This work deals how the one-time recycling of nanocellulose films on their properties.

1. Effect of Recycling on the properties of nanocellulose –Barrier and Mechanical
Properties
Kirubanandan Shanmugam, Humayun Nadeem, Swambabu Varanasi, Gil Garnier, Warren Batchelor
Department of Chemical Engineering, Bioresource Processing Institute of Australia, Monash
University, Melbourne, Vic 3800, Australia.
Address correspondence to E-mail: Warren.Batchelor@monash.edu
Abstract
Plasticbasedpackagingcausessignificantproblemsinthe environment.Theyare neitherrenewable
nor biodegradableandplasticsare accumulatinginthe environment,damagingthe eco-system.
Recyclingalsoremainsproblematic. Sustainable,recyclablematerialswithoutstandingbarrier
performance are requiredtoreplace these syntheticplastics. Nanocelluloseisapotential candidate
to replace syntheticpolymersaspackagingbarrierlayers. Nanocellulose filmshave low oxygen
permeability andreasonable watervapourpermeability. However,the effectonthe fibresand
material of recyclingsuchfilmshasnotbeenwidelyinvestigated. Inthe workreportedhere,we
made nanocellulose filmsviaspraycoatingandthenrecycledthemusingdisintegration,before
formingintofilmswithvacuumfiltration.The formedfilmswere comparedvirginfilmsalso formed
withvacuumfiltration. The recycled filmsretained70% of the strengthof the virginfilms. The
watervapourpermeability (WVP)approximatelydoubled,increasingto1.2 x 10-10
g.m-1
.s-1
Pa-1
.
Investigationsacrossarange of lengthscalespinpointedthatthe likelydifference wasdue to
bundlesof the cellulose nanofibersthathadnotfullyseparated inrecycling.
Introduction
Currently,the syntheticpolymersinfood,medicalandpharmaceutical packagingare neither
renewable norbiodegradable andare accumulatinginthe environment,damagingthe eco-system.
Additionally, recyclingof syntheticpolymeriscomplex due tothe contaminationandthe difficulty of
separatingsyntheticpolymersforreprocessing. Forexample,polyolefinfilmscannotbe reprocessed
intothe original product,asthe recycledproductwouldnotyieldsuitablebarrierperformance,
failingtoreuse the material.Cellulosefibre-basedpackagingmaterials,suchasboxes,cartonsand
paperare renewable,recyclable andbiodegradable butare poorbarriersto oxygenandwaterdue
to the presence of wide pores. Laminatingwithpolymers,suchasLDPE, can yieldproductswith
sufficientbarrierperformance,butatthe expense of recyclabilityand biodegradability). Tocombat
thisproblem,nanocelluloseisunderwidespreadinvestigation. Itisbiodegradeableandrenewable
and nanocellulosefilms possesseslowoxygen (Aulinetal.,2010) and moderate watervapour
permeability,somethingthatcanbe improvedbyformingnanocellulose-nanoparticlecomposites
(Varanasi etal.,2018). There remainsthe questionof the recyclabilityof the filmsandthe effectof
recyclingonthe properties. Thisisaddressedinthisstudy.
Methods
The material testedwasa commercial,never-driedJapaneseMFCwithan average diameterof 73
nm (Varanasi etal.,2013). A large numberof virginNC sheets were preparedbyspraying
(Shanmugametal.,2018; Shanmugametal.,2017). These virginNCsheets were thenrecycled using
laboratorydispersiontechniques,underISOstandardconditions,toproduce nanofibre suspensions.
Followingdispersion,the nanofibre suspensionwasthenformedintosheetsusingvacuumfiltration.
For comparison,anothersetof sheetsfromthe virgin fibreswasalsoformed.

2. The air permeance of driedfilmswasmeasuredwithanL&W air permeance tester. Watervapour
permeabilitywasevaluatedaccordingtothe ASTMstandard(E96/E96M-05) methodusing
anhydrousCalciumChloride. Zero-spanstrengthwasmeasuredwithaPulmactroubleshooter.
Result and Discussion
Table 1 summarisesthe resultsonthe virginandrecycledfibresandfilms. The resultsare presented
inorder of the lengthscale overwhichtheyare measured. Itcan be seenthatthere isno evidence
of observabledifferencesinthe filmsatthe individual fibre levelorat SEM underhighmagnification.
The major differencesshowupatlargerlengthscales. The recycledfilmsare lessdense andhave
pooreroptical uniformityatsmallerlengthscales.Thesedifferencesare probablydue tosmall
aggregatesfromthe virginsheetthathave failedtofullyseparate duringthe recyclingprocess.
These aggregateshave hinderedthe uniform, densepackingof the nanofiberstoforma sheetusing
vacuumfiltration. Thishasthenreducedthe densityof the sheet, increasingthe watervapour
permeabilityanddecreasing the tensile strengthatbothsmall (Varanasi etal.,2012) andlarge (100
mm span) inspection scales.
Table 1 – Effect of Recycling on Properties of NC fibres
Measurement Technique Area
examined
Virgin film Recycled film
SEM Measurement of Fibre diameter 1 micron scale
bar
69 nm 69 nm
SEM Measurement of Film Surface 10 micron scale
bar
No differences
observed
No differences
observed
Optical Profilometry roughness 100 x 90
microns
No differences
observed
No differences
observed
Film density 110 micron
thick
831 kg/m3 741 kg/m3
Zero-span strength Estimated 300
micron span
length
100 Nm/g 72 Nm/g
PPF tester of optical uniformity 1-15 mm
inspection
areas
More uniform Less uniform
Water Vapour Permeability 63.5 mm
diameter circle
of film
5.5x10-11
g/m.s.Pa, 1.2x10-10
g/m.s.Pa,
Air permeability 50 cm2
sample <0.003 µm/Pa.S 0.045 µm/Pa.S
Tensile strength via Instron Method 100 mm test
span
64 Nm/g 42 Nm/g

3. Conclusion:
The recyclingof NC reducesstrengthandbarrierperformance. However,barrierperformance isstill
much betterthanconventional cellulose basedpackaging. The majorissue appearstobe that the
recyclingprocesshasnotcompletelybrokendownthe nanocellulosesheetsinto individual fibres.
Acknowledgements
We acknowledge the assistance of Mr. Hamid Doosthosseini in performing the experiments. The
financial support from the Australian Research Council, Australian Paper, Carter Holt Harvey, Circa,
Norske Skog and Visy through the Industry Transformation Research Hub grant IH130100016 are
acknowledged.
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