2008

This is to certify that the
thesis entitled

TITANATE AND SILANE COUPLING AGENTS BASED
SURFACE MODIFICATION OF CLAY AND THEIR EFECTS
ON THE PERFORMANCE OF POLY(TRIMETHYLENE
TEREPHTHALATE) NANOCOMPOSITES

 

presented by

DHIRAJ HASIJA

LIBRARY
Michigan State
University

has been accepted towards fulfillment
of the requirements for the

 

 

 

MS degree in PACKAGING

 

 

.A Evy/J [(Lmav m ”“741/

Major Professofs Signature

 

April 16 , 2008

Date

MSU is an aflinnative-action, equal-opportunity employer

or-.—.---u-.--g-a— -_..._

 

PLACE IN RETURN BOX to remove this checkout from your record.
TO AVOID FINES return on or before date due.
MAY BE RECALLED with earlier due date if requested.

 

DATE DUE DATE DUE DATE DUE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6/07 p:/ClRC/DateDue.indd-p.1

TITANATE AND SILANE COUPLING AGENTS BASED SURFACE
MODIFICATION OF CLAY AND THEIR EFECTS ON THE PERFORMANCE OF
POLY(TRIMETHYLENE TEREPHTHALATE) NANOCOMPOSITES
By

Dhiraj Hasija

A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
MASTER OF SCIENCE
The School of Packaging

2008

ABSTRACT
TITANATE AND SILANE COUPLING AGENTS BASED SURFACE
MODIFICATION OF CLAY AND THEIR EFFECTS ON THE PERFORMANCE
OF POLY(TRIMETHYLENE TEREPHTHALATE) NANOCOMPOSITES
By
Dhiraj Hasija

In this study, titanate and silane coupling agents modified montmorillonite
clay was embedded in PTT, poly(trimethylene terephthalate) through a melt
processing technique to study the effect of such chemical modification of clay on
the mechanical, thermo-mechanical and barrier properties of PTT clay
nanocomposites. PTT (trade name Sorona® from DuPont) is an engineering
polymer, which can be partially derived from biomass. Montmorillonite Clay was
organically modified with a titanate based coupling agent and a silane coupling
agent and were characterized by different analytical techniques, which validated
the successful modification of montmorillonite clay. In this study, petroleum-
based Sorona® was used. The outcome of this study can be applied to biobased
Sorona”. The tensile modulus, storage modulus and heat deflection temperature
(HDT) of PTT were improved through organo-clay reinforcements. Extruded cast
film of neat PTT had low percent elongation while PTT-clay nanocomposites
Showed quite ductile behavior with no break. The barrier properties of PTT film
were also investigated in extruded cast film nanocomposites. The PTT/titanate
modified clay nanocomposite film was characterized through transmission

electron microscopy (TEM) and polarized light optical microscopy (PLOM).

Dedicated to my family and friends

ACKNOWLEDGEMENTS

First of all, I would like to thank my advisor, Dr. Amar K. Mohanty, for all
his guidance, support and mentoring to complete me this research project. His
high motivations and novel ideas for my work always helped me to gain
knowledge and skills to perform this project. I would like to thank my other
committee members: Dr. Bruce Harte and Dr. Farhang Pourboghrat. They were
very supportive and helping in the completion of this research work. I am highly
obliged to US Army Soldier Systems Center, Natick MA to provide financial
support for this project. I am also very thankful to Dr. Jo Ann Ratto of Natick
Soldier Centre for providing valuable efforts for this project.

I am also very thankful to my colleagues and fellow researchers of Dr.
Amar Mohanty’s research group Ed, Dr Yash, Dr Wu, Dr. Rahul, Abhishek,
Sanjeev, Ajay and Vijoya for sharing their Skills, knowledge and expertise and
helping me in performing my experiments. I am also grateful to the Dr. Selke,
faculty and staff of School of Packaging, MSU. I am thankful to staff members of
Composite Material and Structure Center, Mike, Brian, Kelby and for their help
and co-operation. I am also thankful to Dr Rui Hang of Chemistry department for
XRD experiments. I am also thankful to all my friends and fellow graduate
students of School of Packaging who have provided me the great friendly
atmosphere throughout my Master’s program and research period.

Finally, I would also like to thank my parents, my wife, my teachers and

my friends for their support, motivation and help in my life.

TABLE OF CONTENTS

LIST OF TABLES ................................................................................................ vii
LIST OF FIGURES ............................................................................................. viii
1 Introduction ................................................................................................... 1
2 Background and Literature Review ............................................................... 7
3 Materials and Methods ................................................................................ 27
3.1 Materials .............................................................................................. 27
3.1.1 Poly(trimethylene terephthatale) (PTT) ......................................... 27
3.1.2 Montmorillonite Clay (MMT) .......................................................... 28
3.1.3 Titanate Based Coupling Agent .................................................... 29
3.1.4 Silane Coupling Agent .................................................................. 30
3.2 Methods ............................................................................................... 31
3.3 Surface Modification of Montmorillonite Clay ....................................... 32
3.3.1 Surface Modification of Clay with Titanate Based Coupling Agent 32
3.3.2 Surface Modification of Clay with Silane Coupling Agent .............. 35
3.4 Processing Equipments ....................................................................... 39
3.4.1 DSM Microcompounder ................................................................ 39 ‘
3.4.2 Twin Screw Extruder ..................................................................... 40
3.4.3 Single Screw Cast Film Extruder .................................................. 42
3.5 Characterization ................................................................................... 43
3.5.1 X-ray Photoelectron Spectroscopy (XPS) ..................................... 43
3.5.2 X-ray Diffraction (XRD) ................................................................. 43
3.5.3 Hydrophobic-Hydrophilic Balance ................................................. 44
3.5.4 Dynamic Mechanical Analyzer (DMA) ........................................... 44
3.5.5 Universal Testing Machine ............................................................ 45
3.5.6 Thermal Behaviors (DSC & TGA) ................................................. 46
3.5.7 Barrier Properties .......................................................................... 46
3.5.8 Transmission Electron Microscopy (TEM) ..................................... 47
3.5.9 Polarized Light Optical Microscopy (PLOM) .................................. 47
4 Results and Discussion ............................................................................... 48
4.1 Studies on Surface Modified Clays ...................................................... 49
4.1.1 XPS Analysis ................................................................................ 49
4.1.2 Hydrophobic—Hydrophilic Balance ................................................. 51
4.1.3 XRD Analysis ................................................................................ 53
4.1.4 TGA analysis ................................................................................. 55
4.2 Injection Molded Nanocomposites ....................................................... 62
4.2.1 Tensile Properties ......................................................................... 62
4.2.2 Thermo-mechanical Properties ..................................................... 66
4.3 Extruded Cast Films Nanocomposites ................................................. 69
4.3.1 Tensile Properties ......................................................................... 70

4.3.2 Thermo-mechanical Properties ..................................................... 75
4.3.3 Thermal Properties ....................................................................... 78
4.3.4 Barrier Properties .......................................................................... 81
4.3.5 Structural Analysis (XRD) ............................................................. 82
4.3.6 Morphological Analysis (TEM & PLOM) ........................................ 83

4.4 Comparison of Water vapor and Oxygen barrier properties of Sorona®
with conventional thermoplastics and poly lactide (PLA) ................................ 88
5 Conclusions and Recommendations ........................................................... 91
6 References .................................................................................................. 93

vi

LIST OF TABLES

Table 2.1 Physical properties of Sorona®. After Reference [6] ........................... 10
Table 3.1 Physical properties of natural montmorillonite clay (Cloisite® Na"). After
Reference [60] .................................................................................................... 28
Table 4.1 Nomenclature of the Surface Modified Clays ..................................... 48

Table 4.2 XPS Elemental Analysis of Montmorillonite Clay and Modified Clays 50
Table 4.3 Basal Spacings of Flaw Montmorillonite and Modified Clays .............. 53

Table 4.4 Weight Change of MMT, Organically Modified Clays and Titanate
Modifier ............................................................................................................... 55

Table 4.5 Weight Change (Corrected) of MMT, Organically Modified Clays and
Titanate Modifier ................................................................................................. 56

Table 4.6 Tensile properties of PTT/organo- modified Clay nanocomposites
extruded cast films (Value given in parentheses is Standard Deviation) ............ 70

Table 4.7 Storage Modulus and Tan Delta Peak of PTT/organocla y
nanocomposites extruded cast films (Value given in parentheses is .................. 76 .

Table 4.8 Barrier properties of PTT/organocla y nanocomposites extruded ........ 81

Table 4.9 Basal spacings of raw montmorillonite and modified clays ................. 82

vii

 

LIST OF FIGURES

Figure 2.1 Classification of Biopolymers. After Reference [3] ............................... 8

Figure 2.2 Possible morphologies of polymer/cla y nanocomposites. After
Reference [55] .................................................................................................... 22

Figure 2.3 Oxygen Transmission Rate of Nylon and its nanocomposites [51].... 24

Figure 3.1 Chemical Structure of Poly(Trimethy/ene Terephthalate) .................. 27
Figure 3.2 Chemical Structure of Neopentyl (diallyl)oxy tri(dioctyl) pyrophosphato
Titanate. After Reference [61] ............................................................................ 29
Figure 3.3 Chemical Structure of y-Glycidoxypropyltrimethoxysilane ................. 30

Figure 3.4 Schematic representation of steps followed for this research work... 31

Figure 3.5 Titanate surface modifier (in syringe) added to toluene in crystallizing
dish (left) and clay added to the toluene and modifier in continuous mode (right).

........................................................................................................................... 32
Figure 3.6 Schematic of Surface Modification of MMT Clay ............................... 34
Figure 3.7 Silane Coupling Agent Reaction Scheme .......................................... 36
Figure 3.8 Schematic Representation of Clay Modification with Silane Coupling

Agent .................................................................................................................. 38
Figure 3.9 DSM mini—extruder (top left), mini injection-molder (top right), tensile

mold and tensile beam (bottom) ......................................................................... 39
Figure 3.10 ZSK-30 twin-screw extruder nanocomposites strands in water bath

on left and Pelletizer on right .............................................................................. 41
Figure 3.11 Pilot-scale extrusion schematic diagrams ........................................ 41
Figure 3.12 K L3- 100 Single-screw Extruder (left) and Chill-roll (right) ............... 42
Figure 4.1 Reduction in Hydrophilicity as a Function of Modifier Content ........... 52
Figure 4.2 X-ra y diffraction pattern of raw MMT and modified Clays .................. 54
Figure 4.3 TGA curves of MMT and modified clays and titanate modifier .......... 58

viii

Figure 4.4 Expanded TGA curves of MMT and modified clays ........................... 59

Figure 4.5 TGA curves for derivative weight of MMT and organo- modified Clays

and titanate modifier ........................................................................................... 60
Figure 4.6 Expanded TGA curves for derivative weight of MMT and ................. 61
Figure 4.7 Tensile Modulus of PTT/organocla y nanocomposites ....................... 63
Figure 4.8 Tensile Strength of PTT/organocla y nanocomposites ....................... 64
Figure 4.9 Elongation at break of PTT/organocla y nanocomposites .................. 65’
Figure 4.10 Storage Modulus of PTT/ organocla y nanocomposites ................... 67
Figure 4.11 HDT of PTT and its Nanocomposites .............................................. 68
Figure 4.12 Stress-Strain Curves of PTT and its Nanocomposite Films ............. 73
Figure 4.13 Tensile Strength of PTT and its Nanocomposite Films .................... 74

Figure 4.14 Storage Modulus of PTT and PTT/organo-cla y nanocomposites films
........................................................................................................................... 77

Figure 4.15 DSC curves for extruded cast films of PTT and its nanocomposites79

Figure 4.16 Crystal/inity of extruded cast films of PTT and its nanocompOsites. 80

Figure 4.17 TEM micrograph of NC-1 extruded cast films .................................. 84
Figure 4.18 TEM micrograph of NC-1 extruded cast films at 50nm scale ........... 85
Figure 4.19 PLOM micrograph of Neat PTT films prepared at US Army ............ 86
Figure 4.20 PL OM micrograph of NC-4 films prepared at US Army Natick Soldier
Center Lab @ 50X .............................................................................................. 87
Figure 4.21 Water Vapor Transmission of polymers at 37.8’C and 50-100%RH

(LDPE, PP, Nylon-6 , E VOH and PLA), PTT at 100% RH .................................. 89
Figure 4.22 Oxygen permeabilities of polymers at 23 'C and 0% RH ................. 90

Chapter 1

Introduction

After invention of plastics during 19th century and a rapid growth in last
century, plastics have become the most versatile materials ever developed in
history of mankind. Plastics are the major contributor for modern society in
various fields. Plastics can be seen anywhere such as automobile industry,
aircrafts, packaging, computers, grocery bags and so many. Major contribution of
plastics is manufactured for packaging industry most because of their wide range
of properties, ease of processing and their versatility. Plastic has become
prevalent because these are affordable and can be engineered with a wide range
of properties. Plastics can be tailored for various uses, such as high-density
polyethylene for milk bottles, low-density polyethylene fOr plastic bags,
polyethylene terephthalate for soda and water bottles, polypropylene for ketchup
bottles, expandable polystyrene for egg crates, and polyvinyl chloride for water
pipes. Plastics can be molded into variety of shapes and sizes including
complicated small parts, and can be drawn into thin fibers. Plastics are strong but
lightweight, resistant to being degraded by chemicals, sunlight, and bacteria, and
are thermally and electrically insulating. Plastics that can be remolded again and
again are called thermoplastics, which contribute a major part in packaging. In
this study we will be discussing thermoplastics, which are termed as plastics
everywhere in this study. Plastics have become a critical material in the modern

economy, especially in packaging industry. Plastics can be shaped into thin

flexible films as well as rigid bottles. In earlier stage plastics were developed as
synthetic substitutes for natural materials, such as rubber, which
were once widely used for consumer goods. Most of the plastics, which are used,
are non-biodegradable in nature, which means they remain persistent for long
time. The non-biodegradable nature of conventional polymers and dwindling
petroleum resources are driving forces for extensive research and development
in the field of biobased polymers and their applications. Bio-based and
biodegradable polymers can substitute these conventional polymers and can

help in building an environment friendly world [1 -4].

