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Shri Ramaswamy
Bio-based Products
PHOTO COURTESY OF MN AGRICULTURAL EXPERIMENT STATION
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What goes around, comes around. In the late 1960s polymers were
the hot thing. Twenty years later, the material was, well no longer
so hot. Plastics were an inexpensive commodity, mostly a world of
oil-based resins, pressed, extruded, or blow molded to shape using
low-cost, high-speed production techniques.
Now the field has come alive again. For proof, look no further than
the 2005 Minnesota State Fair. Hundreds of thousands of people at
this year's State Fair picked up that most ubiquitous of giveaways:
the plastic carry-bag. Most were of the normal, petroleum-based
plastic variety, functional to be sure, perhaps even colorful. But
sooner or later, those bags, having done their job, will land unceremoniously
in waste bins-and eventually in landfills.
But clogging landfills is not the only possible destiny for some
fairgoers' bags. The bags that Shri Ramaswamy and his colleagues
at the College gave away had another attribute: They contained plastics
derived from agricultural products, and were (and are) biodegradable.
They were made with poly lactic acid (PLA), which is one of the
biobased polymers recently introduced in the marketplace. "These
corn derived plastics essentially degrade within 30 days. So if
you have the right conditions-temperature, humidity, and bugs [bacteria],
which are typical of industrial compost sites-they go completely
back to water and lactic acid and leave no solid waste pollution,"
Ramaswamy explains.
The use of bio-based PLA plastics in the food industry is growing
faster than a Chia Pet soaked in Miracle-Gro. Consumers value "green"
plastics for their ecological benefits. With the advancement in
technology, and given today's oil prices, bio-based polymers are
very cost competitive to conventional petroleum-based polymers.
Researchers at the University of Minnesota are working to improve
the properties and performance of the bio-based polymers.
Ramaswamy and his colleague, Professor Rich Cairncross from Drexel
University, recently received a grant to study one of the problems
associated with the type of plastic made from corn-derived PLA.
The project is an investigation into the moisture transport and
degradation kinetics of PLA products. "I'm working on the use
of this plastic in water bottles," says Ramaswamy. "Being
bio-based, PLA interacts with moisture and transmits water easily.
This is one of the reasons why PLA degrades so quickly and completely.
At the same time, ease of transport of moisture through PLA can
pose problems in long-term storage and use in applications such
as water bottles. The water will evaporate out of the bottle, right
through the bottle walls.
"The problem we are working on is to better understand how
water moves through PLA," he adds. "What is the relationship
between the molecular architecture of PLA and its ability to transport
water? What can we do to slow it down without negatively affecting
its ability to degrade?"
Are there ways to accomplish both aspects? Ramaswamy is hopeful.
"It's early yet, but we have some ideas on how water is transported
through these materials and how they can be optimized," he
says. "We have more work to do."
Visitors to the University of Minnesota's building at the 2005 State
Fair were eager to learn more about the important work underway
in regard to the ways green materials can replace petroleum-based
products. "Most people we spoke with were surprised that plastics
can be made from corn, and that those plastics are 100 percent biodegradable,"
says Ramaswamy."I talked with school kids-juniors and seniors-and
they were amazed by this."
Ramaswamy sees enormous potential in these technologies to make
a positive impact in the world. "Ultimately, the hope is to
make PLA plastics not from corn kernels but from corn residue. Making
fuels and plastics from plant residues is an enormous opportunity.
In the United States, an estimated billion tons of biomass is available
for us to use. The challenge of the future is to convert more of
it into valuable products."
Written by William Gurstelle
Reprinted with permission from the winter 2006 edition of Spectrum,
a publication of the College of Natural Resources.
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