CARBOXYMETHYL CELLULOSE NANOCOMPOSITES

YongJae Choi Department of Chemical Engineering and John Simonsen Department of Wood Science & Engineering Oregon State University Outline

I. Introduction II. Materials and Methods III. Result and discussion I. Comparison of cellulose nanocrystals (NCC) to microcrystalline cellulose (MCC) II. Thermal cross-linking IV. Conclusions V. Acknowledgements Introduction

„ CMC-based hydrogels and films have many applications, from fruit leathers to medical implants, supports for electrocatalysis and pervaporation membranes „ Biodegradable, biocompatible, non-toxic, renewable natural resource, low cost „ Using MCC as a filler imparts improved mechanical properties to films and gels „ What is the effect of reduced particle size? CMC Synthesis

„ Carboxymethyl cellulose (CMC)

„ Derived from cellulose by carboxymethylation „ Water soluble polymer „ Efficient, inexpensive reaction „ Usually sold as sodium salt Commercial CMC

„ CMC „ First prepared in 1918 „ Commercially produced since 1920 „ Three key parameters to control properties for various applications „ Molecular weight „ Degree of substitution (DS) „ Distribution of the carboxymethyl group Commercial CMC

„ Unique features of CMC

„ Soluble in water

„ Viscosity control

„ Excellent dispersion of MCC

„ Forms strong and transparent film

„ Immiscible in oil and organic solvent

„ High absorbent polymeric material Nanocrystalline Cellulose

„ Stronger than steel and stiffer than aluminum „ Produced by acid hydrolysis of natural cellulose „ Break microfibrils into elementary single crystallites Cellulose Nanocrystal Production

Amorphous region Native cellulose

Crystalline regions Acid hydrolysis

Individual nanocrystals

Individual cellulose polymer NCC

„ Cellulose nanocrystal characterization with TEM „ Average length = 85 nm „ Average width = 3 nm „ Agglomeration due to the attractive force Thermal Dehydration for Cross-linking „ Alcohol 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

„ Materials „ Carboxymethyl cellulose (CMC) „ M.W = 250,000 „ D.S = 1.2 „ Aldrich chemical company „ Cellulose nanocrystal (NCC) „ Derived from cotton cellulose „ Glycerin „ M.W = 92.10 „ Plasticizer „ Fisher Scientific Methods

„ Cellulose nanocrystal preparation „ Grind cellulose in Wiley mill with 40 mesh screen „ Acid hydrolysis at 60°C with 65%(w/w) sulfuric acid for 50 min „ Centrifugation, decant acid, rinse „ Ultrasonic irradiation and/or Waring blender „ Decant „ Ultrafiltration 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 NCC „ Glycerin omitted „ Ultrasonic irradiation „ Form in Petri dish „ Air dry „ Heat treatment at various temperatures for 3 h under nitrogen gas Methods

¾ Mechanical testing (Sintech) ¾ Modulus of rupture (MOR) ¾ Modulus of elasticity (MOE) ¾ Extension at maximum yield strength Methods

¾ Thermal testing (TGA) ¾ Ramp 20°C/min

„ Water dissolution test „ Soak in water at room temperature „ Measure weight loss

„ Water vapor transmission rate „ Film covered jar containing water „ Measure weight loss with time „ Hot-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

200X200X opticaloptical (crossed(crossed polarspolars)) Cross Section of Film

90%CMC/10%Gly 80%CMC/10%NCC/10%Gly Mechanical properties (MOR)

40 Control 30% increase NCC 35 MCC

30

25

20 Tensile strength (MPa) Tensile strength 15 -5 5 15 25 35 % NCC/MCC content Mechanical properties (MOE)

3

2.8 Control 85% increase

2.6 NCC

2.4 MCC

2.2

2

1.8 MOE (GPa)

1.6

1.4

1.2

1 -5 0 5 10 15 20 25 % NCC/MCC content Extension at failure

1.2 60% increase

1

0.8

0.6

Extension (mm) Extension 0.4 control NCC 0.2 MCC

0 -5 5 15 25 35 %NCC or %MCC, wt/wt TGA 110

100 100% NCC l 90 100% CMC 90C 80 85C5N 80C10N 70C20N 70 60C30N

Weight, % origina Weight, 60

50

40 150 200 250 300 350 400 450 Temperature, 0C Dynamic Mechanical Analysis

10

9

8

7 log (G'/Pa) 90C10G 80C10N10G 6 70C20N10G 60C30N10G 5 170 180 190 200 210 220 230 240 Temperature (°C) HEAT TREATMENT

5% NCC in CMC No plasticizer HEAT TREATMENT

94 6

92 5 16% increase 90 4 88

86 3

84 2

Tensile strength,82 MPa

MOR MOE, GPa or % elongation 1 80 MOE Elongation 78 0 0 20 40 60 80 100 120 140 Heat treatment,0C for 3 h, 5% NCC-filled CMC Water Dissolution

60

50

40 120C 100C 30 80C No heat

Weight loss (%) 20

10

0 -5 15 35 55 75 Water immersion Time (hr) Water Dissolution

70

60

50

40

30

20

Weight loss at 3 days (%) at loss Weight 10

0 0 20 40 60 80 100 120 140 Thermal treatment temp. (C) Water Vapor Tranmission Rate

film Lid with hole

jar

water Water Vapor Transmission Rate

2000

1500 11% reduction dy 2

1000 WVTR, g/m WVTR, 500

0 control heat treated Conclusions

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

„ Cross-linking between CMC and NCC can be obtained by heat treatments „ Higher degree of cross-linking is achieved at higher temperature „ Cross-linking composites have improved water resistance „ Cross-linking appears to reduce water vapor permeability slightly Acknowledgement

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