AN ABSTRACT OF THE THESIS OF
YongJae Choi for the degree of Master of Science in Chemical Engineering
presented on June 3, 2005
Title: Cellulose Nanocrystals Filled Carboxymethyl Cellulose Composites
Abstract approved:
Redacted for privacy
WillieE. "Skip" Rochefort
Abstract
Hydrogel polymers are a novel class of hydrophilic materials that have large
application areas in both the industrial and medical fields. Carboxymethyl
cellulose (CMC) has received attention as a hydrogel polymer. Methods to
modify the mechanical properties of gels and films made from CMC are of
interest in our lab and in the commercial marketplace. Also, nanophase
materials have attracted great interest in recent years and have the potential to
provide novel properties to hydrogels. This project investigated cellulose
nanocrystals (NCCs) as a filler in CMC and compared the effects to
microcrystalline cellulose (MCC). The composite material was composed of
CMC, MCC or NCC, with glycerin as a plasticizer. NCC and MCC
concentration ranged from 5% to 30%. Glycerin concentrations were kept
constant at 10%. NCCs improved the strength and stiffness of the resulting
composite compared to MCC. Thermal degradation was also investigated
using thermo gravimetric analysis and NCC was found to affect the
degradation behavior.
In addition, thermal crosslinking between CMC and NCC was studied.
In these experiments, NCC concentrations were kept constant at 5% and
thermal crosslinking was conducted at various temperatures ranging from 80°C
to 120°C. Material properties and water resistance were measured.
Crosslinking improved the strength and stiffness of the composite and also
significantly improved the water resistance.
© Copyright by YongJae Choi
June 3, 2005
All Rights Reserved
Cellulose Nanocrystals Filled Carboxymethyl Cellulose Composites
by
YongJae Choi
A THESIS
submitted to
Oregon State University
In partial of fulfillment of
the requirements for the
degree of
Master of Science
Presented June 3, 2005
Commencement June 2006
Master of Science thesis of YongJae Choi presented on June 3, 2005
APPROVED:
Redacted for privacy
Major ProfessRepresening Chemical Engineering
Redacted for privacy
Head of the Department of Chemical Engineering
Redacted for privacy
Dean of the
School
I understand that my thesis will become part of the permanent collection of
Oregon State University libraries. My signature below authorizes release of my
thesis to any reader upon request.
Redacted for privacy
YongJae Choi, Author
ACKNOWLEDGEMENTS
I would like express my sincere appreciation to Dr. John Simonsen, my
graduate project advisor, for the guidance, mentoring that I have received from
him during my graduate study at Oregon State University. I am impressed by
his scientific approach and optimistic attitude toward research work and I am
sure it affects not only current but also my future life as a professional person.
I would also like to express my gratitude for Dr. Skip Rochefort, Dr.
Alex Chang and Dr. Antonio Torres for agreeing to serve on my academic
committee.
I would like thank God for giving my pretty daughter to me and thank
my father, mother, and wife for the trust and confidence shown to me all the
time during my graduate study.
TABLE OF CONTENTS
Chapter 1-Introduction .................................................................. 1
1.1 Introduction .................................................................. 1
1.1.1 Background: CMC .............................................. 2
1.1.2 Cellulose Nanocrystal ........................................... 3
1.1.3 Thermal Crosslinking of Polymers ............................ 5
1.2 Objective ..................................................................... 7
Chapter 2-Literature Review ............................................................ 8
2.1 CMC Composites ........................................................... 8
2.2 Cellulose Nanocomposites ................................................ 9
2.3 Thermal Crosslinking in Composite materials ........................ 11
Chapter 3-Materails and Methods.................................................... 13
3.1 Materials .................................................................... 13
3.2 Cellulose Nanocrystal Preparation Procedure ......................... 13
3.3 Cellulose Nanocomposite Film Preparation Procedure .............. 14
3.4 Cellulose Nanocrystal Characterization Techniques ................. 15
3.4.1 Transmission Electron Microscope (TEM) ................ 15
3.5 Quality of Dispersion
.................................................... 16
........................................... 16
3.5.2 Scanning Electron Microscopy (SEM) ...................... 16
3.5.1 Optical Microscope
TABLE OF CONTENTS (Continued)
3.6 Material Properties
.17
3.6.1 Mechanical Testing ............................................ 17
3.6.2 Thermal Testing ................................................ 18
3.7 Thermo Crosslinking ..................................................... 18
3.7.1 Procedure ....................................................... 18
3.7.2 Water dissolution test ......................................... 19
3.7.3 Water vapor transmission .................................... 19
Chapter 4-Results and Discussion ................................................... 21
4.1 Comparison of MCC and NCC ......................................... 22
4.1.1 Imaging of Films .............................................. 22
4.1.2 Mechanical Properties ........................................ 24
4.1.3 Thermal Properties ............................................ 31
4.2 Thermal Crosslinking .................................................... 34
4.2.1 Water dissolution .............................................. 34
4.2.2 Thermal Properties ....................................................... 36
4.2.3 Mechanical Properties ......................................... 37
4.2.4 Water vapor transmission ....................................... 40
Chapter 5-Conclusion .................................................................. 42
5.1 Suggestions for Future Work ............................................ 43
Bibliography ............................................................................44
APPENDICES .......................................................................... 47
LIST OF FIGURES
Figure
1. Reaction scheme of the carboxymethylation of cellulose [4] ................. 2
2. Expected crosslinking structure of heat-treated PVA/PAA blend
films[22] ............................................................................. 6
3. TEM image of cellulose nanocrystals .............................................. 21
4. Optical microscope image under crossed polarizers of 90%CMC1 O%Glyceirn and 80%CMC- 1 O%NCC- 1 O%Glycerin Composites .......... 22
5. SEM images of 90%CMC-lO%Glycerin and 80%CMC-1O%NCC1O%Glycerin composite films ...................................................... 23
6. Tensile strength value for NCC and MCC on CMC based films ............. 25
7. Polarized microscopic image of 80%CMC-1O%MCC-1O%Glycerin
composite .............................................................................. 25
8. Tensile modulus value for NCC and MCC on CMC based films ............. 27
LIST OF FIGURES (Continued)
Figure
9. Percent elongation at break ......................................................... 28
10. Storage modulus curve for composite samples ................................. 29
11. Loss factor (Tan ö) curves for composites ...................................... 31
12. TGA curves for NCC composites ................................................ 32
13. Thermal gravimetric curve per time on each temperature .................... 33
14. Temperature-weight loss curves ................................................. 34
15. Percent dissolution vs. time curve for crosslinked NCC/CMC
Composites ........................................................................... 35
16. Dissolution in water (%) after soaking for three days for 3hr heat
treatments at the listed temperature ............................................... 36
LIST OF FIGURES (Continued)
Figure
17. Thermo gravimetric curves for crosslinking composites ..................... 37
18. Tensile strength values for films heat treated for 3 hr at the listed
temperatures ........................................................................ 38
19. Tensile modulus values for films heat treated for 3 hr at the listed
temperatures ........................................................................ 39
20. Percent elongation to failure for NCC/CMC films heat treated for
3hr at the listed temperatures ..................................................... 39
21. Water vapor transmission rate for the films with/without heat
treatmentfor 3 hr ................................................................... 40
LIST OF APPENDIX FIGURES
Figure
Al. Sample shape of dog bone
.47
A2. Titration curve for acid form of CMC with OAN NaOH ..................... 47
A3. Load-deflection curve ............................................................. 48
A4. Thermal gravimetric curves for NCC and CMC films ........................ 48
LIST OF APPENDIX TABLES
Table
Bi. Measurements of tensile test
.49
B2. Datum of dissolution test .......................................................... 50
B3. Mechanical properties of thermal crosslinking composite ................... 50
B4. Water vapor transmission measurements ...................................... 51
Chapter 1- Introduction
1.1 Introduction
Hydrogel polymers are a novel class of hydrophilic materials having
large application areas in both the industrial and medical fields. Hence the
development of new hydrogel composites is of interest to researchers.
