Researchers at Georgia Institute of Technology created a biodegradable material made from cellulose, derived from tree fibres, and chitin, derived from crab shells, that has the potential to replace plastic packaging to keep food fresh.
The new material is made by spraying multiple layers of chitin from crab shells and cellulose from trees to form a flexible film, similar to plastic packaging film. The material is comparable to PET (polyethylene terephthalate), one of the most common petroleum-based materials used as transparent packaging. However, the new material showed up to 67 per cent reduction in oxygen permeability over some forms of PET, meaning it is able to keep food fresher longer.
Cellulose is derived from plants and is the world’s most common natural biopolymer. The paper insuustry is one source for it. Chitin is the second most common biopolymer, and can be found in shellfish, insects and fungi. It is in ample supply from by-products of yje shellfish food industry.
The team devised a method to create a film by suspending cellulose and chitin nanofibers in water and spraying them onto a surface in alternating layers. The chitin nanofibres are positively charged, while cellulose nanocrystals are negatively charged, forming an interface between them.
Once fully dried, the material is flexible, strong, transparent and compostable.
Packaging meant to preserve food needs to prevent oxygen from passing through, Part of the reason the new material is better than conventional plastic is because the crystalline structure of the film forms a gas barrier. Gas molecules have a hard time penetrating a solid crystal. Pet, on the other hand, has a significant amount of non-crystalline content, through which a small gas molecule can find its way.
To make the material competitive with plastic film on cost, a large scale manufacturing process has to be developed. While there are plenty of industrial process available to produce cellulose, methods to produce chitin are still developing.
Photos: Georgia Tech