1. Focus Areas 2/3 Forest Nanomaterials/Control of Water Lignocellulosic Interactions for Modification of Properties

2. Focus Area 2: Forest Nanomaterials
Technical Challenges
Nano-fractionalization and nano-catalysis for separations;
Non covalent disassembly/re-assembly
Entropic effects in the assembly and
disassembly of nanomaterials in forest
materials
Focus Area 2: Forest Nanomaterials
Target:
Liberation and use of nanocellulose
building blocks

3. Cellulose Morphology (William T
Cellulose Morphology (William T. Winter, Cellulose Research Institute, SUNY – ESF, Syracuse NY)
Left – SEM of exploded
Right – schematic of a tracheid - Cote-
Fiber (cell)
White pine tracheids
ESF archives
Wood Cell Schematic
Cote -ESF
Microfibril
Hanna, ESF

4. Cellulose 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 Oct pp513 – 519

5. Nanocrystalline Cellulose
200 nm
William T. Winter, Cellulose Research Institute, SUNY – ESF, Syracuse NY 13210
25% - 30% strength of Carbon Nanotubes

6. Surface Area vs. Aspect Ratio
Montmorillonite Clay:
Length: 1 nm
Diameter: 200 – 400 nm
Aspect Ratio:
0.005 – (200 – 400)
Cellulose Nanocrystals:
Length: 100 nm – several mm
Diameter: 3 – 20 nm
Aspect Ratio:
10 – 10,000
William T. Winter, Cellulose Research Institute, SUNY – ESF, Syracuse NY 13210

7. Crystal and Microfibril Preparation (William T
Crystal and Microfibril Preparation (William T. Winter, Cellulose Research Institute, SUNY – ESF, Syracuse NY)
Extraction, Bleaching:
Dewax- Soxhlet
Mill
Alkali solution
Sodium chlorite
homogenize
Hydrolysis (for nanocrystals):
acid (HCl, H2SO4)
concentrations ( 65%)
temperature (40°C)
hydrolysis time (1 – 2 h)
acid-to-substrate ratio (0.1 – 0.5 mol/g)
Microfibrils
Nanocrystals
+ Acid
20g in 400mkl toluene/200ml ethanol

8. Liberation and Use of Nanocellulose
Need
Identify/develop more commercially attractive methods to liberate nanocellulose, in either the whisker or crystalline forms
Once liberated, nanomaterials must be:
Characterized
Stabilized
Incorporated into existing and new applications

9. Focus Area 3 : Understand the control of water-lignocellulose
interaction for modification of
properties
Target
Understand water forest materials
interactions
Control effects of water on wood and
paper properties
Shed water more efficiently
Technical Challenges
Interfacial properties at nanoscale
Production of hydrophilic/hydrophobic
switchable surfaces
Biological activity control

10. Background
The response of lignocellulosics to moisture (liquid and vapor) is due almost entirely to the supermolecular structure of the biopolymers and nanoscale structures of the composites that comprise the wood fiber
Primary microfibrils – –10 nm in cross-section
Microfibril angle
Degree of crystallinity
Species, growing conditions, processing conditions – all affect interactions between water and lignocellulosics

11. Background
Control/modification of surfaces of lignocellulosic materials using nano coatings or impregnation of nano particles can be used to provide physical/chemical barriers to modify the effect of moisture by changing wetting (hydrophilicity/hydrophobicity) and adhesion forces.
Durability and other end use properties of wood and paper products closely tied to the response to moisture
Interfiber bond strength - paper
Dimensional stability – wood and paper
Decay, fungi, rot, UV stability - wood
Very large volumes of water are handled in the manufacture of forest products. Nano materials which can modify drainage rates and drying could result in significant reductions in energy requirements.

12. WATER VAPOR AS A PROBE TO CHARACTERIZE SURFACES AND NANOSTRUCTURES

15. Softwood Bleached Kraft
WATER VAPOR ACCESSIBLE SURFACE AREA AND SURFACE ENERGY OF ADSORPTION FOR SELECTED MODEL COMPOUNDS AND PULPS
PULP SAMPLE
AVERAGE S. A.
(m2/g)
AVERAGE S.E.A.
(ergs/cm2)
Microgranular Cell.
(model)
103.71
189.85
CarboxyMethyl Cell.
215.89
197.12
Xylan Powder - Larch
349.20
198.14
Softwood Bleached Kraft
173.57
171.87
TMP
226.32
137.14
Radiata Pine Pulp
148.7
175.2
Pine (Russian)
144.4
174.1
Eucalyptus
132.7
187.7

16. Summary Lignocellulosic fiber is a nanocomposite
Water accessible surface area determined by nanostructure which is dependent on species and pulping processes
Surface energy of adsorption
Model compounds show impact of different functional groups and the concentration of those groups on the surface
Pulps show differences due to both pulping process and species
Eucalyptus has a lower accessible surface area, but a significantly higher surface energy of adsorption indicating a higher concentration of hydrophilic groups on the accessible surface

17. Examples

18. Relate to Macroscopic Properties
1 cm
Growth
rings
50 mm
Cell wall layers

19. News, 45 g/m² Moisturized sheet Dry sheet
ESEM - Environmental Scanning Electron Microscope
G. A. Baum 2003

20. Water Droplets on “Nanoseal” Treated 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.

21. Wood 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.