However there is a limitation to the development new hydrogel composites for
industrial applications because the economics of the final product are
important in determining whether or not it will be successful in the
marketplace. Also, in the medical fields, new hydrogel composites must not
exhibit negative effects in the human body. In addition, environmental aspects
have become more important in developing new materials. Hence the new
composites also must allow recycling or destruction without any toxic
emission or residuals at the end of their life cycle.
Carboxymethyl cellulose (CMC) is a very unique material in many of
these respects because it has the potential for excellent material properties by
combination with other substituents. Moreover it is a relatively low cost,
renewable and non-toxic material because CMC is derived from cellulose
which is obtained from natural resources.
2
1.1.1 Background: CMC
Cellulose is one of the naturally occurring biopolymers and the most
abundant and renewable polymer resource in the world today [1]. It is usually
obtained from wood and other plants. Cellulose in its native form is not soluble
in water. However it can be easily rendered water-soluble by the chemical
reaction of its hydroxyl groups (-OH) with hydrophilic substituents.
Carboxymethyl cellulose (CMC) is one such water-soluble cellulose derivative.
CMC contains a hydrophobic polysaccharide backbone and many hydrophilic
carboxyl groups, and hence shows amphiphilic characteristics [2].
Carboxymethyl cellulose (CMC) was first prepared in 1918 and was
already produced commercially in the early 1920's in Germany [3]. It is an
important industrial polymer with a wide range of applications in detergents,
textiles, paper, food, drugs, and oil well drilling operations. Large scale
production of CMC is carried out exclusively by a slurry process, i.e. by
conversion of alkali cellulose swollen in aqueous NaOH and a surplus of an
organic liquid (e.g. ethanol or isopropanol) with monochloroacetic acid or its
sodium salts (Fig. 1).
OH
OR
laqu,NaOH
CCKCOONa
-
(isopcopanol)
0
OCHCOONe
OH
2
R Hoc CHCOøNa
according to D8
Figure 1. Reaction scheme of the carboxymethylation of cellulose [4]
3
Three key parameters of CMC determine its properties and
consequently the applications for which it is used: the molecular weight of the
polymer, the average number of carboxymethyl substituents per
anhydroglucose unit (degree of substitution, DS), and the distribution of the
carboxymethyl substituents along the polymer chain [5-7]. For example, the
glass transition temperature (Tg) decreases with higher DS [8], heat capacity
decreases with higher molecular weight, but increases with higher DS [9] and
viscosity is also affected by all three parameters.
CMC has many unique features as a hydrogel polymer, (1) It is readily
soluble in cold and hot water to give a viscous solution, (2) It has excellent
emulsion and solid dispersion abilities, (3) It forms a strong and transparent
film, (4) It is immiscible in oil, grease and organic solvents, and (5) It is a
highly absorbent polymeric material [10]. Hence CMC has been the subject of
much research in its actual application fields to achieve better properties, some
of these are described in Chapter 2.
1.1.2 Cellulose Nanocrystal
Nanophase materials have attracted great interest in recent years. Their
special properties have predestined them for use in many high-tech fields.
Most of the nanophase materials are prepared from inorganic materials and few
are reported to be obtained from natural products.
There has also been great progress in recent years in the field of
cellulose degradation [11-131.
Because of the cellulose crystal possesses higher strength than steel and
higher stiffness than aluminum among many materials derived from the natural
resources. Hence the composites which are utilized with cellulose nanocrystal
(NCC) as a reinforcing filler may have the potential to achieve excellent
mechanical properties. In addition, NCC has the advantage of cost compared
with other plastics because it is derived from natural resources relatively low
prime cost.
However, it is presently difficult to achieve cellulose nanocrystals with
optimal and reproducible nano-phase properties. As with most dispersed
nanophase materials, aggregation is a problem [14, 15].
Usually, NCC is prepared by acid hydrolysis. Acid hydrolysis of
cellulose was reported by Ranby [16] 40 years ago. Cellulose exists in the form
of microfibrils in cell walls of plants and these microfibrils are just
aggregations of crystallites. Acid hydrolysis breaks down these microfibrils
into elementary single crystallites. The acid hydrolysis of cellulose fibers is a
heterogeneous acid diffusion process in which the acid penetrates the less
ordered regions (i.e) amorphous regions and causes the scission of glycosidic
bonds. The penetration and the glycosidic bond breakage depend on the
hydrolysis conditions such as acid type, hydrolysis temperature and time, and
acid concentration [17]. The reaction proceeds until all the accessible
glycosidic bonds are hydrolyzed. Then this reaction finally reached the socalled level of degree of polymerization (LODP). After reaching LODP the
degree of polymerization (DP) becomes almost constant with time [1 8].
However hydrolysis does not completely stop at LODP, it continues at a slow
rate determined by the number of crystallite ends preset [19]. Hence the
hydrolysis conditions are very important to avoid complete hydrolysis of
cellulose to glucose or even carbonization.
1.1.3 Thermal Crosslinking of Polymers
Polymer crosslinking may be formed in two ways: (1) by starting with
reaction masses containing sufficient amounts of tn- or higher-functional
monomer, (2) by chemically creating crosslinks between previously formed
linear or branched molecules [20]. The latter method requires the knowledge of
the connection between the phenomenological reaction to temperature and the
fundamental concept of molecular structure to induce polymer crosslink.
Crosslinked polymers have different characters depending on the
crosslinking method and the specific conditions employed because these
determine the degree, or extent, of crosslinking. Light crosslinking is used to
impart good recovery (elastic) properties to a polymer to be used as a rubber.
High degrees of crosslinking are used to impart high rigidity and dimensional
stability (under conditions of heat and stress) to polymers [21].
6
One of the methods used to create crosslinks is thermal crosslinking by
heat treatment under certain temperature conditions. This method is normally
used for crosslinking poly(vinyl alcohol) (PVA). Because PVA is a typical
water-soluble polymer, insolubility is required for the application of PVA as
fibers or films. Heat treatment is conventionally utilized to impart water
resistance to PVA. Recently some studies have been published on the thermal
crosslinking of PVA with poly(acrylic acid) (PAA) [22,23]. The hydroxyl
group of PVA and the acetate group of PAA are cross-linked by heat treatment
(Fig. 2).
