Chapter 1

Introduction

Abstract

Polymer nanocomposites are of great importance of today’s scientific world. This

field of science has attracted a lot of attention of the present day scientists. This

introdoctory chapter gives an overview of the recent advances in polymer

nanocomposites. The chapter focuses on the general introduction of the

nanocomposites, their classification and the synthetic routes of nanoparticles and

nanocomposites. The properties of the nanocomposites are covered in the next

section. Specifically the recent literature on polystyrene and ethylene vinyl acetate

based nanocomposites is given in the end. Also the specific objectives of the

present study are elaborated.

Part of this chapter have been communicated for publication in Progress in

Polymer Science

2 Chapter 1

1.1. Introduction

Combining and orienting materials to achieve composite materials with superior

properties are old and well-proven concept; examples of this synergism abound in

nature. For example, wood contains an oriented hard phase for toughness. Other

natural composites are found in teeth, bones, bird feathers and plant leaves. By

defenition a composite is the material created when two or more distinct

components are combined. But this definition is too broad to be useful; even if

limited to polymers, it would include copolymers and blends, reinforced plastics

and materials such as carbon-black filled rubber. Generally composite is a

material consisting of two or more distinct phases with a recognizable interface or

interface boundary. In other words, it is a combination of two or more materials

(reinforcing elements, fillers and composite matrix binders) differing in form or

composition on a macroscale. In a strict sense composites are those materials

formed by aligning extremely strong and stiff continuous fibers in a polymer matrix

or binder. Compared to neat resins, composites have a number of improved

properties including tensile strength, heat distortion temperature and modulus.

Thus, for structural applications, composites have become very popular and are

sold in billion pound quantities. The materials in this class have exceptional

mechanical properties and are often termed advanced composites to distinguish

from chopped fillers or otherwise filled polymers. Composites were used in a wide

variety of applications, as there is a considerable scope for tailoring their structure

to suit the service conditions together with other advantages such as high strength

to weight ratio, low cost etc. The composite materials combine beneficial

properties of its component materials, which are not obtained in one component

by itself.

Composites can be classified with respect to different parameters. The important

ones are described below. The composite material can be classified broadly by

their constituent components. There are mainly three categories of composites:

(a) Natural composite materials: These include wood, bone, bamboo, muscle

and other tissues.

(b) Macro composite (Engineering materials): These include galvanized steel,

reinforced concrete beams, helicopter blades etc.

Chapter 1

Introduction

Abstract

Polymer nanocomposites are of great importance of today’s scientific world. This

field of science has attracted a lot of attention of the present day scientists. This

introdoctory chapter gives an overview of the recent advances in polymer

nanocomposites. The chapter focuses on the general introduction of the

nanocomposites, their classification and the synthetic routes of nanoparticles and

nanocomposites. The properties of the nanocomposites are covered in the next

section. Specifically the recent literature on polystyrene and ethylene vinyl acetate

based nanocomposites is given in the end. Also the specific objectives of the

present study are elaborated.

Part of this chapter have been communicated for publication in Progress in

Polymer Science

2 Chapter 1

1.1. Introduction

Combining and orienting materials to achieve composite materials with superior

properties are old and well-proven concept; examples of this synergism abound in

nature. For example, wood contains an oriented hard phase for toughness. Other

natural composites are found in teeth, bones, bird feathers and plant leaves. By

defenition a composite is the material created when two or more distinct

components are combined. But this definition is too broad to be useful; even if

limited to polymers, it would include copolymers and blends, reinforced plastics

and materials such as carbon-black filled rubber. Generally composite is a

material consisting of two or more distinct phases with a recognizable interface or

interface boundary. In other words, it is a combination of two or more materials

(reinforcing elements, fillers and composite matrix binders) differing in form or

composition on a macroscale. In a strict sense composites are those materials

formed by aligning extremely strong and stiff continuous fibers in a polymer matrix

or binder. Compared to neat resins, composites have a number of improved

properties including tensile strength, heat distortion temperature and modulus.

Thus, for structural applications, composites have become very popular and are

sold in billion pound quantities. The materials in this class have exceptional

mechanical properties and are often termed advanced composites to distinguish

from chopped fillers or otherwise filled polymers. Composites were used in a wide

variety of applications, as there is a considerable scope for tailoring their structure

to suit the service conditions together with other advantages such as high strength

to weight ratio, low cost etc. The composite materials combine beneficial

properties of its component materials, which are not obtained in one component

by itself.

Composites can be classified with respect to different parameters. The important

ones are described below. The composite material can be classified broadly by

their constituent components. There are mainly three categories of composites:

(a) Natural composite materials: These include wood, bone, bamboo, muscle

and other tissues.

(b) Macro composite (Engineering materials): These include galvanized steel,

reinforced concrete beams, helicopter blades etc.

Introduction 3

(c) Micro composite materials: These comprise of metallic alloys, toughened

thermoplastics, sheet molded compounds and reinforced thermoplastics.

The polymeric composites are mainly micro-composites. They are further

classified according to the reinforcement forms into particulate reinforced, fiber

reinforced and laminar composites.

(i) Particulate reinforced composites: These include materials reinforced by

spheres, rods, beads, flakes and many other shapes of roughly equal axes.

The examples are polymeric materials incorporating fillers such as glass

spheres or finely divided powders, polymers with rubber particles etc.

(ii) Fiber reinforced composites: These contain reinforcements having much

greater strength than their cross-sectional dimensions. e.g.: glass fiber

reinforced plastics, carbon fibers in epoxy resins etc.

(iii) Laminar composites: These are composed of two or more layers held together

by the matrix binder. These have two of their dimensions much larger than the

third. e.g.-wooden laminates, glasses, plastics etc.

Particulate composites are classified based on the particle size of the dispersed

phase. More recently, with advances in synthetic techniques and the ability to

readily characterize materials on an atomic scale has generated a lot of interest in

nano-meter size materials. Since nanometre-size grains, fibers and plates have

dramatically increased surface area compared to their conventional-size materials,

the chemistry of these nanosized materials is altered compared to conventional

materials. Thus composites can be classified as micro composites,

nanocomposites and molecular composites.

In 1985 Professor A. Kelly authored an article in Composites Science and

Technology titled ‘‘Composites in Context’’ [1] reviewing the state of the art of the

composite materials. Tremendous developments have been made [2] in many

aspects of composites research and technology during the two decades since the

publication of Kelly’s paper. Recent advances in producing nanostructured

materials with novel material properties have stimulated research to create multi-

functional macroscopic engineering materials by designing structures at the

4 Chapter 1

nanometer scale. Motivated by the recent enthusiasm in nanotechnology,

development of nanocomposites is one of the rapidly evolving areas of

composites research. Nanotechnology can be broadly defined as, ‘‘the creation, processing, characterization, and utilization of materials, devices, and

systems with dimensions on the order of 0.1–100 nm, exhibiting novel and significantly enhanced physical, chemical, and biological properties,

functions, phenomena, and processes due to their nanoscale size’’ [3].

Current interests in nanotechnology encompass nano-biotechnology, nano-

systems, nanoelectronics, and nano-structured materials, of which

nanocomposites are a significant part [4].

The expansion of length scales from meters (finished woven composite parts),

micrometers (fiber diameter), sub-micrometers (fiber/matrix interphase) to

nanometers (nanotube diameter) presents tremendous opportunities for innovative

approaches in the processing, characterization, and analysis/modeling of this new

generation of composite materials. As scientists and engineers seek to make

practical materials and devices from nanostructures, understanding material

behavior across length scales from the atomistic to macroscopic levels is required.

Knowledge of how the nanoscale structure influences the bulk properties will

enable design of the nanostructure to create multi-functional composites.

The challenges in nanocomposites research perhaps can be best illustrated by the

electron micrographs shown in figure 1.1 [5–7], where multi-walled carbon nano-

tubes (MWCNTs, 10–20 nm in diameter) have been deposited on the surface of

carbon fibers (7 µm in diameter) in yarn bundles (measured in millimeters). When

consolidated into a composite, the reinforcement scales span seven orders of

magnitude. Figure 1.2 shows a transmission electron microscope (TEM) image of

the nanocomposite structure near the fiber/matrix interface, where the difference

in reinforcement scales is readily apparent.

Introduction 3

(c) Micro composite materials: These comprise of metallic alloys, toughened

thermoplastics, sheet molded compounds and reinforced thermoplastics.

The polymeric composites are mainly micro-composites. They are further

classified according to the reinforcement forms into particulate reinforced, fiber

reinforced and laminar composites.

(i) Particulate reinforced composites: These include materials reinforced by

spheres, rods, beads, flakes and many other shapes of roughly equal axes.

The examples are polymeric materials incorporating fillers such as glass

spheres or finely divided powders, polymers with rubber particles etc.

(ii) Fiber reinforced composites: These contain reinforcements having much

greater strength than their cross-sectional dimensions. e.g.: glass fiber

reinforced plastics, carbon fibers in epoxy resins etc.

(iii) Laminar composites: These are composed of two or more layers held together

by the matrix binder. These have two of their dimensions much larger than the

third. e.g.-wooden laminates, glasses, plastics etc.

Particulate composites are classified based on the particle size of the dispersed

phase. More recently, with advances in synthetic techniques and the ability to

readily characterize materials on an atomic scale has generated a lot of interest in

nano-meter size materials. Since nanometre-size grains, fibers and plates have

dramatically increased surface area compared to their conventional-size materials,

the chemistry of these nanosized materials is altered compared to conventional

materials. Thus composites can be classified as micro composites,

nanocomposites and molecular composites.

In 1985 Professor A. Kelly authored an article in Composites Science and

Technology titled ‘‘Composites in Context’’ [1] reviewing the state of the art of the

composite materials. Tremendous developments have been made [2] in many

aspects of composites research and technology during the two decades since the

publication of Kelly’s paper. Recent advances in producing nanostructured

materials with novel material properties have stimulated research to create multi-

functional macroscopic engineering materials by designing structures at the

4 Chapter 1

nanometer scale. Motivated by the recent enthusiasm in nanotechnology,

development of nanocomposites is one of the rapidly evolving areas of

composites research. Nanotechnology can be broadly defined as, ‘‘the creation, processing, characterization, and utilization of materials, devices, and

systems with dimensions on the order of 0.1–100 nm, exhibiting novel and significantly enhanced physical, chemical, and biological properties,

functions, phenomena, and processes due to their nanoscale size’’ [3].

Current interests in nanotechnology encompass nano-biotechnology, nano-

systems, nanoelectronics, and nano-structured materials, of which

nanocomposites are a significant part [4].

The expansion of length scales from meters (finished woven composite parts),

micrometers (fiber diameter), sub-micrometers (fiber/matrix interphase) to

nanometers (nanotube diameter) presents tremendous opportunities for innovative

approaches in the processing, characterization, and analysis/modeling of this new

generation of composite materials. As scientists and engineers seek to make

practical materials and devices from nanostructures, understanding material

behavior across length scales from the atomistic to macroscopic levels is required.

Knowledge of how the nanoscale structure influences the bulk properties will

enable design of the nanostructure to create multi-functional composites.

The challenges in nanocomposites research perhaps can be best illustrated by the

electron micrographs shown in figure 1.1 [5–7], where multi-walled carbon nano-

tubes (MWCNTs, 10–20 nm in diameter) have been deposited on the surface of

carbon fibers (7 µm in diameter) in yarn bundles (measured in millimeters). When

consolidated into a composite, the reinforcement scales span seven orders of

magnitude. Figure 1.2 shows a transmission electron microscope (TEM) image of

the nanocomposite structure near the fiber/matrix interface, where the difference

in reinforcement scales is readily apparent.

Introduction 5

Figure 1.1. Variation in reinforcement scales from millimeters to nanometers: (from left) from woven fabric of yarn bundles, to a single carbon fiber with entangled carbon nanotubes grown on the surface [5, 6], to the nanometer diameter and wall structure of the carbon nanotube [7].

A morphological characteristic that is of fundamental importance in the

understanding of the structure–property relationship of nanocomposites is the

surface area/volume ratio of the reinforcement materials. The following section

discusses nanocomposites based upon the three categories of reinforcement

materials: particles (silica, metal, and other organic and inorganic particles),

layered materials (graphite, layered silicate, and other layered minerals), and

fibrous materials (nanofibers and nanotubes).

As illustrated in figure 1.3, the change in particle diameter, layer thickness, or

fibrous material diameter from micrometer to nanometer, changes the ratio by

three orders in magnitude. At this scale, there is often distinct size dependence of

the material properties. In addition, with the drastic increase in interfacial area, the

properties of the composite become dominated more by the properties of the

interface or interphase.

6 Chapter 1

Figure 1.2. TEM micrograph showing the nanotube composite structure directly adjacent to the carbon fiber/polymer matrix interface [6]

Figure 1. 3. Surface area/volume relations for varying reinforcement geometries

1.2. Nanoparticles

Although nanotechnology is widely talked about, there is little consensus about

where the nano-domain begins. In fact, in the recent report [8] by the Royal

Society and the Royal Academy of Engineering in the UK, the definitions of

nanoscience and nanotechnology avoided the use of dimensions at all:

• Nanoscience is the study of phenomena and manipulation of materials at

atomic, molecular, and macromolecular scales, where properties differ

significantly from those at a larger scale.

Introduction 5

Figure 1.1. Variation in reinforcement scales from millimeters to nanometers: (from left) from woven fabric of yarn bundles, to a single carbon fiber with entangled carbon nanotubes grown on the surface [5, 6], to the nanometer diameter and wall structure of the carbon nanotube [7].

A morphological characteristic that is of fundamental importance in the

understanding of the structure–property relationship of nanocomposites is the

surface area/volume ratio of the reinforcement materials. The following section

discusses nanocomposites based upon the three categories of reinforcement

materials: particles (silica, metal, and other organic and inorganic particles),

layered materials (graphite, layered silicate, and other layered minerals), and

fibrous materials (nanofibers and nanotubes).

As illustrated in figure 1.3, the change in particle diameter, layer thickness, or

fibrous material diameter from micrometer to nanometer, changes the ratio by

three orders in magnitude. At this scale, there is often distinct size dependence of

the material properties. In addition, with the drastic increase in interfacial area, the

properties of the composite become dominated more by the properties of the

interface or interphase.

6 Chapter 1

Figure 1.2. TEM micrograph showing the nanotube composite structure directly adjacent to the carbon fiber/polymer matrix interface [6]

Figure 1. 3. Surface area/volume relations for varying reinforcement geometries

1.2. Nanoparticles

Although nanotechnology is widely talked about, there is little consensus about

where the nano-domain begins. In fact, in the recent report [8] by the Royal

Society and the Royal Academy of Engineering in the UK, the definitions of

nanoscience and nanotechnology avoided the use of dimensions at all:

• Nanoscience is the study of phenomena and manipulation of materials at

atomic, molecular, and macromolecular scales, where properties differ

significantly from those at a larger scale.

Introduction 7

• Nanotechnologies are the design, characterization, production and application

of structures, devices and systems by controlling shape and size on the nano

scale.

Figure 1.4. Micrographs of different example nanomaterials: nanopowders of (a) Co; (b) copper oxide; (c) ZnO; and (d) Ag

Nanomaterials cross the boundary between nanoscience and nanotechnology and

link the two areas together, so these definitions are very appropriate. It is

recognized that the size range that provides the greatest potential and, hence, the

greatest interest is that below 100 nm; however, there are still many applications

for which larger particles can provide properties of great interest. Nanoparticles

can come in a wide range of morphologies, from spheres, through flakes and

platelets, to dendritic structures, tubes, and rods. Figure 1.4 shows micrographs of

some examples of nanomaterials. The sophistication of the production processes

for some materials has reached the level in the laboratory where complex three-

dimensional structures such as springs, coils, and brushes have been made [9]

(Figure 1.5).

8 Chapter 1

Figure 1.5. Nanostructures of ZnO synthesized under controlled conditions by thermal evaporation of solid powders [9].

1.3. Nanocomposites

Twenty years ago, the term ‘‘nanocomposite’’ was not very popular. Scientists

used ‘‘hybrid’’ or ‘‘molecular composite’’. Actually, according to World of Science,

the word ‘‘nanocomposite’’ appeared in a paper in the polymer field for the first

time in 1990 when cars equipped with a polymer-clay ‘‘hybrid’’ part were driven

through towns and fields. But since many scientists today use ‘‘nanocomposite’’

instead of ‘‘hybrid’’.

Polymer nanocomposites are polymers that have been reinforced with small

quantities (less than 10%) of nanosized filler particles. The dispersed phase can

be inorganic particles, minerals, modified clays etc. Nanocomposites have been

found to exemplify even more positive attributes than the predecessors do and

thus an understanding of what occurs when nanocomposites of a polymer and

inorganic components are produced is significant. Although particle filled polymer

composites have been extensively studied because of their wide spread

applications in the automobile, household and electrical industries, recently

nanocomposites generate much interest among the various scientists principally,

because of their potential they offer for applications in high performance coatings,

catalysis, electronics, magnetic and biomedical materials. In polymer

nanocomposites research, the primary goal is to enhance the strength and

Introduction 7

• Nanotechnologies are the design, characterization, production and application

of structures, devices and systems by controlling shape and size on the nano

scale.

Figure 1.4. Micrographs of different example nanomaterials: nanopowders of (a) Co; (b) copper oxide; (c) ZnO; and (d) Ag

Nanomaterials cross the boundary between nanoscience and nanotechnology and

link the two areas together, so these definitions are very appropriate. It is

recognized that the size range that provides the greatest potential and, hence, the

greatest interest is that below 100 nm; however, there are still many applications

for which larger particles can provide properties of great interest. Nanoparticles

can come in a wide range of morphologies, from spheres, through flakes and

platelets, to dendritic structures, tubes, and rods. Figure 1.4 shows micrographs of

some examples of nanomaterials. The sophistication of the production processes

for some materials has reached the level in the laboratory where complex three-

dimensional structures such as springs, coils, and brushes have been made [9]

(Figure 1.5).

8 Chapter 1

Figure 1.5. Nanostructures of ZnO synthesized under controlled conditions by thermal evaporation of solid powders [9].

1.3. Nanocomposites

Twenty years ago, the term ‘‘nanocomposite’’ was not very popular. Scientists

used ‘‘hybrid’’ or ‘‘molecular composite’’. Actually, according to World of Science,

the word ‘‘nanocomposite’’ appeared in a paper in the polymer field for the first

time in 1990 when cars equipped with a polymer-clay ‘‘hybrid’’ part were driven

through towns and fields. But since many scientists today use ‘‘nanocomposite’’

instead of ‘‘hybrid’’.

Polymer nanocomposites are polymers that have been reinforced with small

quantities (less than 10%) of nanosized filler particles. The dispersed phase can

be inorganic particles, minerals, modified clays etc. Nanocomposites have been

found to exemplify even more positive attributes than the predecessors do and

thus an understanding of what occurs when nanocomposites of a polymer and

inorganic components are produced is significant. Although particle filled polymer

composites have been extensively studied because of their wide spread

applications in the automobile, household and electrical industries, recently

nanocomposites generate much interest among the various scientists principally,

because of their potential they offer for applications in high performance coatings,

catalysis, electronics, magnetic and biomedical materials. In polymer

nanocomposites research, the primary goal is to enhance the strength and

Introduction 9

toughness of polymeric components using molecular or nanoscale fillers. Most

notable are increased modulus, increased gas barrier, increased heat distortion

temperature, resistance to small molecule permeation, improved ablative

resistance, increase in atomic oxygen resistance and retention of impact strength

etc. Interestingly, these performance improvements are achieved without

increasing the density of the base polymer, without degrading its optical qualities

and without making it any less recyclable. It is a remarkable fact that in addition to

the profound changes in physical properties, which materials display when they

are nanometer in scale, the chemical behavior is profoundly altered as well. When

an inorganic solid is composed of only a few thousands of atoms, it has a great

deal of surface area.

In polymer nanocomposites, a few wt% of each nanofiller is randomly and

homogeneously dispersed on a molecular level in the polymer matrix. When

molded, the mechanical, thermal and barrier properties of these materials are

superior to those of pristine polymers and/or conventional composites. The effects

are very striking, and have become well known since many excellent reviews have

been published [10-13].

In 1985 polymer clay nanocomposites (PCN) was invented at Toyota Central R&D

Labs, Inc. (Toyota) [14,15]. It bore a new concept of polymer nanocomposites,

expanded the field of polymer science including preparation, structure and

interfaces and led to new applications for automotive, electric and food industries.

Passenger cars equipped with a PCN part were launched in 1989, just after 4

years after this discovery. Since then, extensive worldwide research on PCN has

been conducted not only in the industrial sector but also in the academic sector.

Polymers have been successfully reinforced using glass fiber, talc, calcium

carbonate, carbon black and other inorganic fillers. The content of the filler is

usually between 20 and 40 wt% of a composite, and sometimes exceeds 50 wt%

in thermosetting resins. Polymers and fillers are not homogeneously mixed on a

microscopic level, and are composed of different phases. The interface is not

large, and interaction between the polymer (matrix) and the filler is limited.

