Sustainable packaging is a hot topic. Sustainable alternatives
to conventional plastic packaging exist, and generally consist of
biodegradable materials which are either derived from renewable
natural sources, such as polysaccharides (e.g., starch, cellulose,
chitosan, and alginate) or proteins (e.g., gelatin), or made from
natural sugar derivatives (e.g. polylactic acid).
Despite many advantages, some of these materials do not meet
certain standards required in food packaging, such as liquid and
gas barrier properties. Typically, barrier coatings are used to
provide the required barrier properties. However, the use of
plastic-based materials as conventional barrier coatings can
compromise the advantages of using a sustainable core material. The
same is true of plastic coatings on pulp-based materials such as
carboard and paper, which can sometimes even prevent
recycling.
It is therefore encouraging to read that new materials are emerging
as sustainable barrier coatings for applications in
packaging.
Polyelectrolytes are macromolecules that contain a large number of
charged functional groups. Polyelectrolyte complexes (PECs) can be
formed spontaneously through blending oppositely charged
polyelectrolytes where the ionic attraction is the major driving
force. Rather than relying on chemical irreversible crosslinking in
conventional plastics, PECs are formed by reversible ionic
associations without introducing crosslinkers, which can help meet
needs of food and biomedical applications. PECs fabricated with
polysaccharides are termed polysaccharide polyelectrolyte complexes
(PPCs).
This article focuses on PPCs made from carboxymethyl cellulose
(CMC) and chitosan (CS), which when applied to porous paperboard
substrates paperboard using a particular manufacturing process,
were found to exhibit outstanding barrier performance.
A single-step process via ball milling can produce high-solid content PPC solutions useful for creating bio-based coatings with excellent barrier performance
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