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

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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

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Isolation of cellulosic micro/nano fibrils:

Chemical treatments: acid hydrolysis for nano-size fibrils.

Physical treatments: bundles of microfibrils.

Introduction

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(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!

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