Takayanagi et al proposed the concept of a molecular composite, on the basis

10 Chapter 1

that if the filler is of molecular size then mechanical properties could be further

improved, and showed an example of a nylon matrix containing aramide fiber

whose content was 5 wt% and diameter was 30 nm [16,17]. They considered that

if platelets of nanometer dimensions were used instead of fibers, the contact

surface would become much larger. Smectite clay minerals, especially

montmorillonite (MMT), are potential candidates for a platelet-type filler for

molecular composites, since they are composed of several layers of silicates.

These silicates are 1 nm thick and have a cross-sectional area of 100 nm2, which

is very small compared to conventional fillers and also aramide fibers. MMT is the

most common and ubiquitous clay mineral, and it is well known that it undergoes

intercalation and swelling in the presence of water and organic cations [18].

Syntheses of polymers in the presence of MMT have previously been reported,

[19-22] but their major component was clay, and these studies were not intended

to improve polymers but rather to focus scientific interest. A small amount of clay

has been proven to be of key importance for nanocomposites. Actually, it was

discovered that when the clay content was less than 5 wt%, such a molecular

composite, hybrid or nanocomposite could be obtained. While some people

classify PCN into the ‘‘intercalated’’ type, where the structure of the clay is

maintained to some extent, and the ‘‘exfoliated’’ type, where silicate is randomly

and homogeneously dispersed, we focus on the latter, because the former may be

considered a conventional composite in many cases.

The structure of MMT is shown in figure 1.6, and scanning electron microscopy

(SEM) photographs of glass fiber and clay in the polymer matrix are shown in

figure 1.7, where the scales of two photos differ by 100 times.

Introduction 9

toughness of polymeric components using molecular or nanoscale fillers. Most

notable are increased modulus, increased gas barrier, increased heat distortion

temperature, resistance to small molecule permeation, improved ablative

resistance, increase in atomic oxygen resistance and retention of impact strength

etc. Interestingly, these performance improvements are achieved without

increasing the density of the base polymer, without degrading its optical qualities

and without making it any less recyclable. It is a remarkable fact that in addition to

the profound changes in physical properties, which materials display when they

are nanometer in scale, the chemical behavior is profoundly altered as well. When

an inorganic solid is composed of only a few thousands of atoms, it has a great

deal of surface area.

In polymer nanocomposites, a few wt% of each nanofiller is randomly and

homogeneously dispersed on a molecular level in the polymer matrix. When

molded, the mechanical, thermal and barrier properties of these materials are

superior to those of pristine polymers and/or conventional composites. The effects

are very striking, and have become well known since many excellent reviews have

been published [10-13].

In 1985 polymer clay nanocomposites (PCN) was invented at Toyota Central R&D

Labs, Inc. (Toyota) [14,15]. It bore a new concept of polymer nanocomposites,

expanded the field of polymer science including preparation, structure and

interfaces and led to new applications for automotive, electric and food industries.

Passenger cars equipped with a PCN part were launched in 1989, just after 4

years after this discovery. Since then, extensive worldwide research on PCN has

been conducted not only in the industrial sector but also in the academic sector.

Polymers have been successfully reinforced using glass fiber, talc, calcium

carbonate, carbon black and other inorganic fillers. The content of the filler is

usually between 20 and 40 wt% of a composite, and sometimes exceeds 50 wt%

in thermosetting resins. Polymers and fillers are not homogeneously mixed on a

microscopic level, and are composed of different phases. The interface is not

large, and interaction between the polymer (matrix) and the filler is limited.

Takayanagi et al proposed the concept of a molecular composite, on the basis

10 Chapter 1

that if the filler is of molecular size then mechanical properties could be further

improved, and showed an example of a nylon matrix containing aramide fiber

whose content was 5 wt% and diameter was 30 nm [16,17]. They considered that

if platelets of nanometer dimensions were used instead of fibers, the contact

surface would become much larger. Smectite clay minerals, especially

montmorillonite (MMT), are potential candidates for a platelet-type filler for

molecular composites, since they are composed of several layers of silicates.

These silicates are 1 nm thick and have a cross-sectional area of 100 nm2, which

is very small compared to conventional fillers and also aramide fibers. MMT is the

most common and ubiquitous clay mineral, and it is well known that it undergoes

intercalation and swelling in the presence of water and organic cations [18].

Syntheses of polymers in the presence of MMT have previously been reported,

[19-22] but their major component was clay, and these studies were not intended

to improve polymers but rather to focus scientific interest. A small amount of clay

has been proven to be of key importance for nanocomposites. Actually, it was

discovered that when the clay content was less than 5 wt%, such a molecular

composite, hybrid or nanocomposite could be obtained. While some people

classify PCN into the ‘‘intercalated’’ type, where the structure of the clay is

maintained to some extent, and the ‘‘exfoliated’’ type, where silicate is randomly

and homogeneously dispersed, we focus on the latter, because the former may be

considered a conventional composite in many cases.

The structure of MMT is shown in figure 1.6, and scanning electron microscopy

(SEM) photographs of glass fiber and clay in the polymer matrix are shown in

figure 1.7, where the scales of two photos differ by 100 times.

Introduction 11

Figure 1.6. Structure of montmorillonite

Figure 1.7. Comparison of size of glass fiber and montmorillonite in Nylon nanocomposites

1.4. Classification

Nanocomposites can be classified according to the nature of the reinforcing agent

such as nanoparticles, nanoplatelets etc. The following section gives a general

idea regarding the various classes of nanocomposites.

12 Chapter 1

1.4.1. Nanoparticle-reinforced composites

Particulate composites reinforced with micron-sized particles of various materials

are perhaps the most widely utilized composites in everyday materials. Particles

are typically added to enhance the matrix elastic modulus and yield strength. By

scaling the particle size down to the nanometer scale, it has been shown that

novel material properties can be obtained. A few systems are reviewed below for

illustrating the resulting modification in matrix properties. Micron-scale particles

typically scatter light making otherwise transparent matrix materials appear

opaque. Naganuma and Kagawa [23] showed in their study of SiO2/epoxy

composites that decreasing the particle size resulted in significantly improved

transmittance of visible light. Singh et al. [24] studied the variation of fracture

toughness of polyester resin due to the addition of aluminium particles of 20, 35

and 100 nm in diameter. They showed that the initial enhancement in fracture

toughness is followed by decreases at higher particle volume fraction. This

phenomenon is attributed to the agglomeration of nanoparticles at higher particle

volume content.

Lopez and co-workers [25] examined the elastic modulus and strength of vinyl

ester composites with the addition of 1, 2 and 3 wt% of alumina particles in the

sizes of 40 nm, 1 µm and 3 µm. For all the particle sizes, the composite modulus

increases monotonically with particle weight fraction. However, the strengths of

composites are all below the strength of neat resin due to non-uniform particle

size distribution and particle aggregation. The work of Thompson et al. [26] on

metal oxide/polyimide nanocomposite films also noted similar difficulties in

processing. Their study utilized antimony tin oxide (11–29 nm), indium tin oxide

(17–30 nm) and yttrium oxide (11–44 nm) in two space-durable polyimides. The

nanoscale additives resulted in higher stiffness, comparable or lower strengths

and elongation, and lower dynamic stiffness (storage modulus). The dispersion of

metal oxides on a nanometer scale was not achieved. Ash et al. [27] studied the

mechanical behavior of alumina particulate/poly(methyl methacrylate) composites.

They concluded that when a weak particle/matrix interface exists, the mode of

yielding for glassy, amorphous polymers changes from cavitational to shear, which

leads to a brittle-to-ductile transition. This behavior is attributed to increased

Introduction 11

Figure 1.6. Structure of montmorillonite

Figure 1.7. Comparison of size of glass fiber and montmorillonite in Nylon nanocomposites

1.4. Classification

Nanocomposites can be classified according to the nature of the reinforcing agent

such as nanoparticles, nanoplatelets etc. The following section gives a general

idea regarding the various classes of nanocomposites.

12 Chapter 1

1.4.1. Nanoparticle-reinforced composites

Particulate composites reinforced with micron-sized particles of various materials

are perhaps the most widely utilized composites in everyday materials. Particles

are typically added to enhance the matrix elastic modulus and yield strength. By

scaling the particle size down to the nanometer scale, it has been shown that

novel material properties can be obtained. A few systems are reviewed below for

illustrating the resulting modification in matrix properties. Micron-scale particles

typically scatter light making otherwise transparent matrix materials appear

opaque. Naganuma and Kagawa [23] showed in their study of SiO2/epoxy

composites that decreasing the particle size resulted in significantly improved

transmittance of visible light. Singh et al. [24] studied the variation of fracture

toughness of polyester resin due to the addition of aluminium particles of 20, 35

and 100 nm in diameter. They showed that the initial enhancement in fracture

toughness is followed by decreases at higher particle volume fraction. This

phenomenon is attributed to the agglomeration of nanoparticles at higher particle

volume content.

Lopez and co-workers [25] examined the elastic modulus and strength of vinyl

ester composites with the addition of 1, 2 and 3 wt% of alumina particles in the

sizes of 40 nm, 1 µm and 3 µm. For all the particle sizes, the composite modulus

increases monotonically with particle weight fraction. However, the strengths of

composites are all below the strength of neat resin due to non-uniform particle

size distribution and particle aggregation. The work of Thompson et al. [26] on

metal oxide/polyimide nanocomposite films also noted similar difficulties in

processing. Their study utilized antimony tin oxide (11–29 nm), indium tin oxide

(17–30 nm) and yttrium oxide (11–44 nm) in two space-durable polyimides. The

nanoscale additives resulted in higher stiffness, comparable or lower strengths

and elongation, and lower dynamic stiffness (storage modulus). The dispersion of

metal oxides on a nanometer scale was not achieved. Ash et al. [27] studied the

mechanical behavior of alumina particulate/poly(methyl methacrylate) composites.

They concluded that when a weak particle/matrix interface exists, the mode of

yielding for glassy, amorphous polymers changes from cavitational to shear, which

leads to a brittle-to-ductile transition. This behavior is attributed to increased

Introduction 13

polymer chain mobility, due to the presence of smaller particles, and also the

capability to relieve tri-axial stress because of poorly bonded larger particles. An

extensive review of the structure–property relationships in nanoparticle/semi-

crystalline thermoplastic composites has been made by Karger-Kocsis et al [28].

1.4.2. Nanoplatelet-reinforced composites

Two types of nanoplatelet-reinforced composites are reviewed: clay and graphite.

In their bulk state, both clay and graphite exist as layered materials. In order to

utilize these materials most efficiently, the layers must be separated and

dispersed throughout the matrix phase. The morphology of clay/polymer

nanocomposites is illustrated in figure 1.8 [29]. In the conventional miscible state,

the interlayer spacing in a clay particle is at its minimum. When polymer resin is

inserted into the gallery between the adjacent layers, the spacing expands, and it

is known as the intercalated state. When the layers are fully separated, the clay is

considered to be exfoliated.

Figure 1.8. Morphologies of polymer/clay nanocomposites: (a) conventional miscible, (b) partially intercalated and exfoliated, (c) fully intercalated and dispersed and (d) fully exfoliated and dispersed [29].

Figure 1.9 shows the TEM image of a montmorillonite poly (L-lactic acid) (PLLA)

matrix nanocomposite, demonstrating intercalated and exfoliated clay layers [30].

Montmorillonite, saponite, and synthetic mica are commonly used clay materials,

14 Chapter 1

and developments in clay-based nanocomposites have been recently reviewed

[31–33]. The advantages of polymer-based clay nanocomposites include

improved stiffness, strength, toughness, and thermal stability as well as reduced

gas permeability and coefficient of thermal expansion. The pioneering work at

Toyota Research Lab has clearly demonstrated that the addition of small amounts

of montmorillonite clay material significantly enhances the tensile strength, tensile

modulus, and heat degradation temperature (HDT), and reduces the rate of water

absorption in the flow direction.

Figure 1.9. TEM micrograph of a montmorillonite poly (L-lactic acid) nanocomposite, showing both intercalated and exfoliated states [30], Copyright (2003) American Chemical Society.

Table 1.1 shows some properties of two commercially available clay particles with

surface modifications [34,35]. The lack of affinity between hydrophilic silicate and

hydrophobic polymer causes agglomeration of the mineral in the polymer matrix.

Surface modification of clay particles facilitates the compatibility. Table 1.2

illustrates the unique performance of Nylon-6/clay hybrid over a wide range of

mechanical and thermal properties, as summarized by Okada and Usuki [35].

Introduction 13

polymer chain mobility, due to the presence of smaller particles, and also the

capability to relieve tri-axial stress because of poorly bonded larger particles. An

extensive review of the structure–property relationships in nanoparticle/semi-

crystalline thermoplastic composites has been made by Karger-Kocsis et al [28].

1.4.2. Nanoplatelet-reinforced composites

Two types of nanoplatelet-reinforced composites are reviewed: clay and graphite.

In their bulk state, both clay and graphite exist as layered materials. In order to

utilize these materials most efficiently, the layers must be separated and

dispersed throughout the matrix phase. The morphology of clay/polymer

nanocomposites is illustrated in figure 1.8 [29]. In the conventional miscible state,

the interlayer spacing in a clay particle is at its minimum. When polymer resin is

inserted into the gallery between the adjacent layers, the spacing expands, and it

is known as the intercalated state. When the layers are fully separated, the clay is

considered to be exfoliated.

Figure 1.8. Morphologies of polymer/clay nanocomposites: (a) conventional miscible, (b) partially intercalated and exfoliated, (c) fully intercalated and dispersed and (d) fully exfoliated and dispersed [29].

Figure 1.9 shows the TEM image of a montmorillonite poly (L-lactic acid) (PLLA)

matrix nanocomposite, demonstrating intercalated and exfoliated clay layers [30].

Montmorillonite, saponite, and synthetic mica are commonly used clay materials,

14 Chapter 1

and developments in clay-based nanocomposites have been recently reviewed

[31–33]. The advantages of polymer-based clay nanocomposites include

improved stiffness, strength, toughness, and thermal stability as well as reduced

gas permeability and coefficient of thermal expansion. The pioneering work at

Toyota Research Lab has clearly demonstrated that the addition of small amounts

of montmorillonite clay material significantly enhances the tensile strength, tensile

modulus, and heat degradation temperature (HDT), and reduces the rate of water

absorption in the flow direction.

Figure 1.9. TEM micrograph of a montmorillonite poly (L-lactic acid) nanocomposite, showing both intercalated and exfoliated states [30], Copyright (2003) American Chemical Society.

Table 1.1 shows some properties of two commercially available clay particles with

surface modifications [34,35]. The lack of affinity between hydrophilic silicate and

hydrophobic polymer causes agglomeration of the mineral in the polymer matrix.

Surface modification of clay particles facilitates the compatibility. Table 1.2

illustrates the unique performance of Nylon-6/clay hybrid over a wide range of

mechanical and thermal properties, as summarized by Okada and Usuki [35].

Introduction 15

Physical properties Cloisite 30B Nanomer 1.28E

Colour Off white White

Density (g/cm3) 1.98 1.90

D spacing (D001), A0 18.5 >20

Aspect Ratio 200-1000 200-500

Surface area (m2/g) 750 750

Mean particle size (µm) 6 8-10

Table 1.1: Properties of clay platelets

Sample Wt% of

clay, MMT

Tensile strength (MPa)

Tensile Modulus (GPa)

Charpy Impact

strength (kJ/m2)

HDT at 18.5 kg/ cm2 (0C)

Rate of water absorption 250C, 1 day

NCH-5 4.2 107 2.1 2.1 152 0.51

NCC-5 5.0 61 1.0 1.0 89 0.90

Nylon-6 0 69 1.1 1.1 65 0.87

Table 1.2: Properties of Nylon 6/ clay nanocomposites [35]

Luo and Daniel [29] have modeled the Young’s modulus of clay nanocomposites

using a three-phase model: epoxy matrix, exfoliated clay nanolayer, and

intercalated clay cluster (parallel platelet system).

16 Chapter 1

Figure 1.10. Comparison of theoretical models with experimental data for nanocomposite elastic modulus [29].

Figure 1.10 shows that the experimental data lie within the upper (Voigt) and lower

(Reuss) bond predictions and coincide fairly well with the Mori–Tanaka and

Eshelby model predictions. The modeling work of Tsai and Sun [36] demonstrated

that well dispersed platelets in the polymer matrix could significantly enhance the

load transfer efficiency in these composites.

The fracture toughness, KIC, of epoxy matrix (DGEBA) composites reinforced with

intercalated (treated clay, ODTMA) and exfoliated (treated clay, MT2EtOH) clay up

to 10 vol% were compared [23]. Miyagawa and Drzal [37] attribute the high

fracture toughness of intercalated clay composites to crack bridging by clay

particles as well as crack defection due to excellent adhesion of clay/epoxy

interface and clay aggregate strength. On the other hand, the fracture of individual

clay platelets in exfoliated clay composites leads to less rough fracture surface

and lower fracture toughness.

In addition to mechanical properties, the thermal stability, fire resistance and gas

barrier properties of polymer/clay nanocomposites can be enhanced through the

addition of nanometer-scale reinforcement. For example, Ogasawara et al. [38]

have investigated the helium permeability of nanoclay for potential applications in

liquid hydrogen tanks and fuel cells. The addition of nanoclay to the epoxy resin

substantially decreased the gas diffusivity as compared with unreinforced epoxy.

The results are consistent with the Hatta-Taya theory and it was revealed that the

dispersion of platelets is more effective than spherical or fiber-like reinforcement in

Introduction 15

Physical properties Cloisite 30B Nanomer 1.28E

Colour Off white White

Density (g/cm3) 1.98 1.90

D spacing (D001), A0 18.5 >20

Aspect Ratio 200-1000 200-500

Surface area (m2/g) 750 750

Mean particle size (µm) 6 8-10

Table 1.1: Properties of clay platelets

Sample Wt% of

clay, MMT

Tensile strength (MPa)

Tensile Modulus (GPa)

Charpy Impact

strength (kJ/m2)

HDT at 18.5 kg/ cm2 (0C)

Rate of water absorption 250C, 1 day

NCH-5 4.2 107 2.1 2.1 152 0.51

NCC-5 5.0 61 1.0 1.0 89 0.90

Nylon-6 0 69 1.1 1.1 65 0.87

Table 1.2: Properties of Nylon 6/ clay nanocomposites [35]

Luo and Daniel [29] have modeled the Young’s modulus of clay nanocomposites

using a three-phase model: epoxy matrix, exfoliated clay nanolayer, and

intercalated clay cluster (parallel platelet system).

16 Chapter 1

Figure 1.10. Comparison of theoretical models with experimental data for nanocomposite elastic modulus [29].

Figure 1.10 shows that the experimental data lie within the upper (Voigt) and lower

(Reuss) bond predictions and coincide fairly well with the Mori–Tanaka and

Eshelby model predictions. The modeling work of Tsai and Sun [36] demonstrated

that well dispersed platelets in the polymer matrix could significantly enhance the

load transfer efficiency in these composites.

The fracture toughness, KIC, of epoxy matrix (DGEBA) composites reinforced with

intercalated (treated clay, ODTMA) and exfoliated (treated clay, MT2EtOH) clay up

to 10 vol% were compared [23]. Miyagawa and Drzal [37] attribute the high

fracture toughness of intercalated clay composites to crack bridging by clay

particles as well as crack defection due to excellent adhesion of clay/epoxy

interface and clay aggregate strength. On the other hand, the fracture of individual

clay platelets in exfoliated clay composites leads to less rough fracture surface

and lower fracture toughness.

In addition to mechanical properties, the thermal stability, fire resistance and gas

barrier properties of polymer/clay nanocomposites can be enhanced through the

addition of nanometer-scale reinforcement. For example, Ogasawara et al. [38]

have investigated the helium permeability of nanoclay for potential applications in

liquid hydrogen tanks and fuel cells. The addition of nanoclay to the epoxy resin

substantially decreased the gas diffusivity as compared with unreinforced epoxy.

The results are consistent with the Hatta-Taya theory and it was revealed that the

dispersion of platelets is more effective than spherical or fiber-like reinforcement in

Introduction 17

improving the nanocomposite barrier properties. Regarding the other layered

material, the exfoliated graphite or graphene sheet has about the same thickness

as exfoliated clay. It shows high tensile modulus, tensile strength, thermal

conductivity, and low electrical resistivity, comparing to clay platelets. The low

electrical resistivity of exfoliated graphite facilitates the conductivity of polymer

composites when a threshold percolation weight content of the conductive phase

is reached. Fukushima and Drzal [39] studied the resistivity of epoxy matrix

(EPON 828) composites with the addition of vapour grown carbon fiber (VGCF),

carbon black, PAN carbon fiber, exfoliated graphite and milled graphite. The

percolation threshold for exfoliated graphite was around 1 wt%. Zheng and co-

workers [40,41] have also reported about reduced percolation thresholds in

exfoliated graphite nanoplatelet/thermoplastic composites. Song et al [42] have

modeled the von Mises stress distribution in graphite/PAN nanocomposites with

respect to the level of exfoliation. They demonstrated the reduction in the

magnitude of stress concentration with layer thickness at the tip of graphite layers,

aligned with the axial tensile load. Such conclusion is similar to those obtained for

short fiber composites where the dispersion of a fiber bundle has the benefit of

reducing the stress concentration in the matrix material at the bundle ends and

thus, the chance of matrix cracking or plastic deformation. The greatly enhanced

electrical conductivity of polymeric material with the addition of small amount of

graphite platelets has found many practical applications. These include

electromagnetic shielding and heat management of electronic and computer

devices or equipment, electrostatic paint for automobiles and polymer sheath of

electric cables [36]. Nanoclay/polypropylene (PP) composites are being used as

functional parts in automobiles.

