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TOUGH
AS SOYBEANS: THE LONG SEARCH FOR PLANTS WITH OPTIMAL MATERIAL PROPERTIES
STARTS TO PAY OFF
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."
Clip by:
Lori Valigra, Special to The Christian Science Monitor, Cambrige, Mass.
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