Tough as Soybeans
The long search for plants with optimal material properties starts to
Back in 1940, when Henry Ford wanted to test the strength of a car trunk made from an experimental soybean-based material, he stunned onlookers by whacking it with an ax.Skip to next paragraph
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Mr. Ford may have been an eccentric, but he also was way ahead of his time in trying new materials to improve cars. The trunk was made of soy-protein plastic reinforced with glass, a material that proved to be stronger, lighter, and more flexible than conventional car panels. Ford grew many varieties of soybeans in a field near his company's Detroit auto factory to find a plant with the optimal material properties. By doing so, he planted the seed for the new crop of biomaterial composites that are sprouting up today.
Now, more than six decades later, vehicle, lumber, furniture, housing, and other manufacturers are finally seeing the benefits of such "green" materials. New and better composite materials made from plastic combined with natural fibers or plants such as hemp, kenaf, sisal, or soybeans can be manufactured and used for at least the same cost as conventional materials, and sometimes for much less.
The 1998 Ford Cougar, for example, has a polypropylene plastic and kenaf-fiber composite in its interior door panels, and the 2000 Mustang will have that material in its trunk liners. Kenaf is a 14-foot tall, inedible plant in the hibiscus family. The panels are more shatter-resistant than traditional ones made by mixing polypropylene and wood flour or saw dust. In addition, Deere & Co. is using soy-based fiberglass composites in its tractor panels and hay balers.
"The natural fibers are very ductile and they don't splinter, so they manage energy well during side impacts," says Ken Urolini, area manager for door trim engineering at Visteon Automotive Systems, a Ford Motor Co. enterprise in Utica, Mich. Mr. Urolini says natural-fiber composite components weigh about 30 percent less than traditional wood-based materials. And, they cost less because they take half as long to make. Natural-fiber plastic composites are formed when a fiber sheet is heated along with propylene and molded. The now sticky sheet, which forms a stiff panel backing, is then pressed against the door fabric, eliminating the extra step of applying a toxic adhesive.
"We intend to use these composites in new cars including the Mustang, Escort, and Taurus Sable," Urolini says. The only drawback now, he says, is the technology is so new in the United States that Ford has had to import tooling and other capital equipment for pressing the composite panels from Europe, where automakers are further ahead in using natural-fiber composites.
Richard Wool, professor of chemical engineering and director of the Affordable Composites from Renewable Sources program at the University of Delaware in Newark, says the field of composites came into its own in the past 40 years because of two developments: high-performance fibers and high-performance, petroleum-based plastic resins.
"Advances in the field were dominated by defense priorities until the Berlin Wall came down, and then the big push went in the direction of all-natural composites using agricultural bioproducts," Professor Wool says. At the same time, giant companies like Monsanto and DuPont began to focus on the crop business so they could control the hybrids grown. "There may be crops grown especially for composites, just as there are for animal feeds today. So it may be possible to have your crop and eat it too," quips Wool.
Wool's laboratory is making composites that substitute soybean oil for plastic so that a fiber composite will be all natural.
Composites date back to the middle ages, when builders used straw to reinforce building blocks to make castles. The most common composite today is fiberglass. New composites are being created by combining old materials in new ways.
"People are fusing old materials with different physical treatments to make different materials. It's like old-time alchemy," says George Beylarian, founder and president of the Material Connexion, a combination design gallery, innovation clearing house, and new-materials database in New York.