GREEN NANOCELLULOSIC
BARRIERS
Art J. Ragauskas
Yulin Deng
Georgia Institute of Technology
Junyong Zhu
Forest Product Laboratory
October 2013
Objectives and presentation outline
• Study the energy consumption of NFC preparation and their effects
on the NFC properties
• Develop high performance barrier packaging materials from NFCs:
Three approaches
– Thermal treatment of pure NCFs film to achieve high performance films
– Film formation from different solvent
– Improve barrier properties by adding high aspect ratio of nanoclay or graphene to the
NCF films
• Develop several new nanomaterials, including hydrogels prepared
from cross-linked nanofibrillated cellulose, and nanolignin
2
Objective-I: Study the energy consumption
of NCF preparation
•
Common methods for preparing NFCs
– Mechanical homogenization
• Energy Intensive 72-108 GJ/Ton
• High energy costs
– Chemical pretreatment of cellulose with 2,2,6,6-tetramethylpiperidine-1-oxyl
(TEMPO)
• TEMPO is expensive and toxic
Our focus: The relationship of energy consumption and NCF properties using
SuperMassColloider
– Work was done at FPL-USDA
Y. Deng; J. Lee, 2007 AIChE Annual Meeting, Salt Lake City, Nov. 2007.
D. Bondeson; K. Oksman, Cellulose, (2006) 13, 171-180.
A. N. Nakagaito; H. Yano, Applied Physics A: Materials Science and Processing, (2004) 78, 547-552.
S. Iwamoto; A. N. Nakagaito; H. Yano, Applied Physics A: Materials Science and Processing, (2007) 89.
3
Approach: Characterization of cellulose
nanofibrillation by micro grinding
To characterize pulp fibers at different stages of fibrillation using a commercial
grinder and to evaluate the morphological aspects of fibers and its effect on the
performance aspects of cellulose films made from various stages of fibrillation
Experimental
Material used
Mechanical fibrillation
(Fibrillated pulp sampled
periodically)
4
Bleached softwood kraft pulp (BKSP)
Super MassColloider
Characterization of pulp fibers at different
stages of fibrillation
Maximum fibrillation within
2h of grinding
SEM images of samples at different
fibrillation times: (a) pure pulp ; (b) 2 h
Fibrillated to submicron
and nano fibrils
SEM images of samples at different fibrillation times: (a,b,c)
0.25 h; (d,e,f) 0.50 h
5
Characterization of pulp fibers at different
stages of fibrillation
Lateral dimensions of the
smallest nanofibril aggregates
are between 15-40 nm
AFM images of samples at different fibrillation times:
(a) 0.25 h; (b) 2 h
Fibrillation
time (h)
WRV (%)
0
78.2 (1.0)
Cellulase
adsorption
(mg/g
substrate)
16.4 (0.6)
0.25
149.4 (1.2)
21.3 (0.8)
0.50
187.8 (9.8)
28.8 (0.5)
1
203.5 (27.1)
32.8 (1.0)
2
230.8 (18.6)
37.5 (2.4)
4
227.8 (7.9)
36.5 (0.8)
6
248.7 (35.6)
35.5 (0.7)
Degree of fibrillation
6
Degree of polymerization (DP) and crystallinity of
the films at different fibrillation times
NCF film physical properties
(a) 250
(a) 1.8
200
1.4
Density (g/cm3)
Tensile strength (MPa)
1.6
150
100
0.8
0.6
0.2
0
0
0.25
0.5
1
2
4
1
6
(b) 12
10
8
6
4
2
0
0
0.25
0.5
1
2
Fibrillation time (h)
4
2
3
4
5
Fibrillation time (h)
Fibrillation time (h)
Strain (%)
1
0.4
50
0
7
1.2
6
6
7
Conclusions of Objective I: Energy consumption of
NFC preparation
•
Micro grinder could be used to produce nanosized cellulose fibrils (<100 nm in
diameter)
•
At current setup, two hours fibrillation is enough for preparing high quality NFCs.
