CARBOXYMETHYL CELLULOSE NANOCOMPOSITES

YongJae Choi Department of Chemical Engineering

and John Simonsen

Department of Wood Science & EngineeringOregon State University

Outline

I. IntroductionII. Materials and MethodsIII. Result and discussion

I. Comparison of cellulose nanocrystals (NCC) to microcrystalline cellulose (MCC)

II. Thermal cross-linkingIV. ConclusionsV. Acknowledgements

Introduction

CMC-based hydrogels and films have many applications, from fruit leathers to medical implants, supports for electrocatalysis and pervaporation membranesBiodegradable, biocompatible, non-toxic, renewable natural resource, low costUsing MCC as a filler imparts improved mechanical properties to films and gelsWhat is the effect of reduced particle size?

CMC SynthesisCarboxymethyl cellulose (CMC)

Derived from cellulose by carboxymethylationWater soluble polymerEfficient, inexpensive reactionUsually sold as sodium salt

Commercial CMC

CMCFirst prepared in 1918Commercially produced since 1920

Three key parameters to control properties for various applications

Molecular weightDegree of substitution (DS)Distribution of the carboxymethyl group

Commercial CMC

Unique features of CMCSoluble in water Viscosity controlExcellent dispersion of MCCForms strong and transparent filmImmiscible in oil and organic solventHigh absorbent polymeric material

Nanocrystalline Cellulose

Stronger than steel and stiffer than aluminumProduced by acid hydrolysis of natural celluloseBreak microfibrils into elementary single crystallites

Crystalline regions

Amorphous region

Acid hydrolysis

Individual nanocrystals

Individual cellulose polymer

Cellulose Nanocrystal Production

Native cellulose

NCC

Cellulose nanocrystal characterization with TEM

Average length = 85 nmAverage width = 3 nmAgglomeration due to the attractive force

Thermal Dehydration for Cross-linkingAlcohol group of poly(vinyl alcohol) (PVA) and acetic acid group of polyacrylic acid (PAA) are cross-linked under mild heat treatment

Objectives

1. Compare cellulose nanocrystal (NCC) to microcrystal cellulose (MCC) in carboxymethyl cellulose composite film

2. Preliminary investigation of thermal crosslinking between NCC and CMC

Materials and Methods

MaterialsCarboxymethyl cellulose (CMC)

M.W = 250,000D.S = 1.2Aldrich chemical company

Cellulose nanocrystal (NCC)Derived from cotton cellulose

GlycerinM.W = 92.10Plasticizer Fisher Scientific

Methods

Cellulose nanocrystal preparationGrind cellulose in Wiley mill with 40 mesh screenAcid hydrolysis at 60°C with 65%(w/w) sulfuric acid for 50 minCentrifugation, decant acid, rinseUltrasonic irradiation and/or Waring blenderDecantUltrafiltration

Film Formation

Dissolve CMC in water

Mix with NCC or MCC and glycerin

NCC concentration 5% to 30%Glycerin constant at 10%

Pour into Petri dish and air dry

Thermal Cross-linking

Acid form of CMC is achieved by ion exchange (cationic resin) Mix with NCCGlycerin omittedUltrasonic irradiationForm in Petri dish Air dry Heat treatment at various temperatures for 3 h under nitrogen gas

MethodsMechanical testing (Sintech)

Modulus of rupture (MOR)Modulus of elasticity (MOE)Extension at maximum yield strength

Methods

Thermal testing (TGA)Ramp 20°C/min

Water dissolution testSoak in water at room temperatureMeasure weight loss

Water vapor transmission rateFilm covered jar containing waterMeasure weight loss with timeHot-dry room (30°C, 25% humidity)Mass flux (J) = Mass change (g)

Area (m2) * Time (hr)

CMC/NCC/Glycerin Films

90%CMC/10%Gly 80%CMC/10%NCC/10%Gly

Comparison of Microcrystalline Cellulose (MCC) to CNXL in CMC

10% MCC 10% CNXL

200X optical (crossed200X optical (crossed polarspolars))

Cross Section of Film

90%CMC/10%Gly 80%CMC/10%NCC/10%Gly

Mechanical properties (MOR)

15

20

25

30

35

40

-5 5 15 25 35% NCC/MCC content

Tens

ile s

tren

gth

(MPa

)

ControlNCCMCC

30% increase

Mechanical properties (MOE)

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

3

-5 0 5 10 15 20 25

% NCC/MCC content

MO

E (G

Pa)

Control

NCC

MCC

85% increase

Extension at failure

0

0.2

0.4

0.6

0.8

1

1.2

-5 5 15 25 35%NCC or %MCC, wt/wt

Ext

ensi

on (m

m)

controlNCCMCC

60% increase

40

50

60

70

80

90

100

110

150 200 250 300 350 400 450Temperature, 0C

Wei

ght,

% o

rigin

al

100% NCC100% CMC90C85C5N80C10N70C20N60C30N

TGA

Dynamic Mechanical Analysis

5

6

7

8

9

10

170 180 190 200 210 220 230 240Temperature (°C)

log

(G'/P

a)

90C10G80C10N10G70C20N10G60C30N10G

HEAT TREATMENT

5% NCC in CMCNo plasticizer

HEAT TREATMENT

78

80

82

84

86

88

90

92

94

0 20 40 60 80 100 120 140Heat treatment, 0C for 3 h, 5% NCC-filled CMC

Tens

ile s

tren

gth,

MP

a

0

1

2

3

4

5

6

MO

E, G

Pa

or %

elo

ngat

ion

MORMOEElongation

16% increase

Water Dissolution

0

10

20

30

40

50

60

-5 15 35 55 75

Water immersion Time (hr)

Wei

ght l

oss

(%)

120C

100C

80C

No heat

Water Dissolution

0

10

20

30

40

50

60

70

0 20 40 60 80 100 120 140

Thermal treatment temp. (C)

Wei

ght l

oss

at 3

day

s (%

)

water

jar

Lid with holefilm

Water Vapor Tranmission Rate

Water Vapor Transmission Rate

0

500

1000

1500

2000

control heat treated

WVT

R, g

/m2 d

y

11% reduction

Conclusions

At low concentration NCC is well dispersed in the composites without observed agglomeration of celluloseNCC improved the mechanical properties (strength, stiffness and elongation) as a reinforcing filler compared to MCCTGA suggests close association between NCC and CMC

Conclusions

Cross-linking between CMC and NCC can be obtained by heat treatmentsHigher degree of cross-linking is achieved at higher temperatureCross-linking composites have improved water resistanceCross-linking appears to reduce water vapor permeability slightly

Acknowledgement

This project was supported by a grant from the USDANational Research Initiative Competitive Grants Program