Most of the commercially available plastics are conventional petroleum
derived plastics. Conventional petroleum poses certain environmental challenges
because of their non-biodegradable nature and problems related to disposability.
These conventional petroleum based plastics are widely used in packaging and
other industries by virtue of their good properties but these are not friendly to
environment because they are non-biodegradable. This means that these
plastics don’t degrade for years. Plastics play a dominant role in the packaging
applications. Most of the commercially available plastics are non-biodegradable
in nature. In the present scenario, conventional plastics are suffering from higher
resin cost, depleting resources and disposing problems. The incineration of
plastic wastes poses environmental concerns by adding green house gases to
our atmosphere. For these reasons there is lot of thrust on the development of

sustainable, environmentally benign and biodegradable polymers. Biodegradable

polymers are emerging as promising alternatives to conventional polymers. Most
of the biodegradable plastics are produced in batch process. It is a challenge to
find new as well as emerging applications of such biodegradable polymers that
would demand high volume production. The increase in their production volume
can bring down the cost of biodegradable polymers. Biodegradable polymers are
designed to be stable in their intended lifetime and decompose under composting
conditions. Materials made from renewable resources are attaining augmented
importance as world-leading industries and manufacturers seek to replace
dwindling petrochemical-based feedstock with agricultural and biomass based
materials. The best examples of biopolymers derived from renewable resources

are polylactides, polyhydroxyalkanoates, cellulosic plastics and starch plastics. . .

To develop a bio-polymer frOm 100% renewable resources is. highly
desirable, however, the cost - performance attributes are also major criteria to
take into account when applying biopolymers to real world applications. It may
not be desirable to have new materials derived completely from renewable
resources or from biomass if they show inferior performance. To find new
materials containing the maximum permissible content of bio-derived materials
while still maintaining cost-performance attributes is quite challenging as well as
rewarding. One of the best examples of such a ‘green’ polymer is
poly(trimethylene terephthalate) (PTT), DuPont’s Sorona®. Biobased PTT is an
example of polymer, which can be partially derived from biomass. DuPont has

discovered an alternate synthesis of 1,3- propanediol (PDO), which is one of the

raw materials for PTT that can be derived from corn. In petroleum-based PTT
both of the raw materials, 1,3 propanediol and terephthalic acid are made from
petroleum resources. Because they have the same chemical structure,
petroleum-based and biobased PTT are expected to exhibit similar properties
with that of biobased Sorona®. DuPont received the 2003 Presidential Green
Chemistry Challenge Award for biobased Sorona®. This polymer has potential

uses as fibers, films and as an engineering resin [5-7].

Conventional fillers such as minerals, metals, and fibers have been added
to polymers for decades to produce composites with improved mechanical and
thermal properties. High-aspect ratio nano-fillers also provide improvements in
barrier performance and clarity without a significant increase in density, which is
not feasible with conventional composites. The advantage of nanocomposites
over macro composites is that low level 'of nanoparticle (2-5 wt%) is needed to
enhance the properties of matrix as compared to 30-50 wt% of macro sized fillers
such as glass & wood fibers. This is because of exceptionally high aspect ratio
that is length/diameter of nano-sized fillers as compared to macro-sized fillers

[8-12].

The development of polymer/Clay nanocomposites (PCN) is one of the
latest evolutionary steps in polymer technology. Nanocomposites offer the
potential for the diversification and application of polymers due to their excellent

properties such as high heat distortion temperature, dimensional stability,

improved barrier properties, flame retardancy, and enhanced physico/thermo-
mechanical properties. The concept of nanocomposites was first introduced by
researchers from Toyota who made nanocomposites from polyamide 6 and

organophilic clay [13].

For this research study our basic aim is to improve the mechanical,
thermo-mechanical and barrier properties of PTT by incorporation of organically

modified clays. The objectives of this study can be summarized as:

. To surface modify MMT clay with titanate and silane coupling agents and

characterize the modified clay through X-ray photoelectron spectroscopy
' (XPS), X-ray diffraction (XRD), hydrophilic—hydrophobic balance and
thermo-gravimetric analysis (TGA).

o Micro-compounding processing (extrusion followed by injection molding) to
fabricate Sorona®/organoclay nanocomposites. Such micro-compounding
(compounding that needs materials for processing at the level of few grams)
experiments target to screening/optimization studies that would lead to
semi-pilot scale experiments.

. To fabricate semi-pilot scale extruded cast films from neat Sorona® as well
as Sorona®/organoclay nanocomposites.

0 Characterization of nanocomposites for their tensile and thermo-mechanical
properties, barrier properties and morphologies through XRD and

transmission electron microscopy (TEM).

These objectives will be derived in three phases. In the first phase MMT
clay will be modified with titanate and silane based coupling agent. This study will
mainly focus on the modification of MMT clay with titanate coupling agent. The
ratio of titanate coupling agent and MMT clay in the system will be evaluated for

surface characteristic studies to choose the suitable Clay for nanocomposites.

In the second phase, the above selected Clay will be used to fabricate the
PTT based nanocomposites using melt intercalation technique and optimized for
the right composition based on their mechanical and thermo—mechanical
properties. In this phase micro-compounder will be used for fabrication of

nanocomposites.

ln third phase selected composition will be fabricated in twin-screw
extruder followed by cast film extrusion. Finally cast film nanocomposites will be

studied for mechanical, thermo-mechanical and barrier properties.

Chapter 2

Background and Literature Review

Biodegradable and bio-based polymer products, which are produced from
renewable agricultural and biomass feedstock, can make the base for green and
environment friendly, eco-efficient products that can compete and capture
markets currently dominated by products based exclusively on petroleum
feedstock. This is the reason why US government agencies are making the
agendas for using green and environment friendly products as an alternate for
petroleum based sources. On the basis of origin we can divide biopolymers in
three classes: Renewable resource based, Petroleum based biodegradable and
Petro-bio mixed (which are not biodegradable). Figure 2.1 shows classification of

biodegradable polymers on the basis of their origin [3, 14, 15].

Bionanocomposites are gaining lot of attention from last few years due to
the sustainable approach. Bionanocomposites are usually termed for
nanocomposites involving a biopolymer in blend with an organic or inorganic
moiety of nanometric dimensions (at least one dimension in range of 1-100nm).
Darder et al [16] has listed various areas in which biocomposites can be used.
There are lots of areas where biocomposites are being used and can be used in
future in place of conventional petroleum plastic based nanocomposites.
Bionanocomposites are currently being used in life sciences, functional areas

and packaging and have numerous potential for other applications [16-18].

BIOPOLYMERS

 

 

 

 

 

 
   
    
    

     
 

Petro-Bio

Petro- based

Renewable

 

 

 

 

resource Synthetic (Mixed)
based
PLA Polyhydroxy Aliphatic PTT
alkanoate ‘ Polyester (Sorona®)
Cellulosic (Bacterial . _
plastics bio-plastics) Aliphatic-aromatic Polymer
polyester- Blends
Soy plastics
Polyesteramides
Starch Plastics
Polyvinyl alcohols

 

 

 

 

 

 

 

 

Figure 2.1 Classification of Biopolymers. After Reference [3]

In this study we focused on Poly(trimethylene terephthalate) (PTT) which
can be obtained partially from biomass. This polymer has potential uses as

fibers, films and as an engineering resin [6].

PTT has been widely used as textile fibers. Typical physical properties of

Sorona® are listed in Table 2.1 [19].

Sorona® or 3GT (3—Glycol Terephthalate) polymer is one member of a
family of polymers based on fiber-grade 1,3-propanediol. It is a linear
crystallizable polymer having a melting temperature of about 228 °C and a glass
transition temperature (T9) of about 50°C. The structure of PTT has been studied
extensively [20-22]. The valuable properties of Sorona® polymer are derived from
a unique, semi-crystalline molecular structure having a kink. The polymer shape.

is an outcome of the convolutions of the bonds in the trimethylene constituent [6].

Table 2.1 Physical properties of Sorona®. After Reference [6]

 

 

 

 

 

 

 

 

Property Semi-dull Bright
Intrinsic Viscosity (IV), dI/g 1.02 1.02
Hunter B Color 6.7 9.0
Hunter L Color 81 68
Melting Point (‘0) 229 229
TIOz, wt% 0.3 0
Mositure, ppm (as packaged) 120 120
Pellet Size, wt of 50 pellets, g 0.6 0.6

 

10

This zigzag shape means that tensile or compressive forces interpret at
the molecular level to bending and twisting of bonds, rather than simply
stretching. When the polymer is cooled from a liquid state to solid state it forms
crystalline and amorphous regions. With 3GT, the modulus of the crystalline
regions is significantly lower than that of other commercial polymers, such as
PET. Sorona® can be cast into films at settings comparable to polypropylene or
Nylon 6 but process optimization is required to eliminate film brittleness of cast
films. Biaxially oriented films of Sorona® can also be prepared. Modified 3GT
polymers or blends of 3GT with other commercially available polymers (2GT,
4GT, etc.) can be successfully used in films to obtain desirable property
advantages and increased value. For example, the combination of properties of
3GT (oxygen and water vapor barrier and heat sealability) means that in many
food packaging applications a single 3GT or modified 3GT layer may replace

several layers of presently manufactured laminated films [6, 23].

There are various literatures available on poly(trimethylene terephthalate)
(PTT) related to its structure and synthesis [24-26]. There are also literatures for
P'I‘l’ nanocomposites focused on improvement of properties of PTT by
incorporation of organically modified nanoclays [27, 28]. There are also lot of
studies done on rheology, interaction and chemistry of polymer blends and
nanoparticles [29-36]. These literatures are reviewed for this study to get an in

depth knowledge of behavior of PTT and its nanocomposites.

11

In a study by Drown et al [5], researchers focused on improving
mechanical and barrier properties of poly(trimethylene terephthalate) by
incorporation of commercial nanoclays via melt compounding. In this study fully
petroleum based Sorona® was used. Biobased PTT-clay nanocomposites are
also expected to exhibit exactly similar properties with that of petroleum based
PTT-clay nanocomposites. Nanocomposites of Sorona® containing organo-Clays
were produced using melt compounding, e.g. extrusion, followed by injection
molding. The researchers used five commercially available organo-clays at 5
wt% loadings to find the organic modification that achieved the best balance of
mechanical and thermal properties. The increase in tensile modulus of the
nanocomposites versus neat PTT ranged from 31 to 37%. The tensile stress at
yield and break for the neat P'I'I' were 58.5 and 38.5 MPa, respectively. The
increase in the tensile stress at break of the nanocomposites versus neat PTT
ranged from 2 to 53%. The heat deflection temperature (HDT) of the neat PTT
was 88°C, and incorporation of the organo-clays produced increases in HDT up
to 38%. From these results, the organo-clay Cloisite® 25A was selected for
detailed study over the range of loading from 0 to 5 wt%. The thermo-mechanical
properties as measured by the HDT increased monotonically with increasing
organo-clay content. The barrier properties of Sorona® were improved by
addition of Cloisite® 25A, and a loading of 3 wt% was effective in reducing the
oxygen and water vapor permeation. The modulus of biobased and petroleum

derived P'I'I‘ was compared and found to be essentially identical.