PVA
c
-c CHC'
CO
/CH2
CH -
I.
hOC;C--CH
CH-c=o
0
'VA
.;
:
C
OH
.C---CH2--CH C. OH CNGH
ed ?iJtr
*CH2*HLCH2_?H_ PAA
000H
000H
Figure 2. Expected crosslinking structure of heat-treated PVA/PAA blend
films[22]
In this study we utilized this same reaction, but substituted CMC for
PAA and NCC for PVA to achieve a crosslinked composite.
7
1.2 Objectives
(1) To study the effect of NCC as a filler in CMC in comparison to MCC
(2) To study thermal crosslinking between CMC and NCC
r]
Chapter 2-Literature Review
2.1 CMC Composites
Composites incorporating carboxymethyl cellulose have been of great
interest in recent years. CMC has desirable properties with respect to other
polymers, such as good optical properties [24], nontoxicity, biocompatibility,
biodegradability, high hydrophilicity, and good film forming ability [25],
stability against high electrical potential, and thermal stability [26]. Several
reports on the application of CMC in composites have appeared recently [27,
28].
CMC composites are used in membranes for pervaporation. It has been
reported that CMC dense membranes were highly water permselective for
pervaporation in alcohol/water mixtures [29]. Bae and Hong [10, 30] also
studied composite membranes based on CMC. They indicated that their
composite membrane had high selectivity and permeability and it was very
effective in a pervaporation unit for a selective separation of water from
water/ethanol mixtures. They achieved improved pervaporation performance
using CMC composites compared to the current PVA/PAN composite
membrane by GFT Inc.
CMC interactions with proteins have also been studied. For example,
Cark and Glatz described the formation of a complex of CMC with casein by
electrostatic interaction [31]. Lii et al. [32] reported the formation of a CMCcasein complex with covalent bond via electro synthesis. These composites
were very stable to pH and ionic strength changes and exhibited very good
emulsifying properties and increased thermal stability.
Biocompatible carboxymethyl cellulose can form stable films on
pyrolytic graphite electrodes in aqueous solutions and provide a favorable
microenvironment for myoglobin (Mb) and hemoglobin (Hb) to transfer
electrons directly to the underlying electrodes. Good electrocatalytic properties
of the protein-CMC films toward various substrates with biological or
environmental significance, combined with the excellent stability of the films,
indicated that the protein-CMC films have a promising potential in the
fabrication of new generation biosensors or bioreactors based on the direct
electrochemistry of proteins [2].
Also CMC was used in semiconductors with polypyrrole (Ppy) [33].
This report indicated that the presence of CMC in the polymer decreased the
band gap, and the composite with Ppy is a better electronic conductor than Ppy
grown in a non-polyelectrolyte medium.
2.2 Cellulose Nanocomposites
The good mechanical properties of cellulose fibers and their potential
as a strengthening agent in composites were recognized long ago. Since then,
other properties of cellulose such as low density, biodegradability, and origin
from renewable resources have become increasingly important and have
contributed to a rising interest in this material. Recent focus has been directed
10
to cellulose nanocrystals. With an elastic modulus of 138 GPa [34] and a
specific surface of several hundred m2/g, cellulose nanocrystals have the ability
to significantly reinforce thermoplastic polymers at very small filler loadings
[35].
Recently many reports have appeared using cellulose nanocrystals as a
reinforcing filler in polymer matrix system. Some of them have shown
improved properties on their application fields. However they have also
indicated some problems caused by the characteristic of nano-phase materials.
Many literature reports emphasize (1) the dispersion of short fibers into
the matrix during processing and (2) the incompatibility between hydrophobic
thermoplastic matrices and hydrophilic cellulose filler, which usually leads to
low performance of the resulting composites. Processing problems related to
the high viscosity of the molten polymer/fiber system, the formation of
hydrogen bonds between cellulose fiber, and the fact that these fibers are
generally long and mingled, which results in the formation of aggregates, have
been reported in the literature [34,36-3 9], In order to solve some of these
problems, the blending of cellulose fillers with polymer matrices can be done
in an aqueous medium. Both suspensions must be stable, at least during the
time necessary for the mixing of the two components [33, 39].
The dynamic mechanical properties of cellulose-based composites
demonstrate significant improvement of the modulus in the rubbery state of the
matrix even at a low loading of cellulose whiskers [40].
2.3 Thermal Crosslinking in Composite Materials
Many researchers have investigated the thermal crosslinking of
poly(vinyl alcohol) (PVA) because insolubility is required for its application in
fibers or films. Water resistance was achieved by a physical crosslinking
network among small crystals of PVA formed by heat treatment. When heat-.
treated with drawing, PVA fibers become insoluble even in boiling water.
However, the insolubility of PVA thus obtained did not last for extended
periods of time [21].
Blends of PVA and PAA, have been investigated as separation
membrane materials [41-421. According to these studies, the higher
pervaporation separation was obtained with increase of the PAA contents.
They also indicated that the swelling degree of these membranes decreased
with increase of the PAA content up to 20 wt% in their membranes due to the
increase of the crosslinking portion.
Kawakami and Kawashima [43] investigated the intermolecular
crosslinking between PVA and PAA with esterification by dry heat treatment.
According to these studies, the degree of crosslinking was relatively low. The
maximum degree was at most 14% of PAA repeat unit even at the best heattreatment conditions. Such a low degree of reaction often causes practical
problems such as a high level of swelling in water. In this study, they indicated
that a large number of unreacted PVA chains and PAA can leak out into water
if the PVA network is highly swollen. In some cases (e.g. ion-exchange fibers)
12
about 40 mol % of degree of crosslinking reaction is required to suppress such
swelling and leakage. Hence other researches about modification of heat
treatment conditions have been studied improve the crosslinking reaction.
H. Vazquez-torres and J.V. Cauich-rodriguez [44] studied the thermal
characterization of PVA/PAA and PVA/PAAm blend films by crosslinking
through heat treatment. Water retention (absorbency) of these hydrogels was
reduced by thermal treatment and their values depended upon both the heating
time and the blend composition of the PVA/PAA blend. The extent of cross
linking was estimated for PVA/PAA hydrogels by using their absorbency
values in the Flory-Rehner equation. Based on this calculation, the cross
linking degree was higher the longer the heating time for a given blend
composition.
Recently, Yannas and Tobosky were able to crosslink gelatin by a
method of dehydration with vacuum and heat. They postulated that this cross
link was due to formation of interchain amide links. So Soignet, Benerito, and
Pilkington [45] attempted to apply this concept by utilizing cotton cellulose
containing both acid and amine group. They attempted to crosslink cotton
fabrics containing grafted amine and carboxymethyl groups by the
simultaneous application of heat and vacuum. They indicated that the heat and
vacuum treatment removed acid and water from amine group and cotton matrix,
so they can achieve a H-bond cross link between carboxyl group and amine
group in their modified fabrics.
13
Chapter 3-Materials and Methods
3.1 Materials
Sodium carboxymethyl cellulose (Na-CMC, D5 1.2, M.W250,000,
M.P=270°C), was obtained from Aldrich Chemical Company Inc. (Milwaukee,
WI). Glycerin (M.W=92. 10) was obtained from Allied Chemical (General
Chemical Division, Morristown, NJ). Microcrystalline cellulose (MCC, Avicel
PH 101) was provided by FMC Corp. Cellulose nanocrystals (NCCs) were
derived from Whatman #1 filter paper which was obtained from the Whatman
Company (Clifton, NJ).