Current work published
(Hoeger, I. C., Nair, S. S., Ragauskas, A. J. Deng, Y., Rojas, O. J., & Zhu, J. Y.
(2013). Mechanical deconstruction of lignocellulose cell walls and their enzymatic
saccharification. Cellulose 20(2),807-818
Current work being reviewed for publication
(Nair, S. S., Zhu, J. Y., Deng, Y., & Ragauskas, A. J. (2013). Characterization of
cellulose nanofibrillation by micro grinding. Journal of Nanoparticle Research (In
Review)
8
Objective-II: Develop higher performance
barrier packaging from NCFs
• Barrier Packaging
– Serves as Barrier to:
• Air
• Water
• Grease
• Microbes
• Odor
• Used for packaging
–
–
–
–
• Global Packaging Market
• Common Materials
–
–
–
–
Glass
Metals
Petroleum Based Plastics
Wax/Plastic Coated Paper Cartons
Food
Pharmaceutical Products
Cosmetics
Dry goods
– Valued at $3.8 Billion in 2007
– Projected to grow to $4.6 Billion
by 2014
•
Green Packaging
• Non Toxic/Chemically Inert
• Recyclable, Sustainable
• Stable
9
Objective –II: High performance barrier films
from NCFs
Three Approaches:
1. Thermal treatment of pure NCFs film to achieve high
performance films
2. Film formation from different solvent
3. Improve barrier properties by adding high aspect ratio of
nanoclay or graphene to the NCF films
10
Approach-I: High performance barrier films
from thermal treatment of NCFs
Concept: The nanofibrils will form strong internal and external
hydrogen bonding, and many of the hydrogen bonds are
irreversible after heat treatment, like hornification of wood
fibers. Therefore, the water and vapor permeation will be
reduced.
No chemical addition!
Approaches:
• Nanofibrillated cellulose suspension was casted into films and dried
• The films were then heated in the oven at various temperatures
11
Results: Crystallinity and thermal analysis
•
•
Increased crystallinity observed with
increasing temperature of exposure
Both Crystallinity and size of crytallites
showed increasing trend with increasing
temperature of treatment. This is mainly
due to internal hydrogen bonding and
co-crystallization.
•
Reduction in the weight loss of samples
observed from TG Analysis and
degradation at lower temeprature. This
implies
–
Reduction in the moisture content of heat
treated samples
Slight degradation of the material
–
1.75
1.50
71
69
0.090
68
0.085
0.080
67
0.075
66
0.070
65
0.065
20
40
60
80
100
120
140
160
Intensity
3500
3000
2500
0.75
0.50
0.25
0.00
0
50
100
150
120
180
200
250
300
350
400
450
500
Temperature (C)
2000
1500
550
600
Untreated
100C
125C
150C
175C
100
Untreated
100C
125C
150C
175C
4000
1.00
-0.25
Treatment Temperature (C)
4500
80
60
40
20
0
0
1000
50
100
150
200
250
300
350
400
Temperature (C)
500
0
12
-wt% / C
0.095
wt(%)
Crystallinity (%)
Crystallinity (%)
Size of Crystallites(nm)
Size of Crystallites(nm)
70
Untreated
100C
125C
150C
175C
1.25
0.100
8
10
12
14
16
18
20
Diffraction Angle (2)
22
24
26
28
450
500
550
600
Results: Mechanical Properties and hydrophobicity
•
•
Strength of the material decreased with
increasing treatment temperature.
This is due to increase in crystallinity
which causes the material to become
increasingly brittle.
Partially also due to degradation of the
material.
