Volume 17 - 2008
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UNT Research Home | Next-Generation Bioplastics

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Next-Generation Bioplastics



Plants Contribute

To

Eco-friendly,

High-Functioning Materials




By
Sally Bell

Polymer Mechanical and Rheology Laboratory

Nandika D'Souza directs the Polymer Mechanical and Rheology Laboratory at UNT, supervising six graduate students and two undergraduates from UNT's Texas Academy of Mathematics and Science. D'Souza and her team research a variety of topics affecting the development of the next generation of bioplastics, including nanostructured polymers and failure analysis.

The lab, part of the Department of Materials Science and Engineering, is in Discovery Park, UNT's 285-acre research park located four miles north of campus. D'Souza, a recognized expert in polymer nanocomposites, has been an investigator on more than $2 million in research funding at UNT.

Nandika D'Souza

Photo by: Angilee Wilkerson

Corn, bacterial microorganisms and natural fibers such as jute, hemp and kenaf are among the ingredients Nandika D'Souza uses to make eco-conscious bioplastics.

Nandika D'Souza, associate professor of materials science and engineering at the University of North Texas, envisions a future where conventional plastics are replaced with "bioplastics. "These materials — made using corn, bacterial microorganisms or natural fibers such as jute, hemp and kenaf — would look, behave, feel and perform like petroleum-based plastics but also decompose harmlessly and relatively quickly.

The move to these more eco-conscious materials would reduce the need for plastics made with increasingly scarce and expensive petroleum. Those plastics, which take hundreds of years to degrade, lead to clogged landfills and a national reliance on foreign oil.


A Work in Progress

A goal of D'Souza's research into bioplastic packaging materials is the creation of new products that match or surpass the performance of conventional plastics, cardboard, paper coatings and foams.

Biocoatings for the paper packaging in items such as military-grade Meals Ready-to-Eat (MREs), for example, could lead to longer product shelf life while also breaking down in a month or so under high-temperature composting. Or they would decompose naturally within a year in standard landfills, leaving only carbon and hydrogen — basically soil.

"This is an important step as we aim to create even stronger, more efficient, cost effective and environmentally friendly products," D'Souza says. "We already are working to develop bio-engineered products that are structurally sound enough to use as biodegradable packaging but also can be used in medical and building materials. These products are based on completely renewable resources.

"This means in the future we could have materials that wouldn't consume more landfill space, while enhancing our agricultural base, which would help farmers thrive."

The potential impact of D'Souza's work extends far beyond environmental and agricultural benefits. The materials also may have biomedical applications, such as in tissue engineering or in the creation of biopolymer arterial stents that use ibuprofen as a functionalizing agent, which she worked on with engineering students Sunny Ogbomo and Koffi Leonard Dagnon.

"I am getting rewarding experience by being involved in Dr. D'Souza's lab. I call it 'green research work' due to its increased environmental concerns," says Dagnon, a Ph.D. student in materials science and engineering who has worked in the lab as a research assistant since fall 2006.

"If I were not at UNT, I would not be exposed to the university's new and unique instrumentation, such as the Leistritz twin screw extruder for biopolymer blending, the high-resolution scanning electron microscope or the transmission microscope."


Developing New Materials

Nandika D'Souza  works with graduate student Koffi Leonard Dagnon

Photo by: Scott Bauer

Nandika D'Souza, left, works with graduate student Koffi Leonard Dagnon to extrude biopolymers in UNT's Polymer Mechanical and Rheology Laboratory, where D'Souza is researching the development of the next generation of bioplastics.

European companies lead bioplastics research today, and the focus is bridging long polymer chains and various starches with vegetable oils and other natural molecules. (A polymer is a natural or synthetic compound of large molecules made of chemically bonded smaller molecules.) So far, the results are suitable mostly for shopping bags and other flexible films.

The limitation of films, of course, is that they are thin and stretchy. While that's fine for a bag, it certainly doesn't work where rigidity is required, in products such as boxes, for example.

That's where D'Souza — who is interested in harnessing a material's underlying physics and chemistry — comes in.

"I like having an effect on life. It's a challenge," she says. "And I love the fact that there's still a struggle on shelf-life issues that I can help solve."

D'Souza is building on the European work, using Italian polymer pellets as a base. She mixes the pellets with other biodegradable polymers and then measures the biomechanical properties that result.

"Our approach," she says, "is to bring in different materials to retain the biodegradability but enhance the stiffness."

D'Souza works at the almost inconceivable scale of nanometers — one-billionth of a meter. A human hair, by contrast, is immense at 100,000 nanometers wide.

Starting with the polymer pellets, D'Souza adds various nanometer-sized particles, specifically carbohydrate chains called polysaccharides, or other biopolymers that don't dissolve in water, plus a tiny amount of clay. Clay, she points out, has 10 times the stiffness of conventional plastic at the microscopic level at which she works. When a nanostructured wall is formed within the polymer, water and gas permeability is lowered, increasing shelf life.