3.2 Cellulose Nanocrystal Preparation Procedure
The conventional method to make cellulose nanocrystals from various
sources is partial hydrolysis utilizing sulfuric acid [46-48]. The cellulose
source was filter paper which was ground in a Wiley mill to pass a 40 mesh
screen. It was then placed in a 65% H2SO4 (v/v) solution for 50 mm and
heated to 60 °C with medium stirring. The cellulose to acid ratio was 1:10 g/ml.
The mixture remained ivory colored after hydrolysis and was then centrifuged
and decanted. A solution of 5% sodium bicarbonate was added to the
centrifuge solids to neutralize any remaining acid and the centrifugation
repeated several times. After a neutral pH was obtained in the centrifugate,
deionized water was added to the centrifuge solids. This rinse was repeated 23 times. The centrifuge solids were then suspended in distilled water and
14
subjected to ultrasonic irradiation in a "Branson sonifier" 250 for 5 mm at full
power to disperse the NCC. The suspension was then further dispersed in a
Waring blender for 20 mm at the high blending speed. The aqueous suspension
was subjected to ultrafiltration to remove any remaining ions present in the
cellulose suspension. The conductivity of the suspension was monitored with
the aid of an EC tester (Oakton Instruments) periodically during filtration until
the conductivity reached <10 microsiemens (tS/cm). Then the percent solids
in the cellulose suspension were measured by fully drying an aliquot of the
suspension in a vacuum oven at 60°C overnight. This suspension was then used
directly in our experiments.
3.3 Cellulose Nanocomposite Film Preparation Procedure
We made cellulose nanocomposite films having different NCC weight
contents. The composite material was composed of CMC, either NCC or MCC
and glycerin as a plasticizer. Our control film for comparing the effect of NCC
and MCC was made with CMC and Glycerin (90:10 (w/w)). Then other films
were adjusted by controlling the amount of CMC and NCC or MCC. The NCC
or MCC concentrations ranged from 5% to 30%. The glycerin concentration
was kept constant at 10%.
A CMC stock solution was prepared by dissolving Na-CMC in
deionized water at room temperature for 2 hr under medium stirring. An
appropriate amount of NCC suspension was then added to the CMC solution.
15
Glycerin was added and then this solution was mixed at room temperature for
1 hr with medium stirring. The solution was then subjected to ultrasonic
irradiation for 5 mm at full power to disperse the NCC and reduce any
aggregation that may have occurred during the mixing process. This dispersion
was then poured into a Petri dish and air-dried for 3-4 days to obtain a film.
MCC-containing composite films required an additional step to
completely disperse the MCC in the stock solution. The mixture was dispersed
in a Waring blender for 1 5mm immediately prior to pouring into a Petri dish.
3.4 Cellulose Nanocrystal Characterization Techniques
Cellulose nanocrystals are typically characterized for size by
transmission electron microscopy (TEM). They can also be characterized by
dynamic light scattering (photon correlation spectroscopy, PCS). However, this
technique was found to give poor results due to a lack of appropriate
equipment on campus.
3.4.1 Transmission Electron Microscope (TEM)
The particle sizes of the cellulose nanocrystals were determined by
examination in a TEM (Philips CM- 12) operated at 6OkeV and magnification
at 100,000X. The cellulose suspension was subjected to ultrasonic irradiation
for 5 mm to avoid any aggregation of cellulose particles. The cellulose
suspension was dropped on copper grid and then stained with ammonium
16
molybdate (2% aqueous). The coated grid with cellulose nanocrystals is then
subjected to a TEM image analysis.
3.5 Quality of Dispersion
The quality of the NCC dispersion in the composite films was observed
using both an optical microscope and scanning election microscopy (SEM).
The film was cut with a razor blade and mounted to observe the cross section
of the composite films.
3.5.1 Optical Microscope
The films were observed with the aid of an optical microscope (Eclipse
E400, Nikon) and images were obtained using an attached camera
(Photometrics Cool Snap, Division of Roper Scientific, Inc.). The films were
viewed with polarized light in the optical microscope because anisotropic
cellulose crystals rotate light.
3.5.2 Scanning Electron Microscopy (SEM)
The films were observed in cross section with a SEM (AmRay 3300FE,
manufactured by AmRay, mc) operated at 16kV.
17
3.6 Material Properties
Films were tested on a tensile tester (Sintech hG, ) and dynamic
mechanical analyzer (DMA) to measure mechanical properties. Thermal
degradation was also investigated on TGA to analyze thermo gravimetric
behavior in the different temperature range.
3.6.1 Mechanical Testing
The strength and stiffness of the samples were measured with the aid of
a universal testing machine (Sintech hG, MTS System Corp. Eden Prairie,
MN). All the samples (50iim thickness, 10mm width, 40mm length) were cut
to a dog bone shape (see Appendix figure Al). The strain rate was 1mm/mm.
Tensile strength and tensile modulus were calculated based on the loadelongation curve. The elongation at the break was also measured. At least five
specimens were measured for each sample and only those samples breaking in
the middle section were retained in the calculation. Also, mechanical behavior
was measured on a DMA instrument (Pyris Diamond DMA, PerkinElmer
instruments, Boston, MA). The visco-elastic behavior of the composites was
measured as a function of temperature between 50°C-270°C, with a fixed
frequency of 1Hz. Sample dimensions were 50iim thickness, 10mm width,
and 40mm length.
3.6.2 Thermal Testing
The thermal degradation behavior of the composites was investigated
using a thermo gravimetric analyzer (Modulated TGA 2950, TA instruments).
The weight of the samples varied between 2-3 mg. The samples were heated
from room temperature to 400°C at a 20°C/mm heating rate. The test was
conducted under nitrogen gas to avoid oxidation.
3.7 Thermal Crosslinking
NCC-fihled CMC (without glycerin) was also used for a thermal
crosslinking study. The acid form of CMC was obtained by passing a sodium
CMC solution through a cation exchange resin: Dowex® HCR-W2, H,
Mallinckrodt Baker, Inc. (Phillipsburg, NJ).
3.7.1 Procedure
The ion exchange resin was placed in a column and conditioned with
pH 3 hydrochloric acid. The resin was then rinsed with deionized water 3 times.
Then Na-CMC solution was passed through the column. Analysis for sodium
showed almost complete conversion of the CMC to the acid form. The CMC
solution had pH 4 after passing the column and titrated with 0. iN NaOH
solution to measure molar concentration (see Appendix figure A2). The
concentration of the acid form was 2.88 mmol/ g in CMC and it was 60%
conversion. Acid-form CMC solution was then mixed with NCC dispersion in
19
a flask for 1 hr under medium stirring. This mixture was subjected to ultrasonic
irradiation to disperse the NCC. This solution was then poured into a Petri dish
and air-dried for 3-4 days. The obtained films were heated under the liquid
nitrogen gas at various temperature (80, 100, 120 °C) for 3 hr to attain
crosslinked films.
