "Cost is the dominant issue. Cost is what calls the shots. If it was true before, it is true in spades now. Weight reduction is important, but automakers aren't going to pay for it."

GM's Cox disagrees and says, within reason, his company will generally pay more to reduce weight. He notes that GM uses more aluminum, a higher cost material to use than steel, than any other vehicle producer in North America.

Ford's Mielewski notes the influence of plastics on fuel economy is collective. "Since many of the parts being considered for plastics substitution are fairly small, there aren't huge opportunities to save, say, tens of pounds at a time," she says. "When we look at a set of fenders, there is a weight saving opportunity of about 8 lb. But, if you chip away at it, saving a few pounds at a time, it can add up and, combined with other technologies, can significantly improve fuel economy."

New automotive uses of plastics in car seating exemplify how such savings can add up. BASF helped develop the first thermoplastic seat pan in commercial vehicle production. Minnichelli says the nylon pan is meant to simplify the seat assembly and reduce weight by about 6.4 lb per seat. BASF also is working with composite-materials-maker Hexcel on an upright car seat frame made from nylon and glass fiber.

Similarly, Dow is making front seat backs, traditionally metal, out of a blow-molded polycarbonate acrylonitrile-butadiene-styrene blend for a car that is in commercial production. The new backs reduce seat weight by 10 lb apiece.

Plastics can improve fuel efficiency in more ways than mere weight reduction. For example, DuPont developed a nylon water jacket spacer for the 2006 Toyota Crown and the Lexus GS-300. It didn't reduce weight, but it did increase the heat-transfer efficiency between the engine coolant system and the cylinders. DuPont says the component lowers fuel consumption by 1%, or the equivalent of 55 lb of vehicle weight. "That's an example of where they added components that added weight, but it wasn't a lot of weight compared to the fuel that was saved with the addition of the component," Murphy says.

Another indirect way plastics can improve fuel efficiency is by enabling alternative fuel technologies. Dow's Hamilton points out that the batteries used in hybrid fuel vehicles tend to be bulky. Plastics can be employed to free up the space needed for such a part or to improve the vehicles' balance. "When you add 300 lb of battery to the vehicle, you have to deal with package space, where you can put the different components in the vehicle because of the big battery taking up space," he says. "You also have to start dealing with issues of performance and handling, so lightweighting is certainly attractive in that regard."

Plastics makers say they are benefiting from the penetration of European tier-one suppliers into the North American market because they bring expertise in replacing metal parts with plastic. "In Europe, the price of gasoline is significantly higher," Ticona's Ciliberti explains. "These European tier-ones have had to deal with weight issues and fuel efficiency for decades." She says these companies have been pivotal in helping applications such as front-end assemblies, door modules, and seating structures move from metal to plastics.

Robert Cunningham, semicrystalline division engineering team leader at Lanxess, believes the European tier-one suppliers are having a profound influence on the North American automobile market and its incorporation of more plastics. "What we used to see is a lag time of five years between when something was introduced in Europe and when it came to North America," he says. "That gap is getting smaller and smaller."


DuPont's Murphy says this influence is a positive one for plastics suppliers. "There are definitely some technologies related to plastics for automotive uses that have advanced significantly in Europe and that are now just getting legs in North America," he says.

Back In Black
Credit: DuPont photo
DuPont helped develop the first nylon valve covers used in North American vehicles.
Credit: DuPont photo
DuPont helped develop the first nylon valve covers used in North American vehicles.

For example, engine valve covers have traditionally been made of metal or thermoset resins. For several years now, however, some European cars have been fitted with ones made of nylon. The nylon valve cover that DuPont and German valve cover maker G. Bruss developed for the 2004 Chrysler Town & Country and the Dodge Caravan was the first such thermoplastic application in North American vehicles.

Mark Kingsley, general manager for global automotive marketing at GE Plastics, says another important driver for the conversion of traditional materials to plastics is the automaker's desire to stand out. New materials are needed to push the envelope, he says. "Once everyone has the same technology, you have to go back to the materials to find differentiation. Design creates an emotional response, and you do that by achieving a material change."

According to Kingsley, adoption of thermoplastic body panels is one way for automakers to stand out. Moreover, he notes that car companies are coming out with more short-production-run models, which give economic advantages to using plastics in body panels. "We have more plastics in the body panels than we have ever had," he says.

Paul Platte, director for automotive industry innovation at Bayer MaterialScience, says interest in plastic body panels is also driven by weight reduction. "Plastic body panels haven't really been touched yet in the North American market," he says. "They have in Europe because of weight reduction. We are anticipating that interest in thermoplastics for body panels will probably be renewed in light of gas prices and the renewed interest in weight savings."