12

Kelsey et al [37] studied the first-order thermal degradation rates of
poly(trimethylene terephthalate) (PTT) at 240—280°C under non—oxidative
conditions. They observe increase in allyl end groups by 1H NMR (Nuclear
Magnetic Resonance Spectroscopy) which is similar to the rates determined from
the decrease in molecular weight which was measured by intrinsic viscosity. In
this study these researchers found that there is little or no effect on PTT thermal
degradation rates under non-oxidative environments. The thermal stability of
poly(butylene terephthalate) [PBT] was also determined from butenyl end groups
by NMR studies and molecular weight by intrinsic viscosity. They also found that
activation energies (Ea) for both PTT and PBT thermal chain scission are similar
to the reported Eas for poly(ethylene terephthalate) [PET] degradation. However,
P'I'l' and PBT endure molecular weight decrease faster than PET. But catalysts,
additives or the type of synthesis does not manipulate thermal degradation .of

PTT.

There are lot of studies done on crystal structure, mechanical and other
properties of PTT which shows the effect of nanoclays on the crystallization and
properties of PTT which are essential to review for this study in order to gain

knowledge about crystallization kinetics of PTT and its nanocomposites [38-45].
Hu and Lesser [46] also studied the morphology of intercalated

poly(trimethylene terephthalate) (PTT)/clay nanocomposites prepared by the melt

mixing of PTT with quaternary or ternary ammonium salt—modified clays. The

13

researchers studied the morphology and structure, crystallization and melting
behavior, and the dynamic mechanical behavior andwere characterized by X-ray
diffraction, transmission electron microscopy, differential scanning calorimetry,
and dynamic mechanical thermal analysis. The results of the study showed that
the preparation of successful PTT nanocomposites. They found more regular
stacking of the silicate layers at higher clay concentrations and shorter blend
times. As per researchers’ observations as compared with conventionally
compounded composites, the nanoscale-dispersed organophilic clays were more
effective as crystal nucleation agents. The influence of the nanosilicates on the
crystallization and melting behavior of PTT became distinctive when the
concentration of clay was around 3wt %. They concluded from their study-that
changes in the crystallization behavior of the polymer/clay nanocomposites are
not only dependent on the size of the silicates but also on the intrinsic

crystallization characteristics of the polymers.

The non-isothermal crystallization of intercalated PTT/clay
nanocomposites was also investigated by Hu and Lesser [47] by different
methods. They described non-isothermal crystallization of pure PTT by the
Ozawa equation, but found that Ozawa theory is not valid for PTT/clay
nanocomposites. As per their study, addition of clay into PTT decreases the
crystallization half-time whereas increasing the crystallinity and crystallization
rate. The PTT/modified clay nanocomposites have a higher crystallization rate

parameter and a lower crystallization half-time as compared to unmodified

14

clay/PTT composites. They calculated the crystallization activation energy from
Kissinger equation for PTT and PTT clay based nanocomposites, which were
found to be 100 to 230 kJ.moI". As per their study, addition of clay increases the
crystallization activation energy but the clay still acts as an effective nucleating
agent and this effect increases the crystallization rate and crystallinity of PTT.
Further, they observed that modified nanoclays are more effective nucleating
agents than the unmodified nanoclays, and found the most effective nucleating
concentration of nano-clay is between 1-3 wt%. The crystallization half-time, t1”,
decreases as a function of coolingrate, Q, and decreases with an increase in

clay concentration.

Chang et al [48] studied and compared the PET and PTT clay based
nanocomposites. Authors synthesized the nanocomposites; one with
poly(ethylene terephthalate) (PET) and the other with poly(trimethylene
terephthalate) (PTT), by using organically modified clay. They prepared
organically modified clay and polyesters nanocomposites by in-situ interlayer
polymerization method at different organoclay contents and at different draw
ratios to produce monofilaments. They found that thermal stability and tensile
mechanical properties increased with increasing organoclay content at a draw
ratio of 1. However, they also observesd at the same time that values of the
tensile mechanical properties of the hybrid fibers decreased with increasing draw
ratio. They also find that reinforcing effects of the organoclay of the PET hybrid

fibers were higher than those of the PTI' hybrid fibers.

15

Chang et al [49] also studied the effect of different kind of clays in
properties of PTT fibers. They observed a significant impact on thermal stability
and tensile properties in PTT nanocomposites. The increase in draw ratio also

impacted the initial modulus and ultimate strength of PTT hybrid fibers[49].

Liu et al [50] studied the crystallization, morphology and dynamic
mechanical properties of PTT clay based nanocomposites. These researchers
successfully prepared exfoliated PTT/clay nanocomposites via melt intercalation
using a co-rotating twin-screw extruder. They found by their study on
crystallization kinetics that the addition of clay changes the crystallization
behaviors of PTT and enhances the crystallization of PTT, which in turn indicates
of clay as nucleation agents. The morphology of spherulites was observed using
polarized light microscopy, which also agrees with the results of crystallization
kinetics. These researchers pointed that due to the strong interaction between
the specific clay and the PTT matrix, T9 of the nanocomposite was considerably
higher than that of pure PTT. As per their DMA studies they observed the higher
modulus of nanocomposite than neat PTT. They find that temperature higher
than Tg, storage modulus value of the nanocomposite is higher about ten times

than that of neat PTT because of increase in crystallization rate of the PTT.

Mishra et al [31] studied the properties of rubber toughened PTT

nanocomposites. Researchers prepared these nanocomposites using melt

16

mixing technique and observed a percolated network of clay. They also observed

the increase in non-isothermal crystallization by incorporation of clay particles.

For future packaging innovations nanotechnology is the path forward in
the flexible film and rigid plastic industries offering enhanced properties such as
greater barrier protection, increased shelf life and lighter-weight materials.
Polymer nanocomposites can be defined as polymers blended with nano-
particles to produce materials with enhanced properties. They have been in
subsistence for many years, but recently gaining momentum in mainstream
commercial packaging use. Nano materials refers to materials that can be
measured in nanometers i.e. have at least one dimension in nano-metric scale.
In the metric system of measurement, a "nano" equals a billionth so a nanometer

is one-billionth of a meter [51].

Polymer nanocomposites are fabricated by dispersing a filler material i.e.
polymer matrix into nanoparticles such as nanoclays, carbon nanotubes,
nanosilica etc. Nanoparticles have platelets like structure and during
nanocomposites fabrications, these platelets are distributed into a polymer
matrix, creating multiple, parallel layers that form "tortuous path," forming
complex barriers to gases and water vapor [52]. The increase in barrier

properties of polymer by adding nanoclays can be explained by two theories:

17

(a) Creating “tortuous path” in polymer matrix, (Nielsen model) [53] i.e. filling
up free volume of polymer thus making permeants difficult to pass through

the polymer matrix.

(b) Change in local permeability by nanocomposites, as per studied by

Gusev and Lusti [54].

(a) Tortuous path theory: Nanocomposites increase the gas barrier properties by
creating a “tortuous path” that reduced the progress of gas molecules through the
polymer matrix. As per Nielsen Model [53], for platelets of length L and width D,
which are dispersed parallel in polymer matrix, the tortuosity factor (T) can be
expressed as:

T = 1 + (L /2D) (p
where q> is volume fraction of dispersed layered silicate particles.
And relative permeability coefficient of nanocomposites and neat polymer can be
expressed as:

Pnc/ Pn = 1/ [1 + (L l2D) rp]
where Pnc is permeability coefficient of nanocomposites

and Pn in permeability coefficient of neat polymer [53]

(b) This factor explains that presence of silicate layers (nanoclays) changes the

local permeability because of the molecular level of alteration within the polymer

18

matrix. So if clay is more exfoliated (thoroughly dispersed) in polymer matrix it

will decrease the permeation of gases through polymer matrix [54] .

Effectively, when there is more dispersion i.e exfoliation of nanoparticles

throughout a polymer, the permeability is significantly reduced.

Nanoparticles can be used for much lower loading levels than traditional
fillers to achieve optimum performance. Usually, additional levels of nanofillers
are less than 5%, which significantly impacts the weight reduction of
nanocomposite films. This dispersion process results in a high aspect ratio and
surface area, in turn creating higher-performance plastics than with conventional

fillers.

Diverse types of fillers are utilized; the most common is a nanoclay
material called montmorillonite-a layered, smectite clay. These clays in a natural
state are hydrophilic, while polymers are hydrophobic. Montmorillonite (Referred
as MMT hereafter) clay should be organically modified in order to be compatible
with organic polymer. One way to modify clay is by exchanging organic
ammonium cations [positively charged ions] for inorganic cations from the clay
surface. Additional nanofillers include carbon nanotubes (CNT’s), graphite
platelets and carbon nanofibers. Carbon nanotubes are more expensive than
nanoclay fillers, which are readily available and offer superb electrical and

thermal conductivity properties. Two major suppliers of nanoclays in US are

19

Southern clay Products and Nanocor. There are three common methods used to
enhance polymers with nanofillers to produce nanocomposites: melt
compounding, in-situ polymerization and the solvent method. Melt compounding
of the nanofillers into a polymer is done simultaneously when the polymer is
being processed through an extruder, injection molder or other processing
machine. The polymer pellets and filler (clay) are pressed together using shear
forces to help with exfoliation (the process of separating the particles into the
right shape and layer structure) and dispersion. With in-situ polymerization, the
filler is added directly to the liquid monomer during the polymerization state.
Using the solution method, fillers are added to a polymer solution using solvents
such as toluene; chloroform etc to disperse the polymer and filler molecules. AS
the use of solvents is not environmentally friendly, melt processing and in—situ
polymerization are the most widely used methods of nanocomposites production.
Possible morphologies of polymer/clay nanocomposites are shown in Figure 2.2

[55].

The advantages of nanocomposite films are numerous, and the
possibilities for application in the packaging industry are continual. Because of
the nanocomposite process's dispersion patterns, the platelets result in largely
improved performance in gas, oxygen, water barrier, high mechanical strength,
Chemical and thermal stability, heat resistance, good optical clarity, dimensional

stability.

20

A greater part of consumer products that are using nanocomposite
packaging are in the beverage and also food industry. Many different types of
commercial plastics are used for nanocomposites including PP, Polyamides, PET

and PE.

21

_ \
_‘ Layered
Clay
1-
Polymer
a. Agglomerated
— \ POIymer

fl Composites

E§§ 4m
_\ Z

Nanocomposites

Figure 2.2 Possible morphologies of polymer/Ola y nanocomposites. After
Reference [55]

An example of commercial nanocomposites is Nylon nanocomposites,
used as barrier layers for multilayer PET containers which performed much better
than the traditional ethylene vinyl alcohol barrier layers, as nylon has a 50°F
higher melt temperature. Studies show that nylon 6 nanocomposites can achieve
an oxygen transmission rate (OTR) much lower than unfilled nylon 6 as shown in
Figure 2.3. In the case of Honeywell's AegisTM OX barrier nylon resins, which
were designed for multilayer bottle applications, the nanoclay layers also retain
the active oxygen scavengers in the polymer meanwhile reducing OTR
drastically. AegisTM OX oxygen-scavenging compounds provides 6 to 12 months

shelf life for plastic beer bottles which is comparable to glass bottles [51].

23

Oxygen Transmission of Nylon Nanocomposites

 

OTR, cc.mil/100ln2.day

 

 

 

 

 

 

2.5 1
i
2
2 .l
1.5 T
“ .l
0.6
0.5
. 0.1
O L. l_——l , ________ _.

 

 

active passive nylon-6 Nylon-6 nanocomposite Unfilled nylon-6
nanocomposite

Figure 2.3 Oxygen Transmission Rate of Nylon and its nanocomposites [51]

24

Orientation of nanoparticles also has an effect on the success of
nanocomposites. Nanoparticles need to be dispersed throughout polymer so they
are parallel to the material's surface. This position ensures a maximum tortuous
path for the gasses when migrating through the polymer. Compatibility between
the nanofillers and the polymer substrate is also an important factor that is how
they interact with each other. Certain nanofillers need to be modified so they can
interact well with the matrix. A study done by Bhardwaj and Mohanty confirms the
interaction of modified nanostructured dentritic polymer with brittle renewable
based polymer matrix [56]. Another concern is that during the processing state,
there is a possibility of reaggregation, where the particles clump together. In that

case, the creation of the nanocomposites is ineffective [57].

Polymer nanocomposites are the future for the global packaging industry.
Once production and materials coSts decrease, companies will use this
technology to increase their product's stability through the supply Chain to deliver
higher quality to their customers while saving money. Research is also continuing
into other types of nanofillers, allowing new nanocomposites structures with
different, improved properties that will further advance their use in many diverse

packaging applications.