3.7.2 Water dissolution Test
Samples of the crosslinked composites, which were previously
thermally treated at various temperatures, were immersed in distilled water at
room temperature for various periods (15 mm, 1, 3. 7, 15, 24, 72 hr) to
measure their water resistance. The loss of mass experienced by the samples
during immersion was determined by the weight change between the initial
dried sample and that of the same sample after immersion and subsequent
drying in a vacuum oven at 60 °C for 24 hr. Percent dissolution (PD) was
calculated as:
PD = [(Wtd Wtd) / Wtd]100
(1)
Where WtId is the weight of dried film after the immersion test and Wtd is the
initial weight of the dried film.
3.7.3 Water Vapor Transmission
The permeability of the crosslinked composite films was investigated
using a water vapor transmission test. We used a small amount of glue to seal
20
between the edge of the film (thickness = 10 urn) and the lid of ajar filled
about
'/2
full with distilled water. The jar was fitted with a lid containing a 3
cm diameter hole in it and placed in a controlled environmental chamber (30
°C, 30% relative humidity). Mass change was measured at various times and
average water vapor transmission rate (WVTR) was calculated by mass flux
(J):
J=M/(At)
(2)
Where M = weight loss of water (g) at time t
A = area of film available for mass transfer
t = time (day)
(m2)
21
Chapter 4-Results and Discussion
The dimension of a single cellulose nanocrystal (marked with arrows in
Fig. 3) was measured with the aid of Scion image analysis program (Velu
Palaniyandi, private communication). The average length of the fiber was 85
nm and the average width of the fiber was 3 nm. The surface of the NCC was
partially suiphonated during the hydrolysis process. As a result, the
nanocrystals are negatively
charged. Thus they
spontaneously form an
electrostatically stabilized
colloidal suspension.
However agglomeration
does occur, especially over
time. This is common with
many nanophase materials.
Figure 3. TEM image of cellulose nanocrystals
22
4.1 Comparison of MCC and NCC
4.1.1 Imaging of Films
Figure 4. Optical microscope image under crossed polarizers of 90%CMC1 0%Glycerin (left) and 8 0%CMC- 1 0%NC C-i 0%Glycerin (right) composites
The surface of the various composite film samples was observed with the aid
of an optical microscope. Figure 4 compares the control sample (90%CMC and
10% glycerin) with the 80%CMC, 1 0%NCC and 10% glycerin composite film.
The NCC appeared to be well dispersed as no large aggregates were observed.
The structure observed in the image presumably arises from out of focus
nanoparticles. Since they are smaller than the wavelength of light, they cannot
be observed directly. However, they still diffract light and the distorted image
is apparent in Fig. 4.
The cross sections of the composite films were also observed with aid
of SEM. The films were fractured in flexure and the fracture surfaces were
23
viewed (Figure 5).
Figure 5. SEM images of 90%CMC-1O%Glycerin (top) and 80%CMC1 O%NCC- 1 O%Glycerin (bottom) composite films
24
The structure of the fractured surface of the unfilled film was clearly
different than that of the filled nanocomposite film. The unfilled film appeared
to break in "sheets" of polymer and the fracture surface exhibits a layered
structure. On the other hand, the 10% NCC filled film shows a rough fracture
surface, indicating that the fracture mechanism may be altered in the presence
of NCC. On a macro scale, the filled films were more brittle than the unfilled
films.
4.1.2 Mechanical Properties
The influence of filler on tensile strength and tensile modulus in CMC
composite films was investigated. A composition of 90% CMC and 10%
glycerin was selected as a control. Tensile strength is defined as the stress
required for rupture the sample on the load-defection curve. Tensile modulus is
defined as the resistance to deformation by initial slope in the linear elastic
region (see Appendix Figure A3). Extension is the total elongation at the point
where the sample ruptures. The measurements are tabulated in Appendix Table
JI
25
40
35
30
0)
C
+
w 25
(n
C
Control
F-
NCC
20
AMCC
15 +-
0
-5
5
10
20
15
25
30
35
% NCC/MCC content
Figure 6. Tensile strength value for NCC and MCC on CMC based films
NCC-fihled films showed a significant improvement in tensile strength
compared to the control (Fig. 6). The maximum value was observed at 5%
NCC content and was significantly greater than films filled with 5 % MCC.
While the MCC-fihled
samples showed
particulate filler
behavior, in which the
strength decreases with
increasing filler content,
S
-.
Figure 7. Polarized microscopic image of
80%CMC-1O%MCC-1O%Glycerin composite
the NCC-fihled films
showed reinforcement,
26
especially at the low 5% loading. The tensile strength value of composite with
5
% NCC is 17% higher than the control and 30% higher than the
5
% MCC
composite. However at filer contents >5% NCC, the tensile strength value
starts to decrease, probably due to the agglomeration of NCC. The
microcrystalline cellulose does not act as reinforcing filler in this composite,
also probably due to the agglomeration of the MCC, which was observed
optically (Fig. 7).
As already mentioned in chapter 2, other literature reports
incorporating NCCs as filler showed the ability of NCC to significantly
reinforce a polymer matrix system at very small filler loadings. Our study the
supports these findings since we also observe an improvement in strength at a
low concentration.
The tensile modulus value of this composite also shows very significant
increase in the presence of NCC. Figure 8 shows the tensile modulus value of
NCC and MCC composites
27
3
Control
2.8
NCC
26
AMCC
2.4
0
CD
2.2
0
e 1.8
U)
16
-5
0
5
10
15
20
25
% NCC/MCC content
Figure 8. Tensile modulus value for NCC and MCC on CMC based films
The maximum tensile modulus value in the presence of NCC is again
observed at a low filler loading (5%) and it is 60% higher than the control
value and 85% higher than the corresponding MCC composite. The tensile
modulus value decreases above 5% filler contents. MCC does not demonstrate
an improvement of the tensile modulus value in this composite. We speculate
excessive agglomeration may be the cause of this unusual behavior, but more
research is required before a clear understanding can be attained.
28
7
6
5
control
i NCC
MCC
n
5
10
15
20
25
30
35
°/NCC and °AMCC
Figure 9. Percent Elongation at break
Most unusual is the fact that the extent of elongation shows the highest
value at the 5% NCC content. This is not what is expected as a ductile polymer
is filled with a brittle material. The elongation typically decreases with filler
content in most cases. However, in the case of NCC nanoparticles, the
elongation at break is seen to rise about 60% from the control value and the
corresponding MCC value. The cause of this behavior may be crazing of the
polymer matrix (Prof. Steve Eichhom, Manchester University, Manchester,
England, private communication). The small size of the filler particle may
give rise to small crazing cracks in the CMC which actually redirect crack
propagation and result in additional elongation before the material fails.
29
Further work is required to elucidate the mechanism of the unusual rheological
behavior.
Dynamic mechanical analysis (DMA) experiments were performed on
the composites reinforced with 10, 20, 30 wt% of NCC. The temperature was
ramped from 50°C to 250°C, however no significant different was observed
below 170°C.
