Focus Areas 2/3Focus Areas 2/3

Forest Nanomaterials/Control of Forest Nanomaterials/Control of Water Lignocellulosic Interactions Water Lignocellulosic Interactions

for Modification of Propertiesfor Modification of Properties

Technical Challenges

Nano-fractionalization and nano-catalysis for separations;

Non covalent disassembly/re-assembly

Entropic effects in the assembly anddisassembly of nanomaterials in forestmaterials

Focus Area 2: Forest Nanomaterials

Target:

Liberation and use of nanocellulosebuilding blocks

Cellulose MorphologyCellulose Morphology((William T. Winter, Cellulose Research Institute, SUNY – ESF, William T. Winter, Cellulose Research Institute, SUNY – ESF,

Syracuse NY)Syracuse NY)

Fiber (cell)

White pine tracheids

ESF archives

Wood Cell Schematic

Cote -ESF

Microfibril

Hanna, ESF

Cellulose NanowhiskersCellulose Nanowhiskers

Field-emission electron micrograph of freeze-dried cellulose whiskers of nanoscale cross-sectional dimensions prepared at Paprican’s Vancouver laboratory from H2SO4 hydrolyzed bleached Kraft softwood pulp

W. Hamad. Can. Jour. Chem. Eng. 84. Oct. 2006. pp513 – 519

200 nm

Nanocrystalline CelluloseNanocrystalline Cellulose

25% - 30% 25% - 30% strength of strength of Carbon Carbon NanotubesNanotubes

William T. Winter, Cellulose Research Institute, SUNY – ESF, Syracuse NY 13210

0

5

10

15

20

25

0.001 0.1 10 1000

Aspect Ratio (l/d)

Sur

face

Are

a/V

olu

me

in u

nits

of

(2 /

V)1/

3

Surface Area vs. Aspect RatioSurface Area vs. Aspect Ratio

Cellulose Nanocrystals:

Length: 100 nm – several m

Diameter: 3 – 20 nm

Aspect Ratio:

10 – 10,000

Montmorillonite Clay:

Length: 1 nm

Diameter: 200 – 400 nm

Aspect Ratio:

0.005 – 0.0025 (200 – 400)

William T. Winter, Cellulose Research Institute, SUNY – ESF, Syracuse NY 13210

Crystal and Microfibril PreparationCrystal and Microfibril Preparation((William T. Winter, Cellulose Research Institute, SUNY – ESF, William T. Winter, Cellulose Research Institute, SUNY – ESF,

Syracuse NY)Syracuse NY)

Microfibrils

Nanocrystals

+ Acid

• acid (HCl, H2SO4)

• concentrations ( 65%)• temperature (40°C)• hydrolysis time (1 – 2 h)• acid-to-substrate ratio (0.1

– 0.5 mol/g)

Hydrolysis (for nanocrystals):

Extraction, Bleaching:

1. Dewax- Soxhlet

2. Mill

3. Alkali solution

4. Sodium chlorite

5. homogenize

Liberation and Use of NanocelluloseLiberation and Use of Nanocellulose

NeedNeed Identify/develop more commercially attractive Identify/develop more commercially attractive

methods to liberate nanocellulose, in either the methods to liberate nanocellulose, in either the whisker or crystalline formswhisker or crystalline forms

Once liberated, nanomaterials must be:Once liberated, nanomaterials must be: CharacterizedCharacterized StabilizedStabilized Incorporated into existing and new applicationsIncorporated into existing and new applications

Focus Area 3 : Understand thecontrol of water-lignocelluloseinteraction for modification ofproperties

Target Understand water forest materialsinteractions

Control effects of water on wood andpaper properties

Shed water more efficiently

Technical Challenges

Interfacial properties at nanoscale

Production of hydrophilic/hydrophobic switchable surfaces

Biological activity control

BackgroundBackground

The response of lignocellulosics to moisture (liquid and vapor) is The response of lignocellulosics to moisture (liquid and vapor) is due almost entirely to the supermolecular structure of the due almost entirely to the supermolecular structure of the biopolymers and nanoscale structures of the composites that biopolymers and nanoscale structures of the composites that comprise the wood fibercomprise the wood fiber Primary microfibrils – 4 –10 nm in cross-sectionPrimary microfibrils – 4 –10 nm in cross-section Microfibril angleMicrofibril angle Degree of crystallinityDegree of crystallinity

Species, growing conditions, processing conditions – all affect Species, growing conditions, processing conditions – all affect interactions between water and lignocellulosicsinteractions between water and lignocellulosics

BackgroundBackground

Control/modification of surfaces of lignocellulosic materials using Control/modification of surfaces of lignocellulosic materials using nano coatings or impregnation of nano particles can be used to nano coatings or impregnation of nano particles can be used to provide physical/chemical barriers to modify the effect of moisture provide physical/chemical barriers to modify the effect of moisture by changing wetting (hydrophilicity/hydrophobicity) and adhesion by changing wetting (hydrophilicity/hydrophobicity) and adhesion forces. forces. Durability and other end use properties of wood and paper Durability and other end use properties of wood and paper

products closely tied to the response to moistureproducts closely tied to the response to moisture Interfiber bond strength - paperInterfiber bond strength - paper Dimensional stability – wood and paperDimensional stability – wood and paper Decay, fungi, rot, UV stability - woodDecay, fungi, rot, UV stability - wood

Very large volumes of water are handled in the manufacture of Very large volumes of water are handled in the manufacture of forest products. Nano materials which can modify drainage rates forest products. Nano materials which can modify drainage rates and drying could result in significant reductions in energy and drying could result in significant reductions in energy requirements. requirements.

