HIERARCHICAL MATERIALS BASED ON NANOCELLULOSE AND POLY(LACTIC ACID)
Résumé
Nanocelluloses have shown excellent gas barrier properties which makes them of the highest
interest for food packaging applications. However, the nanocelluloses swelling, in presence
of water vapor, thwarts their good gas barrier properties. Consequently, the use of
nanocelluloses in food packaging, while extremely promising, is still a challenge. A multilayer
architecture starting with an hydrophobic layer of poly(lactic acid) (PLA) could be a solution to
protect nanocelluloses. Different studies have been devoted to the use of nanocelluloses as
fillers in a PLA matrix, but here, a new architecture was developed by depositing layers of
nanocelluloses on PLA.
The coverage of PLA films by nanocelluloses was achieved by using a first layer of chitosan.
The surface organization of the nanocellulose layers was studied by AFM.
The cellulose nanocrystals showed orientation (Fig.1a), which was confirmed by FFT treatment
of the images. Concerning the food packaging-related properties, dry and wet O2 barrier
properties were studied on films with different nanocelluloses layer thicknesses.
Results are very promising, with our samples’ O2 permeation several orders of magnitude
lower than PLA, and staying so at high humidity (80% RH).
The multilayer architecture is very efficient to obtain highly perfoming food packaging films and
the protection of the nanocellulose layer by PLA allows to keep this performance over a large
range of relative humidity.
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