1.4.3. Nanofiber-reinforced composites

Vapour grown carbon nanofibers (CNF) have been used to reinforce a variety of

polymers, including polypropylene (PP), polycarbonate (PC), nylon, poly(ether

sulfone) (PES), poly(ethylene terephthalate) (PET), poly(phenylene sulfide) (PPS),

acrylonitrile-butadiene-styrene (ABS) and epoxy. Carbon nanofibers are known to

have wide-ranging morphologies, from structures with a disordered bamboo-like

[43] [Figure 1.11(a)] to highly graphitized ‘‘cup stacked’’ [44,45] [Figure 1.11(b)

18 Chapter 1

and 1.11(c)], where the conical shells of the nanofiber are nested within each

other. Carbon nanofibers typically have diameters on the order of 50–200 nm. Wei

and Srivastava [46] have modeled the mechanical properties of carbon nanofibers

with varying morphology using continuum elastic theory and molecular dynamics

simulations. The axial Young’s modulus of the nanofiber is particularly sensitive to

the shell tilt angle, where fibers that have small tilt angles from the axial direction

show much higher Young’s modulus than fibers with large tilt angles. The wide-

ranging morphology of the carbon nanofiber and their associated properties

results in a broad range of scatter for experimental results on processing and

characterization of nanofiber composites.

Finegan and co-workers [47,48] have investigated the processing and properties

of carbon nanofiber/PP nanocomposites. In their work, they used a variety of as-

grown nanofibers. Carbon nanofibers that were produced with longer gas phase

feedstock residence times were less graphitic but adhered better to the PP matrix,

with composites showing improved tensile strength and Young’s modulus.

Oxidation of the carbon nanofiber was found to increase adhesion to the matrix

and increase composite tensile strength, but extended oxidation reduced the

properties of the fibers and their composites. In their investigation on the nanofiber

composite damping properties, these authors [48] concluded that the trend of

stiffness variation with fiber volume content is opposite to the trend of loss factor

and damping in the composite is matrix dominated.

Ma et al [49] and Sandler et al [50] have spun polymer fibers with carbon

nanofibers as reinforcement. Ma et al utilized a variety of techniques to achieve

dispersion of carbon nanofibers in a PET matrix and subsequently meltspun

fibers. The compressive strength and torsional moduli of the nanocomposite fibers

were considerably higher than that for the unreinforced PET fiber. Sandler et al.

[50] produced fibers from semicrystalline high performance poly (ether ether

ketone) (PEEK) containing up to 10 wt% vapour grown carbon nanofibers. Their

experimental results highlight the need to characterize both the crystalline matrix

morphology and nanocomposites structure when evaluating performance. This is

crucial to understanding the intrinsic properties of the nanoscale reinforcement.

Introduction 17

improving the nanocomposite barrier properties. Regarding the other layered

material, the exfoliated graphite or graphene sheet has about the same thickness

as exfoliated clay. It shows high tensile modulus, tensile strength, thermal

conductivity, and low electrical resistivity, comparing to clay platelets. The low

electrical resistivity of exfoliated graphite facilitates the conductivity of polymer

composites when a threshold percolation weight content of the conductive phase

is reached. Fukushima and Drzal [39] studied the resistivity of epoxy matrix

(EPON 828) composites with the addition of vapour grown carbon fiber (VGCF),

carbon black, PAN carbon fiber, exfoliated graphite and milled graphite. The

percolation threshold for exfoliated graphite was around 1 wt%. Zheng and co-

workers [40,41] have also reported about reduced percolation thresholds in

exfoliated graphite nanoplatelet/thermoplastic composites. Song et al [42] have

modeled the von Mises stress distribution in graphite/PAN nanocomposites with

respect to the level of exfoliation. They demonstrated the reduction in the

magnitude of stress concentration with layer thickness at the tip of graphite layers,

aligned with the axial tensile load. Such conclusion is similar to those obtained for

short fiber composites where the dispersion of a fiber bundle has the benefit of

reducing the stress concentration in the matrix material at the bundle ends and

thus, the chance of matrix cracking or plastic deformation. The greatly enhanced

electrical conductivity of polymeric material with the addition of small amount of

graphite platelets has found many practical applications. These include

electromagnetic shielding and heat management of electronic and computer

devices or equipment, electrostatic paint for automobiles and polymer sheath of

electric cables [36]. Nanoclay/polypropylene (PP) composites are being used as

functional parts in automobiles.

1.4.3. Nanofiber-reinforced composites

Vapour grown carbon nanofibers (CNF) have been used to reinforce a variety of

polymers, including polypropylene (PP), polycarbonate (PC), nylon, poly(ether

sulfone) (PES), poly(ethylene terephthalate) (PET), poly(phenylene sulfide) (PPS),

acrylonitrile-butadiene-styrene (ABS) and epoxy. Carbon nanofibers are known to

have wide-ranging morphologies, from structures with a disordered bamboo-like

[43] [Figure 1.11(a)] to highly graphitized ‘‘cup stacked’’ [44,45] [Figure 1.11(b)

18 Chapter 1

and 1.11(c)], where the conical shells of the nanofiber are nested within each

other. Carbon nanofibers typically have diameters on the order of 50–200 nm. Wei

and Srivastava [46] have modeled the mechanical properties of carbon nanofibers

with varying morphology using continuum elastic theory and molecular dynamics

simulations. The axial Young’s modulus of the nanofiber is particularly sensitive to

the shell tilt angle, where fibers that have small tilt angles from the axial direction

show much higher Young’s modulus than fibers with large tilt angles. The wide-

ranging morphology of the carbon nanofiber and their associated properties

results in a broad range of scatter for experimental results on processing and

characterization of nanofiber composites.

Finegan and co-workers [47,48] have investigated the processing and properties

of carbon nanofiber/PP nanocomposites. In their work, they used a variety of as-

grown nanofibers. Carbon nanofibers that were produced with longer gas phase

feedstock residence times were less graphitic but adhered better to the PP matrix,

with composites showing improved tensile strength and Young’s modulus.

Oxidation of the carbon nanofiber was found to increase adhesion to the matrix

and increase composite tensile strength, but extended oxidation reduced the

properties of the fibers and their composites. In their investigation on the nanofiber

composite damping properties, these authors [48] concluded that the trend of

stiffness variation with fiber volume content is opposite to the trend of loss factor

and damping in the composite is matrix dominated.

Ma et al [49] and Sandler et al [50] have spun polymer fibers with carbon

nanofibers as reinforcement. Ma et al utilized a variety of techniques to achieve

dispersion of carbon nanofibers in a PET matrix and subsequently meltspun

fibers. The compressive strength and torsional moduli of the nanocomposite fibers

were considerably higher than that for the unreinforced PET fiber. Sandler et al.

[50] produced fibers from semicrystalline high performance poly (ether ether

ketone) (PEEK) containing up to 10 wt% vapour grown carbon nanofibers. Their

experimental results highlight the need to characterize both the crystalline matrix

morphology and nanocomposites structure when evaluating performance. This is

crucial to understanding the intrinsic properties of the nanoscale reinforcement.

Introduction 19

Figure 1.11. TEM micrographs of the nanoscale structure of carbon nanofibers showing: (a) disordered bamboo-like structures [43], (b) highly graphitized sidewall of a cup-stacked (molecular models inset) nanofibers showing the shell tilt angle [44] and (c) a nesting of the stacked layers [45], Copyright (2003) American Chemical Society.

Many of the key challenges associated with the processing, characterization and

modeling of carbon nanofiber composites, such as dispersion and adhesion, are

20 Chapter 1

similar to those for nanotube reinforced composites and are discussed in the

following section.

1.4.4. Carbon nanotube-reinforced composites

Since Iijima’s observation over a decade ago [51], numerous investigators have

reported remarkable physical and mechanical properties of carbon nanotubes [52-

54]. They have a density of 1.33–1.40 g/cm3, elastic modulus is comparable to

that of diamond (1.2 TPa), tensile strength much higher than that of high-strength

steel (2 GPa) and has tremendous resilience in sustaining bending to large angles

and restraightening without damage is distinctively different from the plastic

deformation of metals. Also the electric current carrying capability is estimated to

be 1x109 amp/cm2, whereas copper wires burn out at about 1x106 amp/cm2 and

the thermal conductivity is predicted to be 6000 W/m K at room temperature which

is nearly double the thermal conductivity of diamond of 3320 W/m K. Additionally

Single Walled Carbon Nanotubes (SWCNT) are stable up to 28000C in vacuum

and 7500C in air, whereas metal wires in microchips melt at 600–10000C. These

outstanding thermal and electric properties combined with their high specific

stiffness and strength and very large aspect ratios have stimulated the

development of nanotube reinforced composites of thermoset polymers (epoxy,

polyimide, and phenolic), as well as thermoplastic polymers (PP, PS, PMMA,

nylon 12 and PEEK) for both structural and functional applications [51,53,54].

Tai et al. [55] have processed a phenolic-based nanocomposites using MWCNTs,

which were synthesized through the floating catalyst chemical vapor deposition

process with tube diameter <50 nm and length >10 µm. SEM images of brittle

tensile fracture surfaces show fairly uniform nanotube distribution and nanotube

pullout. Enhancement in Young’s modulus and strength due to the addition of

nanotubes was reported. Gojny and co-workers [56] fabricated nanocomposites

consisting of Double Walled Carbon Nanotubes (DWCNT) with a high degree of

dispersion. The resulting composites showed increase of strength, Young’s

modulus and strain to failure at a nanotube content of only 0.1 wt%. In addition,

the nanocomposites showed significantly enhanced fracture toughness as

compared to the unreinforced epoxy.

Introduction 19

Figure 1.11. TEM micrographs of the nanoscale structure of carbon nanofibers showing: (a) disordered bamboo-like structures [43], (b) highly graphitized sidewall of a cup-stacked (molecular models inset) nanofibers showing the shell tilt angle [44] and (c) a nesting of the stacked layers [45], Copyright (2003) American Chemical Society.

Many of the key challenges associated with the processing, characterization and

modeling of carbon nanofiber composites, such as dispersion and adhesion, are

20 Chapter 1

similar to those for nanotube reinforced composites and are discussed in the

following section.

1.4.4. Carbon nanotube-reinforced composites

Since Iijima’s observation over a decade ago [51], numerous investigators have

reported remarkable physical and mechanical properties of carbon nanotubes [52-

54]. They have a density of 1.33–1.40 g/cm3, elastic modulus is comparable to

that of diamond (1.2 TPa), tensile strength much higher than that of high-strength

steel (2 GPa) and has tremendous resilience in sustaining bending to large angles

and restraightening without damage is distinctively different from the plastic

deformation of metals. Also the electric current carrying capability is estimated to

be 1x109 amp/cm2, whereas copper wires burn out at about 1x106 amp/cm2 and

the thermal conductivity is predicted to be 6000 W/m K at room temperature which

is nearly double the thermal conductivity of diamond of 3320 W/m K. Additionally

Single Walled Carbon Nanotubes (SWCNT) are stable up to 28000C in vacuum

and 7500C in air, whereas metal wires in microchips melt at 600–10000C. These

outstanding thermal and electric properties combined with their high specific

stiffness and strength and very large aspect ratios have stimulated the

development of nanotube reinforced composites of thermoset polymers (epoxy,

polyimide, and phenolic), as well as thermoplastic polymers (PP, PS, PMMA,

nylon 12 and PEEK) for both structural and functional applications [51,53,54].

Tai et al. [55] have processed a phenolic-based nanocomposites using MWCNTs,

which were synthesized through the floating catalyst chemical vapor deposition

process with tube diameter <50 nm and length >10 µm. SEM images of brittle

tensile fracture surfaces show fairly uniform nanotube distribution and nanotube

pullout. Enhancement in Young’s modulus and strength due to the addition of

nanotubes was reported. Gojny and co-workers [56] fabricated nanocomposites

consisting of Double Walled Carbon Nanotubes (DWCNT) with a high degree of

dispersion. The resulting composites showed increase of strength, Young’s

modulus and strain to failure at a nanotube content of only 0.1 wt%. In addition,

the nanocomposites showed significantly enhanced fracture toughness as

compared to the unreinforced epoxy.

Introduction 21

Ogasawara et al. [57] reinforced a phenyl ethyl terminated polyimide with Multiple

Walled Carbon Nanotubes (MWCNT), which are a few hundred µm in length and

20–100 nm in diameter. The composites were made by mechanical blending of

the nanotubes in the matrix, melting at 3200C, and curing at 3700C under 0.2 MPa

pressure. The resulting elastic and mechanical properties are shown in Table 1.3.

CNT (wt%) CNT (vol%) Tg (0C) Eb (GPa) σuts (MPa) εmax (%) σ0.2 (MPa)

0 0 335 2.84 115.6 7.6 69.8

3.3 2.3 339 3.07 99.5 4.0 80.5

7.7 5.4 350 3.28 97.6 3.6 84.6

14.3 10.3 357 3.90 95.2 2.6 92.6

Table 1.3. Properties of CNT/polyimide nanocomposites

The addition of MWCNTs enhances the tensile Young’s modulus and reduces the

tensile strength and ultimate strain. Thostenson and Chou [7,58] have

characterized the nanotube structure and elastic properties of a model composite

system of aligned MWCNTs embedded in a polystyrene matrix. Figure 1.12(a)

shows a TEM micrograph of the as-processed 5 wt% nanocomposite film showing

large scale dispersion and alignment of carbon nanotubes in the polymer matrix.

The arrow in figure 1.12(a) indicates the direction of alignment taken as the

principal material direction with a nanotube orientation of 00. The grey lines

perpendicular to the arrow in the TEM micrograph are artifacts from microtome

cutting process. Figure 1.12(b) shows the distribution of nanotube alignment from

the image analysis. Based on the data, the standard deviation of nanotube

alignment from the principal material direction is less than ±150. Thostenson and

Chou have modeled the axial elastic properties of the MWCNT/PS system [7]

using a ‘‘micromechanics’’ approach through defining an equivalent effective fiber

property for the diameter-sensitive carbon nanotube elastic modulus. To

accurately model the elastic properties of the composite, the contribution to the

overall elastic modulus of each nanotube diameter, and the volume fraction that

22 Chapter 1

tubes of a specific diameter occupy within the composite have been taken into

account. Using the knowledge of the tube diameter distribution functions as well

as the nanotube density and volume distribution as functions of tube diameter, the

micromechanics approach identifies the correlation between axial Young’s

modulus, and the diameter, volume fraction and length of nanotubes of the aligned

nanocomposites model system.

Figure 1.12 (a) TEM micrograph of process-induced orientation in nanocomposite ribbons [58] and (b) image analysis of orientation distribution [7]

Experiments by Frogley et al [59] on silicone-based elastomers reinforced with

SWCNTs have shown significant increases in the initial modulus of the

composites, accompanied by a reduction in the ultimate properties. Raman

spectroscopy experiments show a loss of stress transfer to the nanotubes at

around 10–20% strain, suggesting the break-down of the effective interface

between the phases. On the other hand, the reorientation of the nanotubes under

strain in the samples may be responsible for the initial increase in modulus

enhancement under strain. More recently, experiments on silicone elastomer

reinforced with SWCNTs have shown significant increase in stiffness and strength.

However, the relative magnitudes of the improvement decreased with higher

nanotube volume loading because the composite became more brittle [60].

It is highly desirable to present some key properties of nanocomposites in contrast

to the same properties in traditional composites; only a few examples are selected

below.

Introduction 21

Ogasawara et al. [57] reinforced a phenyl ethyl terminated polyimide with Multiple

Walled Carbon Nanotubes (MWCNT), which are a few hundred µm in length and

20–100 nm in diameter. The composites were made by mechanical blending of

the nanotubes in the matrix, melting at 3200C, and curing at 3700C under 0.2 MPa

pressure. The resulting elastic and mechanical properties are shown in Table 1.3.

CNT (wt%) CNT (vol%) Tg (0C) Eb (GPa) σuts (MPa) εmax (%) σ0.2 (MPa)

0 0 335 2.84 115.6 7.6 69.8

3.3 2.3 339 3.07 99.5 4.0 80.5

7.7 5.4 350 3.28 97.6 3.6 84.6

14.3 10.3 357 3.90 95.2 2.6 92.6

Table 1.3. Properties of CNT/polyimide nanocomposites

The addition of MWCNTs enhances the tensile Young’s modulus and reduces the

tensile strength and ultimate strain. Thostenson and Chou [7,58] have

characterized the nanotube structure and elastic properties of a model composite

system of aligned MWCNTs embedded in a polystyrene matrix. Figure 1.12(a)

shows a TEM micrograph of the as-processed 5 wt% nanocomposite film showing

large scale dispersion and alignment of carbon nanotubes in the polymer matrix.

The arrow in figure 1.12(a) indicates the direction of alignment taken as the

principal material direction with a nanotube orientation of 00. The grey lines

perpendicular to the arrow in the TEM micrograph are artifacts from microtome

cutting process. Figure 1.12(b) shows the distribution of nanotube alignment from

the image analysis. Based on the data, the standard deviation of nanotube

alignment from the principal material direction is less than ±150. Thostenson and

Chou have modeled the axial elastic properties of the MWCNT/PS system [7]

using a ‘‘micromechanics’’ approach through defining an equivalent effective fiber

property for the diameter-sensitive carbon nanotube elastic modulus. To

accurately model the elastic properties of the composite, the contribution to the

overall elastic modulus of each nanotube diameter, and the volume fraction that

22 Chapter 1

tubes of a specific diameter occupy within the composite have been taken into

account. Using the knowledge of the tube diameter distribution functions as well

as the nanotube density and volume distribution as functions of tube diameter, the

micromechanics approach identifies the correlation between axial Young’s

modulus, and the diameter, volume fraction and length of nanotubes of the aligned

nanocomposites model system.

Figure 1.12 (a) TEM micrograph of process-induced orientation in nanocomposite ribbons [58] and (b) image analysis of orientation distribution [7]

Experiments by Frogley et al [59] on silicone-based elastomers reinforced with

SWCNTs have shown significant increases in the initial modulus of the

composites, accompanied by a reduction in the ultimate properties. Raman

spectroscopy experiments show a loss of stress transfer to the nanotubes at

around 10–20% strain, suggesting the break-down of the effective interface

between the phases. On the other hand, the reorientation of the nanotubes under

strain in the samples may be responsible for the initial increase in modulus

enhancement under strain. More recently, experiments on silicone elastomer

reinforced with SWCNTs have shown significant increase in stiffness and strength.

However, the relative magnitudes of the improvement decreased with higher

nanotube volume loading because the composite became more brittle [60].

It is highly desirable to present some key properties of nanocomposites in contrast

to the same properties in traditional composites; only a few examples are selected

below.

Introduction 23

It is well known in short fiber composites that the presence of fiber ends induces

stress concentrations in the matrix materials when the composite is subjected to

loading. The nature of stress concentration and the associated singularities have

been studied in terms of the fiber bundle end shape and bundle aspect ratio [61].

Two types of nanotube/matrix interfacial bonding conditions are considered. The

length of nanotube is less than 1 nm whereas the short fibers are of millimeters in

length. The general similarity in local stress concentration is unmistakable. In the

case of uniaxial compression of continuous fiber composite, it is well known that

fiber defects or fiber misalignment may activate fiber bending and subsequent

fiber buckling. Figure 1.13(a) shows slip band formation in a composite with Al2O3

fiber in an aluminium matrix [62].

Figure 1.13 (a) Slip band formation in a composite with Al2O3 fiber in an aluminium matrix [64] and (b) nanoscale buckling of carbon nanotubes in an aligned nanocomposite [63]

The activation and subsequent observation of nanotube buckling in a composite

under compressive loading are much more difficult because of the small size and

alignment of nanotubes. Thostenson and Chou [63] have succeeded in such

experiments. The multiple buckling of individual MWCNTS in a polymer composite

can be seen in figure 1.13(b). An atomistic modeling of elastic buckling of carbon

nanotubes has been performed by Li and Chou [64].

Several key mechanisms of energy dissipation have been identified in the fracture

of short as well as continuous fiber reinforced composites. These are fiber

fracture, fiber pullout, fiber/matrix debonding/crack bridging and matrix cracking.

24 Chapter 1

Figure 1.14 shows schematically these mechanisms operating at a crack tip [65]

as well as the micrographs demonstrating the individual failure modes. It is

interesting to note that all these failure modes have also been observed in

nanotube reinforced polymer composites as demonstrated by Thostenson and

Chou [58] in figure 1.15. One of the reasons of the recent enthusiasm towards

carbon nanotubes as reinforcements for composite materials is their reported high

elastic modulus and strength comparing to those of existing continuous fibers.

Figure 1.14. Key mechanisms of energy dissipation have been identified in the fracture of short as well as continuous fiber reinforced composites [65]

Figure 1.15. Fracture mechanisms in carbon nanotube reinforced composites [58]

Introduction 23

It is well known in short fiber composites that the presence of fiber ends induces

stress concentrations in the matrix materials when the composite is subjected to

loading. The nature of stress concentration and the associated singularities have

been studied in terms of the fiber bundle end shape and bundle aspect ratio [61].

