'Soybeans have natural characteristics that make them ideal for making plastics."

That's one of the best reasons Joshua Otaigbe, an Iowa State University scientist, can give for countless hours spent the past four years developing a new formulation for moisture-resistant, biodegradable soybean plastic.

The polymers in soybean protein closely mimic the desirable properties in petroleum-based plastics, he explains. But the soy plastic must be carefully formulated to allow it to be converted into useful products using commercial plastic processing methods, such as extrusion and injection molding.

Because of the environmental unfriendliness of petroleum-based plastics, research this past decade has focused on developing plastics that biodegrade. Otaigbe has been building on soybean plastics research that began at Iowa State in the early 1990s. Those earliest plastics were never commercialized because they dissolved too quickly and erratically in water, Otaigbe says.

But his new formulation makes soybean plastics more moisture-resistant, giving greater control over the biodegradation process. Better control creates new uses for the plastics, such as food packaging, medical sutures and even sporting goods.

"We want materials that serve their function and then biodegrade in an environmentally friendly manner," he says.

To make the plastic, the engineer adds chemicals and plasticizers, which are low-molecular-weight compounds, to soy protein. One example of a common plasticizer is water, he notes. A proprietary, patent-pending additive that aids in moisture resistance completes the formulation.

After the ingredients have been mixed, Otaigbe uses extrusion and injection-molding to form useable pieces of plastic.

What's next? "We've demonstrated we can make viable plastics out of soybean protein, so the next step is to find industrial partners interested in working with us to scale up the project."

He says that soy-based plastics could be priced comparably to their petroleum-based counterparts. It's tough to predict how many bushels of soybeans could some day be used to make plastic, but the amount is substantial.

Otaigbe's research is funded by the Iowa Soybean Association and the Iowa State University Research Foundation.