25

lmperm®, produced by Nanocor is an example of commercial avialbale
nanocomposites. It showed similar results when it is added to a multilayer PET
structure. It requires no adhesion tie layers to PET and is recyclable. When used

in a 16-02 beer bottle, lmperm® can provide almost seven-month shelf life [58].

The four areas in food industry that will be significantly improved by
nanotechnology are development of nanoscale processing, product
development, new functional materials, design of methods and instrumentation

for food safety and biosecurity [59].

26

Chapter 3

Materials and Methods
3.1 Materials

3.1.1 Poly(trimethylene terephthatale) (PTI')

The poly(trimethylene terephthalate),PT'l' was obtained from DuPont
(Wilmington, DE) under trade name of Sorona®. In this study, petroleum based
Sorona® was used. PTT comes under the family of conventional aromatic
polyesters like poly(ethylene terephthalate) (PET) and poly(butylene
terephthalate) (PBT). The PTT was supplied as pellets and dried in a forced-air
desiccant drier at 125°C for 4 hours prior to use. The chemical structure of PTT is

shown in Figure 3.1.

T O O ’1

II II

n

I

 

 

— —

Figure 3.1 Chemical Structure of Poly(Trimethylene Terephthalate)

PTT has melting point of 228°C and glass transition temperature of about
50°C with density of 1.33 g/CC. It is bright transparent in color without odor
containing 0.3 wt% of Ti02 as additive. It has an intrinsic viscosity of 1.02 mlg '1
. PTT was kept in air tight jar after drying for 4 hours in convection oven because

it is hygroscopic in nature like other polyesters.

27

3.1.2 Montmorillonite Clay (MMT)

The unmodified montmorillonite clay denoted by MMT was supplied by
Southern Clay Products, Inc. (Gonzales, TX) under trade name of Cloisite® Na".
Table 3.1 shows the cation exchange capacity, specific gravity and d-spacing of
this clay. It is natural montmorillonite Clay without any modifier. Clay was predried
at 80°C for about 12 hours before its surface modification. Surface modified clay

was dried at 60°C for about 4 hours prior to fabrication of nanocomposites.

Table 3.1 Physical properties of natural montmorillonite clay (Cloisite‘m Na"). After
Reference [60]

 

 

Cation
Exchange
MMT Clay Capacity (CEO) Specific Basal Spacing
(meq/100g of Gravity (g/cc) (001)-d001 (nm)
clay)
Cloisite” Na” 92.6 2.86 1.17

 

28

3.1.3 Titanate Based Coupling Agent

The titanate-based surface modifier (Kenreact® LlCA-38) as used in this
work is neopentyl (diallyl)oxy tri(dioctyl) pyrophosphato titanate, (Figure 3.2), a
product of Kenrich Petrochemicals, Inc. (Bayonne, NJ). Chemical structure of

titanate modifier sourced from [61].

II II
Hac—HZC—C—CHZ—O—Ti ——O—P—O—P—E—08H£l 2

 

 

Figure 3.2 Chemical Structure of Neopentyl (diallyl)oxy tri(dioctyl)
pyrophosphato Titanate. After Reference [61]

29

3.1.4 Silane Coupling Agent

The silane coupling agent (Dow Corning® Z-6040) selected from various
silane coupling agent based on its functionality was y-
Glycidoxypropyltrimethoxysilane (Figure 3.3). This was purchased from Sigma-

Aldrich and was used as received.

0 _
HzC—CH —CH2—O -—-——CH2 —-CI-I2—CH2—SI \
i O—CHS
O
l
CH3 .

Figure 3.3 Chemical Structure of y-Glycidoxypropyltrimethoxysilane

The non-aromatic solvent i.e. an aliphatic hydrocarbon solvent (Kwik-Dn®
66) was purchased from Ashland Distributions Inc. (Columbus, OH). Toluene
was obtained from Aldrich and was used as received. Laboratory grade ethanol

was purchased from Aaper Alcohol and Chemical Co. (KY).

30

3.2 Methods

 

 

Optimization of the ratio of titanate & silane
coupling agent in montmorillonite clay.

 

First Phase

 

 

Selection of clay and preparation of PTT/organo-
clay nanocomposites by microcompounding.

 

l

 

 

Optimization of clay content in PTT in micro-
compounder.

 

Second Phase

 

 

Evaluation of the mechanical and thermo-
mechanical properties of optimum compositions
using tensile testing machine & dynamic
mechanical analysis.

 

Third Phase

 

. /.\. /.\

 

Twin-Screw extrusion followed by cast film
extrusion and their studies. (Mechanical, Thermo-
mechanical, Barrier and Morphology)

 

Figure 3.4 Schematic representation of steps followed for this research work

31

 

 

 

 

 

3.3 Surface Modification of Montmorillonite Clay

3.3.1 Surface Modification of Clay with Titanate Based Coupling Agent

The surface modification of clay with titanate based coupling agent has
been reported by Monte[62] and in our previous studies [61]. MMT clay (Cloisite‘B’
Na") was modified with titanate coupling agent. In the surface modification
process, the amount of titanate coupling agent was varied in order to get

modified clay with varying titanate contents.

 

Figure 3.5 Titanate surface modifier (in syringe) added to toluene in crystallizing
dish (left) and clay added to the toluene and modifier in continuous made (right).

32

Two different solvents, toluene and Kwik—Dri® 66 were used to carry—out
the surface modification of clay. The MMT clay was dried overnight in vacuum
oven at 80°C. Approximately 300 ml of solvent (toluene or Kwik-Dri® 66) was
placed in a crystallizing-dish and the requisite amount of titanate modifier was
added to the solvent and dispersed using a magnetic stirrer at ambient
temperature. The calculated amount of dried MMT clay was added to the solution
incrementally and stirred for 3 hours. The Clay was allowed to settle and the
excess solvent was decanted, followed by several washings in order to remove
the unreacted and excess modifier and possible byproducts. The schematic
representation of the surface treatments are shown in Figure 3.5 and Figure 3.6.
Finally, the excess solvent was decanted and the clay dried overnight at ambient

conditions followed by drying in a vacuum oven for 5 hours at 55°C before use.

33

 

MMT Clay

 

 

 

 

 

 

 

 

 

 

 

Washing for three
times with solvent

 

 

 

 

 

 

l Step H
Constant St 111

Titanate coupling Step I stirring for 3 ep

agent —’ hrs in solvent —’
Organo-clay
ready for

V . .

nanocomposites Step I Drying at 55 C Step V
fabrication I for 5 hours In ‘

 

 

 

vacuum oven

 

 

Step IVl

 

 

Overnight drying at
ambient temperature

 

Figure 3.6 Schematic of Surface Modification of MMT Clay

34

 

 

3.3.2 Surface Modification of Clay with Silane Coupling Agent

The surface modification of clay with a silane coupling agent has been
reported by Hongping et al [63]. In the adopted process, an ethanol/water
mixture was used as the solvent to carry-out the surface modification of clay, the
amount of silane coupling agent was kept at a constant ratio with aqueous
solution of ethanol and clay. Prior to treatment, MMT clay was dried overnight in
a vacuum oven at 80°C. A solution of ethanol and deionized (DI) water was
prepared in ratio of 95:5 and the calculated amount of acetic acid was added to
the solution to maintain its pH in the range of 4.5-5.5. Then, the silane coupling
agent was added and stirred for 10 minutes using a magnetic stirrer at ambient
temperature; dried MMT was added to the solution incrementally and stirred for 1

houn

35

O ——C
/ \ /O H3
HzC-CH —CH2 ——O —CH2 —-CH2—Cl-12—Si\ + 3 H20
| 0 _CH3
I
CH3
(Gamma-Glycidoxypropyltri methoxysilane) DI Water
/0\ /OH OH
Hzc—CH —CH2 —0 —CH2 —CH2—CI-I2 —Si\ + I
i OH 3 _(_:_I-I3
OH
I
I
Silanol (htemediate product) i By-product
+ (IDH
l M (MMT)
Cloisite Na +
O _
/ \ O M (MMT)
HzC—CH —CH2 —O —CH2 —CI-I2—Cl-12 —S|i\OH + H20
OH
By—product

Silane Modified Clay

Figure 3.7 Silane Coupling Agent Reaction Scheme

36

The excess solvent was decanted followed by several washings in order
to remove the unreacted and excess modifier and possible byproducts. The
silane coupling agent reaction with the clay surface is shown in Figure 3.7 and a
schematic representation of the surface treatment process is shown in Figure
3.8. The excess solvent was then decanted; the clay was dried overnight at
ambient conditions and then dried in a convection oven for 5 hours at 80°C,

ground and subsequently dried in a vacuum oven at 80°C for 1 hour.

37

 

 

DI water (acidified) MMT Clay
+Ethanol-10 min stir

S III
Constant
Silane coupling stirring for 1 Step IV’ Washing for three

agent hrs in solution times with Ethanol

Step V l

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Organo-clay St v11 Drying at 80° C _ .
ready for . :P for 5 hours, 1 hr tep VI Overnight drying at
nanocomposrtes drying in L— ambrent temperature
fabrication vacuum oven

 

 

 

 

 

 

Figure 3.8 Schematic Representation of Clay Modification with Silane Coupling
Agent

38

3.4 Processing Equipments
3.4.1 DSM Microcompounder

Polymer melt compounding was done using micro compounding
equipment (TS/l-02, DSM, Netherlands). Photographs of the mini compounding

system are shown in Figure 3.9.

 

Figure 3.9 DSM mini-extruder (top left), mini injection-molder (top right), tensile
mold and tensile beam (bottom)

39

The mini extruder is equipped with conical co-rotating screws having
length of 150 mm, UD ratio of 18 and net capacity of 15 cc. The attached
injection-molding unit is capable of 160-psi injection force. P'l'l' and modified clay
were weighed as per calculated compositions for specific processing conditions
and fed into mini extruder. After extrusion, the melted materials were transferred
through a preheated cylinder to the mini injection molder which was preset to a
mold temperature of 85°C to obtain the desired specimen samples for various
measurements and analysis. Neat PTT and PTT based nanocomposites were
processed at 250°C and 150 rpm for cycle times of 3 minutes and 6 minutes,

respectively.

3.4.2 Twin Screw Extruder

The pilot-scale (may also be termed “semi pilot-scale”) blending was
carried out using a twin screw extruder ZSK-30 (Figure 3.10). PTT pellets were
placed into the blend resin feeder. For the nanocomposites, clay was placed into
the clay feeder. Small feeding screws were used to control the feed rate for resin
and clay. The materials were melted and mixed in the extruder section and
forced through the die as strands. Initially, a master batch containing 20 wt%

modified clay was prepared.

These melt compounded strands were then cooled in water bath and the

strands were cut into pellets using a pelletizer. After drying in a vacuum oven at

40

100°C overnight, the master batch pellets were added to neat PTT resin to obtain
3 wt.% and 5 wt.% clay nanocomposites. The temperature profile of the ZSK-30
twin-screw extruder was 235, 240, 240, 240, 245, 245 °C corresponding from
Zonel to Zone 6; the screw speed was 100 rpm. The torque of extruder was kept
at 60%. A photograph showing a schematic view of master batch followed by

nanocomposites fabrication at the desired clay content is shown in Figure 3.11.

 

Figure 3.10 ZSK-30 twin-screw extruder nanocomposites strands in water bath

on left and Pelletizer on right

a ..
in.
‘ _ PTT Pellets + Master Batch Pellets
PTT Pellets . Organo - Modified
Pilot - Scale C ay Q
Extrusron

_. *1

PTT ( 80%) + Clay ( 20%) PTT - 3 WT%/5 WT% Nanocomposites

Master Batch

Figure 3.11 Pilot-scale extrusion schematic diagrams

41

3.4.3 Single Screw Cast Film Extruder

Cast films of neat PTI' and PTT based 3 wt.% and 5 wt.% Clay
nanocomposites were prepared using a single screw extruder, Killion KLB-IOO,
Figure 3.12. The temperature of the extruder was kept at 260,265 and 260°C for
Zone1 to Zone 3 respectively. Temperature of clamp ring, adapter and external

die was kept at 265, 260 and 250°C respectively.

The melt temperature was 250°C. The temperature of chill-roll was kept at
12° C and take-off speed of the chill-roll was 18 rpm. The average thickness of

film was 3.5 mils.

 

Figure 3.12 KLB-100 Single-screw Extruder (left) and Chill-roll (right)

42

3.5 Characterization

3.5.1 X-ray Photoelectron Spectroscopy (XPS)

Surface elemental analysis of the clays was performed using XPS. The
XPS measurements were performed using a Physical Electronics PHI-5400
ESCA workstation. The X-ray source was a polychromatic magnesium anode
(1254 eV). The analyzer was operated in the fixed energy mode employing a
pass energy of 89.45 eV for survey scans and 17.9 eV for utility scans. Clay
samples were affixed to the specimen holder with double-sided tape. Semi-
quantitative information was obtained by measuring the 01s and 015 peak areas
and applying the appropriate sensitivity factors. Each composition of clay was

tested for single sample.

