Nature is known to produce all kinds of biopolymers which
have proven to be extremely utile and have the potential to replace synthetic
polymers. One such area for its application is in food packaging. In recent
times, researchers at Georgia Institute of Technology have been successful in
synthesizing a material from two of the most abundant biopolymers found on
earth, cellulose and chitin. They have developed a spray-based method to
produce a multilayered film using chitin nanofiber and cellulose nanocrystals.
Chitin is composed of N-acetyl glucosamine which are formed by linear construct
of these monomers, therefore its called a homopolymer. Cellulose is another
homopolymer made up of glucose with crosslinks formed between the linear chains
of glucose and it is the most abundant polymers available in nature. Cellulose
nanocrystals and chitin nanofibers both have a high young’s modulus making them
rigid and though materials and also due to their complex structures when they
are formed into composites, act as good barriers to oxygen and other atmospheric
gases.
Prof. Carson Meredith, the team lead devised a spray-based method
to produce a composite layers of cellulose nanocrystals (CNCs) and chitin nanofibers
(ChNFs). To form the alternate layers they used the electrical properties of
these materials to bind them together, you see CNCs are negatively charged and
ChNFs are positively charged when they are suspended in water. The team sprayed
these biopolymers in alternating layers onto a compostable inert substrate. In
order for this composite to be suitable for food packaging applications, it is
a prerequisite for these materials to be impermeable to oxygen to an extent
that would prevent the food from oxidatizing and turning rancid. Therefore, when
tested and compared to conventional PET (extensively used for food packaging)
they discovered that there was a 67% reduction in the oxygen permeability for the
CNC and ChCF composite. The fibers and nanocrystals have an extremely complex
structure, which prevents oxygen molecules from disrupting the crystalline structure and penetrating the layers. The more layers they added the lesser the oxygen permeability.
An excellent green and sustainable packaging material, but
now the question remains “Is it suitable for economic scaled-up manufacturing?”.
Cellulose nanocrystals have several method to be mass produced but chitin
nanofibers have to be extracted from several animal sources such as crustaceans,
insects, etc. Hence, the manufacturing techniques are still in its neophytic
stage.
We, hope that more similar researches provide solutions for this barrier
blocking us from shifting to a greener and environment friendly future.
Jessie Marsh
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