10
3-
8
0
o7
D)
[ci
5
I
170
180
190
I
200
210
220
230
240
Temperature (°C)
Figure 10. Storage modulus curve for composite samples
Below 210 °C, the decrease of the storage modulus (G') in the
composites was moderate. However, above 210°C increasing NCC filler
content gave higher G' values. Other systems have shown similar behavior
where the reinforcement due to filler is especially evident above the glass
30
transition temperature (Tg). The Tg of CMC varies greatly depending upon the
moisture content of the polymer, but generally is about 180 °C for 0% moisture
content. Thus the increased storage modulus values above 210 °C are
probably above the Tg in this system. This effect is most likely due to
percolation [491. This means that the filler content is high enough that a
continuous network of filler particles is formed, acting as a rigid reinforcement
for the soft polymer matrix above the Tg. Similar behavior due to percolation
has been reported for other nanocomposite materials [50-521. According to the
report [51, 52], percolation occurred at low concentration between 2% and 3%
volume in the nanocomposite. The theoretical percolation threshold for
particles with aspect ratios of about 50 is approximately 1% [53]. Thus the
filled polymer systems studied in this project should all be well above the
percolation threshold. Above 240°C the storage modulus rapidly decreased
due to the degradation of cellulose and the melting of the CMC.
The increase in thermal performance of the composites was also
observed in the loss factor (Tan 6) (Figure 11).
0
7
5
0
2
1
-r
200
220
240
260
Temperature (°C)
Figure 11. Loss factor (Tan 6) curves for composites
The maximum of the tan 6 peak for relaxation increased with
increasing NCC content. Similar behavior has been reported for other filled
composites [35, 54]. The shift in tan 6 may be explained by the same
percolation mechanism described above. These results suggest that NCC has a
strong effect on the thermal degradation behavior of the tested composites.
4.1.3 Thermal Properties
Thermogravimetric analysis (TGA) has been widely used to rapidly
determine the thermal stability of various substances. In our study the thermal
behavior of NCC in CMC composite was investigated using TGA. A sample
TGA graph is shown in appendix figure A4. The degradation behavior of pure
32
CMC film shows the weight loss starting at its melting point (270°C) and has a
very narrow temperature range of degradation. Pure NCC films start to degrade
at a lower temperature (230°C) than CMC, but show a very broad degradation
temperature range. The degradation behaviors for all the glycerin-containing
composite films are shown in Figure 12.
100
80
-90C lOG
.2
85C5N10G
60
1
*-8001ON1OG
----70C20N10G
6003ON1OG
40
150
200
250
300
350
400
Temperature (°C)
Figure 12. TGA curves for NCC composites
As expected, the thermal degradation of the composite films is
intermediate between the pure CMC and pure NCC. However, the relationship
does not appear to be in direct proportion to the composition. In the DTGA
data (Fig 13), NCC composites show only two major peaks for the threecomponent mixtures. The first peak (270-290 °C) is thought to represent the
33
degradation of filler and plasticizer, and the second peak represents the
degradation of CMC in presence of filler and plasticizer. The first peak at
290 °C, presumably from the glycerin since it is present in the 90C lOG
sample, increases in area, but does not shift significantly in temperature until
the NCC content is 20% or greater. The second peak moves slightly to right
with higher NCC concentration. Figure 14 shows the temperature range where
10% to 40% weight loss occurs. These data indicate that there may be a close
association between the NCC and the glycerin and/or CMC at low filler
concentrations.
--90C lOG
a)
E
8505N10G
1
--80Cl0Nl0G
'70C2oN lOG
--60C30Nl0G
08
0.6
0.4
4-
.c 0.2
0 '-i
-0,2
iiii_M
I
I
150
200
250
I
300
350
400
Temperature (°C)
Figure 13. Thermal gravimetric curve per time on each temperature
34
45
40
35
__ 30
U)
U)
225
-
20
15
10
+--iU'Yo N(.X
-_______________
51
270
300
330
Temperature (°C)
Figure 14. Temperature-weight loss curves
4.2 Thermal Crosslinking
4.2.1 Water Dissolution
Cellulose nanocrystals (NCC) are not soluble in water. So if the CMC
is crosslinked with NCC, the resulting composite can exhibit water resistance
even though CMC is a hydrogel polymer. In this study, the degree of
crosslinking was estimated by measuring the percent dissolution (Fig. 15 and
Appendix Table B2).
35
40
-+-- 120C
C
0
1000
--*-- 800
0
(0
(0
No heat
20
75
Soaking Time (hr)
Figure 15. Percent dissolution vs. time curve for crosslinked NCC/CMC
composites
From the results of dissolution test, we can see the significant water
resistance achieved by thermal crosslinking. The composite which is not heat
treated shows a 50 % water solubility within 3hr and almost 60% weight loss
after 3days. The lightly crosslinked film (at 80°C) shows better water
resistance than the no heat treatment film. From these data we conclude that
higher temperatures give higher degrees of crosslinking and therefore
improved water resistance in these composite films (Fig. 16).
36
70
0
40
30
,d)
0
20
3day
1day
10
0
20
40
60
80
100
120
140
Temperature (°C)
Figure 16. Dissolution in water (%) after soaking for three days for 3 hr heat
treatments at the listed temperatures.
4.2.2 Thermal Properties
Thermal crosslinking did not show any notable change in the TGA
degradation behavior (Fig. 17).
37
100
90
80
'I,
170
60
50
40
100
150
200
250
300
350
400
Temperature (°C)
Figure 17. Thermo gravimetrie curves for crosslinking composites
4.2.3 Mechanical Properties
As mentioned previously (chapter 4.1) NCC was observed to enhance
the strength and stiffness of CMC/Gly/NCC composites. The CMC/NCC
composite prepared here without glycerin showed a relatively high tensile
strength value which increased with increasing heat treatment temperature (Fig.
18, Appendix Table B3). Evidently the crosslinks resulting from thermal
treatment lead to increased strength.
95
cL
90
4-.
I4-.
C')
u 80
CI)
cJ)
F 75
20
40
60
80
100
120
1 40
Temperature (°C)
Figure 18. Tensile strength values for films heat treated for 3 hr at the listed
temperatures
As expected, the tensile modulus values also increased with increasing
heat treatment temperature (Fig. 19).
Increased crosslinking typically leads to increased brittleness in the
resulting composite. Percent elongation to failure in the heat treated samples
decreased by
25% (Fig. 20). However, the decrease in % elongation was
insignificant from the 80 °C sample to the 120 °C sample, although the tensile
strength and tensile modulus increased significantly.
39
3
a-25
0
0
E
Cl)
1)
05
0
20
40
60
80
100
Temperature (°C)
120
140
Figure 19. Tensile modulus values for films heat treated for 3 hr at the listed
temperatures.
4
0
0
o
I
L
r
o
Li]
20
40
60
80
100
Temperarture (°C)
120
140
Figure 20. Percent elongation to failure for NCC/CMC films heat treated for 3
hr at the listed temperatures.
