Introduction to Natural Nanomaterials

Kristiina Oksman Niska

Wood and Bionanocomposites

Composite Center Sweden

Luleå University of Technology

The 2nd International Musical Instruments Seminar, 14-16 September 2011, Joensuu, Finland

Introduction Nanomaterials from biomass Separation processes Properties Preparation of nanocomposites Examples of nanocomposites and

other nanomaterials based on cellulose Conclusions

Outline

Nanocellulosic materials– Nanofibers/fibrils– Nanocrystals/whiskers– <100 nm in one

dimension Nanocomposites

– Polymer where the nano-sized cellulose is used to improve the properties

Nanocelluloses and nanocomposites

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Cellulose nanocomposites/nanofib*/nanowhiskers/nanocrystals/microfib*

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Cavaille et al Grenoble, FranceNanocrystals & composites

Research on nanocellulose materials and composites: 1995-2011 ( ISI Web of Sci. Sept 2011)

Taniguchi and Okamora, Niigata, JapanMicrofibrillated Cellulose

Glasser, Virginia Tech, USAWinter et al, Suracuse, USANanocrystals and composites

Yano et al, Kyoto, Japan, Zimmermann et al EMPA, SwitzerlandOksman et al NTNU, NorwaySimonsen et al, Oregon, USASain et al, UofT, Canada

Research interests are focussed on Raw materials sources & separation Large scale / pilot scale production methods Chemical modifications Properties Composite materials development Modelling Assembling of organized structures Product design

Increased industrial interest to use agro or forest based nanomaterials

Activities today

Cellu Comp, Carrot Stix™ www.cellucomp.com

H Yano, Kyoto, Japan

Sport goods: With over 50,000 Carrot Stix rods sold during 2009, the Carrot Stix was the best-selling product in its price category (Nanopatents and Innovations March 2010)

Hierarchical structure of wood

Soft wood fiber, diam 20-30 mm, length 2-5 mm Nanofibers, diam <100 nm, length > mm Crystallites, width < 5 nm, length < 300 nm Mechanical properties increases with decreased size Softwood = E-modulus about 12 GPa and strength

100 MPa Wood nanocrystals = E-modulus about 140 GPa and

strength 10000 MPa

Examples of nanofibers and nanocrystals

Cellulose nanofibersCellulose nanocrystals Bacterial cellulose Collagen nanofibrils

Cellulose crystals/whiskers originate from wood, plants or crops, width ~ 5 nm, length >200 nm depending on the source

Cellulose nanofibers originate from wood, plants, crops or bacteria width below 100 nm, length up to µm scale

Collagen fibrils orginate from animal sources, width 50-500 nm length up to mm scale

Nanosize?

Water molecule < 1 nm

Bacteria ~1,000 nmBlood cells ~ 6,000 nm

Kristiina ~1,550,000,000 nm

Width of a strand of hair ~ 100,000 nmAnts ~ 6,000,000 nm

1 nm

1 m

1 mm

1 μm

Nanometer scale

gettyimages® / www.eas.int / www.cabrillo.edu

Separation of nanocelluloses:Nanofibers and nanocrystals

Mechanical treatments Ultra fine grinding High pressure

homogenizing Ultra sonication Cryo crushing

Chemical treatments Acid hydrolysis Enzymatic treatment

Mechanical vs chemical treatmentCellulose nanofibers from saw dust

Highly coiled and entangled fibers: Ø 10-20 nm, L microns

Straight and rigid units: Ø 1.5-3 nm, L microns

Mechanical separation of nanofibers

Soaking in water and mixing

Fiber suspensionRefining (grinding) Is

olati

on p

roce

ss

Repeated until gel formation

Wood

Bleaching (Chlorite )

Purifi

catio

n

Pretreaments(Tempo, Enzymes)

Nanofiber suspension

Cellulose

Nanofibers from biobased resourcesBarley straw Grass straw Oat straw Carrot residueCellulose

500 nm

Ethanol

500 nm

Methanol

Sample preparation for Electron Microscopy

Solvent exchange

Drying

Coating with gold

Dried fibers from water

No coating

Nanopaper preparation

CNF dispersed in water

Vacuum filtration

Hot pressing

Mechanical properties of the nanofiber networks

Nanofiber papers prepared by vacuum filtration and pressing

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E-Modulus (GPa)

Strength (MPa)

Strain at break (%)

Woodfiber 1.3 ± 0.3 16 ± 1 2.4 ± 0.7

Woodnanofiber 11.2 ± 0.8 183 ± 14 5.0 ± 0.9

Residue (sludge)

12.5± 0.4 151 ± 4 2.8 ± 0.6

Carrot 13.3 ± 0.8 204 ± 25 3.1 ± 0.5

Wood, sludge and carrot nanopapers have similar properties Reduced fiber size better network better mech. prop

Isolation of cellulose nanocrystals/whiskers

D. Bondeson, A. Mathew, K. Oksman, Cellulose, 13 (2), 2006, 171-180

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HCL or H2SO4

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Heating

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Sonication

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Centrifugation

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Dialysis

1.H2O

+MCC

MCC Cellulose whiskers

200 nm20 m

10 – 15 m

Acid hydrolysis with HCL or H2SO4

amorphous cellulose

crystalline cellulose

100 nmLength: < 300 nm

Width: < 10 nm

Characterization of crystals

Flow birefringence between polarized filters

AFM

Elementary fibrils

Amorphous regions

Crystalline regions

Microcrystalline cellulose: crystalline and amorphous regions

Crystals/whiskers have high crystallinity

XRD before and after separation

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Dimensions measurement using AFM

