- Hoping to curb the impending plastic apocalypse, scientists across the world are scrambling to develop sustainable and biodegradable materials that can offer the same practical benefits as petroleum-derived polymers.
And in the latest encouraging blow against single-use food packaging specifically – the largest source of humanity’s 6.3 billion metric ton and growing collection of plastic waste – researchers from the Georgia Institute of Technology have created a flexible film that could soon replace the convenient yet unrecyclable, non-decaying environmental scourge that is plastic wrap.
The novel product is made by spraying alternating layers of chitin and cellulose fibers, sourced from discarded crab shells and wood pulp, respectively, onto a polylactic acid (PLA) base.
Chitin, the primary component of arthropod exoskeletons and fungal cell walls, and cellulose, the molecule that gives plants and single-celled algae their structure, are the most abundant organic polymers on the planet, whereas PLA is produced from starchy plants such as corn or cassava.
The team’s study, published in the journal ACS Sustainable Chemistry, shows that the film is not only comparable to plastic cling film, it performs many of the same tasks better.
"The main benchmark that we compare it to is PET, or polyethylene terephthalate, one of the most common petroleum-based materials in the transparent packaging you see in vending machines and soft drink bottles," lead author J. Carson Meredith said in a statement. "Our material showed up to a 67 percent reduction in oxygen permeability over some forms of PET, which means it could in theory keep foods fresher longer."
According to Professor Meredith, the team had been studying chitin for a separate project when they realized the fiber’s molecular properties could make it well suited for packaging.
"We recognized that because the chitin nanofibers are positively charged, and the cellulose nanocrystals are negatively charged, they might work well as alternating layers in coatings because they would form a nice interface between them," Meredith said, explaining that food-preserving films must block gases.
"It's difficult for a gas molecule to penetrate a solid crystal, because it has to disrupt the crystal structure," Meredith said. "Something like PET on the other hand has a significant amount of amorphous or non-crystalline content, so there are more paths easier for a small gas molecule to find its way through."
Unfortunately, the film still lets too much water vapor through for it to be commercially viable as of now, but the authors are optimistic that tweaks in the production process and/or formula will remedy this.
Perhaps the most exciting aspect of the organic material is that no additional chitinous creatures or trees would need to be harvested to provide the raw fibers; the seafood and paper industries already likely produce enough unused byproduct.
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