16
Ultimate Tensile Strength (GPa)
Tensile Strain at Max. Load
1.20
14
1.15
12
1.05
1.00
10
0.95
0.90
8
0.85
0.80
6
0.75
0.70
4
Untreated
13
100
125
150
Treatment Temperature (C)
175
105
0M
0.01M
0.1M
Contact Angle
180
100
95
90
160
85
140
80
120
75
100
70
80
65
60
60
55
40
Untreated
100
125
150
Treatment Temperature (C)
175
Contact Angle ()
1.10
Hydrophobicity greatly enhanced for
heat treated membranes
– Contact angle increased from ~64o
to 95°
– Water retention value in neutral pH
reduced by almost 2 folds and 3
folds in 0.1M NaOH solution
200
Tensile Strain at Max. Load (%)
Ultimate Tensile Strength (GPa)
1.25
•
Water Retention Value (g/m2)
•
Barrier properties
•
Significant reduction in both oxygen and water vapor permeability upon heat treatment
– Almost 25 fold reduction in Oxygen permeability
Untreated
175°C/3
hours
14
Untreated
175°C/3
hours
Oxygen Permeability (cc.m/m2.day.kPa)
More than 2 fold reduction in water vapor permeability
Reduction in porosity of the material (observed from cross section SEM images)
Increase in hydrophobicity
SEM images showed shrinkage of fibers, densification and reduction of porosity after
heat treatment
0.20
Oxygen Permeability
Water Vapor Permeability
0.18
60000
55000
0.16
0.14
50000
0.12
45000
0.10
40000
0.08
0.06
35000
0.04
30000
0.02
25000
0.00
Untreated
100
125
150
Treatment Temperature (C)
175
Water Vapor Permeability (g.m/m2.day.kPa)
–
–
–
–
Oxygen Permeability for various petroleum based
and biodegradable polymers
15
Material
Oxygen Permeability (cc.μm/m2.day.kPa)
Poly Ethylene Terepthalate
10-50
Polypropylene (Biaxially Oriented)
0.575
Polyvinyl alcohol
0.2
Ethylene vinyl alcohol
0.01-0.1
Polyvinylidene chloride
0.1-3
Whey Protien (Glycerol Plasticizer 25-60 wt%)
50-325
Poly Lactic Acid (PLA)
160
Thermally Treated (175 °C, 3 hours) CNF film
(This work)
0.007
Conclusions of thermal treatment for barrier film
preparation
• Enhanced Barrier Properties can be obtained via controlled thermal
exposure due to:
– Increase in Crystallinity
– Closure of pores
– Increased hydrophobicity
• Some drawbacks
– Degradation of material
– Loss of strength
Current work being reviewed for publication
Sharma, S., Xiaodan, Z., Nair, S. S., Ragauskas, A. J., Zhu, J. Y., & Deng, Y. High
performance green barrier films from thermal treatment of cellulose nanofibrils.
16
Approach II: Study the effect of solvent on
the NCF film properties
The effect of solvent on NCF membrane formation has not been well
studied
• There are less than 5 research articles that examine the interaction
between cellulose and solvents other than water
• Will the barrier property differ if different solvents are used in film
formation?
– Study the physical and permeability characteristics
– Determine the bonding mechanism that causes the physical
properties and structure
17
Preliminary Data: Solvent replacement
•
•
SEM images of the films show differences in the pore structure of the films.
Both surface and cross section show marked differences
– Need to determine the mechanism of bond formation in different solvents
Acetone
Methanol
Ethanol
Acetone
Water
Methanol
Cross Section
18
Ethanol
Water
Surface
Solvent replacement: Solvent retention
•
Films casted from water show a different amount of solvent retention
–
•
This provides with an indication of the interaction of free hydroxyls with different solvents
Films cast from different solvents also show different water retention
– This indicates differences in the pore structure and free hydroxyls of the dried membranes
•
This also shows that the different structures shown in the SEM images have an effect on
the properties of the membranes.