3.5.2 X-ray Diffraction (XRD)

X-ray powder diffraction (XRD) patterns of the clays were obtained using
a Rigaku 200B X-ray diffractometer (45 W, 100 mA) equipped with a CuKa
radiation source (A= 0.1541 nm) and a curved graphite crystal monochromator at
a scanning rate of O.5°lmin. The dam basal spacings were calculated from the 28
values. Each composition of Clay and extruded cast films was tested for single

' sample.

43

3.5.3 Hydrophobic-Hydrophilic Balance

To determine the relative moisture uptake of the various clays, they were
first prepared by drying in a convection oven at 80°C for 8 hours followed by 4
hours under vacuum at 80 °C. Samples of each were placed into plastic weighing
dishes and introduced into a conditioning chamber held at 43% relative humidity
by the use of a saturated potassium carbonate solution, ASTM E-104. The
dishes were weighed periodically to determine when equilibrium (saturation of
the clay) had occurred. Once equilibrium had been reached, the Clays were dried
in triplicate in a convection oven at 110°C for 8 hours. Samples of each

composition of clay were tested in triplicate.

3.5.4 Dynamic Mechanical Analyzer (DMA)

Storage modulus measurements of samples were obtained using a TA
Instruments 0800 dynamic mechanical analyzer, (TA Instruments, DE). Single
cantilever mode was used for injection-molded samples whereas tension mode
was used for film samples. Samples were tested at a frequency of 1 Hz and 15
pm amplitude over the temperature range of 30 to 140°C at a ramp rate of
2°C/min. Samples of each composition of injection molded specimen of PTT and
PTT nanocomposites were tested in triplicate.

Beam specimens of dimension 2 x 12 x 60 mm were fabricated using the

DSM mini-extruder and mini injection molder. A dynamic mechanical analyzer

44

DMA 0800 (TA Instruments, DE) with 3-point load fixture was used for HDT
(Heat Deflection Temperature) measurements. The HDT was measured
according to ASTM D-648. The support span was 50 mm, the mid-point stress
was fixed at 0.455 MPa and HDT was measured at 0.195% strain. The samples
were heated from 30 to 160°C at a ramp rate of 2°C/min. Five samples of each
composition of injection molded specimen of PTT and PTT nanocomposites were

tested to calculate HDT.

3.5.5 Universal Testing Machine

A United Testing System model SFM-20 test frame was used for
measuring tensile strength and percent elongation of the extruded cast films
following ASTM D882-02 standard. A sample width of 1 inch and gage length of
4 inches with a grip separation speed of 0.4 in/min were used. The samples were
conditioned for 48 hours at 23°C and 50% relative humidity prior to testing. The
tensile properties of the injection-molded materials were measured using the
SFM-20 according to ASTM D 638 for the measurement of the modulus of
elasticity, tensile strength and percent elongation. A sample width of 0.19 inches
and gage length of 1 inch with crosshead speed of 0.1 in/min were used. Flash
was removed from the edges of the coupons using 1200 grit silicon carbide
coated abrasive paper prior to testing. Five samples of each composition of
injection molded specimen and extruded cast films of P'l'l' and PTT

nanocomposites were tested for tensile properties.

45

3.5.6 Thermal Behaviors (DSC & TGA)

Differential Scanning Calorimetry (DSC) technique was used to measure
the melting and crystallization temperatures and crystallinity of PTT and PTT
nanoclays based nanocomposites. A 0100 (TA instruments, DE) differential
scanning calorimeter was used for these behaviors. The testing was carried out
at the temperature range of 30°C to 270°C at scanning rate of 20°C/min.

Samples of each composition of extruded cast films were tested in triplicate.

Thermogravimetric analysis (TGA) of the titanate and silane coupling
agents and organically modified clays was carried out using a 2950 TGA (TA
Instruments, DE) to measure the weight loss with respect to temperature.
Approximate 20 mg of sample was placed in aluminum pans and heated-to
600°C at 20 °Clmin with a nitrogen purge. Each composition of clay and coupling

agents were tested for single sample.

3.5.7 Barrier Properties

The water vapor and oxygen permeability of neat PTT and
nanocomposite films were measured using a MOCON® Permatran-W® 3/33 MG
and Ox-Tran® 2/21, respectively. Extruded cast films of nominal thickness of 3.5
mils were tested for their water vapor and oxygen permeabilities. The
temperature and relative humidity (RH) of Permatran-W® 3/33 MG was 37°C and
100% respectively and operated in continuous mode. The temperature and RH

used in the Ox-Tran® 2/21 was 23°C and 0% respectively and permeant

46

concentration was kept at 100% and operated in continuous mode. 50 cm2 area
films were tested for oxygen and water vapor permeation. Samples of each
composition of extruded cast films of PTT and PTT nanocomposites were tested

in triplicate.

3.5.8 Transmission Electron Microscopy (T EM)

A transmission electron microscope (T EM) (Jeol 100 CX) was used to
analyze the morphology of extruded cast films nanocomposites at an
acceleration voltage of 100 kV. Film samples were embedded in an epoxy resin
and cured for 24 hours followed by sectioning using an ultra-microtome. Thin-film
specimens with a thickness of 70 nm were used for TEM observation. Single -

sample of P'IT nanocomposites was observed under TEM

3.5.9 Polarized Light Optical Microscopy (PLOM)

Micrographs of neat PTT and PTT nanocomposites were taken using an
Olympus BH-2 optical microscope and images were captured using a RT Color
Spot digital camera. A single sample of each composition of extruded cast films

of PTT and PTT nanocomposites were observed under PLOM.

47

Chapter 4

Results and Discussion

The detailed nomenclature of the clays is given in Table 4.1.

Table 4.1 Nomenclature of the Surface Modified Clays

 

 

 

 

 

 

 

 

Clay Ratio of Clay
Designation Solvent Modifier to Titanate
Modifier
MMT NIA NlA N/A
Tl,90:10(ToI) Toluene Titanate 90:10
Ti,85:15(ToI) Toluene TItanate 85:15
Ti,95:5(KD) Kwik-Dri" 66 Titanate 95:5
Ti,9o:10(KD) Kwik-Dri’ 66 Titanate 89.8:10.2
Ti,85:15(KD) Kwik-Dri° 66 Titanate 85:15
Si (Et) Ethanol-I- Water Silane 98:2

 

48

4.1 Studies on Surface Modified Clays
4.1.1 XPS Analysis

The MMT Clay was modified with the titanate coupling agent using varied
loadings and two solvents. The modified clays were studied by XPS elemental
analysis to gain more information about the modification process. There are
various available literatures which report clay exfoliation and nanocomposites
with enhanced properties due to clay surface modification [13, 64, 65]. X-ray
photoelectron spectroscopy utilizes photoelectrons emitted from the sample and
energy-dispersive analysis to determine elemental composition. The XPS

elemental analysis of MMT and modified clays is shown in Table 4.2.

The analysis of as received MMT Clay shows the presence of silicon,
aluminum, oxygen and sodium — which are components of the Clay’s structure.
The surface also contains carbon and nitrogen. Some of the oxygen is present as
hydroxyl groups on the surface of clay. These hydroxyl groups are targeted to
exchange with alkyl-titanate complex of the titanate surface modifier during
treatment. The XPS analysis Shows a reduction in the oxygen concentration of
the modified clays. The presence of titanium and phosphorous on the modified
clays indicates that modifier has reacted with clay surface. The increase in
carbon content is due to alkyl chains of the modifier which reacted with the MMT
clay surface. There is also reduction of silicon and aluminum in modified clays as
modifier layer is covering the surface of clay. XPS analysis shows that there is

an increase in the carbon content in titanate modified clays as compared with

49

MMT clay, possibly due to an increased amount of grafted titanate modifier

present on the clay. The silane modified clay, Si (Et) also shows an increase in

silicon (as shown in Table 4.2) due to surface grafting of silane coupling agent

with clay.

Table 4.2 XPS Elemental Analysis of Montmorillonite Clay and Modified Clays

 

 

 

 

 

 

 

 

 

Element Ti, Ti, Ti, Ti,
MMT 90:10 85:15 90:10 85:15 Si (Et)

(T 0|) (Toll (KD) (KD)
Carbon 22.81 28.51 31 .97 29.20 34.80 21 .21
Nitrogen 0.71 0.50
Oxygen 51 .94 47.82 45.08 47.39 44.37 53.29
Sodium 1.99 2.87 2.39 2.81 2.04 2.09
Aluminum 6.74 5.53 5.06 5.45 5.25 6.72
Silicon 15.80 13.12 12.53 13.16 11.68 16.69
Phosphorous 1 .66 1 .56 1 .67 1 .56
Titanium 0.49 0.91 0.33 0.30

 

50

4.1.2 Hydrophobic-Hydrophilic Balance

The clays treated with the titanate modifier were examined to determine
the reduction of the hydrophilicity of the clay surfaces, as gauged by their
moisture uptake at 43% relative humidity. Both solvent systems were examined.
The unmodified clay adsorbed 61.4 mg H20/g clay, the treated clays adsorbed
from 50.7 to 61.8 mg HZO/g clay. Figure 4.1 shows the percent change in the

moisture uptake of the modified versus MMT clay.

The system using toluene as the solvent had decreased moisture uptake
as the concentration of the titanate coupling agent increased, which is indicative
of the Clay’s surface becoming more hydrophobic with increased coverage by the
modifier. On the other hand, the system with Kwik-Dri as the solvent had erratic
behavior with respect to modifier concentration. Whether this is due to the nature

of the solvent is unclear.

51

10.0

 

 

 

 

 

 

 

 

> e Toluene
5 5.0 a I Kwik-Dri
'8 11 90,10 A Unmodified
g 0.0 e; i W)
E
c
:9
g -5 0 ~
g: 1185215
In (K0)
5 -10.0 ~
3 (Tel)
3 -15.0 -
a. TI, 85:15
(Tol) {
-20.0 1 . fl .
0.00 0.20 0.40 ‘ 0.60 0.80 1.00

Titanium Content on Clay Surface (atomic %)

Figure 4.1 Reduction in Hydrophilicity as a Function of Modifier Content

52

4.1.3 XRD Analysis

X-ray diffraction (XRD) analysis was performed on the MMT clay and
modified clays. The XRD results show an increase in d-spacing of up to 21% in
Ti, 90:10 (T ol) as well as Si (Et) clay. Table 4.3 provides the basal spacings of
MMT clay and the titanate modified clays. Figure 4.2 shows the corresponding

XRD curves for powder clays.

Table 4.3 Basal Spacings of Raw Montmorillonite and Modified Clays

 

 

 

 

 

Material 26° d spacing(A)
MMT 7.90 9.71

Ti, 90:10 (ToI) 7.55 11.70

Ti, 85:15 (ToI) 7.80 11.33

Ti, 85:15 (KD) 8.7 10.16

 

53

Intensity (cps)

400 *1

200 i

 

Figure 4.2 X-ra y diffraction pattern of raw MMT and modified clays
A: MMT; B: Ti, 90:10 (T Cl); C: Ti, 85:15 (ToI); D: Ti, 85:15 (KD)

E: Si (Et)

 

 

 

2 theta (')

54

4.1.4 TGA analysis

The weight loss of titanate modifier, MMT clay and organically modified
clays was measured using TGA. Table 4.4 shows the weight loss of MMT,
organically modified clays and titanate modifier between 100° C and 600°C. This
table shows the uncorrected weight change of organically modified clays

because there is some weight change in MMT clay also due to the

dehydroxylation of Si-OH groups.

Table 4.4 Weight Change of MMT, Organically Modified Clays and Titanate

 

 

 

 

 

 

Modifier
Clay Wt @(73m1g())0°C Wt ((13000 Wt change
MMT 5.402 5.317 0.016
Ti,85:15 (Tol) 3.034 2.964 0.024
Ti,85:15 (KD) 4.011 3.891 0.031
Si (Et) 2.399 2.347 0.022
Titanate Modifier 32.547 11.339 1.870

 

Table 4.5 shows the corrected weight change values of organically
modified clays by subtracting their uncorrected weight change values from the
weight change value of MMT clay. Weight change of organically modified clays is

given as loss of modifier per gram of clay.

