Currently, consumer products, from compostable plastic cups to liquid laundry detergent packaged in cardboard, are increasingly boosting their sustainable and renewable origins.
At present, scientists from the
Georgia Institute of Technology have developed a material extracted from crab shells and tree fibers, with the ability to replace the flexible plastic packaging used to maintain the freshness of food.
The new material, which has been reported in the
ACS Sustainable Chemistry and Engineering journal on July 23, 2018, is produced by spraying multiple layers of chitin from crab shells and cellulose from trees to create a flexible film analogous to plastic packaging film.
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. 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.
J. Carson Meredith, Professor in Georgia Tech’s School of Chemical and Biomolecular Engineering
Cellulose, derived from plants, is the most common natural biopolymer found on Earth, followed by chitin, which can be found in insects, shellfish, and fungi.
The researchers developed a technique for producing a film by suspending chitin nanofibers and cellulose in water and spraying them onto a surface in alternating layers. Upon being completely dried, the material becomes transparent flexible, compostable, and strong.
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.
J. Carson Meredith, P rofessor in Georgia Tech’s School of Chemical and Biomolecular Engineering
The research group also included Meisha Shofner, an associate professor in the School of Materials Science and Engineering and the interim executive director of the Renewable Bioproducts Institute; John R. Reynolds, a professor in the schools of Chemistry and Biochemistry and Materials Science and Engineering; and Chinmay Satam, a graduate student at Georgia Tech.
The researchers had been analyzing chitin for a different reason when they thought whether it could be applied in food 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,” stated Meredith.
Packaging intended to preserve food has to prevent the entry of oxygen. One reason for the new material to enhance upon traditional plastic packaging as a gas barrier is due to the film’s crystalline structure.
It’s difficult for a gas molecule to penetrate a solid crystal, because it has to disrupt the crystal structure,” stated 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.”
For many years, environmentalists have searched for renewable means to replace petroleum-based materials in consumer products. The quantity of cellulose already being produced and a handy supply of chitin-rich byproducts remaining from the shellfish food industry have probably ensured adequate material to make the new films a viable flexible-packaging alternative, stated Meredith.
Yet, there is more research to be performed. A manufacturing process that increases the economy of scale will have to be devised to make the innovative material eventually competitive with flexible packaging film on cost. Furthermore, although industrial processes for the mass production of cellulose are fully developed, techniques for producing chitin are still in their infancy, stated Meredith. Moreover, more studies are also needed to enhance the potential of the material to block water vapor.
The Georgia Tech Renewable Bioproducts Institute and the Georgia Research Alliance supported this study.
Dr Carson Meredith from Georgia Tech’s School of Chemical & Biomolecular Engineering has developed a sustainable, flexible packaging wrap that is comprised of cellulose nanocrystals from wood pulp and chitin nanofibers which can be found in the discarded shells of crabs and shrimp. (Video credit: Brice Zimmerman, Georgia Tech)