Tip broadening effect

Sample preparation

1 μm 1 μm

62.2 nm 40.8 mV

Height image Amplitude image

pair Height (nm)

blue 8.776

red 5.402

green 5.171

1 μm

Cellulose nanocrystals from bioresidues

Large scale production of cellulose nanocrystals? We have found that lignin residue from bioethanol production

has a high cellulose content This cellulose can be separated to nanocrystals using only

mechanical processing

Oksman et al, Biomass and Bioenergy 35(2011)146-152

Cellulose based nanocomposites

Cellulose nanofibers or crystals as reinforcements or additives in polymers

Interesting properties−High mechanical properties−High thermal stability−Large surface area −Bio-compatible−Light weight−Optically transparent−High water binding capacity

Nanocomposites and their processing

Films/ sheets Solvent casting For nanofibers and crystals Polymer is dissolved in a solvent,

nanocelluloses are added and the solvent is evaporated

Usually water soluble polymers are used

Thermoset composites Nanopaper sheets are

impregnated with thermoset resin High nanofiber content Good mechanical properties

Melt compounding

Feeding of nanocrystals/fibers in to the extruder is a challenge

Dry feeding Masterbach with high nanocellulose

content Diluted during extrusion

Liquid feeding Fibers/crystals are dispersed

in a liquid Removal liquid Degradation the polymer

Freeze drying and granulation

+

Nanocellulose fibers and crystals, thermplastic matrix

Content is low < 5% Industrial process Possible to injection mould

Motor

Feeding

Heating and Mixing

Other possibilities to use nanocellulose

Continuous nanofibers Electrospinning of nanofibers Aligned cellulose fibers Reinforced with nanocrystals Improve fiber properties

Coatings Use nanocellulose to improve

adhesion between fibers and resin

Improve mechanical properties of the laminate, paper etc

Improve barrier properties

Electrospinning of nanofibers

Several nanofibers are spun and collected on the collector

Polymer nanofibers

More possibilities

Aerogels, extremly lightweight materials Aerogels are solid materials with a

density as low as 2 mg/cm3

Both whiskers and nanofibers Freeze and supercritical CO2 drying

Colored thin films Nanowhiskers Self-assembling Surface structure

Araki J; Wada M; Kuga S; Okano T. Langmuir 2000, 16, 2413

Cranston E and Gray D, Biomacromolecules 7 (2006) 2522

Cellulose nanocomposites for medical use

Composites with cellulose nanofibers (Domsjö cellulose)

• Strength 28-40 MPa and strain 20-30% at body temperature and high moisture conditions*

• Biocompatible

*Santis de R, et al. Comp Sci Technol 2004;64:861-871

LTU Dr. AP Mathew (TEM-PLANT EU-project)

Mechanical properties of cellulose-collagen nanocomposites for ligament application

Effect of simulated body conditions and sterilization

SamplesStrength

(MPa)Strain

(%)E-Modulus

(GPa)

Collagen 56.2 ± 12.8 2.7 ± 1.2 3.5 ± 0.7

Cell-Coll 96.2 ± 12.2 1.4 ± 0.5 7.4 ± 0.8

XCell-Coll 186.2 ± 34.2 2.4 ± 0.5 14.5 ± 0.7

Cell-Coll (95RH 37°C) 35.1 ± 2.7 28.0 ± 3.1 -

XCell-Coll (95RH 37°C) 42.3 ± 4.7 19.0 ± 4.2 -

Cell-Coll (95RH 37°C)_ste 37.4 ± 3.7 17.4 ±4.7 -

XCell-Coll (95RH 37°C)_ste 57.8 ± 12.7 15.1 ± 4.1 -

Prototypes

Stable in PBS medium (phosphate buffered saline)

NFPD Tubules Braided NFPDBraided XColl-Cell

Possible applications

High-strength spun fibers and textiles Advanced composite materials Films for barrier and other properties Additives for coatings, paints, lacquers and adhesives Optical devices Electronic applications, lightweight batteries Pharmaceuticals and drug delivery Bone and ligament replacements Hydrogels Aerogels Improved paper, packaging applications New building products Additives for food and cosmetics Separation membranes

Some conclusions Increased interest for natural and renewable

nanomaterials Bio based residues can be used for separation

of natural nanomaterials Nanomaterials are separated to nanosize using

chemical/mechanical processing Nanocomposites processing methods are

casting, impregnation, compounding, spinning, freeze and supercritical CO2 drying

Nanomaterials can be used in medical applications, aerogels, nanomembranes coatings, textiles, composites, packaking appl. etc.

Thank you for listening…

Thank my research team for all results and hard work

Yield of the separation process of nanocelluloses

Cellulose content and yield was highest for lignin residue followed by oat straw > carrot residue > barley straw > grass straw

Materials Lignin residue

Oatstraw

Carrotresidue

Barleystraw

Grassstraw

Yield 48% 23% 20% 14% 13%