Two types of nanotube/matrix interfacial bonding conditions are considered. The

length of nanotube is less than 1 nm whereas the short fibers are of millimeters in

length. The general similarity in local stress concentration is unmistakable. In the

case of uniaxial compression of continuous fiber composite, it is well known that

fiber defects or fiber misalignment may activate fiber bending and subsequent

fiber buckling. Figure 1.13(a) shows slip band formation in a composite with Al2O3

fiber in an aluminium matrix [62].

Figure 1.13 (a) Slip band formation in a composite with Al2O3 fiber in an aluminium matrix [64] and (b) nanoscale buckling of carbon nanotubes in an aligned nanocomposite [63]

The activation and subsequent observation of nanotube buckling in a composite

under compressive loading are much more difficult because of the small size and

alignment of nanotubes. Thostenson and Chou [63] have succeeded in such

experiments. The multiple buckling of individual MWCNTS in a polymer composite

can be seen in figure 1.13(b). An atomistic modeling of elastic buckling of carbon

nanotubes has been performed by Li and Chou [64].

Several key mechanisms of energy dissipation have been identified in the fracture

of short as well as continuous fiber reinforced composites. These are fiber

fracture, fiber pullout, fiber/matrix debonding/crack bridging and matrix cracking.

24 Chapter 1

Figure 1.14 shows schematically these mechanisms operating at a crack tip [65]

as well as the micrographs demonstrating the individual failure modes. It is

interesting to note that all these failure modes have also been observed in

nanotube reinforced polymer composites as demonstrated by Thostenson and

Chou [58] in figure 1.15. One of the reasons of the recent enthusiasm towards

carbon nanotubes as reinforcements for composite materials is their reported high

elastic modulus and strength comparing to those of existing continuous fibers.

Figure 1.14. Key mechanisms of energy dissipation have been identified in the fracture of short as well as continuous fiber reinforced composites [65]

Figure 1.15. Fracture mechanisms in carbon nanotube reinforced composites [58]

Introduction 25

1.4.5. Nanocomposite fibrils

The potential for development of advanced continuous fibers with nanoscale diameter

is attractive. Conventional mechanical spinning techniques are limited to producing

fibers of micrometer diameters. As reviewed recently by Dzenis [66], electrospinning

enables the production of polymer nanofibers from polymer solutions or melts in high

electric fields. The charged jet is elongated and accelerated by the electric field and

can be deposited on a substrate. The potential of electrospun nanocomposite fibrils is

exemplified below.

First, the work of Ko et al [67] has demonstrated that continuous, PAN-based

nanocomposite fibrils with SWCNT can be produced using electrospinning process.

The alignment of SWCNTs in the fibril was achieved through flow and charge-induced

orientation as well as confinement effect. Figure 1.16 is a micrograph showing the

alignment of nanotubes near the nozzle area. The composite fibril was carbonized at

7500C and graphitized at 11000C in nitrogen environment.

Figure 1.16. TEM image of PAN-based nanocomposite fibrils with SWCNT showing alignment of the carbon nanotubes [67]

Electrospinning can be used for the production of nanocomposite fibrils with

various polymers. Viculis et al. [68] have utilized eletrospinning for studying the

elastic properties of nanoplatelet/PAN nanocomposite fibrils. Ko et al [69]

processed carbon nanotube reinforced spider silk by electrospinning approach

having strengths approaching 4 GPa and strain-to-failure exceeding 35%. Another

26 Chapter 1

example of the nanoparticle composite filament can be found in the work of

Mahfuz et al [70]. The reinforcement phase of the composite is a mixture of

carbon particles (50–200 nm) and semi-crystalline whiskers (2–8 µm in diameter,

100–200 µm in length, 1.8 g/cm3 density) produced by catalytic chemical vapor

deposition and the matrix is a linear low density polyethylene (LLDPE). Kumar et al

[71, 72] have succeeded in demonstrating the enhancement in modulus, strength,

and energy absorption of PBO/SWCNT composite fibers.

1.4.6. Nanocomposite films

In addition to the creation of fibrils that can be used as potential fiber

reinforcement in composites, the creation of large-scale nanocomposite films

offers potential for the creation of macroscopic parts through the use of traditional

composites manufacturing processes. The approach of magnetically aligning

SWCNTs was first given by Walters et al [73].

Figure 1.17. Aligned nanotube bucky-papers [74]

Wang et al [74] has demonstrated the high volume loading of SWCNT alignment in

bucky paper using a stable SWCNT suspension prepared by sonicating a

SWCNT/water/surfactant mixture. The filtration system was then placed inside the

magnet bore and a bucky paper of 387 cm2 (60 in.2) x17.8 µm was produced in 10 h

Introduction 25

1.4.5. Nanocomposite fibrils

The potential for development of advanced continuous fibers with nanoscale diameter

is attractive. Conventional mechanical spinning techniques are limited to producing

fibers of micrometer diameters. As reviewed recently by Dzenis [66], electrospinning

enables the production of polymer nanofibers from polymer solutions or melts in high

electric fields. The charged jet is elongated and accelerated by the electric field and

can be deposited on a substrate. The potential of electrospun nanocomposite fibrils is

exemplified below.

First, the work of Ko et al [67] has demonstrated that continuous, PAN-based

nanocomposite fibrils with SWCNT can be produced using electrospinning process.

The alignment of SWCNTs in the fibril was achieved through flow and charge-induced

orientation as well as confinement effect. Figure 1.16 is a micrograph showing the

alignment of nanotubes near the nozzle area. The composite fibril was carbonized at

7500C and graphitized at 11000C in nitrogen environment.

Figure 1.16. TEM image of PAN-based nanocomposite fibrils with SWCNT showing alignment of the carbon nanotubes [67]

Electrospinning can be used for the production of nanocomposite fibrils with

various polymers. Viculis et al. [68] have utilized eletrospinning for studying the

elastic properties of nanoplatelet/PAN nanocomposite fibrils. Ko et al [69]

processed carbon nanotube reinforced spider silk by electrospinning approach

having strengths approaching 4 GPa and strain-to-failure exceeding 35%. Another

26 Chapter 1

example of the nanoparticle composite filament can be found in the work of

Mahfuz et al [70]. The reinforcement phase of the composite is a mixture of

carbon particles (50–200 nm) and semi-crystalline whiskers (2–8 µm in diameter,

100–200 µm in length, 1.8 g/cm3 density) produced by catalytic chemical vapor

deposition and the matrix is a linear low density polyethylene (LLDPE). Kumar et al

[71, 72] have succeeded in demonstrating the enhancement in modulus, strength,

and energy absorption of PBO/SWCNT composite fibers.

1.4.6. Nanocomposite films

In addition to the creation of fibrils that can be used as potential fiber

reinforcement in composites, the creation of large-scale nanocomposite films

offers potential for the creation of macroscopic parts through the use of traditional

composites manufacturing processes. The approach of magnetically aligning

SWCNTs was first given by Walters et al [73].

Figure 1.17. Aligned nanotube bucky-papers [74]

Wang et al [74] has demonstrated the high volume loading of SWCNT alignment in

bucky paper using a stable SWCNT suspension prepared by sonicating a

SWCNT/water/surfactant mixture. The filtration system was then placed inside the

magnet bore and a bucky paper of 387 cm2 (60 in.2) x17.8 µm was produced in 10 h

Introduction 27

under magnetic fields of 17.3–25 Tesla (Figure 1.17). Laminated composites were

made by epoxy resin infiltration of stacked bucky papers with 59.8 wt% of SWCNT.

1.5. Preparation of Nanoparticles

Polymer nanocomposites contain a rigid filler component (this can be fiber, filler or

nanoscopic organic component) dispersed within a flexible polymer matrix on a

nanoscale level. The rigid portion, with high modulus and high strengths, usually

has high melting temperature, is insoluble in organic solvents, and combining it

with the flexible polymer is thermodynamically unfavorable. Therefore it is very

difficult to prepare a nanocomposite, and phases may undergo segregation during

processing and end use. Hydrodynamic effects and physi or chemisorption of

matrix at filler surface govern the reinforcement.

The first step of nanomaterial research is the preparation of uniform nanoparticles

and/or nanoparticle arrays with correct chemical composition and structure.

Preparation of nanoparticles can be achieved through a wide variety of different

routes: some have been around for many years; others are far more recent. In

essence, there are four generic routes to make nanoparticles: wet chemical,

mechanical, form-in-place, and gas-phase synthesis. It is worth exploring each of

these basic routes, as the resultant materials can have significantly different

properties, depending on the route chosen to fabricate them, and some routes are

more aligned with the fabrication of certain classes of materials.

a) Wet chemical processes

These include colloidal chemistry, hydrothermal methods, sol-gels and other

precipitation processes. Essentially, solutions of different ions are mixed in well-

defined quantities and under controlled conditions of heat, temperature, and

pressure to promote the formation of insoluble compounds, which precipitate out

of solution. These precipitates are then collected through filtering and/or spray

drying to produce a dry powder. The advantages of wet chemical processes are

that a large variety of compounds can be fabricated, including inorganics,

organics, and also some metals, in essentially cheap equipment and significant

quantities. Another important factor is the ability to control particle size closely and

to produce highly monodisperse materials. However, there are limitations with the

28 Chapter 1

range of compounds possible, bound water molecules can be a problem, and

especially for sol-gel processing, the yields can be quite low.

New processes that might overcome some of these problems are being

developed, such as high-throughput microreactors [75]. For bulk production, large

quantities of starting materials may be required, which can be expensive. Having

the nanoparticles well dispersed in a suspension, however, is an advantage if

further surface treatment is required to encapsulate or functionalize their surface.

An adjunct to these processes is those involving biological materials that provide a

template into which inorganic materials can be grown. Since biological materials,

such as porphyrin [76] and ferritins [77], are highly reproducible, the resulting

nanomaterials can be made to an extremely specific size with a high degree of

accuracy. However, the range of sizes may be limited by the availability and

structure of suitable template materials. These are being used to manufacture

materials such as magnetic materials for use in high-density storage devices.

b) Mechanical processes

These include grinding, milling and mechanical alloying techniques. Provided that one

can produce a coarse powder as a feedstock, these processes utilize the age-old

technique of physically pounding coarse powders into finer and finer ones, similar to

flour mills. Today, the most common processes are either planetary or rotating ball

mills. The advantages of these techniques are that they are simple, require low-cost

equipment and, provided that a coarse feedstock powder can be made, the powder

can be processed. However, there can be difficulties such as agglomeration of the

powders, broad particle size distributions, contamination from the process equipment

itself, and often difficulty in getting to the very fine particle sizes with viable yields. It is

commonly used for inorganics and metals, but not organic materials.

c) Form-in-place processes

These include lithography, vacuum deposition processes such as physical vapor

deposition (PVD) and chemical vapor deposition (CVD), and spray coatings. These

processes are more geared to the production of nanostructured layers and coatings,

but can be used to fabricate nanoparticles by scraping the deposits from the collector.

However, they tend to be quite inefficient and are generally not used for the fabrication

Introduction 27

under magnetic fields of 17.3–25 Tesla (Figure 1.17). Laminated composites were

made by epoxy resin infiltration of stacked bucky papers with 59.8 wt% of SWCNT.

1.5. Preparation of Nanoparticles

Polymer nanocomposites contain a rigid filler component (this can be fiber, filler or

nanoscopic organic component) dispersed within a flexible polymer matrix on a

nanoscale level. The rigid portion, with high modulus and high strengths, usually

has high melting temperature, is insoluble in organic solvents, and combining it

with the flexible polymer is thermodynamically unfavorable. Therefore it is very

difficult to prepare a nanocomposite, and phases may undergo segregation during

processing and end use. Hydrodynamic effects and physi or chemisorption of

matrix at filler surface govern the reinforcement.

The first step of nanomaterial research is the preparation of uniform nanoparticles

and/or nanoparticle arrays with correct chemical composition and structure.

Preparation of nanoparticles can be achieved through a wide variety of different

routes: some have been around for many years; others are far more recent. In

essence, there are four generic routes to make nanoparticles: wet chemical,

mechanical, form-in-place, and gas-phase synthesis. It is worth exploring each of

these basic routes, as the resultant materials can have significantly different

properties, depending on the route chosen to fabricate them, and some routes are

more aligned with the fabrication of certain classes of materials.

a) Wet chemical processes

These include colloidal chemistry, hydrothermal methods, sol-gels and other

precipitation processes. Essentially, solutions of different ions are mixed in well-

defined quantities and under controlled conditions of heat, temperature, and

pressure to promote the formation of insoluble compounds, which precipitate out

of solution. These precipitates are then collected through filtering and/or spray

drying to produce a dry powder. The advantages of wet chemical processes are

that a large variety of compounds can be fabricated, including inorganics,

organics, and also some metals, in essentially cheap equipment and significant

quantities. Another important factor is the ability to control particle size closely and

to produce highly monodisperse materials. However, there are limitations with the

28 Chapter 1

range of compounds possible, bound water molecules can be a problem, and

especially for sol-gel processing, the yields can be quite low.

New processes that might overcome some of these problems are being

developed, such as high-throughput microreactors [75]. For bulk production, large

quantities of starting materials may be required, which can be expensive. Having

the nanoparticles well dispersed in a suspension, however, is an advantage if

further surface treatment is required to encapsulate or functionalize their surface.

An adjunct to these processes is those involving biological materials that provide a

template into which inorganic materials can be grown. Since biological materials,

such as porphyrin [76] and ferritins [77], are highly reproducible, the resulting

nanomaterials can be made to an extremely specific size with a high degree of

accuracy. However, the range of sizes may be limited by the availability and

structure of suitable template materials. These are being used to manufacture

materials such as magnetic materials for use in high-density storage devices.

b) Mechanical processes

These include grinding, milling and mechanical alloying techniques. Provided that one

can produce a coarse powder as a feedstock, these processes utilize the age-old

technique of physically pounding coarse powders into finer and finer ones, similar to

flour mills. Today, the most common processes are either planetary or rotating ball

mills. The advantages of these techniques are that they are simple, require low-cost

equipment and, provided that a coarse feedstock powder can be made, the powder

can be processed. However, there can be difficulties such as agglomeration of the

powders, broad particle size distributions, contamination from the process equipment

itself, and often difficulty in getting to the very fine particle sizes with viable yields. It is

commonly used for inorganics and metals, but not organic materials.

c) Form-in-place processes

These include lithography, vacuum deposition processes such as physical vapor

deposition (PVD) and chemical vapor deposition (CVD), and spray coatings. These

processes are more geared to the production of nanostructured layers and coatings,

but can be used to fabricate nanoparticles by scraping the deposits from the collector.

However, they tend to be quite inefficient and are generally not used for the fabrication

Introduction 29

of dry powders, although some companies are beginning to exploit these processes.

A number of universities and companies are developing variations on these

processes, such as the electrostatic spray assisted vapor deposition process [78].

d) Gas-phase synthesis

These include flame pyrolysis, electro-explosion, laser ablation, high-temperature

evaporation and plasma synthesis techniques. Flame pyrolysis has been used for

many years in the fabrication of simple materials such as carbon black and fumed

silica and is being used in the fabrication of many more compounds. Laser

ablation is capable of making almost any nanomaterial, since it utilizes a mix of

physical erosion and evaporation. However, the production rates are extremely

slow and most suited to research uses. The heat source is very clean and

controllable and the temperatures in the plasmas can reach in excess of 9000°C,

which means that even highly refractory materials can be processed. However,

this also means that the technique is unsuitable for processing organic materials.

The production of fullerenes and carbon nanotubes is a specific subset of gas-

phase synthesis techniques. Many variations have been explored and patented in

the years since they were discovered [79]. All the techniques essentially involve

the controlled growth of a nanotube on a catalyst particle through the cracking of

carbon rich gases such as methane.

As can be seen, there are a multitude of different methods employed to

manufacture nanoparticles and carbon nanotubes. All are being used, some

commercially, and each has its merits and drawbacks. However, it is clear that

most of the methods will be utilized in commercial production at some stage since,

although the materials are nominally the same, the characteristics of the materials

produced by each process are not always equivalent and can have different

properties. The manufacturing routes that become commercially successful,

therefore, will predominantly be those for which the materials have been

developed at the same time as the application.

Some of these preparation techniques commonly employed are described briefly

with some specific examples in the following section.

30 Chapter 1

1.5.1. Microemulsion methods

Preparation of nanoparticles using reverse micelles can be dated back to the

pioneer work of Boutonnet et al [80]. In 1982 they first synthesized monodispersed

Pt, Rh, Pd, Ir nanoparticles with diameters of 3–6 nm. After that, many nanoparticles

were synthesized and the method of preparing nanoparticles using reverse micelles

became a worldwide interest in nanoscience and nanotechnology.

The general method to synthesizing nanoparticles using reverse micelles is

schematically illustrated in figure 1.18. This can be divided into three cases. The

first one is the mixing of two reverse micelles. Due to the coalescence of the

reverse micelles, exchange of the materials in the water droplets occurs, which

causes a reaction between the cores. Since the diameter of the water droplet is

constant, nuclei in the different water cores cannot exchange with each other. As

a result, nanoparticles are formed in the reversed micelles. The second case is

that one reactant (A) is solubilized in the reversed micelles while another reactant

(B) is dissolved in water. After mixing the two reverse micelles containing different

reactants (A and B), the reaction can take place by coalescence or aqueous

phase exchange between the two reverse micelles.

Figure 1.18. Schematic illustration of various stages in the growth of

nanoparticles in microemulsions [81]

There are essentially three procedures to form nanoparticles by reversed micelles:

precipitation, reduction and hydrolysis. Precipitation is usually applied in the

synthesis of metal sulfate, metal oxide, metal carbonate and silver halide

Introduction 29

of dry powders, although some companies are beginning to exploit these processes.

A number of universities and companies are developing variations on these

processes, such as the electrostatic spray assisted vapor deposition process [78].

d) Gas-phase synthesis

These include flame pyrolysis, electro-explosion, laser ablation, high-temperature

evaporation and plasma synthesis techniques. Flame pyrolysis has been used for

many years in the fabrication of simple materials such as carbon black and fumed

silica and is being used in the fabrication of many more compounds. Laser

ablation is capable of making almost any nanomaterial, since it utilizes a mix of

physical erosion and evaporation. However, the production rates are extremely

slow and most suited to research uses. The heat source is very clean and

controllable and the temperatures in the plasmas can reach in excess of 9000°C,

which means that even highly refractory materials can be processed. However,

this also means that the technique is unsuitable for processing organic materials.

The production of fullerenes and carbon nanotubes is a specific subset of gas-

phase synthesis techniques. Many variations have been explored and patented in

the years since they were discovered [79]. All the techniques essentially involve

the controlled growth of a nanotube on a catalyst particle through the cracking of

carbon rich gases such as methane.

As can be seen, there are a multitude of different methods employed to

manufacture nanoparticles and carbon nanotubes. All are being used, some

commercially, and each has its merits and drawbacks. However, it is clear that

most of the methods will be utilized in commercial production at some stage since,

although the materials are nominally the same, the characteristics of the materials

produced by each process are not always equivalent and can have different

properties. The manufacturing routes that become commercially successful,

therefore, will predominantly be those for which the materials have been

developed at the same time as the application.

Some of these preparation techniques commonly employed are described briefly

with some specific examples in the following section.

30 Chapter 1

1.5.1. Microemulsion methods

Preparation of nanoparticles using reverse micelles can be dated back to the

pioneer work of Boutonnet et al [80]. In 1982 they first synthesized monodispersed

Pt, Rh, Pd, Ir nanoparticles with diameters of 3–6 nm. After that, many nanoparticles

were synthesized and the method of preparing nanoparticles using reverse micelles

became a worldwide interest in nanoscience and nanotechnology.

The general method to synthesizing nanoparticles using reverse micelles is

schematically illustrated in figure 1.18. This can be divided into three cases. The

first one is the mixing of two reverse micelles. Due to the coalescence of the

reverse micelles, exchange of the materials in the water droplets occurs, which

causes a reaction between the cores. Since the diameter of the water droplet is

constant, nuclei in the different water cores cannot exchange with each other. As

a result, nanoparticles are formed in the reversed micelles. The second case is

that one reactant (A) is solubilized in the reversed micelles while another reactant

(B) is dissolved in water. After mixing the two reverse micelles containing different

reactants (A and B), the reaction can take place by coalescence or aqueous

phase exchange between the two reverse micelles.

Figure 1.18. Schematic illustration of various stages in the growth of

nanoparticles in microemulsions [81]

There are essentially three procedures to form nanoparticles by reversed micelles:

precipitation, reduction and hydrolysis. Precipitation is usually applied in the

synthesis of metal sulfate, metal oxide, metal carbonate and silver halide

Introduction 31

nanoparticles. In this method two reverse micelles containing the anionic and

cationic surfactants are mixed. Because every reaction takes place in a

nanometer-sized water pool, water-insoluble nanoparticles are formed. Table 1.4

lists some of the important nanoparticles prepared by microemulsion technique.