Table 4.5 Weight Change (Corrected) of MMT, Organically Modified Clays and
Titanate Modifier

 

 

 

 

Cl a 33% Wt @ Wt Wt change
y (mg) 600 °C (mg) change (corrected)

Ti,85:15 (ToI) 3.034 2.964 0.024 0.008

Ti,85:15 (KD) 4.011 3.891 0.031 0.015

Si (Et) 2.399 2.347 0.022 0.006

 

56

MMT clay shows a decrease of 16.0 mg per gram of clay whereas
organically modified clays shows decrease of up to 14.8 mg loss per gram of clay
as given in table 4.5. Figure 4.3 shows the weight loss curves of titanate modifier,
MMT clay and organically modified clays and figure 4.4 shows the expanded
curves of MMT clay and organically modified Clays in range of 100 °C to 600 °C
to evaluate the extent of dehydroxylation and loss of modifier. As shown in figure
15 MMT Clay shows a smooth weight loss whereas organically modified clays
showed onset points where the organic modifier began to decompose. Clays
Ti,85:15 (ToI) and Ti,85:15 (KD) have a decomposition temperature of around
260 °C which is the decomposition temperature of titanate modifier. Figure 4.5
and 4.6 shows the derivative weight curves for titanate modifier, MMT clay and

organically modified Clays.

57

Weight (‘16)

110 A C D
100 ,
90

80 1 t.
70 <
60 1
5‘” k
40

301

 

20 i ‘ — ‘77_-——_T—__T —._'WY_ ' _ ' '_—_ _‘T_ — T‘ "— ’T’——_—T' __‘—_"' —‘—T_' " __ "- ‘—___l

0 1 00 200 300 400 500 600
Temperature (°C)

Figure 4.3 TGA curves of MMT and modified clays and titanate modifier
A: MMT, B: Ti,85:15 (T ol), C: Ti,85:15 (KD), D: Si (Et), E: Titanate Modifier

58

Weight(%)

991)~

98.5 J\ A

981)“
B
Cr

97.5 1 “~ D

 

 

971l1 “"

....- \

96ll1

95:51

95.0 i— --—-——T——— — ._ . _ ---.__ E_-.- __..._E__- g
100 200 300 400 500 600

Temperature (°C)

Figure 4.4 Expanded TGA curves of MM T and modified clays
A: MMT, B: Ti,85:15 (ToI), C: Ti,85:15 (KD), D: Si (El)

59

2151

21)“ 3|
:/

"l

l

l

*1
:1.
05-« A D .il
' BC :
W
or)—
200 300 400 500 600

0
Temperature (°C)

d
01

Der. Wt (96/ °C)
2;

 

Figure 4.5 TGA curves for derivative weight of MMT and organo- modified
clays and titanate modifier
A: MMT, B: Ti,85:15 (Tol), C: Ti, 85:15 (KD), D: Si (Et), E: Titanate Modifier

60

0.025 1|

0.020 1

   

9
0
d
01
1—

Der. wt (96/ °C)
.0
O
8

 

 

 

100 200 300 400 500 600
Temperature (°C)
Figure 4.6 Expanded TGA curves for derivative weight of MM T and

modified clays
A: MMT, B: Ti,85:15 (ToI), C: Ti,85:15 (KD), D: Si (Et)

61

 

4.2 Injection Molded Nanocomposites
4.2.1 Tensile Properties

As discussed earlier, two different solvents; toluene (an aromatic organic
solvent) and Kwik-Dri® 66 (a non-aromatic, aliphatic hydrocarbon solvent) were
used in the surface modification process. We studied the effect of such two

solvent-based modifications on the performance of the resulting nanocomposites.

The tensile modulii data of neat PTT and its nanocomposites are shown in
Figure 4.7. The 3 wt.% loading of Ti,90:10 (ToI) clay and Ti,90:10 (KD) clay
showed an improvement in modulus versus the neat PTT by 8.5 and 4.3%
respectively. The 5 wt.% loading of Ti,90:10 (ToI) clay increased the modulus of
PTT by around 18%. PTT containing 3 wt.% Ti,90:10 (ToI) Clay nanocomposites
exhibits the maximum increase of 6% of tensile strength as compared to neat
PTT from 57.3 MP8 to 60.6 MPa and maximum elongation at break of 10.5 %

among the three nanocomposites (Figures 4.8 and 4.9).

62

 

 

3.5

3.0 1~

 

 

2.5 '1‘ T .i.

 

I-I

 

2.0 .

1.5 1*

1.0 1*

Tensile Modulus (GPa)

0.5

 

 

 

 

 

 

 

 

 

 

 

0.0

Samples

Figure 4.7 Tensile Modulus of PTT/organocla y nanocomposites
A: Neat PTT, B: PTT-3 wt% Ti,90:10 (ToI), C: PTT-3 wt% 71,90:10(KD), D:
PTT-5 wt% Ti,90:10 (To!)

63

 

\I
O

 

 

 

O)

o
1—

19-1
1-4

I'm-l

 

Tensile Strength (MPa)
'6‘ ‘6’ S S

...s
o

 

 

 

 

 

 

 

 

 

 

 

Samples "

Figure 4.8 Tensile Strength of PTT/organocla y nanocomposites
A: Neat PTT; B: PTT-3 wt% Ti,90:10 (ToI); C: PTT-3 wt% 77,90:10 (KD;, D:
PTT-5 wt% Ti, 90:10 ( Tol)

64

 

 

 

 

12 --

 

Elongation at break (%)

 

 

 

A B C
Samples

Figure 4.9 Elongation at break of PTT/organocla y nanocomposites
A: PTT-3 wt%Ti,90:10 (ToI); B: PTT-3 wt% Ti,90:10 (KD);
C: PTT—5 wt% Ti, 90:10 (To!)

65

4.2.2 Thermo-mechanical Properties

Storage modulus measurements were performed on injection-molded
samples. The storage modulus of neat PTT and its nanocomposites are reported
at 30°C to determine the effect of organO-modified clays on the
thermomechanical properties of PTT. Of the four nanocomposites studied, PTT
containing 5 wt.% Ti,90:10 (T ol) clay exhibited the maximum storage modulus of
3.01 GPa, which is 28% more the storage modulus of neat PTT which is 2.35
GPa. PTT with 5 wt.% Ti,90:10 (KD) exhibits an increase of 23%. The storage

modulus results indicate that toluene and Kwik-Dri” 66 exhibit similar results,

The heat deflection temperature of PTT and its nanocomposites were
measured using DMA Q-800 analyzer. The specimens were heated from 30 to
160°C at rate of 2°C/min. The PTT with 5 wt.% Ti,90:10 (KD) clay
nanocomposites exhibit the maximum I-IDT of the materials studied, 106°C, an
increase of 21% over neat PTT with HDT of 88°C. PTT 3 wt.% Ti,90:10 (ToI) and
Ti,90:10 (KD) clay nanocomposites exhibited an increase of 16 and 10%
respectively, Figure 4.11. HDT plays an important role in deciding the thermal
applications of polymers. Due to high HDT of PTT and its nanocomposites it can
be used for thermal resistant packaging applications such as microwavable
packaging. As compared with PLA (polylactides) which is 100% biobased
polymers has a low HDT of around 60°C is not suitable for such kind of

applications.

66

 

Storage Mod. (GPa)

9°
01

 

l
l

 

 

 

I“
or

 

I-I-t

I"
o

—b
0|

_L
o

0.5

 

 

 

 

 

 

 

 

 

 

 

 

 

0.0

 

 

A B C D E F
Samples

Figure 4.10 Storage Modulus of PTT/ organocla y nanocomposites
A: Neat PTT; B: PTT-3 wt% Ti,90:10 (T oi); C: PTT-3 wt% Ti,90:10 (KD);

D: PTT-3 wt% 77,85:15 (KD); E: PTT-5 wt% Ti,90:10 (T OI);F: PTT-5 wt%
Ti,90:10 (KD)

67

 

HDT ('C)

 

140

120 ~

 

 

 

1001

 

I-I

80

601

40'

20‘

 

 

 

 

 

 

 

 

 

 

 

Samples 1

Figure 4.11 HDT of PTT and its Nanocomposites
A: Neat PTT; B: PTT-3 wt% Ti,90:10 (T oi); C: PTT-3 wt% Ti,90:10 (KD);
D: PTT-5 wt% Ti,90:10 (To!)

68

4.3 Extruded Cast Films Nanocomposites

Titanate modified clays of varying titanate modifier and silane coupling
agent contents were used to study their effectiveness on the performance of the
resulting nanocomposites films. The nomenclature of nanocomposites extruded

cast films made from the above listed clays is represented as:

NC-1: PTT w/ 3 wt.% Ti, 90:10 (T ol) clay
NC-2: PTT w/ 3 wt.% Ti, 85:15 (T ol) clay
NC-3: PTT w/ 3 wt.% Ti, 85:15 (KD) clay
NC-4: PTT w/ 5 wt.% Ti, 85:15 (KD) clay
NC-5: PTT w/ 3 wt.% Si (Et) clay
NC-6: PTT w/ 5 wt.% Si (Et) clay

69

4.3.1 Tensile Properties

The results on tensile properties of the nanocomposites are summarized

in Table 4.6 and Figures 4.12 and 4.13.

Table 4.6 Tensile properties of PTT/organo- modified clay nanocomposites
extruded cast films (Value given in parentheses is Standard Deviation)

 

 

 

 

 

 

 

Material Tensile Strength at Elongation at break
yield (MPa) (%)

Neat PTT €02.65) (3;)

NC-1 33.") 1.13.21.

”0'2 34.35) 622k

NC-3 $52.13 .212...

”0‘4 (315:) (323)

NC'5 (311.11) bilgk

 

7O

The tensile properties of neat PTT film and PTT/titanate modified clay
nanocomposites films were measured at 0.4 inch/min cross head speed. It is
quite interesting to observe that neat PTT film breaks while nanocomposites films
show quite ductile behavior with no breakage, Figure 4.12. Neat PTT film showed
a brittle failure whereas nanocomposites exhibit no failure. The tensile strengths
of nanocomposites films were found to be inferior versus the neat PTT film,
Figure 4.13. The major achievement in this project is ductile behavior of PTT 3
wt.% nanocomposites films. To strengthen our view we observed the
nanocomposites films under microscope and found there were voids in films
which can help in improving elongation. There are some literatures available
which explain the behavior of voids on tensile properties. It was'found that due to
lack of interaction between nano-reinforcement and polymer, nano-reinforcement
can act as void. The decrease of strength may be attributed to poor interfacial
adhesion of organoclay with the PTT matrix under the present conditions of
nanocomposite fabrication. The voids present in 3 wt% nanocomposites films
can allow a larger volume of the matrix in the deformation zone and thereby

increasing the elongation to break [66, 67].

As evident from the stress-strain curves toughness of 3wt%
nanocomposites films was drastically improved. Toughness is the area under
stress-strain curve. Due to such increase in toughness these films can be good
choice for high impact films in packaging. The main concern was the color of film

which is not consumer appealing which may be improved but that can be used

71

for military based packaging. Due to voids the barrier is not expected to improve
but some high barrier polymers such as EVOH can be co-extruded with PTT
based nanocomposites films to improve the performance and thus can be used

for extended shelf life packaging films.

72

404

 

Stress (Mpa)

 

 

0 ,_ ._.. -,—- ________.-____ ..,____z . .1

0 5 10 15 20 25 30 35 40 45 50
Elongation (%)

 

, __,. *WT‘I’” -..1__ . .__

 

Figure 4.12 Stress-Strain Curves of PTT and its Nanocomposite Films
A: Neat PTT, B: NC- 1, C: NC-2, D: NC-3, E: NC-4

73

Tensile Strength (MPa)

 

50

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

40
T T
T 1 i 1
l 1 T
30 .. 1
20 -
10 ~~
0
Neat P'l'l' NC-1 NC-2 NC-3 NC-4 NC-5

Samples

Figure 4.13 Tensile Strength of PTT and its Nanocomposite Films

74

4.3.2 Thermo-mechanical Properties

Storage modulus measurements were obtained using a dynamic
mechanical analyzer in the tension mode for the film samples. The storage
modulus of neat PTT and its nanocomposites were measured at 30°C to
determine the effect of the organoclays on thermo-mechanical properties of PTT
films. Of the two nanocomposites films, NC-4 had the highest storage modulus of
1.99 GPa. The data of DMA studies are shown in Table 4.7 and Figure 4.14. The
storage modulus of nanocomposites showed marginal improvement and the
maximum tan delta peak was nearly same for both neat PTT and its
nanocomposites. Tan delta peak represents the glass transition temperature (T9)

of polymer which was around 60°C for PTT and its nanocomposites.