One of her early successes has been developing a way to reduce the amount of clay added from about 30 percent of the new biomaterial's weight to just 1 to 2 percent by swelling it in a chemical bath that weakens the bonds between its nanometer-thin structural plates.

"I have an engineering approach," she says. "I'm looking at properties. I study stiffness. I look at architectures. I tend not to have a viewpoint partial to any particular materials or solutions."


Better MRE Packaging, Foam

D'Souza's work is supported by various federal grants, led by one from the U.S. Army Natick Soldier Research, Development and Engineering Center. NSRDEC wants to reduce waste left behind after military operations, so it is funding up to $40,000 annually for three years to develop biodegradable fiberboard and paper coatings used for soldiers' MRE packaging containers.

The military's goal is to have biodegradable and compostable MRE fiberboard containers that are lighter but still meet performance requirements.

"Annually, there are more than 40 million MREs procured by the military with about 14,000 tons of MRE packaging waste each year," says Jo Ann Ratto, the principal investigator at NSRDEC on this "Lightweight and Compostable Military Packaging" project funded by the U.S. Department of Defense Strategic Environmental Research and Development Program. "This coupled with the rising costs of disposal has dramatically increased the need to investigate alternative materials to combat ration packaging waste.

"Dr. D'Souza's expertise and innovation in polymer nanocomposites first led us to work with her on MRE food packaging, and she has proved to be a collaborator on whom I can trust and rely. She is dedicated to her students and her research."

NSRDEC also funds a three-year grant to investigate biodegradable packaging foams that could potentially be disposed of in the marine environment. This research is in support of the U.S. Navy's Waste Reduction Afloat Protects the Sea (WRAPS) program. The foams are made with supercritical carbon dioxide (a gas that flows like a liquid). Unlike conventional foam manufacturing processes that release harmful chemicals such as ammonia, the carbon dioxide supercritical foam technology is considered environmentally benign, D'Souza says.

She is confident about the ultimate success of her projects and says that she hasn't encountered technical obstacles so much as difficulty finding the time and resources to do the work.


International Support

D'Souza plans to look to her peers for support. She is convinced that scientists in other disciplines and from the developing world can be the best partners in helping turn good ideas into usable technology, and she is working to develop the research partnerships to do this.

The kenaf fibers she's been using to create another new breed of bioplastics that also have improved structural properties come from the greenhouse of Kent Chapman, professor of biological sciences and director of UNT's Center for Plant Lipid Research.

"I think the futuristic lab requires interdisciplinary collaboration," says D'Souza, adding that kenaf-based products might include a fiberglass substitute, paper items or canvasses.

Medical applications in collagen and cornea prostheses form the basis of her partnership with Dan Dimitrijevich, director of the Laboratories of Human Cell and Tissue Engineering at the Cardiovascular Research Institute of the UNT Health Science Center at Fort Worth.

And D'Souza isn't stopping at UNT. She is reaching out to researchers in other countries to help her solve the challenges she encounters in her lab such as the need for additional plant-derived materials to test and use in the creation of new bioplastics.

For the last two years, she has been partnering with Lucia H. Innocentini-Mei, a chemical engineer in the School of Chemical Engineering at the State University of Campinas-UNICAMP in Brazil, to obtain a bacteria-based product that can be used to create a potentially environmentally friendly substitute for traditional plastics such as polyethylene and polystyrene.

"Collaborating with other researchers is key to solving some of these global issues," D'Souza says. In developing countries researchers learn to be "creative with what they have" because the money just isn't there to import chemicals, she says.

"They have experience synthesizing the chemicals from local resources, but they don't have the instrumentation we (in Western nations) have to measure the results."


A Bright Future

D'Souza thinks she is perhaps two years from achieving her goals in developing paper biocoatings.

However, she expects to have preliminary testing results soon for the degradation of supercritical foams in oceans. While she hopes that some of her first products will be in commercial production within a few years, D'Souza knows adoption may be slow initially because bioplastics will cost 20 to 30 percent more than conventional plastics.

But she doesn't expect that drawback to remain.

"I believe the cost of today's oil-based solutions will go up so much that bioplastics will be economically viable," she says.

So bioplastics would not only reduce landfill clogging and lessen reliance on foreign oil, they also would be cost effective in the reasonably foreseeable future — a perfect environmental trifecta.

"In the past, bio-products had been inferior and performed worse than products made from fossil fuel-based materials. But that is no longer the case," D'Souza says. "We are making progress.

"The mechanical properties of these new bioplastics are holding up — they are structurally sound, can perform at the same high level and do not cause the same damage to our environment."



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