No Nanomaterial Method/result Ref

1 Platinum, palladium, rhodium, iridium

Reverse micelles 80,82

2 Gold and silver Reverse micelles 83

3 Copper Reverse micelles 84

4 Gold and silver Reverse micelles 85,86

5 PbS Reverse micelles 87,88

6 CaCO3 Reverse micelles, particles of 5.4 nm 89,90

7 TiO2 Hydrolysis method in which the metal alkoxides react with water droplets in the reverse micelles

91-93

8 ZrO2 Hydrolysis method in which the metal alkoxides react with water droplets in the reverse micelles

94

9 BaFe12O19 particles By mixing the two reverse micelles 95

10 BaCO3 nanowires Reverse micelles 96

Table 1.4. Nanoparticles prepared by microemulsion methods

1.5.2. Pyrolysis

Pyrolysis is a chemical process in which chemical precursors decompose under

suitable thermal treatment into one solid compound and unwanted waste evaporates

away. Pyrolysis preparation is important and powerful in many specific systems. More

and more nanomaterials have been prepared using this method and modified

processing. This method has some advantages: the reaction process is easy to

control, the as-prepared substances are of variety, and the product is of high purity.

The drawbacks are that the high temperature may lead to wide size distribution and

particle agglomeration. The selective precipitation could be used to compensate

32 Chapter 1

above method, for obtaining specific sized nanoparticles after pyrolysis. However, the

choices of precursors and dispersion situation are important, and the thermal source

chosen is another factor for the successful preparation, the third factor is heat-

treatment processes. Careful heating of precursors may avoid particle agglomeration.

A large variety of nanomaterials were prepared by this method. A brief account of the

selected nanosystems is given in Table 1.5.

No Nanomaterial Method/result Ref

1 Ag nanoparticles AgOH precipitate in AgNO3, heating, 1-100 nm 97

2 Au nanoparticles AuO3 decomposes into elements around 3500C, 5 nm

98

3 Ag nanoparticles Laser-liquid-solid interaction technique from a solution composed of silver nitrate, distilled water, ethylene glycol and diethylene glycol, 5 nm

99

4 Spherical Ni particles From nitrate solution by spray pyrolysis in an H2-N2 atmosphere

100

5 ZnS and CdS fine particles

Ultrasonic spray-pyrolysis method 101

6 Carbon nanotubes or aligned nanotube

Pyrolysis 102

7 Carbon nanotubes Pyrolysis of organometallic precursors 103

8 Al2O3-TiO2 composite oxide nanocrystals

Poly(ethylene glycol) (PEG) sol-gel method 104

Table 1.5. Nanoparticles prepared by pyrolysis method

1.5.3. Forced Hydrolysis and Chemical Co-Precipitation

The simple forced hydrolysis and chemical co-precipitation technique is widely

used in industry and research to synthesize oxide complexes. The processing

parameters of starting raw materials, reaction temperature, solution pH, titration

rate, even stirring rate have effect on properties of final precipitates, such as

particle size, particle size distribution, particle shape, even stoichiometry. Jiang

prepared nanoparticles of yttrium oxide of 10 nm by this method [105]. A number

of metal hydroxides or oxides have been prepared by using the hydrolysis

technique (gadolinium, terbium, samarium, Cerium [106] and zirconium [107].

Introduction 31

nanoparticles. In this method two reverse micelles containing the anionic and

cationic surfactants are mixed. Because every reaction takes place in a

nanometer-sized water pool, water-insoluble nanoparticles are formed. Table 1.4

lists some of the important nanoparticles prepared by microemulsion technique.

No Nanomaterial Method/result Ref

1 Platinum, palladium, rhodium, iridium

Reverse micelles 80,82

2 Gold and silver Reverse micelles 83

3 Copper Reverse micelles 84

4 Gold and silver Reverse micelles 85,86

5 PbS Reverse micelles 87,88

6 CaCO3 Reverse micelles, particles of 5.4 nm 89,90

7 TiO2 Hydrolysis method in which the metal alkoxides react with water droplets in the reverse micelles

91-93

8 ZrO2 Hydrolysis method in which the metal alkoxides react with water droplets in the reverse micelles

94

9 BaFe12O19 particles By mixing the two reverse micelles 95

10 BaCO3 nanowires Reverse micelles 96

Table 1.4. Nanoparticles prepared by microemulsion methods

1.5.2. Pyrolysis

Pyrolysis is a chemical process in which chemical precursors decompose under

suitable thermal treatment into one solid compound and unwanted waste evaporates

away. Pyrolysis preparation is important and powerful in many specific systems. More

and more nanomaterials have been prepared using this method and modified

processing. This method has some advantages: the reaction process is easy to

control, the as-prepared substances are of variety, and the product is of high purity.

The drawbacks are that the high temperature may lead to wide size distribution and

particle agglomeration. The selective precipitation could be used to compensate

32 Chapter 1

above method, for obtaining specific sized nanoparticles after pyrolysis. However, the

choices of precursors and dispersion situation are important, and the thermal source

chosen is another factor for the successful preparation, the third factor is heat-

treatment processes. Careful heating of precursors may avoid particle agglomeration.

A large variety of nanomaterials were prepared by this method. A brief account of the

selected nanosystems is given in Table 1.5.

No Nanomaterial Method/result Ref

1 Ag nanoparticles AgOH precipitate in AgNO3, heating, 1-100 nm 97

2 Au nanoparticles AuO3 decomposes into elements around 3500C, 5 nm

98

3 Ag nanoparticles Laser-liquid-solid interaction technique from a solution composed of silver nitrate, distilled water, ethylene glycol and diethylene glycol, 5 nm

99

4 Spherical Ni particles From nitrate solution by spray pyrolysis in an H2-N2 atmosphere

100

5 ZnS and CdS fine particles

Ultrasonic spray-pyrolysis method 101

6 Carbon nanotubes or aligned nanotube

Pyrolysis 102

7 Carbon nanotubes Pyrolysis of organometallic precursors 103

8 Al2O3-TiO2 composite oxide nanocrystals

Poly(ethylene glycol) (PEG) sol-gel method 104

Table 1.5. Nanoparticles prepared by pyrolysis method

1.5.3. Forced Hydrolysis and Chemical Co-Precipitation

The simple forced hydrolysis and chemical co-precipitation technique is widely

used in industry and research to synthesize oxide complexes. The processing

parameters of starting raw materials, reaction temperature, solution pH, titration

rate, even stirring rate have effect on properties of final precipitates, such as

particle size, particle size distribution, particle shape, even stoichiometry. Jiang

prepared nanoparticles of yttrium oxide of 10 nm by this method [105]. A number

of metal hydroxides or oxides have been prepared by using the hydrolysis

technique (gadolinium, terbium, samarium, Cerium [106] and zirconium [107].

Introduction 33

1.5.4. Sol-gel Processing

Among the physical and chemical methods devised for preparation of nanoscaled

materials, synthesis from atomic or molecular precursors such as the sol-gel route

can give better control of particle size and homogeneity in particle distribution. The

sol-gel processing, which is based on inorganic polymerization reactions, can

loosely be defined as the preparation of inorganic oxides such as glasses and

ceramics by wet chemical methods [108-110].

The sol-gel processing can control the structure of a material on a nanometer

scale from the earliest stages of processing. This technique to material synthesis

is based on some organometallic precursors, and the gels may form by network

growth from an array of discrete particles or by formation of an interconnected 3-D

network by the simultaneous hydrolysis and polycondensation of organometallic

precursors. The size of the sol particles and the cross-linking between the

particles depend upon some variable factors such as pH, solution composition,

and temperature etc. Thus by controlling the experimental conditions, one can

obtain the nanostructured target materials in the form of powder or thin film.

Several nanoparticles can be synthesized by the sol-gel processing. Some of

them are listed below in table 1.6.

No Nanomaterial Method/Result Ref

1 PTMO/TMOS nanocomposites

Silica sol-gel, 20 nm 111

2 MgAl2O4 spinel Heterometallic alkoxide, 30 nm 112

3 TiO2 Sol-gel hydrolysis of (Ti(OC3H7)4), followed by hydrothermal treatment, 10 nm

113

Table 1.6. Nanoparticles prepared by sol-gel synthesis

1.5.5. Chemical vapor deposition (CVD)

In chemical vapor deposition (CVD), the vaporized precursors are introduced into

a CVD reactor, where the precursor molecules adsorb onto a substrate held at an

elevated temperature. These adsorbed molecules will be either thermally

decomposed or reacted with other gases/vapors to form a solid film on the

substrate. Such a gas–solid chemical reaction at the surface of a substrate is

34 Chapter 1

called the heterogeneous reaction. Because a number of chemical reactions may

occur in the CVD process, CVD is considered to be a process of potentially great

complexity as well as one of great versatility and flexibility. It can be used to grow

a variety of materials including metals, semiconductors, and ceramics. The solid

films can be made as amorphous, polycrystalline, or single crystalline materials

with the desired properties, depending on the growth conditions. In general,

particle formation in the gas phase in a CVD process should be avoided because

this will not only considerably deplete the reactants, leading to a non–uniform film

thickness, but also incorporate the undesirable particles in the growing film.

However, under certain experimental conditions, particle formation in the gas

phase can be used to synthesize nanosize powders or particles. Gas–phase

nucleation and controlled growth of the particles are of prime concern in the

growth processes. The particle–size range is controlled by the number of nuclei

formed in the reactor and the concentration of the condensing species. Nowadays,

CVD is employed with respect to atmospheric pressure to synthesise

nanoparticles of various shape and size. This process is later modified as

chemical vapour condensation (CVC) [114,115]). Some other modified CVD

processes are particle-precipitation-aided chemical vapour deposition and

catalytic chemical vapour deposition and these methods can produce various

nanostructured materials in narrow distribution and size. Table 1.7 shows some

examples of the nanomaterials prepared by this technique.

No Nanomaterial Method/Result Ref

1 Semiconductor Quantum Dots

CVD, <15 nm 116-119

2 Nanosized SnO2, Fe2O3, ZnO

CVD, 2-5 nm 120-122

3 TiO2 CVD, 60 nm at 10000C 123

4 Carbides (SiC) CVD, ~9 nm 124

5 TiN PP-CVD, 5 nm 125

6 Carbon Nanotubes CCVD, diameter ~ 1 nm 126,127

7 Carbon Nanotubes Combination of CVD and template–synthesis methods, aligned CNTs with diameter ~ 20-200 nm

128

Table 1.7. Nanoparticles prepared by chemical vapour deposition technique.

Introduction 33

1.5.4. Sol-gel Processing

Among the physical and chemical methods devised for preparation of nanoscaled

materials, synthesis from atomic or molecular precursors such as the sol-gel route

can give better control of particle size and homogeneity in particle distribution. The

sol-gel processing, which is based on inorganic polymerization reactions, can

loosely be defined as the preparation of inorganic oxides such as glasses and

ceramics by wet chemical methods [108-110].

The sol-gel processing can control the structure of a material on a nanometer

scale from the earliest stages of processing. This technique to material synthesis

is based on some organometallic precursors, and the gels may form by network

growth from an array of discrete particles or by formation of an interconnected 3-D

network by the simultaneous hydrolysis and polycondensation of organometallic

precursors. The size of the sol particles and the cross-linking between the

particles depend upon some variable factors such as pH, solution composition,

and temperature etc. Thus by controlling the experimental conditions, one can

obtain the nanostructured target materials in the form of powder or thin film.

Several nanoparticles can be synthesized by the sol-gel processing. Some of

them are listed below in table 1.6.

No Nanomaterial Method/Result Ref

1 PTMO/TMOS nanocomposites

Silica sol-gel, 20 nm 111

2 MgAl2O4 spinel Heterometallic alkoxide, 30 nm 112

3 TiO2 Sol-gel hydrolysis of (Ti(OC3H7)4), followed by hydrothermal treatment, 10 nm

113

Table 1.6. Nanoparticles prepared by sol-gel synthesis

1.5.5. Chemical vapor deposition (CVD)

In chemical vapor deposition (CVD), the vaporized precursors are introduced into

a CVD reactor, where the precursor molecules adsorb onto a substrate held at an

elevated temperature. These adsorbed molecules will be either thermally

decomposed or reacted with other gases/vapors to form a solid film on the

substrate. Such a gas–solid chemical reaction at the surface of a substrate is

34 Chapter 1

called the heterogeneous reaction. Because a number of chemical reactions may

occur in the CVD process, CVD is considered to be a process of potentially great

complexity as well as one of great versatility and flexibility. It can be used to grow

a variety of materials including metals, semiconductors, and ceramics. The solid

films can be made as amorphous, polycrystalline, or single crystalline materials

with the desired properties, depending on the growth conditions. In general,

particle formation in the gas phase in a CVD process should be avoided because

this will not only considerably deplete the reactants, leading to a non–uniform film

thickness, but also incorporate the undesirable particles in the growing film.

However, under certain experimental conditions, particle formation in the gas

phase can be used to synthesize nanosize powders or particles. Gas–phase

nucleation and controlled growth of the particles are of prime concern in the

growth processes. The particle–size range is controlled by the number of nuclei

formed in the reactor and the concentration of the condensing species. Nowadays,

CVD is employed with respect to atmospheric pressure to synthesise

nanoparticles of various shape and size. This process is later modified as

chemical vapour condensation (CVC) [114,115]). Some other modified CVD

processes are particle-precipitation-aided chemical vapour deposition and

catalytic chemical vapour deposition and these methods can produce various

nanostructured materials in narrow distribution and size. Table 1.7 shows some

examples of the nanomaterials prepared by this technique.

No Nanomaterial Method/Result Ref

1 Semiconductor Quantum Dots

CVD, <15 nm 116-119

2 Nanosized SnO2, Fe2O3, ZnO

CVD, 2-5 nm 120-122

3 TiO2 CVD, 60 nm at 10000C 123

4 Carbides (SiC) CVD, ~9 nm 124

5 TiN PP-CVD, 5 nm 125

6 Carbon Nanotubes CCVD, diameter ~ 1 nm 126,127

7 Carbon Nanotubes Combination of CVD and template–synthesis methods, aligned CNTs with diameter ~ 20-200 nm

128

Table 1.7. Nanoparticles prepared by chemical vapour deposition technique.

Introduction 35

1.5.6. Aerosol Methods

Research into condensation and growth of materials from a vapor has been occurring

since the early 1900's but only until the early 1960's has it been formulated in a more

concise way. Starting with methods previously applied to atmospheric aerosol

condensation Sutugin and Fuchs [129] were able to apply the classical theory to get a

first glimpse at the importance that the competing processes of coalescence and

aggregation play. The works done in the 1990's by Flagan and co-workers [130] and

Windeler et al [131] have greatly improved the understanding and application of

aerosol condensation theory. With the process of initial nucleation of nanocrystal

nuclei unknown, they were still able to formulate a theory that incorporates Brownian

collision, aggregation and coalescence growth through surface area minimization and

solid state diffusion and agglomerate versus single particle formation. There are three

essential processing stages. Evaporation of the bulk material in an inert environment,

transport of the vapor through a temperature gradient and collection of the produced

nanocrystals are the very general ideas. A brief account of the nanomaterials

prepared by this technique is given in table 1.8.

No Nanomaterial Method/Result Ref

1 Titania IGC method, 30 nm 130

2 Nickel nanocrystals Gas Blow Arc Reactor, 6-25 nm 132

3 Luminescent Si nanoparticles

Spark Ablation, diameter 2-10 nm 133, 134

4 Titania Arc Evaporated Cluster Source, diameter 1-100 nm

135, 136

5 Titania Gas Phase Reaction in a free jet, 20 nm 137

6 Si Laser Ablation, 3 nm 138

7 Oxides Diffusion Cloud Chamber, diameter ~ 50 nm 139

8 Nanocrystals of W, Cu and Ag

Sputtering, diameter 10-60 nm 140

9 Nanoparticles Au and TiO2

Magneton Sputtering, diameter 7-15 nm 141

Table 1.8. Nanoparticles prepared by aerosol methods

36 Chapter 1

1.5.7. Polyol Method or Induced Crystallization

The growth of a particular crystalline phase or modification of morphology of

certain materials has been the goal of material scientists over past several years.

It has been known that inorganic materials such as alkali halides, talc, clay,

minerals etc., especially in fine particulate form can act as nucleating agent for

crystallization of polymers [142-146], and in some instance the polymer grows

epitaxially on the inorganic substrates [147,148]. However, the influence of

polymers on the growth of inorganic crystals has not been studied very

extensively. Biomineralisation especially has drawn considerable interest because

of the fascinating features observed, such as growth of certain inorganic

compounds (calcium carbonate, phosphates, iron oxides, etc.) by the biological

systems in most unusual morphological forms which at the same time show single

crystal type diffraction patterns [149-151]. These systems are quite complex,

involving many types of macromolecules, and the exact role of the polymeric

substances-proteins, long chain fatty acids etc in controlling the morphology is not

yet fully understood.

Radhakrishnan and coworkers studied the crystallization behavior of inorganic

salts such as cupric chloride, calcium chloride, potassium carbonate etc in

polymeric media and found that the crystallization of the polymer or its orientation

can influence the inorganic salts as well [152-154]. Calcium sulphate was also

prepared by this in-situ technique [155].

1.6. Critical issues in nanocomposites

Just as in traditional fiber composites, the major challenges in the research of

nanocomposites can be categorized in terms of the structures from nano to micro

to macro levels. There is still considerable uncertainty in theoretical modeling and

experimental characterization of the nano-scale reinforcement materials,

particularly nanotubes. Then, there is a lack of understanding of the interfacial

bonding between the reinforcements and the matrix material from both analytical

and experimental viewpoints. Lastly, the challenges at the level of

nanocomposites have mainly to do with the following issues related to composites

processing:

Introduction 35

1.5.6. Aerosol Methods

Research into condensation and growth of materials from a vapor has been occurring

since the early 1900's but only until the early 1960's has it been formulated in a more

concise way. Starting with methods previously applied to atmospheric aerosol

condensation Sutugin and Fuchs [129] were able to apply the classical theory to get a

first glimpse at the importance that the competing processes of coalescence and

aggregation play. The works done in the 1990's by Flagan and co-workers [130] and

Windeler et al [131] have greatly improved the understanding and application of

aerosol condensation theory. With the process of initial nucleation of nanocrystal

nuclei unknown, they were still able to formulate a theory that incorporates Brownian

collision, aggregation and coalescence growth through surface area minimization and

solid state diffusion and agglomerate versus single particle formation. There are three

essential processing stages. Evaporation of the bulk material in an inert environment,

transport of the vapor through a temperature gradient and collection of the produced

nanocrystals are the very general ideas. A brief account of the nanomaterials

prepared by this technique is given in table 1.8.

No Nanomaterial Method/Result Ref

1 Titania IGC method, 30 nm 130

2 Nickel nanocrystals Gas Blow Arc Reactor, 6-25 nm 132

3 Luminescent Si nanoparticles

Spark Ablation, diameter 2-10 nm 133, 134

4 Titania Arc Evaporated Cluster Source, diameter 1-100 nm

135, 136

5 Titania Gas Phase Reaction in a free jet, 20 nm 137

6 Si Laser Ablation, 3 nm 138

7 Oxides Diffusion Cloud Chamber, diameter ~ 50 nm 139

8 Nanocrystals of W, Cu and Ag

Sputtering, diameter 10-60 nm 140

9 Nanoparticles Au and TiO2

Magneton Sputtering, diameter 7-15 nm 141

Table 1.8. Nanoparticles prepared by aerosol methods

36 Chapter 1

1.5.7. Polyol Method or Induced Crystallization

The growth of a particular crystalline phase or modification of morphology of

certain materials has been the goal of material scientists over past several years.

It has been known that inorganic materials such as alkali halides, talc, clay,

minerals etc., especially in fine particulate form can act as nucleating agent for

crystallization of polymers [142-146], and in some instance the polymer grows

epitaxially on the inorganic substrates [147,148]. However, the influence of

polymers on the growth of inorganic crystals has not been studied very

extensively. Biomineralisation especially has drawn considerable interest because

of the fascinating features observed, such as growth of certain inorganic

compounds (calcium carbonate, phosphates, iron oxides, etc.) by the biological

systems in most unusual morphological forms which at the same time show single

crystal type diffraction patterns [149-151]. These systems are quite complex,

involving many types of macromolecules, and the exact role of the polymeric

substances-proteins, long chain fatty acids etc in controlling the morphology is not

yet fully understood.

Radhakrishnan and coworkers studied the crystallization behavior of inorganic

salts such as cupric chloride, calcium chloride, potassium carbonate etc in

polymeric media and found that the crystallization of the polymer or its orientation

can influence the inorganic salts as well [152-154]. Calcium sulphate was also

prepared by this in-situ technique [155].

1.6. Critical issues in nanocomposites

Just as in traditional fiber composites, the major challenges in the research of

nanocomposites can be categorized in terms of the structures from nano to micro

to macro levels. There is still considerable uncertainty in theoretical modeling and

experimental characterization of the nano-scale reinforcement materials,

particularly nanotubes. Then, there is a lack of understanding of the interfacial

bonding between the reinforcements and the matrix material from both analytical

and experimental viewpoints. Lastly, the challenges at the level of

nanocomposites have mainly to do with the following issues related to composites

processing:

Introduction 37

1.6.1. Dispersion

Uniform dispersion of nanoparticles, and nanotubes against their agglomeration due

to van der Waals bonding is the first step in the processing of nanocomposites. Beside

the problems of agglomeration of nanoparticles, exfoliation of clays and graphitic

layers are essential. SWCNTs tend to cluster into ropes and MWCNTs produced by

chemical vapor deposition are often tangled together like spaghettis. The separation

of nanotubes in a solvent or a matrix material is a prerequisite for aligning them.

