A team of ISU researchers has improved environmentally friendly, biodegradable plastics based on corn and soy proteins with small clay particles.

David Grewell, assistant professor of agricultural and biosystems engineering, said the new composites are much different from current plastics on the market because they are made without petroleum products and are very easily biodegraded.

“Tons of petroleum-based plastics are put into landfills every day,” Grewell said. “It could sit there intact for years.”

He said the plastics made from plant proteins, however, could be designed to break down after only a number of months if desired.

The plastics are crafted by unfolding the plant proteins with solvents such as water or glycerin, then reorganizing the proteins into plastic polymers.

However, these plastics are relatively weak in their raw form and must be reinforced by other materials.

“The properties [of the raw protein polymers] are not the best for plastics,” said Michael Kessler, assistant professor of materials science and engineering. “That’s why nanoclay platelets are added: for strength and integrity.”

Nanoclays are microscopic particles of clay only about 10 to 20 billionths of a meter thick.

Since the tiny pieces of clay tend to stick together due to electrostatic forces, the researchers have turned to high-powered, high-frequency sound waves, or ultrasonics, to break up the particles evenly for use as a reinforcing agent in the plastics.

Grewell said when combined, the protein polymers and clay particles make up nanocomposites and are much stronger than the raw plastics alone.

“There are samples that have the consistency of soft urethane or soft rubber, and some of the hardest are like low-density polyethylene, like a milk jug,” Grewell said.

Grewell and his research team are currently assessing the mechanical strength and toughness of the materials, while Kessler’s group is characterizing the microscopic structures of the composites.

Several companies have taken an interest in the nanocomposite plastics, such as Vermeer Manufacturing Co. of Pella and Vibroacoustic Solutions of Ames.

Some proposed applications for the materials are biodegradable hay bale wrappers and pots for plants that can be put into the soil with a plant and gradually wear away as the plant’s roots grow.

Grewell said depending on the application, the plastics could enter the market fairly soon.

“If this turns out to be a success, it could have a huge impact in Iowa since it would be drawing on soy and corn,” Grewell said.