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article imagePlastic packaging alternative derived from crab shells and trees

By Karen Graham     Jul 24, 2018 in Science
A new material made from substances common in crab shells and tree fibers could replace the flexible plastic packaging used to keep food fresh.
We have heard it time and time again — the world is turning into one big rubbish bin and the oceans are choking on a material that has been made to last forever — plastics.
But that may soon change, thanks to researchers at the Georgia Institute of Technology. They have developed an environmentally-friendly, biodegradable and compostable material that could replace plastic packaging.
Triple-layer flexible film
The material is a flexible film made from multiple layers of chitin from crab shells and cellulose from trees. Crabs, you say? Chitin is a fibrous substance consisting of polysaccharides that is present in shellfish, insects, fungi and the scales of fish.
A close-up of the wing of a leafhopper; the wing is composed of chitin.
A close-up of the wing of a leafhopper; the wing is composed of chitin.
Chitin has proved useful for several medicinal, industrial and biotechnological purposes, including food processing, and to increase the strength of paper products.
Cellulose is a biopolymer and is an important structural component of the primary cell wall of green plants, including trees, and many forms of algae and the oomycetes. The cellulose content of cotton fiber is 90 percent, that of wood is 40–50 percent, and that of dried hemp is approximately 57 percent.
Using chitin and cellulose, the researchers sprayed multiple, alternating layers of the two materials to form a flexible film that can compete with plastic packaging film.
Wood pulp and cellulose are added as fillers to many foods consumers buy  and is an accepted practic...
Wood pulp and cellulose are added as fillers to many foods consumers buy, and is an accepted practice in the industry.
“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,” J. Carson Meredith, a professor in Georgia Tech's School of Chemical and Biomolecular Engineering, said in a statement, reports R & D Magazine.
“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.”
Keeping foods fresh
The effectiveness of this new material at keeping food fresh is due to its crystalline structure that keeps gas molecules like oxygen from penetrating the material. PET, on the other hand, has quite a bit of amorphous or non-crystalline content, making it easier for oxygen molecules to find a path through the material.
Plastic wrap on food container
Plastic wrap on food container
And the wrapping around a food product needs to work well enough to keep oxygen away from the food to minimize spoiling, according to ZME Science.
“We had been looking at cellulose nanocrystals for several years and exploring ways to improve those for use in lightweight composites as well as food packaging, because of the huge market opportunity for renewable and compostable packaging, and how important food packaging overall is going to be as the population continues to grow,” said Professor Meredith.
It will be a big step forward when we find a way to replace plastics that are petroleum-based products. One major problem to overcome is finding a cost-effective manufacturing process to produce the new plastic commercially. Also, unlike the industrial processes used to produce cellulose commercially, the methods for producing chitin in mass quantities is still relatively new.
The study authors also say that more research is also needed to improve the material’s ability to block water vapor.
This very interesting study was published in ACS Sustainable Chemistry & Engineering on July 23, 2018.
More about chitin, Cellulose, Plastic, Renewables, Green
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