2.5
Solvent Retention Value(g/m2)
Water Retention Value (g/m2)
20
18
16
14
12
10
8
6
4
2
0
Acetone
Ethanol
Methanol
Membrane Cast From
19
Water
2.0
1.5
1.0
0.5
0.0
Water
Ethanol
Methanol
Solvent
Acetone
XRD and FTIR studies: Solvent replacement
•
Both XRD and FTIR spectrum show differences in the membranes cast form different
solvents
– XRD measurement show that there is difference in the crystallinity of films cast from different
solvents
– FTIR measurement shows difference in the –OH/Hydrogen bonding region(~3600-3200cm-1)
and C-H stretch (~2900 cm-1)
•
0.12
Water
Acetone
Ethanol
Methanol
0.10
0.08
0.06
Intensity
Absorbance Units
This information indicates that there is a fundamental difference in the way NCFs bond in
the presence of different solvents and the properties can be tuned based on the different
Water
mechanisms
4000
Acetone
0.04
0.02
0.00
-0.02
3500
3000
0.12
2500
2000
1500
1000
500
Water Scaled
Acetone Scaled
Ethanol Scaled
Methanol
0.10
0.08
0.06
0.04
0.02
0.00
-0.02
-0.04
-0.06
4000
20
4000
Crystallinity %
Scaled Absorbance
4500
3500
3000
2500
2000
1500
1000
500
0
70.0
69.5
69.0
68.5
68.0
67.5
67.0
Ethanol
Methanol
5
Water
3500
3000
2500
2000
1500
Wavenumber cm-1
1000
500
10
15
2(
Acetone
20
Ethanol
Membrane Cast From
25
Methanol
30
Solvent replacement: Gas and water vapor barrier
•
Barriers different for different films made from different solvents
21
Carbon Dioxide
Nitrogen
0.0000005
Permeability (cc.m/m2.sec.Pa)
Water Vapor Permeability (g.m/m2.kPa.Day)
– This shows that different morphology and different cross sectional structures have effect on the
permeability
– Permeability may be tuned (for both water and gas) by selecting the appropriate solvent.
0.0000004
0.0000003
0.0000002
0.0000001
0.0000000
Acetone
Ethanol
Methanol
Cast from Solvent
Water
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Acetone
Ethanol
Methanol
Membrane Cast From
Approach III: Barrier film with high aspect
ratio nanofiller (clay or graphene) addition
• Synthesize/Fabricate composite NFC membranes with high aspect
ratio Nano-filler materials to enhance barrier properties
– Graphene (Expensive, but a good model particles)
– Clays
• Model the inherent diffusion process to compare with existing
empirical models
22
Nano-fillers: Background
23
•
Filler materials aid in filling in any unclosed pores and enhance the tortuosity of the
barrier – this hinders diffusion
•
Filler materials are usually highly crystalline and have low affinity for the permeant – this
reduces effective sorption
•
Very low amounts of fillers have been shown to have great degree of enhancement of
barrier for various polymers
Nano-fillers: Barrier properties
•
2.5% (w/w) Graphene and Clay/NFC barrier membranes showed marked improvement in
Oxygen and water vapor permeability
– High aspect ratio nano-filler materials will increase the tortuosity and hinder the diffusion
process
– Gases/ Vapors are also usually insoluble in the filler materials they hinder the sorption process
as well.
SEM images show an asymmetric membrane, which even though better is not ideal, our
goal is to fabricate a well dispersed and exfoliated composite.
