North Carolina State University researchers have developed biodegradable materials that could aid efforts to reduce plastic film, like ones used in grocery bags.
The material looks like plastic, but it's made using large molecules called biopolymers from natural materials. One polymer is called agarose, which comes from seaweed, and the other is called chitosan, which makes crab shells hard.
The film is formed from agarose, with chitosan embedded into it. The researchers used the chitosan to form a series of fibers that provide structural reinforcement in the plastic-like film.
N.C. State Chemical and Biomolecular Engineering professor Orlin Velev said the resulting film is strong. And, this approach could help replace petroleum-based plastics used in items like food packaging.
“Packaging is one of the most notorious applications that are in essence a peril to the environment,” Velev said. “Packaging is an application where you take petroleum, you make a polymer, then you use this polymer only once. If not discarded properly, this polymer is going to produce microplastics and be a danger to sea life.”
Alternatively, that packaging could end up in a garbage dump, where Velev said it would degrade very slowly. According to the Organisation for Economic Co-operation and Development — an international group that works to promote public policy — only 9% of plastic waste is recycled.
Velev said using seaweed-derived agarose is a common option researchers have explored when it comes to replacing plastic film. However, it has its challenges. One being that when an agarose film touches water, it becomes “mushy.”
But, when the agarose is reinforced with chitosan, the film becomes about four times stronger, no longer falling apart when in use. And, using this reinforcement method helps the film remain biodegradable – something that Velev said would have been affected, had researchers instead tried to chemically modify the agarose.
“Our improvement in this case is really thinking about reinforcement on a scale that is larger than the molecular scale,” Velev said. “We avoid some of the issues that would occur when you try to mix agarose and chitosan molecularly. So, we really have made improvements in understanding, and controlling and using the morphology of the biopolymers in order to make better materials.”
Velev said the next research goals are to figure out how to make the film in large amounts, and make it less permeable to air and water.
