David Grewell, an assistant professor of agricultural and biosystems engineering at Iowa State University, is working with a team of fellow researchers to reinforce biorenewable, biodegradable plastics with nanoclays (pieces of clay that are just 10 to 20 billionths of a meter thick). These plastics are produced when glycerin, a byproduct of biodiesel production, and water are added to a soy or corn protein. The glycerin acts to lengthen and straighten the compact protein molecule, but the resulting plastics lack strength.

Nanoclays have been successfully added to petrochemical polymers to enhance factors like strength and vapor barrier properties, and Grewell's group is investigating if similar results can be seen in protein-based polymers. The research team is using surface-treated clays to enhance mixing and have already seen evidence that vapor barrier properties can be improved.

 "It's not easy to work with those tiny pieces of clay. They tend to stick together in clumps because of electrostatic forces," said Michael Kessler, an Iowa State assistant professor of materials science and engineering who's also working on the project. "Those clay platelets need to be separated and mixed evenly throughout the plastic to be much good as a reinforcing agent."

The researchers are turning to high-powered ultrasonics—high-frequency sound waves too high for human hearing—to separate and disperse the platelets. It's a technology Grewell knows a lot about: he worked for 10 years in research and development for the Branson Ultrasonics Corp. of Danbury, Conn., and used ultrasonics to freeze strawberries, process rice and handle many other applications.

According to Grewell, the potential applications for plastics created with crop proteins include disposable wraps for hay bales, pots for plants and packaging for the food industry.

For additional information, contact David Grewell at (515) 294-2036 or dgrewell@iastate.edu. Iowa State's website is located at www.iastate.edu.