75

Table 4.7 Storage Modulus and Tan Delta Peak of PTT/organocla y
nanocomposites extruded cast films (Value given in parentheses is
Standard Deviation)

 

Storage Modulus Tan Delta Maximum

 

 

 

 

 

Material (GPa) (°C)

Neat PTT 1.63 (0.06) 59.9 (0.3)
NC-1 1.77 (0.08) 59.3 (0.6)
NC-2 1.74 (0.05) 61.2 (0.3)
NC-3 1.82 (0.10) 58.8 (0.4)
NC-4 1.99 (0.05) 59.6 (0.9)

 

76

Storage Modulus (GPa)

 

2.5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.0 1 I
l
T T
T I .L l
1
1.5 1
1.0 1
0.5 1
0.0
Neat NC-1 NC-2 NC-3 NC-4

Samples

Figure 4.14 Storage Modulus of PTT and PTT/organoclay
nanocomposites films

77

4.3.3 Thermal Properties

Differential Scanning Calorimetry (DSC) was used to study the
crystallization behavior of extruded cast films of neat PTT and PTT/titanate Clay
based nanocomposites. Neat PTT films were also prepared by pressing injection
molded blocks and both are compared. As per DSC results there was no
significant increase in crystallinity in PTT/ titanate modified clay based
nanocomposites extruded cast films. The % crystallinity was calculated by the
formula

(AH/ AH100)* 100 = % crystallinity
Where AH is enthalpy of crystallization of PTT sample

And AHIOO is the enthalpy of crystallization of 100% crystalline PTT

78

 

Heat Flow (mW)

 

 

 

r
5 3.
'3
u.‘
.,°...
0 a i3 a
5 1 r _
-10
I.
i
-15 » , , ~ , — ”97-F—
40 80 120 160 200 240

Temp (°C)

Figure 4.15 DSC curves for extruded cast films of PTT and its
nanocomposites

A: Neat PTT B: NC-3 (Unstretched area), C: NC-3 (Stretched area) D:
NC-4

79

 

 

°/o crystalllnlty

50 1F-—11-—~—A-—A 11~ 1~--——-1--W 1— --——- -—-— -—-——— -- --

45 1
40 1 I i I ,
35 1
30 1
25 1

201

 

151

 

 

 

 

 

Samples

Figure 4.16 Crystallinity of extruded cast films of PTT and its
nanocomposites

A: Neat PTT B: NC-3 (Unstretched area) C: NC-3 (Stretched area)
D:NC-4

80

4.3.4 Barrier Properties

The barrier properties of neat PTT and its nanocomposites formed as
extruded cast films containing 3 and 5 wt.% of titanate modified clay were
measured. Table 4.8 lists permeabilities of oxygen and water vapor through

extruded cast films of neat PTT and its nanocomposites for 50 cm2 area films.

Morphological studies of these films showed the presence of voids and
agglomeration of clay platelets in nanocomposites which may be due to
incompatibility between PTT matrix and organically modified clays. This may be

reason for unexpected barrier behavior of nanocomposites extruded cast films.

Table 4.8 Barrier properties of PTT/organocla y nanocomposites extruded
cast films (Value given in parentheses is Standard Deviation)

 

 

 

. 02 Permeability Water Vapor Permeation
Mater'a' (cc.mil/100in2.day.atm) (gm.mi|/1 001n°.day.atm)
Neat PTT 5.8 (0.7) 3.5 (0.1)

NC-4 6.7 (0.3) 4.1 (0.2)

 

81

4.3.5 Structural Analysis (XRD)

X-ray diffraction studies of PTT-titanate clay and silane clay based
nanocomposites extruded films were conducted to measure the extent of
exfoliation/intercalation of clay platelets in the nanocomposites. To measure the
d-spacing in films, film sample was mounted on a slit where film sample is
exposed to X-ray directly. Table 4.9 shows the basal spacing of PTT based
nanocomposites. NC-4 shows maximum increase in d-spacing of 31% versus

MMT clay.

Table 4.9 Basal spacings of raw montmorillonite and modified clays
(Value given in parentheses is Standard Deviation)

 

 

 

 

 

 

Material 26° d spacing(A)
MMT 7.90 9.71
NC-3 7.00 12.63
NC-4 6.90 12.81
NC-5 7.35 12.02
NC-6 7.10 12.45

 

82

4.3.6 Morphological Analysis (T EM 81 PLOM)

Transmission electron microscopy (TEM) was used to examine the
morphology of extruded cast films nanocomposites. The TEM micrographs of
NC-1 (Figure 4.17 and 4.18) Show intercalation and agglomeration of clay
platelets in PTT matrix. The exfoliation of clay is not the only criteria to get
enhanced properties of polymer. The polymer/clay interfacial adhesion plays a

vital role in properties of polymer, which needs to be further studied.

Polarized light optical microscopy (PLOM) was also used to study the
morphological properties of PTT based nanocomposites extruded cast films. Film
prepared at US Army Natick Soldier Center labs are shown here. Films prepared
at School of Packaging were similar to US Army lab films. PLOM Shows that
there were voids and clay agglomeration in PTT based nanocomposites extruded
cast films, Figure 4.20, whereas in neat PTT films, Figure 4.19, there were less
structural and morphological defects which can be a reason for poor barrier

properties of PTT-titanate clay based nanocomposites.

83

 

Figure 4.17 TEM micrograph of NC-1 extruded cast films

84

 

Figure 4.18 TEM micrograph of NC-1 extruded cast films at 50nm scale

85

 

Figure 4.19 PLOM micrograph of Neat PTT films prepared at US Army
Natick Soldier Centre Lab @ 50X

86

 

Figure 4.20 PLOM micrograph of NC-4 films prepared at US Army Natick
Soldier Center Lab @ 50X

87

4.4 Comparison of Water vapor and Oxygen barrier properties of Sorona®
with conventional thermoplastics and poly lactide (PLA)

Extruded cast films of neat PTT (Sorona®) were tested for water vapor and
oxygen barrier properties on MOCON® Permatran-W® 3/33 MG and Ox-Tran®
2/21 respectively. Literature data of commercially available thermoplastics and
PLA were taken to compare the water vapor transmission and oxygen
permeability. We have compared the barrier data of low density polyethylene
(LDPE), polypropylene (PP), nylon-6, poly(ethylene terephthalate) (PET) sourced
from [68], poly(lactic acid) (PLA) sourced from [69] and ethylene vinyl alcohol
(EVOH) sourced from [70] with our fabricated PTT cast films. Units are converted
to compare the permeability values. It was found that PTT exhibits better water
vapor barrier than Nylon-6, PLA and EVOH but lower than LDPE and PP as
shown in Figure 2.2. It was observed that oxygen barrier of PTT is higher than
LDPE, PP and PLA but lower than Nylon-6 and EVOH as shown in Figure 2.3.

The oxygen barrier and water vapor barrier of PTT films are comparable to PET.

From oxygen permeability and water vapor transmission data, it is clearly
evident that PTT (Sorona®) is much better barrier to oxygen and water vapor
than PLA, which is 100% renewable based polymer. It can be inferred that
Sorona® which is partially bio-based is a better option in cost-performance

attribute than 100% bio-based polymers.

88

25-

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 4.21 Water Vapor Transmission of polymers at 37.8'C and 50-
100%RH (LDPE, PP, Nylon-6, E VOH and PLA), PTT at 100% RH

89

201
C
3
m A
'9 6
5,3 15 1
gs
#- 8
32
a E .
T. E 10
o 9
.‘5
3
5_
0 I I ' 3 l: ]
LDPE PP Nylon-6 PLA PET EVOH PTT

 

600

500 1

.b
O
0

Oxygen Permeability
(cc.mlI/100ln2.day.atm)
N 0)
8 8

100 1

Figure 4.22 Oxygen permeabilities of polymers at 23 'C and 0% RH

 

 

 

 

 

 

 

 

m

H

 

LDPE

PP

Nylon-6

90

PLA

PET

EVOH

PTT

 

Chapter 5

Conclusions and Recommendations

Poly (trimethylene terephthalate), PTT (Sorona®) is an emerging biobased
polymer from DuPontW' that can be made from bio—derived 1, 3 propanediol and
petroleum-based terephthalic acid. In this piece of research work, PTT/titanate
modified clay (organoclay) nanocomposites were successfully fabricated through
melt processing technique. MMT clay was modified with different levels of
titanate based organic modifier and silane coupling agent with the target to
optimize the titanate modifier loading in clay. XPS, XRD and hydrophilic-
hydrophobic balance data validated the successful modification of MMT clay with
titanate modifier. Injection molded nanocomposites and cast film nanocompOsites
were fabricated and characterized. Neat PTT cast film showed gauge bands
while PTT/organoclay nanocomposites films were quite even in width and
thickness. The tensile modulus and storage modulus of PTT improved by 18%
and 28% respectively upon reinforcement with 5 wt% of titanate modified
organoclay. Similarly, the heat deflection temperature of PTT improved by 21%
with 5 wt% loading of organoclay. Neat PTT and PTT with 5 wt% organoclay
nanocomposites film showed brittle failure at a percent elongation value of 5.75
and 3.25%, whilst 3 wt% organoclay nanocomposites films showed quite ductile
behavior with no breakage. The transmission electron microscopy (TEM)
analysis of PTT/titanate modified clay nanocomposite film revealed intercalated
and agglomeration type morphology of the nanocomposites. Polarized light

optical microscopy (PLOM) studies showed that there were voids and clay

91

agglomeration in PTT organoclay nanocomposites films which can be
responsible for increasing the permeability of these films. The voids present in 3
wt.% nanocomposites films can allow a larger volume of the matrix in the

deformation zone and thereby increasing the elongation to break.

As for future recommendations, the following options can be utilized for
optimum properties of PTT and organically modified nanoclays based
nanocomposites:

- Use of twice functionalized clay might be a good option to improve
compatibility between PTT and clay.

- Use of PTT and tough polymer based blends for improvement of properties.

0 Extensive studies on rheology

0 Processing optimization

92

10.

References

Environment Literacy Council [Accessed 24 February.2007]; Available
from: http://wwwenviroliteracvorq/arlicle.php/1 188.html

Bhardwaj, R., Mohanty, A. K., Drzal, L. T., Pourboghrat. F., and Misra, M.,
Renewable Resource-Based Green Composites from Recycled Cellulose
Fiber and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Bioplastic.
BioMacromolecules, 2006. 7: p. 2044-2051.

Mohanty, A. K., Misra, M., and Drzal, L. T., Sustainable Bio-Composites
from Renewable Resources: Opportunities and Challenges in the Green
Materials World. Journal of Polymers and the Environment, 2002. 10: p.
19-26.

Mohanty, A. K., Misra, M., and Drzal, L. T., Natural Fibers, Biopolymers
and Biocomposites. 2005, Taylor & Francis/CRO Press Boca Raton, FL.

Drown, E. K., Mohanty, A. K., Parulekar, Y., Hasija, D., Harte, B. R., M.
Misra, and Kurian, J. V., The surface characteristics of Organoclays And
Their Effect on the Properties of Poly(Trimethylene Terephthalate)
Nanocomposites. Composites Science and Technology, 2007. 67(15-16):
p. 3168-3175.

Kurian, J. V., A New Polymer Platform for the Future — Sorona from Corn
Derived 1,3-Propanediol”. Journal of Polymers and the Environment 2005.
13(2): p. 159-167.

Ritter, S. K., GREEN REWARDS: Presidential honors recognize
innovative syntheses, process improvements, and new products that
promote pollution prevention. Chemical 8 Engineering News, 2003.
81 (26): p. 30-35.

Akkapeddi, M. K., Glass Fiber Reinforced Polyamide-6 Nanocomposites.
Polymer Composites, 2004. 21(4): p. 576-585.

Brauer, S., Polymer Nanocomposites (Magazine Article). Business
Communications Company Inc, 2000: p. 13-14.

lshak, Z. A. M., Leong, Y. W., Steeg, M., and Karger-Kocsis, J.,
Mechanical Properties of Woven Glass Fabric Reinforced in Situ
Polymerized Poly(butylene terephthalate) Composites. Composites
Science and Technology, 2007. 67(3-4): p. 390-398.

93

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

Li, H., Jia, Y., Mamtiminc, G., Jiang, W., and An, L., Stress Transfer and
Damage Evolution Simulations of Fiber-reinforced Polymer-matrix
Composites. Materials Science and Engineering A, 2006. 425: p. 178-184.

Liu, W., Mohanty, A. K., Drzal, L. T., Misra, M., Kurian, J. V., Miller, R. W.,
and Strickland, N., Injection Molded Glass Fiber Reinforced
Poly(trimethylene terephthalate) Composites: Fabrication and Properties
Evaluation. Industrial 81 Engineering Chemistry Research, 2005. 44: p.
857-862.

Giannelis, E. P., Krishnamoorti, R., and Manias, E., Polymer-Silicate
Nanocomposites: Model Systems for Confined Polymers and Polymer
Brushes. Advances in Polymer Science, 1999. 138: p. 107-147.