WATER VAPOR AS A PROBE TO WATER VAPOR AS A PROBE TO CHARACTERIZE SURFACES AND CHARACTERIZE SURFACES AND

NANOSTRUCTURESNANOSTRUCTURES

M OISTURE P ICK UP AND RELATIVE HUM IDITY vs. TIM E

5 10 15 20 25 30 35 40 45

TIME (hours)

2.18

2.20

2.22

2.24

2.26

2.28

2.30

MO

IST

UR

E P

ICK

UP 0

10

20

30

40

50

60

70

80

RE

LA

TIV

E H

UM

IDIT

Y

W ATER VAPOR ADSORPTION ISTHOERM

CELLULOSE POW DER (CF 11)

0.0 0.2 0.4 0.6 0.8 1.0

RELATIVE VAPOR PRESSURE (p/p0)

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

FM

C/(p

/p0)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

FR

AC

TIO

NA

L M

OIS

TU

RE

CO

NT

EN

T (F

MC

)

WATER VAPOR ACCESSIBLE SURFACE AREA AND WATER VAPOR ACCESSIBLE SURFACE AREA AND SURFACE ENERGY OF ADSORPTION FOR SELECTED SURFACE ENERGY OF ADSORPTION FOR SELECTED

MODEL COMPOUNDS AND PULPSMODEL COMPOUNDS AND PULPSPULP SAMPLEPULP SAMPLE AVERAGE S. A.AVERAGE S. A.

(m(m22/g)/g)

AVERAGE S.E.A.AVERAGE S.E.A.

(ergs/cm(ergs/cm22))

Microgranular Cell.Microgranular Cell.

(model)(model)103.71103.71 189.85189.85

CarboxyMethyl Cell.CarboxyMethyl Cell.

(model)(model)215.89215.89 197.12197.12

Xylan Powder - LarchXylan Powder - Larch

(model)(model)349.20349.20 198.14198.14

Softwood Bleached KraftSoftwood Bleached Kraft 173.57173.57 171.87171.87

TMP TMP 226.32226.32 137.14137.14

Radiata Pine PulpRadiata Pine Pulp 148.7148.7 175.2175.2

Pine (Russian)Pine (Russian) 144.4144.4 174.1174.1

EucalyptusEucalyptus 132.7132.7 187.7187.7

SummarySummary

Lignocellulosic fiber is a nanocompositeLignocellulosic fiber is a nanocomposite Water accessible surface areaWater accessible surface area determined by determined by

nanostructure which is dependent on species and nanostructure which is dependent on species and pulping processespulping processes

Surface energy of adsorptionSurface energy of adsorption Model compounds show impact of different functional Model compounds show impact of different functional

groups and the concentration of those groups on the groups and the concentration of those groups on the surfacesurface

Pulps show differences due to both pulping process Pulps show differences due to both pulping process and speciesand species

Eucalyptus has a lower accessible surface area, but a significantly Eucalyptus has a lower accessible surface area, but a significantly higher surface energy of adsorption indicating a higher higher surface energy of adsorption indicating a higher concentration of hydrophilic groups on the accessible surfaceconcentration of hydrophilic groups on the accessible surface

ExamplesExamples

1 cm

Growthrings

50 m

Cell wall layers

Relate to Macroscopic PropertiesRelate to Macroscopic Properties

ESEM - Environmental Scanning Electron Microscope

Dry sheet Moisturized sheet

News, 45 g/m²News, 45 g/m²

G. A. Baum 2003

Water Droplets on “Nanoseal” Water Droplets on “Nanoseal” Treated WoodTreated Wood

Nanoparticles adhere directly to the substrate molecules (molecular bonding) and assemble into an invisible ultra-thin nanoscopic mesh providing a long lasting, self-cleaning, hydrophobic surface. The wood is protected against decay, fungi and rot. It is dimensionally and UV stable. It will not wear off and cannot be removed by water, normal cleaning agents or high pressure equipment.

Wood Surface Repels Water DropletsWood Surface Repels Water Droplets

Water droplets rest on a wood surface impregnated with BASF’s “Lotus Spray”

The surface is superhydrophobic . Thus contact area between the surface of the wood and the water is reduced to a minimum, and the adhesive forces are greatly decreased making the water drops assume a globular form.