Source: Nathan Cardozo/CC BY-SA 2.0By adding natural rubber to bioplastic in an effort to make bioplastic less brittle, researchers from Ohio State University have developed a new type of bioplastic that may be an appropriate alternative to the petroleum-based plastics commonly used in the packaging of food.

Hoping to reduce the brittleness and stiffness of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), which is a biodegradable polymer, researchers melted rubber into the PHBV along with organic peroxide and trimethylolpropane triacrylate (TMPTA) to act as a coagent. The final result was a bioplastic that was 100% more flexible and 75% tougher than PHBV alone. Enhanced by natural rubber’s elasticity and ductility, the mixture offers a suitable and inexpensive alternative to other bioplastic mixtures that were generally too weak to hold up to shipping and handling or microwaving and freezing.

"Previous attempts at this combination were unsuccessful because the softness of the rubber meant the product lost a lot of strength in the process," said lead author Xiaoying Zhao, a postdoctoral researcher in Ohio State's Department of Food Science and Technology.

While the addition of the rubber caused a loss of strength in the PHBV, the Ohio State mixture lost only 30% strength compared to 80% in earlier studies.

"Imagine trying to pull a block of concrete apart with your hands. That's testing its strength. But karate chopping it with your hand or foot is testing its toughness — how easily it breaks," said study co-author Katrina Cornish. "You can never pull it apart, but if you're strong enough you can break it."

To strengthen the mixture even more, the research team is exploring biodegradable materials including eggshells, coffee grounds and tomato skins to act as potential fillers for fortifying the mixture. Likewise, they are looking at invasive grasses removed from waterways. The team acknowledges that whatever they use, it must meet with the often stringent standards that guide the food industry.

For more on the research, go to the journal Polymers.