1.6.2. Alignment

Because of their small sizes, it is exceedingly difficult to align the nanotubes in a

polymeric matrix material in a manner accomplished in traditional short fiber composites.

The lack of control of their orientation diminishes the effectiveness of nanotube

reinforcement in composites, whether for structural or functional performance.

1.6.3. Volume and rate

High volume and high rate fabrication is fundamental to manufacturing of

nanocomposites as a commercially viable product. The lessons learned in the

fabrication of traditional fiber composites have clearly demonstrated that the

development of a science base for manufacturing is indispensable. Efficiency in

manufacturing is pivotal to the future development of nanocomposites.

1.6.4. Cost effectiveness

Besides high volume and high rate production, the cost of nanocomposites also

hinges on that of the nanoreinforcement material, particularly, nanotubes. It is

anticipated that as applications for nanotubes and their composites increase the

cost will be dramatically reduced.

1.7. Preparation of Nanocomposites

Making good samples of polymer matrix nanocomposites is a challenging area

that draws considerable effort. Researchers have tried a variety of processing

techniques to make polymer matrix nanocomposites. Creating one universal

technique for making polymer nanocomposites is difficult due to the physical and

chemical differences between each system and various types of equipment

38 Chapter 1

available to researchers. Each polymer system requires a special set of

processing conditions to be formed, based on the processing efficiency and

desired product properties. The different processing techniques in general do not

yield equivalent results. Polymer nanocomposites were prepared by several

methods. Broadly all these methods can be divided into two such as ex-situ and

in-situ. In ex-situ both the polymer and the nanofiller are taken separately and

mixed together. These methods are discussed below.

1.7.1. Melt intercalation or melt blending method

This method involves annealing, statically or under shear, a mixture of the polymer

and nanofiller above the softening point of the polymer. This method has great

advantages over either in-situ intercalative polymerization or polymer solution

intercalation. First, this method is environmentally benign due to the absence of organic

solvents. Second, it is compatible with current industrial process, such as extrusion and

injection molding. The melt intercalation method allows the use of polymers which were

previously not suitable for in-situ polymerization or solution intercalation.

Recently, the melt intercalation technique has become the standard for the

preparation of polymer nanocomposites especially for layered nanocomposites.

During polymer intercalation from solution, a relatively large number of solvent

molecules have to be desorbed from the host to accommodate the incoming polymer

chains. The desorbed solvent molecules gain one translational degree of freedom,

and the resulting entropic gain compensates for the decrease in conformational

entropy of the confined polymer chains. Therefore, there are many advantages to

direct melt intercalation over solution intercalation. For example, direct melt

intercalation is highly specific for the polymer, leading to new hybrids that were

previously inaccessible. In addition, the absence of a solvent makes direct melt

intercalation an environmentally sound and an economically favorable method for

industries from a waste perspective.

In order to understand the thermodynamic issue associated with nanocomposite

formation, Vaia et al. [156,157] applied a mean-field statistical lattice model, reporting

that calculations based on the mean field theory agree well with experimental results

[156]. Although there is an entropy loss associated with the confinement of a polymer

Introduction 37

1.6.1. Dispersion

Uniform dispersion of nanoparticles, and nanotubes against their agglomeration due

to van der Waals bonding is the first step in the processing of nanocomposites. Beside

the problems of agglomeration of nanoparticles, exfoliation of clays and graphitic

layers are essential. SWCNTs tend to cluster into ropes and MWCNTs produced by

chemical vapor deposition are often tangled together like spaghettis. The separation

of nanotubes in a solvent or a matrix material is a prerequisite for aligning them.

1.6.2. Alignment

Because of their small sizes, it is exceedingly difficult to align the nanotubes in a

polymeric matrix material in a manner accomplished in traditional short fiber composites.

The lack of control of their orientation diminishes the effectiveness of nanotube

reinforcement in composites, whether for structural or functional performance.

1.6.3. Volume and rate

High volume and high rate fabrication is fundamental to manufacturing of

nanocomposites as a commercially viable product. The lessons learned in the

fabrication of traditional fiber composites have clearly demonstrated that the

development of a science base for manufacturing is indispensable. Efficiency in

manufacturing is pivotal to the future development of nanocomposites.

1.6.4. Cost effectiveness

Besides high volume and high rate production, the cost of nanocomposites also

hinges on that of the nanoreinforcement material, particularly, nanotubes. It is

anticipated that as applications for nanotubes and their composites increase the

cost will be dramatically reduced.

1.7. Preparation of Nanocomposites

Making good samples of polymer matrix nanocomposites is a challenging area

that draws considerable effort. Researchers have tried a variety of processing

techniques to make polymer matrix nanocomposites. Creating one universal

technique for making polymer nanocomposites is difficult due to the physical and

chemical differences between each system and various types of equipment

38 Chapter 1

available to researchers. Each polymer system requires a special set of

processing conditions to be formed, based on the processing efficiency and

desired product properties. The different processing techniques in general do not

yield equivalent results. Polymer nanocomposites were prepared by several

methods. Broadly all these methods can be divided into two such as ex-situ and

in-situ. In ex-situ both the polymer and the nanofiller are taken separately and

mixed together. These methods are discussed below.

1.7.1. Melt intercalation or melt blending method

This method involves annealing, statically or under shear, a mixture of the polymer

and nanofiller above the softening point of the polymer. This method has great

advantages over either in-situ intercalative polymerization or polymer solution

intercalation. First, this method is environmentally benign due to the absence of organic

solvents. Second, it is compatible with current industrial process, such as extrusion and

injection molding. The melt intercalation method allows the use of polymers which were

previously not suitable for in-situ polymerization or solution intercalation.

Recently, the melt intercalation technique has become the standard for the

preparation of polymer nanocomposites especially for layered nanocomposites.

During polymer intercalation from solution, a relatively large number of solvent

molecules have to be desorbed from the host to accommodate the incoming polymer

chains. The desorbed solvent molecules gain one translational degree of freedom,

and the resulting entropic gain compensates for the decrease in conformational

entropy of the confined polymer chains. Therefore, there are many advantages to

direct melt intercalation over solution intercalation. For example, direct melt

intercalation is highly specific for the polymer, leading to new hybrids that were

previously inaccessible. In addition, the absence of a solvent makes direct melt

intercalation an environmentally sound and an economically favorable method for

industries from a waste perspective.

In order to understand the thermodynamic issue associated with nanocomposite

formation, Vaia et al. [156,157] applied a mean-field statistical lattice model, reporting

that calculations based on the mean field theory agree well with experimental results

[156]. Although there is an entropy loss associated with the confinement of a polymer

Introduction 39

melt with nanocomposite formation, this process is allowed because there is an entropy

gain associated with the layer separation, resulting in a net entropy change near to zero.

Thus, from the theoretical model, the outcome of nanocomposite formation via polymer

melt intercalation depends primarily on energetic factors, which may be determined from

the surface energies of the polymer and nanofiller, especially the layered ones.

Polystyrene was the first polymer used for the melt intercalation technique with

alkylammonium cation modified MMT and there are a large number of reports of

preparation of nanocomposites by this technique (Table 1.9).

No Nanocomposite Method/result Ref

1 PS/MMT Heated at 650C, new peaks in WAXS 157-159

2 PEO/Na+MMT Heated at 800C, fully intercalated 160, 161

3 N6/clay Twin Screw extruder at 2400C, Exfoliation for low loading intercalation for high loading

162-166

4 PP/MMT PP-OH as compatibilizer, intercalated structure 167-173

5 PE-g-MMT Extent of exfoliation and intercalation depends on the hydrophilicity of the PE-g-MA and the chain length of the organic modifier in the clay

174

6 EPDM/clay Vulcanization process, exfoliated structure 175

7 PET/MMT Mini twin-screw extruder at 2850C, delaminated/intercalated structure

176

8 PLA/OMLS Extruder at 1950C 177, 178

9 PP/CaCO3 Melt mixing, good dispersion for low loading 179,180

10 PU/Silica Melt mixing, curing at 1000C, particle size 12 nm, agglomeration from 40%

181

11 PP/SiO2 Styrene grafting on particles, irradiated, melt mixing with PP

182

12 HDPE/PP Melt mixing and extrusion, HDPE matrix and PP nanofibrils of 30-150nm diameter

183

13 PE/MMT Melt intercalation 184

14 PE/MMT Extruder, melt intercalation Photo oxidative degradation

185

15 PE/OMMT Melt blending in brabender, thermal degradation is less for nanocomposites

186

16 Starch Clay Melt intercalation, thermal stability and biodegradation depends on filler content

187-189

17 PCL/Clay Melt intercalation 190,191

Table 1.9. Examples of nanocomposite preparation by the melt blending technique

40 Chapter 1

The in-situ method is mainly used for the layered hosts and polymers. Here

usually the monomer is taken and subsequent polymerization is occurring in the

reaction medium. The preparative methods are divided into two main groups

according to the starting materials and processing techniques:

1.7.2. Intercalation of polymer or pre-polymer from solution

This is based on a solvent system in which the polymer or pre-polymer is soluble

and the nanofiller usually used is layered one such as silicates, hydroxides which

are swellable. The layered filler is first swollen in a solvent, such as water,

chloroform or toluene. When the polymer and layered material solutions are

mixed, the polymer chains intercalate and displace the solvent within the

interlayers. Upon solvent removal, the intercalated structure remains, resulting in

polymer layered nanocomposite.

Water-soluble polymers, such as polyethylene oxide (PEO) [192], polyvinyl alcohol

(PVA) [193], polyvinyl pyrrolidone (PVP) [194] and polyethyl vinyl acetate (PEVA)

[195], have been intercalated into the clay galleries using this method. Examples

from non-aqueous solvents are nanocomposites of polycaprolactone (PCL)/clay

[196] and polylactic acid (PLA)/clay [197] in chloroform as a co-solvent, and high-

density PE (HDPE) with xylene and benzonitrile [198]. Nematic liquid crystal PLS

nanocomposites have also been prepared using this method in various organic

solvents, such as toluene and DMF [199].

The thermodynamics involved in this method are described in the following. For

the overall process, in which polymer is exchanged with the previously

intercalated solvent in the gallery, a negative variation in the Gibbs free energy is

required. The driving force for the polymer intercalation into layered silicate from

solution is the entropy gained by desorption of solvent molecules, which

compensates for the decreased entropy of the confined, intercalated chains [156].

Using this method, intercalation only occurs for certain polymer/solvent pairs. This

method is good for the intercalation of polymers with little or no polarity into

layered structures, and facilitates production of thin films with polymer-oriented

clay intercalated layers. However, from commercial point of view, this method

Introduction 39

melt with nanocomposite formation, this process is allowed because there is an entropy

gain associated with the layer separation, resulting in a net entropy change near to zero.

Thus, from the theoretical model, the outcome of nanocomposite formation via polymer

melt intercalation depends primarily on energetic factors, which may be determined from

the surface energies of the polymer and nanofiller, especially the layered ones.

Polystyrene was the first polymer used for the melt intercalation technique with

alkylammonium cation modified MMT and there are a large number of reports of

preparation of nanocomposites by this technique (Table 1.9).

No Nanocomposite Method/result Ref

1 PS/MMT Heated at 650C, new peaks in WAXS 157-159

2 PEO/Na+MMT Heated at 800C, fully intercalated 160, 161

3 N6/clay Twin Screw extruder at 2400C, Exfoliation for low loading intercalation for high loading

162-166

4 PP/MMT PP-OH as compatibilizer, intercalated structure 167-173

5 PE-g-MMT Extent of exfoliation and intercalation depends on the hydrophilicity of the PE-g-MA and the chain length of the organic modifier in the clay

174

6 EPDM/clay Vulcanization process, exfoliated structure 175

7 PET/MMT Mini twin-screw extruder at 2850C, delaminated/intercalated structure

176

8 PLA/OMLS Extruder at 1950C 177, 178

9 PP/CaCO3 Melt mixing, good dispersion for low loading 179,180

10 PU/Silica Melt mixing, curing at 1000C, particle size 12 nm, agglomeration from 40%

181

11 PP/SiO2 Styrene grafting on particles, irradiated, melt mixing with PP

182

12 HDPE/PP Melt mixing and extrusion, HDPE matrix and PP nanofibrils of 30-150nm diameter

183

13 PE/MMT Melt intercalation 184

14 PE/MMT Extruder, melt intercalation Photo oxidative degradation

185

15 PE/OMMT Melt blending in brabender, thermal degradation is less for nanocomposites

186

16 Starch Clay Melt intercalation, thermal stability and biodegradation depends on filler content

187-189

17 PCL/Clay Melt intercalation 190,191

Table 1.9. Examples of nanocomposite preparation by the melt blending technique

40 Chapter 1

The in-situ method is mainly used for the layered hosts and polymers. Here

usually the monomer is taken and subsequent polymerization is occurring in the

reaction medium. The preparative methods are divided into two main groups

according to the starting materials and processing techniques:

1.7.2. Intercalation of polymer or pre-polymer from solution

This is based on a solvent system in which the polymer or pre-polymer is soluble

and the nanofiller usually used is layered one such as silicates, hydroxides which

are swellable. The layered filler is first swollen in a solvent, such as water,

chloroform or toluene. When the polymer and layered material solutions are

mixed, the polymer chains intercalate and displace the solvent within the

interlayers. Upon solvent removal, the intercalated structure remains, resulting in

polymer layered nanocomposite.

Water-soluble polymers, such as polyethylene oxide (PEO) [192], polyvinyl alcohol

(PVA) [193], polyvinyl pyrrolidone (PVP) [194] and polyethyl vinyl acetate (PEVA)

[195], have been intercalated into the clay galleries using this method. Examples

from non-aqueous solvents are nanocomposites of polycaprolactone (PCL)/clay

[196] and polylactic acid (PLA)/clay [197] in chloroform as a co-solvent, and high-

density PE (HDPE) with xylene and benzonitrile [198]. Nematic liquid crystal PLS

nanocomposites have also been prepared using this method in various organic

solvents, such as toluene and DMF [199].

The thermodynamics involved in this method are described in the following. For

the overall process, in which polymer is exchanged with the previously

intercalated solvent in the gallery, a negative variation in the Gibbs free energy is

required. The driving force for the polymer intercalation into layered silicate from

solution is the entropy gained by desorption of solvent molecules, which

compensates for the decreased entropy of the confined, intercalated chains [156].

Using this method, intercalation only occurs for certain polymer/solvent pairs. This

method is good for the intercalation of polymers with little or no polarity into

layered structures, and facilitates production of thin films with polymer-oriented

clay intercalated layers. However, from commercial point of view, this method

Introduction 41

involves the copious use of organic solvents, which is usually environmentally

unfriendly and economically prohibitive.

Some of the important polymer nanocomposites prepared by this method is given

in Table 1.10.

No Nanocomposites Comments Ref.

1 PEO/MMT Different polar solvents used, good stability towards solvents

192

2 PEO/Na+MMT Acetonitrile as solvent, d-spacing increased from 0.98nm to 1.36nm

200

3 PEO/MMT Chloroform as co-solvent 201-203

4 PDMS/MMT Sonicating a mixture of silanol terminated PDMS and organosilicate

204

5 Polyimide/MMT Effect of OMLS 205

6 Polyimide/MMT Solvent cast method, exfoliation at low MMT and partial exfoliation high loading

206

7 PLA/MMT Dissolving in hot chloroform, clay in tactoid form

207

8 HDPE/MMT Dissolving in a mixture of xylene and benzonitrile, partial exfoliation

199

9 PVA/MMT MMT/water suspension containing dissolved PVA.

208-210

10 PS-PI/OMLS Dissolved in toluene, intercalated structure 211,212

11 HBP/MMT Dispersed in deionised water 213

12 PP/Alumina Polymer in solution 214

13 PE Solution blending 184

14 Starch clay Solution method, thermal degradation depends on clay dispersion, re association of starch chains

215

15 PPV/Silica Solution blending, Kinetics of thermal degradation

216

Table 1.10. Examples of nanocomposite preparation by the intercalation of polymer technique

42 Chapter 1

1.7.3. In-situ intercalative polymerization method

In this method, the layered material is swollen within the liquid monomer or a

monomer solution so the polymer formation can occur between the intercalated

sheets. Polymerization can be initiated either by heat or radiation, by the diffusion

of a suitable initiator, or by an organic initiator or catalyst fixed through cation

exchange inside the interlayer before the swelling step. Although inter-lamellar

polymerization techniques using appropriately modified layered silicate or

synthetic layered silicates [217,218] have long been known, the field of polymer

layered silicate (PLS) nanocomposites gained momentum recently due to the

report of a N6/MMT nanocomposite from the Toyota research group [219], where

very small amounts of layered silicate loadings resulted in pronounced improvements

in thermal and mechanical properties. Table 1.11 gives a brief account of the major

nanocomposites developed by this technique.

No Nanocomposite Method, Result Ref

1 N6/MMT Ring opening polymerization of caprolactum 219-222

2 PA12/MMT In-situ polymerization 223

3 PCL/MMT Dispersion of MMT in liquid caprolactone 224, 225

4 PU/MMT In-situ polymerization 226-228

5 PMMA/MMT OMLS dispersed in MMA, intercalated 229, 230

6 PP/MMT Soluble metallocene catalysts to intercalate inside silicate layers, and coordination polymerization of propylene

231, 232

7 PE/MMT Brookhart’s single component palladium-based complex, fluorohectorite

233

8 PE/MMT MMT-OH and ethylene polymerization by fixing a Ti-based Ziegler–Natta catalyst

234

9 PE/MMT Polymerization filling technique 235, 236

10 PET/MMT Exfoliation of clays into ethylene glycol 237-239

11 Epoxy/MMT Dispersion of OMLS into DGEBA 240-245

12 PA6/Silica In-situ polymerization of ε-caproamide 246

13 PMMA/alumina Monomer and particles sonicated, initiator and chain transfer agent, polymn

247-249

14 PE/clay In-situ polymerization 234, 250

15 PCL/Clay In-situ polymerization 251

Table 1.11. Examples of nanocomposite preparation by the in-situ intercalative polymerization technique

Introduction 41

involves the copious use of organic solvents, which is usually environmentally

unfriendly and economically prohibitive.

Some of the important polymer nanocomposites prepared by this method is given

in Table 1.10.

No Nanocomposites Comments Ref.

1 PEO/MMT Different polar solvents used, good stability towards solvents

192

2 PEO/Na+MMT Acetonitrile as solvent, d-spacing increased from 0.98nm to 1.36nm

200

3 PEO/MMT Chloroform as co-solvent 201-203

4 PDMS/MMT Sonicating a mixture of silanol terminated PDMS and organosilicate

204

5 Polyimide/MMT Effect of OMLS 205

6 Polyimide/MMT Solvent cast method, exfoliation at low MMT and partial exfoliation high loading

206

7 PLA/MMT Dissolving in hot chloroform, clay in tactoid form

207

8 HDPE/MMT Dissolving in a mixture of xylene and benzonitrile, partial exfoliation

199

9 PVA/MMT MMT/water suspension containing dissolved PVA.

208-210

10 PS-PI/OMLS Dissolved in toluene, intercalated structure 211,212

11 HBP/MMT Dispersed in deionised water 213

12 PP/Alumina Polymer in solution 214

13 PE Solution blending 184

14 Starch clay Solution method, thermal degradation depends on clay dispersion, re association of starch chains

215

15 PPV/Silica Solution blending, Kinetics of thermal degradation

216

Table 1.10. Examples of nanocomposite preparation by the intercalation of polymer technique

42 Chapter 1

1.7.3. In-situ intercalative polymerization method

In this method, the layered material is swollen within the liquid monomer or a

monomer solution so the polymer formation can occur between the intercalated

sheets. Polymerization can be initiated either by heat or radiation, by the diffusion

of a suitable initiator, or by an organic initiator or catalyst fixed through cation

exchange inside the interlayer before the swelling step. Although inter-lamellar

polymerization techniques using appropriately modified layered silicate or

synthetic layered silicates [217,218] have long been known, the field of polymer

layered silicate (PLS) nanocomposites gained momentum recently due to the

report of a N6/MMT nanocomposite from the Toyota research group [219], where

very small amounts of layered silicate loadings resulted in pronounced improvements

in thermal and mechanical properties. Table 1.11 gives a brief account of the major

nanocomposites developed by this technique.