Mohanty, A. K., Misra, M., and Drzal, L. T., Surface modifications of
natural fibers and performance of the resulting biocomposites: An
overview. Composites Interfaces, 2001. 8: p. 313-343.

Mohanty, A. K., Misra, M., and Hinrichsen, G., Biofibres, biodegradable
polymers and biocomposites: An overview. Macromolecular Materials and
Engineering, 2000. 276/277: p. 1—24

Darder, M., Aranda, P., and Ruiz-Hitzky, E.,. Bionanocomposites: A New
Concept of Ecological, Bioinspired, and Functional Hybrid Materials.
Advanced Materials, 2007. 19: p. 1309-1319.

Ruiz-Hitzky, E., Aranda, P., and Darder, M., Bottom-Up Nanofabn‘cation:
Supramolecules, Self-Assemblies, and Organized Films. 2007: American
Scientific Publishers.

Ruiz-Hitzky, E., M.Darder, and P.Aranda, Functional biopolymer
nanocomposites based on layered solids. Journal of Materials Chemistry,
2005. 15: p. 3650-3662.

Sorona Technical Information Brochure. [Accessed 27 July.2006];
Available from: www.dupont.com.

Whited, G. M., Bulthuis, B., Trimbur, D. E., and Gatenby, A. A., Method of
production of 1 ,3-propanediol by recombinant organisms comprising
genes for vitamin B-12 transport in European Patent EP1076708, DuPont,
1999

Burch, R. R., Dorsch, R. R., Laffend, L. A., and Nagarajan, V., 1,3-

Propanediol and polymer derivatives from a fermentable carbon source in
International Patent WO 0111070, DuPont, 2001

94

22.

23.

24.

25.

26.

27.

28.

29.

30.

31.

32.

33.

Emptage, M., Haynie, S., Laffend, L., Pucci, J., and Whited, 6., Process
for biological production of 1,3-propanediol with high titer in International
Patent WO 0112833; European Patent EP 1204755, DuPont, 2001

Low temperature heat sealable polyester film and method for producing
same in US Patent application 20020012807 A1 (1/31/2002), 2002

Desborough, l. J., Hall, I. H., and Neisser, J. 2., The Structure of
Poly(trimethylene terephthalate). Polymer, 1979. 20: p. 545.

Pyda, M., Boller, A., Grebowicz, J., Chuah, H., Lebedev, B. V., and
Wunderlich, 3., Heat capacity of poly(trimethylene terephthalate). Journal
of Polymer Science Part B: Polymer Physics, 1998. 36(14): p. 2499-2511.

Traub, H. L., Hirt, P., Herlinger, H., and Oppermann, W., Synthesis and
properties of fiber-grade poly(trimethylene terephthalate). Angewandte
Makromolekulare Chemie, 1995. 230(1 ): p. 179-187.

Khonakdar, H. A., Jafari, S. H., and Asadinezhad, A., A Review on
Homopolymer, Blends, and Nanocomposites of Poly(trimethylene
terephthalate) As a New Addition to the Aromatic Polyesters Class. Iranian
Polymer Journal, 2008. 17(1): p. 19-38.

Ou, C.-F., Nanocomposites of Poly(trimethylene terephthalate) with
Organoclay. Journal of Applied Polymer Science, 2003. 89: p. 3315-3322.

Catsiff, E. H. and Hewett, W. A., The interaction of two dissimilar polymers
in solution. Journal of Polymer Science, 1962. 6(23): p. S30-S32.

Krigbaum, W. R. and Wall, F. T., Viscosities of binary polymeric mixtures.
Journal of Polymer Science, 1950. 5(4): p. 505-514.

Mishra, J. K., Chang, Y.-W., and Choi, N. 8., Preparation and
Characterization of Rubber- Toughened Poly(trimethylene terephthalate)
/Organoclay Nanocomposite. Polymer Engineering and Science, 2007.
47(6): p. 863-870.

Okada, A. and Usuki, A., The chemistry of polymer-clay hybrids. Materials
Science and Engineering: C, 1995. 3(2): p. 109-115.

Rudin, A., Hoegy, H. L. W., and Johnston, H. K., Estimation of Viscosities

of mixed polymer solutions. Journal of Applied Polymer Science, 1972.
16(5): p. 1281-1293.

95

34.

35.

36.

37.

38.

39.

40.

41.

42.

43.

44.

Shu, Y.-C. and Hsiao, K.-J., Rheology, Thermal Characteristics,
Crystallinity, Tenacity and Density of Cationic Dyeable Polycaproamide/
Cationic Dyeable Poly(trimethylene terephthalate) Polyblended Fibers.
Journal of Applied Polymer Science, 2007. 106: p. 644-651.

Usuki, A., Kojima, Y., Kawasumi, M., Okada, A., Fukushima, Y., Kurauchi,
T., and Kamigaito, 0., Synthesis of nylon 6-clay hybrid. Journal of
Materials Research, 1993. 8(5): p. 1179-1184.

Williamson, G. R. and Wright, 8., Interactions in binary polymer systems.
Journal of Polymer Science Part A: General Papers, 1965. 3(11): p. 3885-
3891.

Kelsey, D. R., Kiibler, K. S., and Tutunjian, P. N., Thermal Stability of
poly(trimethylene terephthalate). Polymer, 2005.46: p. 8937—8946.

Chuah, H. H., Orientation and Structure Development in Poly(trimethylene
terephthalate) Tensile Drawing. Macromolecules, 2001. 34: p. 6985-6993.

Ho, R.-M., Ke, K.-Z., and Chen, M., Crystal Structure and Banded
Sphemlite of Poly(trimethylene terephthalate). Macromolecules, 2000. '
33(20): p. 7529-7537.

Hong, P.-D., Chung, W.-T., and Hsu, C.-F., Crystallization kinetics and
morphology of poly(trimethylene terephthalate). Polymer, 2002. 43(11): p.
3335-3343.

Jang, S. S. and Jo, W. H., Phase Transformation of Poly(trimethylene
terephthalate) in Crystalline State: An Atomistic Modeling Approach.
Fibers and Polymers, 2000. 1(1): p. 18-24.

Wang, B., Li, C. Y., Hanzlicek, J., Cheng, S. 2. D., Phillip H. Geil,
Grebowicz, J., and Ho, R.-M., Poly(trimethylene terephthalate) crystal
structure and morphology in different length scales. Polymer, 2001.
42(16): p. 7171-7180.

Wu, J., Schultz, J. M., Samon, J. M., Pangelinan, A. B., and Chuah, H. H.,
In situ study of structure development in poly(trimethylene terephthalate)
fibers during stretching by simultaneous synchrotron small- and wide-
angle X-ray scattering Polymer, 2001 . 42(16): p. 7141-7151.

Yang, J., Sidoti, G., Liu, J., Geil, P. H., Li, C. Y., and Cheng, S. 2. D.,

Morphology and crystal structure of CTFMP and bulk polymerized
poly(trimethylene terephthalate).Polymer, 2001. 42: p. 7181-7195.

96

45.

46.

47.

48.

49.

50.

51.

52.

53.

54.

55.

56.

Zhang, J., Study of Poly(trimethylene terephthalate) as an Engineering
Thermoplastics Material. Journal of Applied Polymer Science, 2004. 91: p.
1657-1666.

Hu, X. and Lesser, A. J., Effect of a silicate filler on the crystal morphology
of poly(trimethylene terephthalate)/cla y nanocomposites. Journal of
Polymer Science, Part B: Polymer Physics, 2003.41: p. 2275-2289

Hu, X. and Lesser, A. J., Non-Isothermal Crystallization of
Poly(trimethylene terephthalate) (PTT)/Cla y Nanocomposites.
Macromolecular Chemistry and Physics, 2004. 205: p. 574-580.

Chang, J.-H., Kim, S. J., and Im, S., Poly(trimethylene terephthalate)
nanocomposite fibers by in situ intercalation polymerization: therrno-
mechanical properties and morphology (I). Polymer, 2004. 45: p. 5171-
5181.

Chang, J.-H., Mun, M. K., and Kim, J.-C., Poly(trimethylene terephthalate)
Nanocomposite Fibers Comprising Different Organoclays:
Thermomechanical Properties and Morphology. Journal of Applied
Polymer Science, 2006. 102: p. 4535-4545.

Liu, Z., Chen, K., and Yan, D., Crystallization, morphology, and dynamic
mechanical properties of poly(trimethylene terephthalate)/cla y
Nanocomposites. European Polymer Journal, 2003. 39: p. 2359-2366.

Mohan, A. M., Nanotechnology offers big benefits for packaging.
Packaging Digest, 2005. 42(10): p. 50-56.

Ray, 8. S. and Okamato, M., Biodegradable Polylactide and Its
Nanocomposites: Opening a New Dimension for Plastics and Composites.
Macromolecular Rapid Communications, 2003. 24: p. 815-840.

Nielsen, L. E., Models for the Permeability of Filled Polymer Systems.
Journal of Macromolecular Science, Part A, 1967. 1(5): p. 929-942.

Gusev, A. A. and Lusti, H. R., Rational Design of Nanocomposites for
Barrier Applications. Advanced Materials, 2001. 13(21): p. 1641-1643.

Hay, J. N. and Shaw, S. J., Organic-inorganic hybrids-the best of both
worlds? Euro physics News, 2003. 34(3).

Bhardwaj, R. and Mohanty, A. K., Modification of Brittle Polylactide by

Novel Hyperbranched Polymer-Based Nanostructures.
BioMacromolecules, 2007.8: p. 2476-2484.

97

57.

58.
59.

60.

61.

62.

63. ‘

64.

65.

66.

67.

Lau, K.-t., Gu, C., and Hui, D., A critical review on nanotube and
nanotube/nanocla y related polymer composite materials. Composites Part
B: Engineering, 2006. 37(6): p. 425-236.

Nanocor® Case Study. [Accessed 15 April.2007]; Available from:
httpzllwww.nanocor.com/Cases/case impermasp.

Sherman, L. M. Chasing Nanocomposites. [Accessed 02 May.2007];
Available from: http://mptonline.com/articles/200411fa_2.html

Southern Clay Products, Technical Bulletin Cloisite® Na”. [Accessed 25
April.2008]; Available from:
httpzllwwwscprod.com/product bulletins/PB%j200loisite%20NA+.pgf.

Parulekar, Y. S. and Mohanty, A. K., Effect of Titanate-Based Surface on
Hydrophilicity and Inter/a yer Spacing of Montmorillonite Clay for Polymer
Nanocomposites. Journal of Nanoscience and Nanotechnology, 2005. 5:
p. 2138-2143.

Monte, S. J. and Sugerman, 6., Processing of composites with titanate
coupling agents - a review”. Polymer Engineering 81 Science, 1984.
24(18): p. 1369-1382.

He, H., Duchet, J., Galy, J., and Gerard, J. J., Grafting of swelling clay
materials with 3=aminopropyltriethoxysilane. Journal of Colloid and
Interface Science 2005. 288(1): p. 171 -1 76.

Fornes, T. D. and Paul, D. R., Structure and Properties of
Nanocomposites Based on Nylon-11 and - 12 Compared with Those
Based on Nylon-6. Macromolecules, 2004. 37(20): p. 7698-7709.

Mehta, S., Mirabella, F. M., Rufener, K., and Bafna, A., Thermoplastic
olefin/Ola y nanocomposites: Morphology and mechanical properties.
Journal of Applied Polymer Science, 2004. 92: p. 928-936.

Ajayan, P. M., Schadler, L. S., and Braun, P. V., Polymer-based and
polymer-filled nanocomposites, in Nanocomposite Science and
Technology. 2003, WILEY-VCH Verlag.

Petersson, L. and Oksman, K., Biopolymer based nanocomposites:
Comparing layered silicates and microcrystalline cellulose as
nanoreinforcement. Composites Science & Technology, 2006. 66: p.
2187-2196.

98

68.

69.

70.

Tock, R. W., Permeabilities and water vapor transmission rates for

commercial polymer films. Advances in Polymer Technology, 1983. 3(3):
p. 223-231.

Natureworks LLC, PLA 40420 Biaxially Oriented film general purpose
datasheet [Accessed 04 August.2006]; Available from:
http://www.natureworksllc.com/download bulletin.asp?ig=48.

E VAL Americas, E VOH F-series barrier data. [Accessed 18 May.2007];
Available from: httpzllwww.eval.be/upI/1lus/dOC/199 4 6 a.pdf

99

 

 

 

 

r
..
m .
v

I III IIII'IIIIIII

[ATE UNIVERSITY LIBRARIES

Ii

[MICHIGAN
II I II
I
1293 02956 5011

I

3