4.2.4 Water Vapor Transmission
Water vapor transmission rate (WVTR) through the crosslinked films
was determined and WVTR was calculated by mass flux (J):
J=M/(At)
(2)
Where M = weight loss of water (g) at time t
A
t
area of film available for mass transfer
(m2)
time (day)
Thermal crosslinking under 120 °C reduced the water vapor
permeability in this composite material from 1480 g/ m224hr to 1320 g/
m224hr for test conditions of 30 °C and 30% relative humidity (Fig. 21 and
Appendix Table B4). This is a reduction of 11 % in WVTR.
9
8
7
6
0)
0
0)4
3
eat)
:ed)
I
0
000
1.00
2.00
3.00
4.00
5.00
6.00
time (day)
Figure 21. Water vapor transmission rate for the film with / without heat
treatment for 3 hr
7.00
41
The WVTR of other cellulose based systems is reported in the literature
[55-58].
However, they are not directly comparable since they were conducted
at different temperatures and relative humidities. For example in composites
composed of corn-zein (CZ) and Me cellulose (MC), WVTR decreased from
1226 gI m224hr to 1060 g! m224hr with increasing MC content in the
composite
[571.
In another study using acrylic latex, carboxymethyl cellulose,
ethylene glycol and other compounds, the resulting films showed a WVTR of
2200 g/ m224hr
[58].
The results of this study are in general agreement with
those listed in the literature.
42
Chapter 5-Conclusion
Cellulose nanocrystals (NCCs) have successfully been shown to
improve the material properties of carboxymethyl cellulose (CMC) composite
films. At low filler content (5%), NCC was well dispersed without observed
agglomeration of NCC, also, at this filler loading, NCC showed a 30% increase
in tensile strength and an 85% increase in tensile modulus comparing to MCC
filled composite films.
Unusual behavior was observed in elongation to break of the films.
Although NCC is a very brittle filler material, elongation increased by 60% at
the 5% filler loading in a CMC (containing 10% glycerin as a plasticizer)
composite film. NCC content appeared to have an effect on the thermal
behavior in NCC-filled CMC (with glycerin plasticizer) composites.
Crosslinking between CMC and NCC was successfully obtained by
heat treatment. Higher temperatures induced higher degrees of crosslinking,
resulting in improved mechanical properties (tensile strength and tensile
modulus). Crosslinking the films also gave remarkable water resistance to this
system. Water vapor transmission rates (WVTRs) decreased slightly in
crosslinked composites compared to composites not undergoing a heat
treatment.
43
5.1 Suggestions for Future Work
Material properties in our system were improved by incorporating NCC
as a reinforcing filler. The improvement was a function of filler content. Filler
contents lower than 5% may improve the material properties even further due
to good dispersion of the nanoparticles in the composite. Also, the unusual
elongation behavior and thermal behavior of the films deserve more research.
In addition, we have shown the possibility of thermal crosslinking
between CMC and NCC. The material properties of the crosslinked composites
can be changed by various factors: NCC size, shape and content, DS of CMC,
heating temperature and time, among other factors. Further research on the
crosslinked systems are justified and suggested to determine the applicability
of these systems to various industrial fields.
Bibliography
[1] J.Gao, L.G.Tang, Cellulose Science(Chinese), Science Press, Beijing, 1996,
p.1-12
[2] H. Huang et al. Bioelectrochemistry, 2003, 61, p.29-38
[3] K.Balser, L.Hoppe, T.Eicher, M.Wendel, A.J.Astheimer, Ullmann's Encyci.
md. Chem., 5th ed., Vol. AS (1986). p.461
[4] Thomas Heinze and Kary Pfeiffer, Die Angewandte Makromelekulare
Chemie, 1999, 266, p.37-45
[5] Kamide, K., Okajima, K.,Kowsaka, K., Matsui, T., Nomura, S. and Hikichi,
K. Polym. J., 1985, 17(8), p.909-918
[6] Reuben, J. and Conner, H.T., Carbohydr. Res., 1983, 115, p.1-13
[7] Baar, A. and Kulicke, W.-M., Macromol. Cell. Phys., 1994, 195, p.l4&31492
[8] Huand, Yuhui., Li, Zuomei., Ma, Zhiyi., Chemical journal of Chinese
universities, 1990, 11(8), p.882-886
[9] K.Nakamura, T.Harakeyama, H.Hatakeyama, Kobunshi Ronbunshu, 1996,
53(12), p.860-865
[101 K.S.Bae, Y.K.Hong and J.M.Lee, Seni Gakkaishi, 1996, 52(12), p.650656
[11] Klaus, U., Cellulose Chem. Technol., 1996, 30, p.3-12
[12] Mushtaq, A., David, C.A., Christian, D.E., Alan, M.E. and Robin, K.H.,
Cellulose, 1996, 3, p.77-99
[13] Seves, A.M., Sora, S.N., Testa, G. and Rossi, E., Cellulose Chem.
Technol., 1998, 32, p.197-208
[14] Li, G.K. and Pan, S.H., Chinese Pat., 1994, 2L941583.X
[15] Xue, M.D., Revol, J.F. and Gray, D.G., Cellulose, 1998, 5, p.19-32
[16] Ranby, B.G.,Discussions Faraday Soc, 1951, 11, p.158-164
[17] Xiao-fang Li, En-yong Ding and Guo-kang Li, Chinese Journal of
Polymer Science, 2001, 19(3), p.291-296
[18] Millet, M.A., Moore, W.E and Saeman, J.F, Ind.Eng..Chem, 1954, 46,
p.1493-1497
[19] Fan, L.T.G., M.M. and Lee, Y.H., Cellulose Hydrolysis. 1987,
Newyork: Springer-Verlag
[20] Stephen L. Rosen, Fundamental principles of polymeric materials. 2nd
edition
[21] George Odian, Principles of polymerization. 3rd edition, p.17-18
[22] K.Kumeta, I.Nagashima, S.Matsui, K.Mizoguchi, Journal of applied
polymer science, 2003, 90, p.2420-2427
[23] Fei Jianqi and Gu Lixia, European polymer journal, 2002, 38, p.16531658
[24] F.H.Cheung, D.Bloom and G.G.Steven, J. Mat. Sci, 1990, 25, p.3814
45
[25] A.B.Savage, A.E.Young, A.T.Maasberg, Cellulose and cellulose
derivatives, in E. Ott, H.M, M.W. Grafflin (Eds.), High Polymers, Vol 5,
Jnterscience, New York, 1954
[26] A.F. Diaz and B.Hall, IBM J. Res Develop, 1983, 21, p.342
[27] J.M.Felix and P.Gatenholm, J. Appl. Polym. Sci., 1993, 50, p.699
[28] T.Schimidzu et al., J. Chem, Soc. Chem. Commun. 1987, 33, p.27
[29] C.E.Reineke., J.A.Jagodzinski. and K.R.Denslow., J. Membrane Sci.,
1987, 32, p.207
[30] K.S.Bae., Y.K.Hong., S.W.Lee., and J.M.Lee. Journal of the Korean fiber
Society, 1995, 32(11), p.1082-1089
[31] K.M.Clark, C.E.Glatz, Chem. Eng. Sci. 1992, 47, p.215-224
[32] H.Zaleska, P.Tomasik, C.Y.Lii, Food Hydrocolloids, 2002, 16, p.215-224
[33] P.Herrasti, P.Ocon, H.Sanfa Bian, L.A.Avaca, C.R.Alves, J. Mat. Sci.