No Nanocomposite Method, Result Ref

1 N6/MMT Ring opening polymerization of caprolactum 219-222

2 PA12/MMT In-situ polymerization 223

3 PCL/MMT Dispersion of MMT in liquid caprolactone 224, 225

4 PU/MMT In-situ polymerization 226-228

5 PMMA/MMT OMLS dispersed in MMA, intercalated 229, 230

6 PP/MMT Soluble metallocene catalysts to intercalate inside silicate layers, and coordination polymerization of propylene

231, 232

7 PE/MMT Brookhart’s single component palladium-based complex, fluorohectorite

233

8 PE/MMT MMT-OH and ethylene polymerization by fixing a Ti-based Ziegler–Natta catalyst

234

9 PE/MMT Polymerization filling technique 235, 236

10 PET/MMT Exfoliation of clays into ethylene glycol 237-239

11 Epoxy/MMT Dispersion of OMLS into DGEBA 240-245

12 PA6/Silica In-situ polymerization of ε-caproamide 246

13 PMMA/alumina Monomer and particles sonicated, initiator and chain transfer agent, polymn

247-249

14 PE/clay In-situ polymerization 234, 250

15 PCL/Clay In-situ polymerization 251

Table 1.11. Examples of nanocomposite preparation by the in-situ intercalative polymerization technique

Introduction 43

In addition to these three major processing methods, other fabrication

techniques have been also developed. These include solid intercalation [252],

covulcanization [175], and the solgel method [253]. Some of these methods

are in the early stages of development and have not yet been widely applied.

1.8. Properties of nanocomposites

Nanocomposites consisting of a polymer and nanofiller (modified or not)

frequently exhibit remarkably improved mechanical and materials properties

when compared to those of pristine polymers containing a small amount

(≤5 wt%) of layered silicate. Improvements include a higher modulus,

increased strength and heat resistance, decreased gas permeability and

flammability, and increased biodegradability of biodegradable polymers. The

main reason for these improved properties in nanocomposites is the stronger

interfacial interaction between the matrix and layered silicate, compared with

conventional filler reinforced systems. The following section will cover up some

of the important areas of composite properties cited in literature.

1.8.1. Mechanical Properties

Tensile and flexural properties

The tensile modulus of a polymeric material has been shown to be remarkably

improved when nanocomposites are formed. PA6 nanocomposites prepared

through the in-situ intercalative ring opening polymerization of ω-caprolactam,

leading to the formation of exfoliated nanocomposites, exhibit a drastic

increase in the tensile properties at rather low filler content [254]. The main

reason for the drastic improvement in tensile modulus in PA6 nanocomposites

is the strong interaction between matrix and silicate layers via formation of

hydrogen bonds. Mechanical properties of the various nanocomposites are

depicted in Table 1.12.

44 Chapter 1

No Nanocomposite Result Ref

1 PA6/OMLS Modulus increased from 1 to 3 GPa 222,255

2 PPCN Modulus increased from 600 to 1200 MPa 172

3 PP/OMLS Depends on compatibilizer properties 256

4 PP/CN Tensile modulus and strength improved 300 and 50%

171

5 Epoxy/MMT Modulus showed drastic improvement, exfoliated structure

243, 244

6 PLA/OMLS Flexural modulus improved 257

7 PP/CaCO3 Young’s modulus increased with loading while TS and YS decreased

180, 258

8 PP/SiO2 Young’s modulus less for grafted ones & reverse for TS

182

9 HDPE/PP All mechanical increased 183

10 PP/Alumina Increase in Young’s modulus 214

11 PMMA/alumina Drop in YM and increment in TS 247-249

12 PA6/Clay 2% and 5% clay increased Young’s modulus to 40 and 100%

259

13 PA6/Clay Linear increase in YM for both intercalated and exfoliation

260

14 Semicrystalline nanocomposites

Fracture toughness and fracture mechanisms

261

15 Nanocomposites Modeling of mechanical properties 262

16 Copolymer latex/MMT

Modeling of mechanical properties 263

17 N6/acrylate rubber/clay

High toughness and stiffness 264

18 RPET/MMT Improved yield strength and modulus, delaminated structure 265

19 PMMA/CaCO3 Improvement in Young’s modulus and abrasion resistance 266

20 PA-6/MMT/glass fibers

Higher flexural modulus and compressive strength at high temperatures 267

Table 1.12. Polymer nanocomposites showing mechanical properties

Introduction 43

In addition to these three major processing methods, other fabrication

techniques have been also developed. These include solid intercalation [252],

covulcanization [175], and the solgel method [253]. Some of these methods

are in the early stages of development and have not yet been widely applied.

1.8. Properties of nanocomposites

Nanocomposites consisting of a polymer and nanofiller (modified or not)

frequently exhibit remarkably improved mechanical and materials properties

when compared to those of pristine polymers containing a small amount

(≤5 wt%) of layered silicate. Improvements include a higher modulus,

increased strength and heat resistance, decreased gas permeability and

flammability, and increased biodegradability of biodegradable polymers. The

main reason for these improved properties in nanocomposites is the stronger

interfacial interaction between the matrix and layered silicate, compared with

conventional filler reinforced systems. The following section will cover up some

of the important areas of composite properties cited in literature.

1.8.1. Mechanical Properties

Tensile and flexural properties

The tensile modulus of a polymeric material has been shown to be remarkably

improved when nanocomposites are formed. PA6 nanocomposites prepared

through the in-situ intercalative ring opening polymerization of ω-caprolactam,

leading to the formation of exfoliated nanocomposites, exhibit a drastic

increase in the tensile properties at rather low filler content [254]. The main

reason for the drastic improvement in tensile modulus in PA6 nanocomposites

is the strong interaction between matrix and silicate layers via formation of

hydrogen bonds. Mechanical properties of the various nanocomposites are

depicted in Table 1.12.

44 Chapter 1

No Nanocomposite Result Ref

1 PA6/OMLS Modulus increased from 1 to 3 GPa 222,255

2 PPCN Modulus increased from 600 to 1200 MPa 172

3 PP/OMLS Depends on compatibilizer properties 256

4 PP/CN Tensile modulus and strength improved 300 and 50%

171

5 Epoxy/MMT Modulus showed drastic improvement, exfoliated structure

243, 244

6 PLA/OMLS Flexural modulus improved 257

7 PP/CaCO3 Young’s modulus increased with loading while TS and YS decreased

180, 258

8 PP/SiO2 Young’s modulus less for grafted ones & reverse for TS

182

9 HDPE/PP All mechanical increased 183

10 PP/Alumina Increase in Young’s modulus 214

11 PMMA/alumina Drop in YM and increment in TS 247-249

12 PA6/Clay 2% and 5% clay increased Young’s modulus to 40 and 100%

259

13 PA6/Clay Linear increase in YM for both intercalated and exfoliation

260

14 Semicrystalline nanocomposites

Fracture toughness and fracture mechanisms

261

15 Nanocomposites Modeling of mechanical properties 262

16 Copolymer latex/MMT

Modeling of mechanical properties 263

17 N6/acrylate rubber/clay

High toughness and stiffness 264

18 RPET/MMT Improved yield strength and modulus, delaminated structure 265

19 PMMA/CaCO3 Improvement in Young’s modulus and abrasion resistance 266

20 PA-6/MMT/glass fibers

Higher flexural modulus and compressive strength at high temperatures 267

Table 1.12. Polymer nanocomposites showing mechanical properties

Introduction 45

The Young’s modulus tends to increase with the volume fraction of inclusions in

every case. In some systems, there is a critical volume fraction at which

aggregation occurs and the modulus goes down [206, 268–271]. In general, there

is also an increase in modulus as the size of the particle decreases. Interaction

between matrix and filler may play an important role in the effects of the

nanoparticles on composite properties [268–270]. For polymer systems capable of

having a higher degree of crystallinity, the increase in modulus with decreasing

particle size is found to be greater in systems with poor interaction between filler

and matrix as opposed to those with good interaction. However, the overall trend

of the modulus of polymer nanocomposites is not found to be greatly dependent

upon the nature of the matrix nor the interaction between filler and matrix [272].

For composites with good interaction between filler and matrix, the yield stress

tends to increase with increasing volume fraction and decreasing particle size,

similarly to the increase in modulus under same conditions. The pattern changes

when there is poor interaction between the matrix and particles. The addition of

nanoparticles with poor interaction with the matrix causes the yield stress to

decrease, compared to the neat matrix, regardless of the filler concentration or

size. The tensile strength follows a similar pattern as that observed for the yield

stress. There is no uniform trend with respect to the volume fraction of particles for

the ultimate stress. Poor filler–matrix interaction leads to a decrease in the

ultimate and yield stress as compared to the pure matrix system [272].

1.8.2. Dynamic mechanical analysis

DMA has been used to study the temperature dependence of storage modulus

and loss modulus upon nanocomposites formation under different experimental

procedures. The nanocomposites showed remarkable improvement in storage

modulus. This behavior is explained on the basis of good interaction between the

polymer and the filler particles [177]. Some prominent results are described in

Table 1.13.

46 Chapter 1

No Nanocomposite Result Ref

1 PMMA/SPN10 G’ increases for all temperatures, Tg shifted to left, intercalated structure

273

2 PPCN Two peaks for tanδ three relaxations 171, 274

3 N6/OMLS G’ increases for all temperatures, intercalated structure

259

4 PA6/Clay Storage modulus increased with filler content 260, 275

5 PVDF/clay Storage modulus increased with filler content 276

6 Epoxy/clay Exfoliated structure, fast increase in storage modulus

277

7 PBT/MMT Improved dynamic mechanical properties 278

8 PVA/Laponite Dynamic mechanical properties increased, Swelling decreased 279

Table 1.13. Polymer nanocomposites showing dynamic mechanical properties

In general, viscoelastic properties tend to be higher in nanocomposites than in

pure polymer systems. When there is good filler–matrix interaction, the storage

modulus generally increases with increasing volume fraction. The modulus also

seems to increase as the particle size decreases. Overall, the storage modulus

tends to increase with the presence of nanoparticles in a composite system.

1.8.3. Heat distortion temperature

Most of the nanocomposite studies report Heat distortion temperature HDT as a

function of filler content, characterized by the procedure given in ASTM D-648.

Kojima et al. [254] first showed that the HDT of pure PA6 increases up to 900C

after nanocomposite preparation with OMLS. In their further work [277] they

reported the clay content dependence of HDT of PA6/MMT nanocomposites. In

N6/MMT nanocomposites, there is a marked increase in HDT from 650C for the

neat N6 to 1520C for 4.7 wt% nanocomposite. Beyond that wt% of MMT, the HDT

of the nanocomposites level off.

The HDT change for the nanocomposites with respect to the filler content have

been analysed by various research groups. A brief account of the systems is given

below (Table 1.14):

Introduction 45

The Young’s modulus tends to increase with the volume fraction of inclusions in

every case. In some systems, there is a critical volume fraction at which

aggregation occurs and the modulus goes down [206, 268–271]. In general, there

is also an increase in modulus as the size of the particle decreases. Interaction

between matrix and filler may play an important role in the effects of the

nanoparticles on composite properties [268–270]. For polymer systems capable of

having a higher degree of crystallinity, the increase in modulus with decreasing

particle size is found to be greater in systems with poor interaction between filler

and matrix as opposed to those with good interaction. However, the overall trend

of the modulus of polymer nanocomposites is not found to be greatly dependent

upon the nature of the matrix nor the interaction between filler and matrix [272].

For composites with good interaction between filler and matrix, the yield stress

tends to increase with increasing volume fraction and decreasing particle size,

similarly to the increase in modulus under same conditions. The pattern changes

when there is poor interaction between the matrix and particles. The addition of

nanoparticles with poor interaction with the matrix causes the yield stress to

decrease, compared to the neat matrix, regardless of the filler concentration or

size. The tensile strength follows a similar pattern as that observed for the yield

stress. There is no uniform trend with respect to the volume fraction of particles for

the ultimate stress. Poor filler–matrix interaction leads to a decrease in the

ultimate and yield stress as compared to the pure matrix system [272].

1.8.2. Dynamic mechanical analysis

DMA has been used to study the temperature dependence of storage modulus

and loss modulus upon nanocomposites formation under different experimental

procedures. The nanocomposites showed remarkable improvement in storage

modulus. This behavior is explained on the basis of good interaction between the

polymer and the filler particles [177]. Some prominent results are described in

Table 1.13.

46 Chapter 1

No Nanocomposite Result Ref

1 PMMA/SPN10 G’ increases for all temperatures, Tg shifted to left, intercalated structure

273

2 PPCN Two peaks for tanδ three relaxations 171, 274

3 N6/OMLS G’ increases for all temperatures, intercalated structure

259

4 PA6/Clay Storage modulus increased with filler content 260, 275

5 PVDF/clay Storage modulus increased with filler content 276

6 Epoxy/clay Exfoliated structure, fast increase in storage modulus

277

7 PBT/MMT Improved dynamic mechanical properties 278

8 PVA/Laponite Dynamic mechanical properties increased, Swelling decreased 279

Table 1.13. Polymer nanocomposites showing dynamic mechanical properties

In general, viscoelastic properties tend to be higher in nanocomposites than in

pure polymer systems. When there is good filler–matrix interaction, the storage

modulus generally increases with increasing volume fraction. The modulus also

seems to increase as the particle size decreases. Overall, the storage modulus

tends to increase with the presence of nanoparticles in a composite system.

1.8.3. Heat distortion temperature

Most of the nanocomposite studies report Heat distortion temperature HDT as a

function of filler content, characterized by the procedure given in ASTM D-648.

Kojima et al. [254] first showed that the HDT of pure PA6 increases up to 900C

after nanocomposite preparation with OMLS. In their further work [277] they

reported the clay content dependence of HDT of PA6/MMT nanocomposites. In

N6/MMT nanocomposites, there is a marked increase in HDT from 650C for the

neat N6 to 1520C for 4.7 wt% nanocomposite. Beyond that wt% of MMT, the HDT

of the nanocomposites level off.

The HDT change for the nanocomposites with respect to the filler content have

been analysed by various research groups. A brief account of the systems is given

below (Table 1.14):

Introduction 47

No Nanocomposite Result Ref

1 PP/CN HDT increased from 109 to 1520C 172

2 PLA/OMLS Changed from 76 to 1110C, load dependent 257

3 N6/MMT Improved HDT for exfoliated, up to 340C after annealing, change in Tg and hydrogen bonding after annealing 280

Table 1.14. Polymer nanocomposites showing heat distortion temperature

The increase of HDT due to nanofiller dispersion is a very important property

improvement for any polymeric material, not only from application or industrial

point of view, but also because it is very difficult to achieve similar HDT

enhancements by chemical modification or reinforcement by conventional filler.

1.8.4. Thermal Stability

Generally, the incorporation of filler into the polymer matrix was found to enhance

thermal stability by acting as a superior insulator and mass transport barrier to the

volatile products generated during decomposition. Blumstein [217] first reported

the improved thermal stability of a nanocomposite that combined PMMA and MMT

clay. These PMMA nanocomposites were prepared by free radical polymerization

of MMA intercalated in the clay. He showed that the PMMA that was intercalated

(d spacing increase of 0.76 nm) between the galleries of MMT clay resisted the

thermal degradation under conditions that would otherwise completely degrade

pure PMMA. TGA data revealed that both linear and cross-linked PMMA

intercalated into MMT layers have a 40–500C higher decomposition temperature.

Blumstein argues that the stability of the PMMA nanocomposite is due not only to

its different structure, but also to the restricted thermal motion of the PMMA in the

gallery.

Recently, there have been many reports concerned with the improved thermal

stability of nanocomposites prepared with various types of nanofillers and polymer

matrices [33,281,282]. Very few important examples of the thermal studies of

nanocomposites are described in Table 1.15.

48 Chapter 1

No Nanocomposite Result Ref

1 PSF/MMT Significant thermal stability 283

2 SAN/Clay Increased onset of degradation 250C more 284

3 Epoxy-Silica Maximum Stiffness and thermal properties 29

4 NR/Clay

ENR/clay

Enhancement in thermal properties 285

5 PMMA/Pd Increase in oxidative thermal stability 286

6 PP/OMMT Thermo-oxidative degradation 287

7 PA6/Clay Injection moulded, thermal degradation depends on the % of water

288

8 N6/MMT Onset of degradation increased for low filler loading, activation energy increased

289,290

9 PVC/clay Polymer forms a carbonaceous char, clay stabilizes the allelic species

291

10 PVC/clay Enhances rapid decomposition, reduces the maximum decomposition rate and temperature of onset of decomposition

292

11 PBT/MMT Improved thermal stability, storage modulus 293

12 EPDM/clay Melt blending, photodegradability increased with filler content

294

13 PCL/MMT Improved thermal stability and good mechanical properties

295

14 Epoxy/clay Thermal stability depends on filler loading, exfoliated has high properties than intercalated

296,297

Table 1.15. Polymer nanocomposites showing thermal properties

The role of nanofiller in the nanocomposite structure may be the main reason for

the difference in TGA results of these systems compared to the previously

reported systems. The filler (inorganic or nanoclay) acts as a heat barrier, which

enhances the overall thermal stability of the system, as well as assist in the

formation of char after thermal decomposition. In the early stages of thermal

decomposition, the filler would shift the decomposition to higher temperature. After

that, this heat barrier effect would result in a reverse thermal stability. In other

words, the stacked silicate layers or nanofiller could hold accumulated heat that

could be used as a heat source to accelerate the decomposition process, in

conjunction with the heat flow supplied by the outside heat source.

Introduction 47

No Nanocomposite Result Ref

1 PP/CN HDT increased from 109 to 1520C 172

2 PLA/OMLS Changed from 76 to 1110C, load dependent 257

3 N6/MMT Improved HDT for exfoliated, up to 340C after annealing, change in Tg and hydrogen bonding after annealing 280

Table 1.14. Polymer nanocomposites showing heat distortion temperature

The increase of HDT due to nanofiller dispersion is a very important property

improvement for any polymeric material, not only from application or industrial

point of view, but also because it is very difficult to achieve similar HDT

enhancements by chemical modification or reinforcement by conventional filler.

1.8.4. Thermal Stability

Generally, the incorporation of filler into the polymer matrix was found to enhance

thermal stability by acting as a superior insulator and mass transport barrier to the

volatile products generated during decomposition. Blumstein [217] first reported

the improved thermal stability of a nanocomposite that combined PMMA and MMT

clay. These PMMA nanocomposites were prepared by free radical polymerization

of MMA intercalated in the clay. He showed that the PMMA that was intercalated

(d spacing increase of 0.76 nm) between the galleries of MMT clay resisted the

thermal degradation under conditions that would otherwise completely degrade

pure PMMA. TGA data revealed that both linear and cross-linked PMMA

intercalated into MMT layers have a 40–500C higher decomposition temperature.

Blumstein argues that the stability of the PMMA nanocomposite is due not only to

its different structure, but also to the restricted thermal motion of the PMMA in the

gallery.

Recently, there have been many reports concerned with the improved thermal

stability of nanocomposites prepared with various types of nanofillers and polymer

matrices [33,281,282]. Very few important examples of the thermal studies of

nanocomposites are described in Table 1.15.

48 Chapter 1

No Nanocomposite Result Ref

1 PSF/MMT Significant thermal stability 283

2 SAN/Clay Increased onset of degradation 250C more 284

3 Epoxy-Silica Maximum Stiffness and thermal properties 29

4 NR/Clay

ENR/clay

Enhancement in thermal properties 285

5 PMMA/Pd Increase in oxidative thermal stability 286

6 PP/OMMT Thermo-oxidative degradation 287

7 PA6/Clay Injection moulded, thermal degradation depends on the % of water

288

8 N6/MMT Onset of degradation increased for low filler loading, activation energy increased

289,290

9 PVC/clay Polymer forms a carbonaceous char, clay stabilizes the allelic species

291

10 PVC/clay Enhances rapid decomposition, reduces the maximum decomposition rate and temperature of onset of decomposition

292

11 PBT/MMT Improved thermal stability, storage modulus 293

12 EPDM/clay Melt blending, photodegradability increased with filler content

294

13 PCL/MMT Improved thermal stability and good mechanical properties

295

14 Epoxy/clay Thermal stability depends on filler loading, exfoliated has high properties than intercalated

296,297

Table 1.15. Polymer nanocomposites showing thermal properties

The role of nanofiller in the nanocomposite structure may be the main reason for

the difference in TGA results of these systems compared to the previously

reported systems. The filler (inorganic or nanoclay) acts as a heat barrier, which

enhances the overall thermal stability of the system, as well as assist in the

formation of char after thermal decomposition. In the early stages of thermal

decomposition, the filler would shift the decomposition to higher temperature. After

that, this heat barrier effect would result in a reverse thermal stability. In other

words, the stacked silicate layers or nanofiller could hold accumulated heat that

could be used as a heat source to accelerate the decomposition process, in

conjunction with the heat flow supplied by the outside heat source.

Introduction 49

1.8.5. Fire retardancy

The Cone calorimeter is one of the most effective bench-scale methods for

studying the fire retardant properties of polymeric materials. Fire properties such

as the heat release rate (HRR), heat peak, smoke production and CO2 yield, are

vital to the evaluation of the fire safety of materials.

In 1976 Unitika Ltd, Japan, first presented the potential flame retardant properties

of PA6/layered silicate nanocomposites [298]. Then in 1997 Gilman et al reported

detailed investigations on flame retardant properties of PA6/layered silicate

nanocomposite [299]. Subsequently, they chose various types of nanocomposite

materials and found similar reductions in flammability [291, 300, 301]. Recently

Gilman et al reviewed the flame retardant properties of many nanocomposites in

detail [302]. They have shown that the MMT-based nanocomposites exhibit

reduced flammability. The peak HRR is reduced by 50–75% for PA6, PS and PP-

g-MA nanocomposites. It is concluded that the MMT must be nanodispersed for it

to affect the flammability of the nanocomposites. However, the clay need not be

completely delaminated. In general, the nanocomposites flame retardant

mechanism involves a high-performance carbonaceous-silicate char, which builds

up on the surface during burning. This insulates the underlying material and slows

the mass loss rate of decomposition products.

