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Green Nanocomposites Reinforced with Cellulosic Crystals Isolated Hardwood
Residues and Juvenile Poplar
Qingzheng Cheng and Jingxin Wang
Division of Forestry and Natural ResourcesWest Virginia UniversityMorgantown, WV, USA
Cellulose nanocrystals: Higher mechanical properties, Bio-nanocomposites: High performance, and lightweight
green materials.
Cheng et al. Composites: Part A 40 (2009) 218–224
Introduction
2
Cellulosic micro/nano fibrils: Basic structural unit of wood cell wall Generated during plant photosynthesis High strength and potential reinforcement for polymer materials
Kretschmann et al, 2006Wood cell wall structure
Fengel, D., and G. Wegener. 1984
Introduction
3
Isolation of cellulosic micro/nano fibrils:
Chemical treatments: acid hydrolysis for nano-size fibrils.
Physical treatments: bundles of microfibrils.
Introduction
4
(Cheng et al. 2010. J Appl Poly Sci)
Nanocomposites
Nanocomposite:At least one-dimensional the nm scale (1-100).
Fabrication: (1) Film casting (2) Compression or extrusion processes
Introduction
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Isolate cellulose nanocrystals
Characterize cellulosic nanocrystals
Reinforce biodegradable polymers
Characterize the mechanical and thermal properties of the nanocomposites.
Objectives
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QTL Mapping Population
P. trichocarpa93-968
Washington
P. deltoidesILL-101
S. Illinois
F1: 52-225P. deltoides
D124Minnesota
BC1, Family 52124, 796 progeny
Hybrid poplarCrossing design for production of the quantitative trait locus (QTL) mapping pedigree
Two poplar sources used: 93-968 (PT1, grandmother) & Hybrid poplar (BC1, offspring)
Materials
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3-year old hybrid poplar plantation 1-year old coppiced poplar in a stool bed
Materials
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Other cellulose resources: Yellow poplar (YP) and Microcrystalline Cellulose (MCC)Polymer: Poly(vinyl alcohol) (PVA)
Materials
Poplar roots 1-year old stem-wood
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Isolate cellulose nanocrystals (CNC)from wood and MCC
Hybrid poplaror
wood residue
Milled pass1 mm screen
Lignin removedby acidified
sodium chlorite3g/10g wood
Once per hourFour hours @ 75 °C
Acid hydrolysis(H2SO4)
(60%, 45 °C, 2h)
Wash bydeionizedwater withcentrifuge
Dialysedagainst
deionizedwater
MCC
Ultrasonic treatment
Cellulosenanocrystals
Experiment
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Composite from PVA and fibrils by casting:
PVA (10%)water solution
Stir andultrasonic
Dry in an oven(60 ºC) to films
Vacuum ina desiccatorNanocrystal
SuspensionOr MCC
Sample # Thickness (µm) Cellulose content (%)* PVA content (%)
1 120-150 0 100
2 120-150 1 99
3 120-150 2 98
4 120-150 5 95
Experiment
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Digital light microscopy SEM
Experiment
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Tensile test (ASTM D1708):
Speed: 1 mm/min
Specimens: width: 5 mmLength: 20 mm (total 40mm)
Thermal test (TGA):
Temperature: romm to 400 C Heating rate: at a 20 C/minNitrogen gas: 20 ml/min
Experiment
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Wood particles before and after lignin is removed
Results
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Wood samples, particles before and after lignin is removed
Cellulose suspensions in water
Results
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SEM and AFM images of self assembly formed bundles of nanocrystals
PVA film and cellulosic nanocomposites
Typical stress strain curves of pure PVA (left) and cellulosic nanocomposites (right).
Results
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Results
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Results
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Results
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TGA results
Derivative thermogravimetric (DTG) Thermograms of neat PVA and its nanocomposites with 2% and 5% HP nanofibers
Results
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Cellulose nanocrystals can be isolated from MCC, yellow poplar, hybrid poplar, and black cottonwood using chemical methods.
Most of nanocrystals were bundles of single nanocrystals and the average diameter of the crystals was about 21 nm.
The nanocrystals can be used to reinforce PVA, but they may have different effects on PVA tensile properties.
Cellulose nanocrystals have much better performance than untreated MCC for PVA reinforcement.
The degradation temperature of cellulosic nanocomposites is higher compared with neat PVA.
Conclusions
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Thanks!
22