Wood waste and crab shells may find use in compostable food wrap
Cellulose and chitin are the world's first- and second-most common biopolymers, found in plants and crustacean shells (among other places) respectively. Georgia Tech scientists have now devised a method of combining the two, to produce plastic-like compostable food wrap.
Led by Prof. J. Carson Meredith, the research team is producing the material by suspending wood-derived cellulose nanocrystals and crab-shell-derived chitin nanofibers in water, and then spraying the solutions onto a reusable polymer substrate in alternating layers – the negatively-charged cellulose nanocrystals bond well with the positively-charged chitin nanofibers.
Once it has dried and been peeled off the substrate, the resulting transparent film is flexible, strong and compostable. What's more, it may also outperform traditional non-compostable plastic wrap when it comes to keeping food from spoiling.
"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," says Meredith. "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."
That reduced permeability is due to the presence of the nanocrystals.
"It's difficult for a gas molecule to penetrate a solid crystal, because it has to disrupt the crystal structure," explains Meredith. "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."
Ultimately the biopolymer-based film could not only replace current plastic films that don't biodegrade after being thrown away, but it could also conceivably make use of wood waste generated at mills, and crab shells discarded by the seafood industry. Before that can happen, however, the costs of producing the material at an industrial scale will have to be brought down.
A paper on the research was recently published in the journal ACS Sustainable Chemistry and Engineering.
Source: Georgia Tech