Cellulose nanocomposites processing: challenges and

possibilities

Kristiina Oksman University of Oulu

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Content

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‒  Processesusedforpreparingcellulosenanocomposites‒  Challengestobesolved‒ Meltprocessingofnanocomposites‒  Someexamples‒  FiDiProprojectatOulu‒  Summary

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Research on cellulose nanocomposites processing: 1995-2015 (ISI Web of Sci. July 2015)

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1995-2000 2004 2006 2008 2010 2012 2014

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Oksman et al. Review in Composites part A, 83 (2016) 2-18

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Popular processing methods

Solu%oncas%ng‒  Polymerisdissolvedandmixedwithnanocelluloses‒  Solventisevaporated‒  RestrictedtoflatfilmsMeltprocessing‒  BatchorconDnuousmixing‒  Possibletomakedifferentshapes,largescaleFoaming‒  Freezedrying‒  Foamingusingblowingagentsorgasandpressure

<

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Popular processing methods

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Fiberspinning‒  Dryspinning,meltspinning,wetspinning‒  Electrospinning

Impregna%on ‒  Nanofibernetworkimpregnatedwithpolymer‒  ParDallydissolvedcellulose(all-cellulose)

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Challenges

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‒  DispersionanddistribuDonofNCinpolymer‒  InterfacialadhesionbetweenNCandpolymer‒  RemovethesolventwithoutaffecDngthepolymerorinterface

‒  Alignmentofnanofibersinthecomposite‒  Controlthefeedingofnanomaterialintheextruder‒  Freezedriednanocellulosescancausehealthproblem‒  ImpregnaDonofdensenanofibernetworkwithpolymer

S Geng LTU, In-situ polym.

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Batch processing

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‒  Twin-screwmicro-extrudersorBrabenderblenders‒  Smallscale,batchsize5-15ml‒  Onlysmallamountofmaterialisneeded‒  Polymerismeltedfirstandnanocelluloseisusuallyaddedasfreezedriedpowder

‒  LongprocessingDme10-20min‒  Usuallyatm.orvacuumvenDngarenotaccessible‒  Difficulttodispersenanomaterials‒  LongprocessingDmedegradethepolymer‒  Goodwaytotestmaterialbutnoteasytoconverttoindustry

Oksman et al. Review in Composites part A, 83 (2016) 2-18

DSM

Brabender

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•  Haakemini-extruder•  3Dmes,pelleDzingstepbetween

extrusions•  PLAmatrix•  Cellulosenanocrystals5%•  Anionicsurfactantwasusedas

dispersionaid5,10,20%

Dispersion and characteristics of surfactant modified cellulose whiskers nanocomposites Daniel Bondeson & Kristiina Oksman

Freeze dried CNC

Freeze dried S-CNC

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modified cellulose whiskers nanocomposites DANIEL BONDESON 1 and KRISTIINA OKSMAN 1,2,∗

Materials Modulus (GPa)

Strength (MPa)

Strain (%)

PLA-S5 2.6 + 0.1 35.1 + 3.6 1.8 + 0.3

PLA-CNC5-S5 3.1 + 0.2 52.4 + 0.4 3.1 + 0.2

SurfactantimproveddispersionCNC improved mechanical properties

Dispersion and characteristics of surfactant modified cellulose whiskers nanocomposites Daniel Bondeson & Kristiina Oksman

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Continuous twin screw-extrusion

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‒  Co- and counter-rotating twin screw extruders ‒  Co-rotating is better in mixing and dispersing ‒  More effective in removal of volatiles and moisture

and is also more flexible ‒  Feeding of NC is a challenge

OksmanK;MathewAP;BondesonD;KvienI.Comp.Sci.Technol.66(2006)2776–2784

FreezedryingandgranulaDon

•  +

Liquid-assisted feeding ‒  Fibers/crystals are dispersed in a

liquid ‒  Removal liquid during process

Dry feeding ‒  Master-batch with high nanocellulose

content ‒  Diluted during extrusion

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Co-rotaDngtwinscrewextruder300rpm,3kg/h,185-200°C

SolventevaporaDon

LiquidconsisDngofCNF,solventsandplasDcizer(GTA)

Blown film with CNF Fraunhofer (Hendrik Roch)

PLA-20GTA-1CNF

PLA

PLA-20GTA

Herrera et al, CSTE, 106 (2015) 149-155

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SIPN nanocomposites based on PLA-PU and CNC PhD student Jatin Sethi

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AIM:CreateIPNnanocompositeswithsynergisDceffects‒  S-IPNofPLA(70wt%)andPU(30wt%)wassuccessfullycreatedandfurtherreinforcedbyCNCs.

‒  ConDnuousPUnetworkinPLAmatrix,CNCarelocatedinPUphase

‒  AddiDonofCNCenhancedmechanicalandthermalproperDesofthenanocomposites

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Dispersion of sugar beat nanofibers Dr Maiju Hietala and Dr Sunanda Sain

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Aim:studyre-dispersionofnanofiberswithoutchemicaltreatmentsoraddiDves

‒  Wehaveuserawmaterialwhichiseasytoseparatetonanosize,cheap(residue)andalsousedasourcecontainingpecDn

‒  RawmaterialwasbleachedbeforefibrillaDon,

‒  DriedSB-CNFfilmswerere-dispersedinwater

Re-dispersion

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Dispersion of sugar beat nanofibers Dr Maiju Hietala and Dr Sunanda Sain

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‒  Resultsconfirmedthatsugarbeatnanofiberscanbere-dispersedajerdried

‒  ViscosityoftheredispersedNFwasclosetoundriedNF‒  Re-dispersedNFformsagel,andnanofibersarevisibleinmicroscopyimages

‒  MechanicalproperDesofnanofibernetworkbasedonre-dispersedmaterialhadsimilarsDffnessand~70%ofthestrengthcomparedtooriginalNF

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Summary

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‒  MostcommonprocessingmethodsaresolventcasDng,extrusion,foaming,spinning,impregnaDon

‒  Challengestodispersethenanocelluloses,createagoodinterface,removalofsolvents,feedthenanocelluloseintotheextrusionprocess

‒  Batchprocesswheremicro-extrudersorBrabenderblendershavebeenused,theseareforsmallscaletesDngwhereonlylimlematerialisavailable

‒  Twinscrewextrusionisapromisingprocessifindustrialscaleandlargeseriesisthetarget

‒  Liquidfeedingisagoodwaytofeedanddispersenanomaterials‒  IntheFiDiPro-projectweareworkingwithdispersionofnanofibers,

developmentofimpregnaDonprocessanddevelopingnanocompositeswithIPNstructure