GE's Noryl GTX resin, an alloy of polyphenylene oxide and nylon, has been used on the fenders of the Volkswagen New Beetle for years to give them that distinctive egg-shaped design. More recently, Noryl GTX is being used to make the Hummer H3's front and rear fenders, which, GE says, are the first thermoplastic truck fenders in North America. Kingsley says the application combines weight reduction, the economic advantages of using plastics in low-production-volume vehicles, and sleek design. "That is an extremely difficult part to make if you try to stamp it out of metal," he says.

But plastics have faced challenges in body panels, says Dow's Hamilton, whose company has previously taken a shot at them. "The industry has not been successful in getting a product that can give you the necessary finish and the coefficient of linear thermal expansion," he says.

Kingsley acknowledges that plastics expand a couple orders of magnitude more than metal in the face of high temperatures. This phenomenon, he says, is a barrier to using plastics in door panels, which have to fit precisely with the metal frame and other components. In fenders, the problem is circumvented because the part is fixed at both ends and expands along the curvature. GE is also developing plastics reinforced with nanoparticles that form a cobweblike lattice structure inside the plastic and reduce the expansion.

As it is in body panels, styling is also promising to be a driver for the replacement of glass with plastic, Exatec's Kaiser says. The joint venture is developing technology that plasma-coats polycarbonate with a glasslike film to make the plastic scratch-resistant, thereby solving a problem that has kept thermoplastics out of such applications.

Kaiser says the technology will allow for complex window shapes to be made for the first time. Also, like plastics that have replaced metal, features such as locator pins and holes can be molded directly into the plastic glazing itself. Kaiser says the technology can be applied to every glass surface in the car but the front windshield, owing to regulations.

Bayer's Platte says polycarbonate is being used in 14 automotive glazing applications, 11 of which employ Bayer polycarbonate. The applications are generally side windows and panoramic roofs, he says, and thus haven't used the scratch resistance of the Exatec technology. Kaiser says Exatec is now working with OEMs on material testing and prototype development.

According to Platte, the current applications are being driven by weight reduction and impact resistance. They tend to be flat planes like the glass they replaced. But, as in the case of polycarbonate headlights, automakers are expected to take advantage of the design freedom over time. "We are only in the first generation," he says.

The design advantages of plastics in glazing and other parts is showcased in the zaZen, a concept car made by the Swiss company Rinspeed and incorporating a number of Bayer materials. The vehicle is covered by a polycarbonate dome, has a large holographic brake light, and even has seats made from polycarbonate and a transparent polyurethane gel. "All of these technologies are an exaggeration of what production models would, in fact, adopt. They are meant to demonstrate what could be," Platte says.

Plastic's success in the automotive industry comes largely at the expense of steel. According to the American Chemistry Council, regular steel comprised 44.5% of the weight of the average light vehicle in North America in 1994, compared with 41% in 2004.

But the steel companies haven't been idle. They have been developing lightweight, high-strength, and dual-phase materials that have made steel a tougher competitor. From 1994 to 2004, the high- and medium-strength-steel content of light vehicles has increased from 8.7% to 11.9%. "The steel industry has tried to come back as hard as it can and fight for its market with the other raw materials," Ticona's Ciliberti says.

DuPont's Murphy says the benefit of replacing a steel part with a plastic one is usually significant enough that a car maker won't go back. "Typically if something has a business case to make it go from metal to plastic, some tweaks in the metal materials here and there aren't going to change the cost benefit," he says.

But Tony O'Driscoll, sales and marketing manager for the Americas at Ticona, has seen such flip-flops. For example, fuel rails for diesel engines had moved from steel to polyphenylene sulfide years ago. However, technology advances in diesel engines led to the need for the rails to withstand higher temperatures and pressures, giving rise to the use of steel once again in the application.

And metal and plastics can succeed by working together. Lanxess' engineering polymers business has enjoyed a big lift from its metal-hybrid technology, in which metal parts are inserted into a mold, resin is injected, and a hybrid material is formed.

One of the technology's first automotive applications, in the late 1990s, was for the Ford Focus' front-end assembly, where it helped integrate 11 different features-such as brackets to hold head lamps in place and mounting points for the radiator-into one part. Now there are 45 different models on the road with the hybrid front end, including the Nissan Ultima, Chrysler 300, Hyundai Sonata, Dodge Charger, and Ford Five Hundred.

"Hybrid technology definitely put us on the map for structures," Lanxess' Cunningham says. "We penetrated a market that plastics had struggled with for quite some time."

Dow is also working on a hybrid technology. Its technology uses an adhesive to bond metal to glass-fiber-reinforced polypropylene. The technology's use in the front-end assembly of the Volkswagen Polo last year reduced weight versus a previous version by 25% and lowered costs by 10%, Dow says.

Plastics frequently offer advantages over metal and glass, and those advantages are increasing in this era of $3.00-per-gal gasoline. Still, plastics makers acknowledge that they won't take over every single vehicle component and that plastics and traditional materials will always work together. "I don't think there should be the goal of the all-plastic car," GE's Kingsley says. "All materials have to find their natural place. I welcome that."


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