Oxygen Permeability(cc.m/m2.day.kPa)
•
24
25m
100m
0.011
0.010
0.009
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
Pure MFC
MFC + 2.5% Graphene
Membrane Type
MFC + 2.5% Clay
Objective III: Develop other functional NFC
nanomaterials
1. Hydrogels prepared from cross-linked nanofibrillated cellulose
2. Lignin nanomaterials
25
Hydrogels prepared from cross-linked
nanofibrillated cellulose
Objective
•
Develop NFC cross-linked PVEMA-PEG hydrogels and to investigate the effect of
different concentration of NFC on its physical properties
•
Difference in physical properties of hardwood and softwood NFC cross-linked
PMVEMA-PEG matrices
Experimental
Matrix - Poly(methyl vinyl ether-co-maleic acid (PMVEMA)-Polyethylene glycol (PEG)
(At 6.7:1 ratio)
Filler – Nanofibrillated softwood and hardwood pulp
26
Schematic representation of the crosslinking reaction
chemistry of PMVEMA, PEG and NFC
Evidence of
possible
esterification
between hydroxyl
group of NFC and
matrix
Schematic representation of the crosslinking
reaction chemistry of PMVEMA, PEG and NFC
FTIR comparative spectra of (A) are a: 25% softwood NFC
+ 75% matrix (25SWNFC) and b: 100% softwood NFC
(100SWNFC) (B) are a: 25% hardwood NFC + 75% matrix
(25HWNFC) and b: 100% hardwood NFC (100HWNFC)
27
Swelling ratio and gel content of cross-linked hydrogels with
softwood nanocellulose and hardwood nanocellulose
Swelling ratio of cross-linked nanocomposites with (a) softwood nanocellulose (b) hardwood
nanocellulose
Sample
Gel content (%)
Gel content of the cross-linked and
non crosslinked nanocomposites
28
25SWNFC
36.2
Non crosslinked 25SWNFC
No gel
50SWNFC
58.2
75SWNFC
84.8
Non crosslinked 75HWNFC
48.1
25HWNFC
19.4
Non crosslinked 25HWNFC
No gel
50HWNFC
60.8
75HWNFC
80.4
Non crosslinked 75HWNFC
43.0
Thermal properties of crosslinked hydrogels
TGA (left) and DTG (right) of softwood nanocomposite hydrogels (SWNFC)
and hardwood nanocomposite hydrogels (HWNFC)
29
Thermal and mechanical properties of crosslinked
hydrogels
Tonset values
Sample
Tonset (0C)
25 SWNFC
154
50SWNFC
168
75SWNFC
204
25HWNFC
156
50HWNFC
170
75HWNFC
209
Tonset for PVEMA-PEG
(matrix) is 1470C
Mechanical property of PVEMA-PG and crosslinked hydrogels
30
Sample
Tensile strength (MPa)
E-modulus (GPa)
Strain (%)
PVEMA-PEG
2.64 ± 0.33
0.23 ± 0.70
0.82 ± 0.01
25 SWNFC
14.81 ± 1.42
0.60 ± 0.15
3.4 ± 0.40
50SWNFC
20.12 ± 0.81
0.75 ± 0.22
2.85 ± 0.02
75SWNFC
31.38 ± 0.20
1.60 ± 0.07
2.07 ± 0.06
25HWNFC
9.44 ± 0.50
0.46 ± 0.10
3.0 ± 0.40
50HWNFC
12.07 ± 2.0
0.77 ± 0.12
2.66 ± 0.08
75HWNFC
20.41 ± 1.40
1.65 ± 0.23
1.6 ± 0.30
Conclusions of Objective III : Develop other
functional NFC
• In situ co-cross-linking of NFC with PVMEVA-PEG matrix lead to the
development of nanocomposite hydrogels with enhanced physical properties
• The crosslinked hydrogels attained high water absorption at 25% (256% for
softwood and 174% for hardwood) nanofibrillated cellulose
• The thermal stability, mechanical strength and modulus increased with the
increase in amount of nanocellulose in crosslinked hydrogels
Current work being reviewed for publication
(Nair, S. S., Zhu, J. Y., Deng, Y., & Ragauskas, A. J. (2013). Hydrogels prepared
from crosslinked microfibrillated cellulose. ACS Sustainable Chemistry &
Engineering (In Review)
31
Leverage Funding
• Future industry lead consortium
– Packaging
– Transportation industry
– Pulp producers: lower cost production
• Individual industry sponsored projects
• BRDI, DOE/Advanced Manufacturing, NSF
32
GT/Partner Nanocellulose Facilities
Acknowledgment
USDA-FPL
33