Tough as Soybeans
The long search for plants with optimal material properties starts to
CAMBRIDGE, MASS. — 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.
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.
Liat Margolis, director of research at the Material Connexion, says today's fiber composites are replacing traditional petroleum-based products, such as the resins in thermoset plastics, which are toxic and not readily biodegradable. By comparison, kenaf fiber mixed with a thermal plastic like polypropylene can be remelted and reused more easily.
"Kenaf stalks, which are comparable in strength to carbon or glass, are replacing fiberglass, and polypropylene is replacing liquid resin, which eliminates a lot of the toxic chemicals for workers," Ms. Margolis says.
For consumers to buy environmental materials, they must be equal or better in performance than traditional products, says David Saltman, vice president of marketing and new-product development at Kafus Industries Ltd. in Calabasas, Calif. "Consumers will buy environmental materials, but they won't pay extra for them," he says.
According to Plastics Technology magazine, prices for natural fibers range from 3 cents per pound for jute to 25 cents per pound for kenaf, while glass fibers are 50 cents to 75 cents per pound. But when natural fibers are made into mats, the price rises to $1 to $1.50 per pound.
Kafus Bio-Composites, a Kafus Industries subsidiary, has an agreement for joint development of biocomposites with Visteon. In October 1999, Kafus began commercial production of natural-fiber composites at its plant in Elkhart, Ind.
The long-fibered kenaf-composite panels that Visteon sells to Ford are more flexible and shatter-resistant during accidents than fiberglass, Mr. Saltman says. Kenaf composites also can be used to make chairs, raised flooring for computer rooms, packaging, and containers, he adds.
Kenaf looks like hemp. It grows fully in seven months, tolerates drought, and does not require extensive herbicides. It grows in regions where cotton and tobacco thrive. Kenaf Industries also is using it to make paper for commercial newsprint. It has a 20,000-acre kenaf farm in Raymondville, Texas.
"We're using a crop that is totally renewable on a yearly basis, rather than cutting down 20-year-old forests," says David Agneta, president of Kafus Bio-Composites in Dedham, Mass.
Kenaf isn't the only natural fiber that has caught the imagination of engineers and designers. Global Resource Technologies (GROT) of Madison, Wis., is using jute, sisal, wood, coir, flax, straw, kenaf, and even denim to make everything from plastic wood and tables to shipping pallets and piggy banks. Its products are still in the development stage.
"Fibers are lower cost and stiffer, and you can mold them, which you can't do with pure wood," says Colin Felton, technical manager at GROT. "And, they're recyclable."
The company chops fibers and blends them with molten plastic in ratios of up to 70 percent fiber by weight. A table top looks much like today's particle board, but it is as much as half the weight because ribs can be molded to trim heft while retaining strength. And because a round table top, for example, can be molded, there isn't the 30 percent waste that comes with sawing the edges off of a square piece of particle board or natural wood.
"Plastic composites can replace wood in many applications. Although the basic material costs are high, less material is used, so there is much less waste," Mr. Felton says. And the composites can be melted down and reused up to five times.
That's the case with GROT's denim composite shipping pallets, made from jean scraps from nearby Lands' End, the catalog clothing company.
Denim composite pallets are much stronger than wood. They cost about $20 to $30 apiece and last up to 100 trips. Wood pallets cost $7 to $10 apiece and last only about three trips, Felton says.
Besides, Felton adds, "Wood is becoming more scarce, and materials like jute and kenaf are plentiful."
(c) Copyright 2000. The Christian Science Publishing Society