Letter, 2002, 21, p.679-683
[34] Nishino, T., Takano, K., Nakamae, K J., Polym. Sci. Part B, Polym. Phys.,
1995, 33, p.1647
[35] Chazeau, L., Cavaille, J.Y., Canova, G., Dendievel, R. Boutherin, B.J.,
Appl. Polym. Sci. 1999, 71, p.1797-1808
[36] C.Klason, J.Kubat and H.E.Stromvall, Intern. J. Polym. Mat. 1984, 10,
159
[37] P.Hajji, H.Y.Cavaille, V.Favier, C.Gauthier and G.Vigier, Polym.
Compos. 1994, 17(4), p.612
[38] A.Boldizar, C.Klason, J.Kubat, P.Naslund and P.Saha, Tnt. J. Polym.
Mater. 1987, 11, p.229
[39] A.Dufresne, J.Y.Cavaille and M.Vignon, Appi. Polym. Sci. 1997, 64,
p.1185
[40] M.Matos Ruiz, J.Y.Cavaille, A.Dufresne, J.F.Gerard and C.Graillat,
Composite Interfaces, 2000, 7(2), p.1 17-131
[41] Rhim,J.W, Yoon,S.W, Kim,S.W, Lee,K.H., J. Appl. Polym. Sci, 1997, 63,
p.521
[42] Rhim,J.W, Kim,Y.K., J. Appl. Polym. Sd., 2000, 75, p.1699
[43] Kawakami, H., Kawashima, K., Kobunshi Kagaku, 1960, 17, P.273, 316,
319
[44] H.Vazquez-torres, J.V.Cauich-rodriguez, C.A.Cruz-ramos, J. Appl. Polym.
Sci., 1993, 50, p.777-792
[45] D.M.Soignet., R.R.Benerito., and M.W.Pilkington., Textile research
journal, 1696, 39(4), p.485-496
[46] Li, Guokang.; Ding, Enyong.; Li, Xiaofang., Faming Zhuanli Shenqing
Gongkai Shuomingshu, 2002, p.5,6
[47] M.Grunert and W.T.Winter, Book of Abstracts, 2 19th ACS National
Meeting, San Francisco, CA, March 26-30, 2000
[48] Dong, X.M., Revol, J.-F.,Gray, D.G., Cellulose, 1998, 5, p.19
[49] L.H.Speriling, Physical Polymer Science, 3rd Edition, p.363-365
[50] M.N. Angles, A. Dufresne, Macromolecules, 2001, 34, p.2921-2931
46
[51] Dubief, D., E. Samain, A. Dufresne, Macromolecules, 1999, 32, P.57655771
[52] Cappozi, C.J., Rutgers University, SURF/REU 2003 Fellow
[53] Garboczi, E.J., K.A. Snyder, J.F. Douglas. Phys. Rev. E., 1995, 52(1), p.
8 19-828
[54] D.Dubief, E.Samain, A.Dufresne. Macromolecules, 1999, 32, p.57655771
[55] T.Azuma, H.Shibaoka, K.Yamagishi, M.Masami, Jpn,Kokai Tokkyo
Koho, 1991, p.4
[56] D.J.Carmody, H.Viazmensky, B.L.Nyberg, B.J.Persson, U.S.
Pat.Appl.Publ, 2005, p.9
[57] H.Y.Koh, M.S.Chiiman, Food Science and Biotechnology, 2002, 11(3),
p.310-315
[58] James R Hunt, U.S. 1990, p.5
47
APPENDICES
W
WO
L
LO
D
Dimension
mm
Width of narrow section
6
Width of over-all
10
Length of narrow section
6
Length of over-all
40
Distance between grips
18
Figure Al. Sample shape of dog bone
12
10
8
x
4
2
0
0
2
4
6
8
10
12
14
0.1 N NaOH (ml)
Figure A2. Titration curve for acid form of CMC with 0.1 N NaOH
18
Is
16
14
12
-10
w8
C.)
4
8001ON1OG
2
----.±
0.2
-2
0.4
0.6
0.8
Extension (mm)
Figure A3. Load-deflection curve
100
4.z
60
40
150
200
250
300
350
400
Temperatur (°C)
Figure A4. Thermo gravimetric curves of pure NCC and CMC films.
49
Table Bi. Measurements of tensile test
Sample
85C5N10G
8001ON1OG
Extension
Sample
9001OG
(MPa)
TM*
(GPa)
35.89
2.75
6.25
37.79
2.58
33.55
2.46
35.50
(MPa)
27.31
1.38
4.13
5.04
29.43
1.53
3.80
5.21
30.60
1.50
3.42
2.80
30.80
1.52
33.55
2.53
29.63
1.81
28.47
2.58
4.48
24.96
1.40
4.06
31.80
2.51
4.40
29.78
1.40
4.00
32.97
2.18
4.82
27.30
1.62
3.50
34.53
2.37
27.10
1.24
85C5M10G
28.09
7OC2ON1OG
6OC3ON1OG
Exten-
TM*
(GPa)
1.55
30.22
2.52
4.32
33.73
2.72
31.20
2.70
32.18
29.06
8OC1OM1OG
21.70
1.26
4.56
21.09
1.29
4.12
20.27
1.54
2.35
23.78
1.25
2.28
21.05
1.59
20.86
1.34
2.89
7OC2ON1OG
28.09
3.53
30.82
3.24
17.15
1.48
3.00
27.12
3.24
20.08
1.29
2.50
27.31
20.47
1.25
27.70
23.20
1.26
* where TS = Tensile Strength, TM = Tensile Modulus
50
Table B2. Datum of dissolution test
Wt loss (%)
Time"hr
at 120°C
'
/
0.25
Wt loss (%)
at 100°C
Wt loss (%)
484
6.06
11.67
14.16
16.09
16.10
6.42
6.72
6.67
7.27
8.00
8.33
8.40
1
3
7
15
24
72
6.12
7.56
8.86
9.62
10.87
11.89
at 80°C
16.81
18.92
Wt loss (%)
at No heat
38.18
51.59
50.00
51.61
54.84
55.34
57.89
Table B3. Mechanical properties of thermal crosslinking composites
Heat treatment
temperature (°C)
TS (MPa)*
TM (GPa)*
Elongation (%)
120
92.64
2.72
3.7
93.37
2.4
3.1
91.91
1.73
4.6
91.67
1.85
3.6
89.2
2.14
3.4
86.06
1.83
4.2
83.13
1.68
5
89.23
1.74
3.8
80.21
1.43
4.9
79.72
1.69
4.7
78.61
1.69
5
100
80
noheat
* where TS
Tensile Strength, TM = Tensile Modulus
51
Table B4. Water vapor transmission measurements
Weight
Change (g)
Area (m2)
Time (hr)
1.43
9.62E-04
22
67.59
4.21
9.62E-04
71
61.66
8.57
9.62E-04
143
62.32
crosslinking
1 .29
9.62E-04
22
60.98
at 120°C
4.14
9.62E-04
71
60.64
7.77
9.62E-04
143
56.50
Sample
Uncrosslinking
Mass Flux
(J)