Since the decreased flammability of nanocomposites is one of the most important

properties, the results of some of the most recent studies on flame retardant

properties of nanocomposites are reported in Table 1.16.

No Nanocomposite Result Ref

1 Clay nanocomposites

Mechanisms of fire retardancy as barrier formation and increase in melt viscosity

303

2 PA-6/clay High thermal stability and low flammability, model fitting 304

3 PE/Brazilian clay Improved flammability due to barrier effect 305

4 PP/clay Improved fire resistance and thermal properties 306

5 HDPE/clay Good flame retarding properties wrto clay loading 307

Table 1.16. Polymer nanocomposites showing fire properties

50 Chapter 1

1.8.6. Gas barrier properties

Nanofillers are believed to increase the barrier properties by creating a maze or

‘tortuous path’ (see figure 1.19) that retards the progress of the gas molecules

through the matrix resin. The direct benefit of the formation of such a path is

clearly observed in polyimide/clay nanocomposites by dramatically improved

barrier properties, with a simultaneous decrease in the thermal expansion

coefficient [205,283,308]. The polyimide/layered silicate nanocomposites with a

small fraction of organomodified layered silicates (OMLS) exhibited reduction in

the permeability of small gases, e.g. O2, H2O, He, CO2, and ethyl acetate vapors

[283]. For example, at 2 wt% clay loading, the permeability coefficient of water

vapor was decreased ten-fold with synthetic mica relative to pristine polyimide.

By comparing nanocomposites made with layered silicates of various aspect

ratios, the permeability was seen to decrease with increasing aspect ratio.

Figure 1.20. Schematic representation of path to be adopted for the barrier molecules of the conventional and nanocomposite

Introduction 49

1.8.5. Fire retardancy

The Cone calorimeter is one of the most effective bench-scale methods for

studying the fire retardant properties of polymeric materials. Fire properties such

as the heat release rate (HRR), heat peak, smoke production and CO2 yield, are

vital to the evaluation of the fire safety of materials.

In 1976 Unitika Ltd, Japan, first presented the potential flame retardant properties

of PA6/layered silicate nanocomposites [298]. Then in 1997 Gilman et al reported

detailed investigations on flame retardant properties of PA6/layered silicate

nanocomposite [299]. Subsequently, they chose various types of nanocomposite

materials and found similar reductions in flammability [291, 300, 301]. Recently

Gilman et al reviewed the flame retardant properties of many nanocomposites in

detail [302]. They have shown that the MMT-based nanocomposites exhibit

reduced flammability. The peak HRR is reduced by 50–75% for PA6, PS and PP-

g-MA nanocomposites. It is concluded that the MMT must be nanodispersed for it

to affect the flammability of the nanocomposites. However, the clay need not be

completely delaminated. In general, the nanocomposites flame retardant

mechanism involves a high-performance carbonaceous-silicate char, which builds

up on the surface during burning. This insulates the underlying material and slows

the mass loss rate of decomposition products.

Since the decreased flammability of nanocomposites is one of the most important

properties, the results of some of the most recent studies on flame retardant

properties of nanocomposites are reported in Table 1.16.

No Nanocomposite Result Ref

1 Clay nanocomposites

Mechanisms of fire retardancy as barrier formation and increase in melt viscosity

303

2 PA-6/clay High thermal stability and low flammability, model fitting 304

3 PE/Brazilian clay Improved flammability due to barrier effect 305

4 PP/clay Improved fire resistance and thermal properties 306

5 HDPE/clay Good flame retarding properties wrto clay loading 307

Table 1.16. Polymer nanocomposites showing fire properties

50 Chapter 1

1.8.6. Gas barrier properties

Nanofillers are believed to increase the barrier properties by creating a maze or

‘tortuous path’ (see figure 1.19) that retards the progress of the gas molecules

through the matrix resin. The direct benefit of the formation of such a path is

clearly observed in polyimide/clay nanocomposites by dramatically improved

barrier properties, with a simultaneous decrease in the thermal expansion

coefficient [205,283,308]. The polyimide/layered silicate nanocomposites with a

small fraction of organomodified layered silicates (OMLS) exhibited reduction in

the permeability of small gases, e.g. O2, H2O, He, CO2, and ethyl acetate vapors

[283]. For example, at 2 wt% clay loading, the permeability coefficient of water

vapor was decreased ten-fold with synthetic mica relative to pristine polyimide.

By comparing nanocomposites made with layered silicates of various aspect

ratios, the permeability was seen to decrease with increasing aspect ratio.

Figure 1.20. Schematic representation of path to be adopted for the barrier molecules of the conventional and nanocomposite

Introduction 51

Some important studies on gas barrier properties are given below (Table 1.17).

No Nanocomposite Result Ref

1 PLA/synthetic mica O2 gas permeability decreased 150% 309

2 PUU/OMLS

H2O-vapour permeability decreased dramatically

310

3 PLS Modeling of barrier properties 311

4 PHB/MMT Barrier properties enhanced 312

5 Soybean oil/ organoclay

Significant improvement in vapor barrier performance, thermal stability and storage modulus

313

6 Epoxy/MMT

Reduced He gas permeability, gas diffusivity decreased and gas solubility increased 314

7 N6/MMT

Superior barrier properties to helium, dihydrogen, dioxygen and water, various models applied 315

8 PE/MMT

Gas barrier properties depends on the filler matrix interaction at interphase 316

9 PP/SEBE/clay

Reduction in permeation of gases, increase in hardness, discoloration 317

10 PP/fumed silica

Permeability of gases reduced, enhancement in storage modulus 318

Table 1.17. Examples of polymer nanocomposites showing barrier properties

1.8.7. Optical transparency

Since most of the nanofillers employed have size in between 1-100 nm, when

nanofillers are dispersed in a polymer matrix, the resulting nanocomposite is

optically clear in visible light. So studies of optical transparency of

nanocomposites are very important. Table 1.18 shows examples of a few

nanocomposites with optical transparency.

52 Chapter 1

No Nanocomposite Result Ref

1 PVA/Na+MMT Retains high transparency of PVA 210

2 PLS High transparent films 33

3 PP/MMT Transparent films 319

4 Epoxy/MMT In higher exfoliation degree more transparent 320

5 TiO2/Epoxy High refractive index, surface planarity 321

6 PEG/silica Transparent coatings, decrease in contact angle 322

7 PE/MMT LOI increases, improved flame retardancy and microhardness, good optical transparency 323

8 PMMA/MgAl LDH High transparency and thermal properties 324

9 PP/SiO2 Spherulite growth rate decreased w.r.t. particle size and high transparent PP materials 325

10 P(BuA)/CNT High optical transparency and electrical conductivity 326

11 Epoxy/TiO2 High refractive index (2.8) thin film, excellent optical transparency 327

Table 1.18. Examples of polymer nanocomposites showing optical transparency

1.8.8. Biodegradability

Another interesting and exciting aspect of nanocomposites technology is the

significant improvement of biodegradability after nanocomposite preparation with

nanofillers. Tetto et al. [328] first reported results on the biodegradability of

nanocomposites based on PCL, reporting that the PCL/OMLS nanocomposites

showed improved biodegradability compared to pure PCL. The improved

biodegradability of PCL after nanocomposites formation may be due to a catalytic

role of the OMLS in the biodegradation mechanism, but this is not clear. Table

1.19 lists some of the recent investigations of biodegradability of polymer

nanocomposites.

Introduction 51

Some important studies on gas barrier properties are given below (Table 1.17).

No Nanocomposite Result Ref

1 PLA/synthetic mica O2 gas permeability decreased 150% 309

2 PUU/OMLS

H2O-vapour permeability decreased dramatically

310

3 PLS Modeling of barrier properties 311

4 PHB/MMT Barrier properties enhanced 312

5 Soybean oil/ organoclay

Significant improvement in vapor barrier performance, thermal stability and storage modulus

313

6 Epoxy/MMT

Reduced He gas permeability, gas diffusivity decreased and gas solubility increased 314

7 N6/MMT

Superior barrier properties to helium, dihydrogen, dioxygen and water, various models applied 315

8 PE/MMT

Gas barrier properties depends on the filler matrix interaction at interphase 316

9 PP/SEBE/clay

Reduction in permeation of gases, increase in hardness, discoloration 317

10 PP/fumed silica

Permeability of gases reduced, enhancement in storage modulus 318

Table 1.17. Examples of polymer nanocomposites showing barrier properties

1.8.7. Optical transparency

Since most of the nanofillers employed have size in between 1-100 nm, when

nanofillers are dispersed in a polymer matrix, the resulting nanocomposite is

optically clear in visible light. So studies of optical transparency of

nanocomposites are very important. Table 1.18 shows examples of a few

nanocomposites with optical transparency.

52 Chapter 1

No Nanocomposite Result Ref

1 PVA/Na+MMT Retains high transparency of PVA 210

2 PLS High transparent films 33

3 PP/MMT Transparent films 319

4 Epoxy/MMT In higher exfoliation degree more transparent 320

5 TiO2/Epoxy High refractive index, surface planarity 321

6 PEG/silica Transparent coatings, decrease in contact angle 322

7 PE/MMT LOI increases, improved flame retardancy and microhardness, good optical transparency 323

8 PMMA/MgAl LDH High transparency and thermal properties 324

9 PP/SiO2 Spherulite growth rate decreased w.r.t. particle size and high transparent PP materials 325

10 P(BuA)/CNT High optical transparency and electrical conductivity 326

11 Epoxy/TiO2 High refractive index (2.8) thin film, excellent optical transparency 327

Table 1.18. Examples of polymer nanocomposites showing optical transparency

1.8.8. Biodegradability

Another interesting and exciting aspect of nanocomposites technology is the

significant improvement of biodegradability after nanocomposite preparation with

nanofillers. Tetto et al. [328] first reported results on the biodegradability of

nanocomposites based on PCL, reporting that the PCL/OMLS nanocomposites

showed improved biodegradability compared to pure PCL. The improved

biodegradability of PCL after nanocomposites formation may be due to a catalytic

role of the OMLS in the biodegradation mechanism, but this is not clear. Table

1.19 lists some of the recent investigations of biodegradability of polymer

nanocomposites.

Introduction 53

No Nanocomposite Result Ref

1 Aliphatic polyester/clay

Biodegradability decreased 328

2 PLA/CN Enhanced biodegradability 257, 329

3 PLA/Clay Biodegradability increased 330

4 Plant oil silica hybrids Biodegradable, excellent flexibility 331

5 PBS/clay Improved mechanical properties, easily biodegradable

332

6 PLA/chitosan Improved mechanical, thermal and biodegradability 333

Table 1.19. Examples of polymer nanocomposites with biodegradable properties

1.8.9. Rheology

In order to understand the processibility of these materials, i.e. the final stage

of any polymeric material, one must understand the detailed rheological

behavior of these materials in the molten state. Understanding the rheological

properties of nanocomposites melts is not only important in gaining a

fundamental knowledge of the processibility, but is also helpful in

understanding the structure–property relationships in these materials.

Rheological behavior of polymer nanocomposites got great attention and some

of the important reports are listed below in Table 1.20.

No Nanocomposite Result Ref

1 PCL/MMT Improved rheological behavior 334

2 N6/MMT Rheology depends on molecular weight of N6 164

3 PP/MMT Rheology depends on the amount of filler 335

4 MXD6/clay Nanocomposite morphology, rheology, polymer crystallization behavior, haze, and CO2 gas permeability were done 336

Table 1.20. Examples of polymer nanocomposites showing rheological properties

54 Chapter 1

1.8.10. Other properties

Polymer nanocomposites also show improvement in most general polymeric

properties. For example, in addition to the decreased permeability of liquids and

gases, nanocomposites also show significant improvement in solvent uptake for

specific applications. Scratch resistance is another property that is strongly

enhanced by the incorporation of layered silicates [337]. The potential to use

polyaniline (PANI)-based nanocomposites as electrorheologically sensitive fluids

[338] or to use the combination of dispersed layered silicates in a liquid crystal

medium is also an attractive application. This could result in a stable electro-

optical device that is capable of exhibiting a bistable and reversible electro-optical

effect between an opaque and transparent state [172]. Finally, nanocomposites

have been used in highly technical areas such as in the improvement of ablative

properties in aeronautics [198]. Table 1.21 gives some specific examples of

polymer nanocomposites with special properties.

No Nanocomposite Result Ref

1 Epoxy/clay Water uptake reduced 339

2 Starch Cellulose whiskers

Decrease in water sensitivity and increase in thermo-mechanical properties

340

3 PANI/clay/EPDM Good absorption performances with good thermal and mechanical properties, application as antistatic packaging layers 341

4 Bionanocomposites Potential perspectives on food packaging applications 342

5 PC/Aluminium carboxylates

Scratch and abrasion resistant coatings 343

6 Polysiloxanes/

CNT or ITO

Good thermo-optical properties, spacecraft applications 344

7 Acrylic polyol/ surface treated silica

Scratch proof nanocomposite coatings 345

8 Epoxy/ZnO High-visible light transparency and high-UV light shielding efficiency 346

Table 1.21. Examples of polymer nanocomposites with miscellaneous properties

Introduction 53

No Nanocomposite Result Ref

1 Aliphatic polyester/clay

Biodegradability decreased 328

2 PLA/CN Enhanced biodegradability 257, 329

3 PLA/Clay Biodegradability increased 330

4 Plant oil silica hybrids Biodegradable, excellent flexibility 331

5 PBS/clay Improved mechanical properties, easily biodegradable

332

6 PLA/chitosan Improved mechanical, thermal and biodegradability 333

Table 1.19. Examples of polymer nanocomposites with biodegradable properties

1.8.9. Rheology

In order to understand the processibility of these materials, i.e. the final stage

of any polymeric material, one must understand the detailed rheological

behavior of these materials in the molten state. Understanding the rheological

properties of nanocomposites melts is not only important in gaining a

fundamental knowledge of the processibility, but is also helpful in

understanding the structure–property relationships in these materials.

Rheological behavior of polymer nanocomposites got great attention and some

of the important reports are listed below in Table 1.20.

No Nanocomposite Result Ref

1 PCL/MMT Improved rheological behavior 334

2 N6/MMT Rheology depends on molecular weight of N6 164

3 PP/MMT Rheology depends on the amount of filler 335

4 MXD6/clay Nanocomposite morphology, rheology, polymer crystallization behavior, haze, and CO2 gas permeability were done 336

Table 1.20. Examples of polymer nanocomposites showing rheological properties

54 Chapter 1

1.8.10. Other properties

Polymer nanocomposites also show improvement in most general polymeric

properties. For example, in addition to the decreased permeability of liquids and

gases, nanocomposites also show significant improvement in solvent uptake for

specific applications. Scratch resistance is another property that is strongly

enhanced by the incorporation of layered silicates [337]. The potential to use

polyaniline (PANI)-based nanocomposites as electrorheologically sensitive fluids

[338] or to use the combination of dispersed layered silicates in a liquid crystal

medium is also an attractive application. This could result in a stable electro-

optical device that is capable of exhibiting a bistable and reversible electro-optical

effect between an opaque and transparent state [172]. Finally, nanocomposites

have been used in highly technical areas such as in the improvement of ablative

properties in aeronautics [198]. Table 1.21 gives some specific examples of

polymer nanocomposites with special properties.

No Nanocomposite Result Ref

1 Epoxy/clay Water uptake reduced 339

2 Starch Cellulose whiskers

Decrease in water sensitivity and increase in thermo-mechanical properties

340

3 PANI/clay/EPDM Good absorption performances with good thermal and mechanical properties, application as antistatic packaging layers 341

4 Bionanocomposites Potential perspectives on food packaging applications 342

5 PC/Aluminium carboxylates

Scratch and abrasion resistant coatings 343

6 Polysiloxanes/

CNT or ITO

Good thermo-optical properties, spacecraft applications 344

7 Acrylic polyol/ surface treated silica

Scratch proof nanocomposite coatings 345

8 Epoxy/ZnO High-visible light transparency and high-UV light shielding efficiency 346

Table 1.21. Examples of polymer nanocomposites with miscellaneous properties

Introduction 55

1.9. Applications

In the forgoing discussion, it has been observed that nanocomposites have set the

current trend in the novel materials drawing considerable interest due to the

unusual properties displayed by them. Several authors have adopted various

techniques to prepare nanocomposites. However, the techniques they utilized are

very cumbersome which require careful control of various parameters such as pH,

moisture, temperature etc. In recent years significant progress has been achieved

in the synthesis of various types polymer nanocomposites and in the

understanding of the basic principles, which determine their optical, electronic and

magnetic properties. As a result nanocomposite based devices, such as light

emitting diodes, photodiodes, photovoltaic solar cells and gas sensors, have been

developed, often using chemically oriented synthetic methods such as soft

lithography, lamination, spin-coating or solution casting. Milestones on the way in

the development of nanocomposite based devices were the discovery of the possibility of filling conductive polymer matrices, such as PANI, poly(thiophenes),

substituted poly(paraphenylenevinylenes) or with semiconducting nanoparticles:

CdS, CdSe, CuS, ZnS, Fe3O4 or fullerenes, and the opportunity to fill the polymer

matrix with nanoparticles of both n- and p- conductivity types, thus providing

access to peculiar morphologies, such as interpenetrating networks, p-n nano

junctions or fractal p-n interfaces, not achievable by traditional microelectronics

technology. The peculiarities in the conduction mechanism through a network of

semiconductor nanoparticle chains provide the basis for the manufacture of highly

sensitive gas and vapor sensors. These sensors combine the properties of the

polymer matrix with those of the nanoparticles. It allows the fabrication of sensor

devices selective to some definite components in mixtures of gases or vapors.

Magnetic phenomena, such as super paramagnetism, observed in polymer-

nanocomposites containing Fe3O4 nanoparticles in some range of concentrations,

particle sizes, shapes and temperatures, provide a way to determine the limits to

magnetic media storage density.

Over the last decades, the polymer nanocomposites application have gained their

commercial footing, due in large part to the efforts of resin manufacturers,

compounding and master batch producers who now offer user friendly products.

56 Chapter 1

Nanocomposites differ from traditional plastic composites in that they provide

these properties with minimal impact on articles weight and they do so without

providing penalties. Lastly in packaging nanocomposites deliver with good clarity,

a combination not possible using traditional composites approaches.

The first commercial application of polymer nanocomposites was the use of

clay/nylon-6 nanocomposites as timing belt covers for cars [347]. Also

nanocomposites were used as a step assistant component and in the doors of

automobiles [348]. More recently, clay/PP nanocomposites were used for

structural seat backs and for automotive fuel lines and fuel system components. In

addition to automotive applications, polymer nanocomposites have been used to

improve barrier resistance in beverage applications such as barrier liner materials

for enclosure applications [349], for drink packaging applications [350] and

polyethylene terephthalate (PET) bottle applications [351].

1.10. Polystyrene based nanocomposites

Polystyrene is a polymer made from the monomer styrene, a liquid hydrocarbon

that is commercially manufactured from petroleum. At room temperature,

polystyrene is normally a solid thermoplastic, but can be melted at higher

temperature for molding or extrusion, then resolidified. Pure solid polystyrene is a

colorless, hard plastic with limited flexibility. It can be cast into molds with fine

detail. Polystyrene can be transparent or can be made to take on various colors. It

is economical and is used for producing plastic model assembly kits, plastic

cutlery, CD "jewel" cases, and many other objects where a fairly rigid, economical

plastic of any of various colors is desired.

PS is a strong and brittle plastic that can easily be injected, extruded or blow

moulded for making it a very useful and versatile manufacturing material. The

nanocomposites of PS can be prepared by several routes like in-situ

polymerization [352], bulk polymerization [242], solution blending [353] and melt

blending [199, 302, 354]. A brief look into the reports available in literature about

polystyrene nanocomposites are listed below (Table 1.22):

Introduction 55

1.9. Applications

In the forgoing discussion, it has been observed that nanocomposites have set the

current trend in the novel materials drawing considerable interest due to the

unusual properties displayed by them. Several authors have adopted various

techniques to prepare nanocomposites. However, the techniques they utilized are

very cumbersome which require careful control of various parameters such as pH,

moisture, temperature etc. In recent years significant progress has been achieved

in the synthesis of various types polymer nanocomposites and in the

understanding of the basic principles, which determine their optical, electronic and

magnetic properties. As a result nanocomposite based devices, such as light

emitting diodes, photodiodes, photovoltaic solar cells and gas sensors, have been

developed, often using chemically oriented synthetic methods such as soft

lithography, lamination, spin-coating or solution casting. Milestones on the way in

the development of nanocomposite based devices were the discovery of the possibility of filling conductive polymer matrices, such as PANI, poly(thiophenes),

substituted poly(paraphenylenevinylenes) or with semiconducting nanoparticles:

CdS, CdSe, CuS, ZnS, Fe3O4 or fullerenes, and the opportunity to fill the polymer

matrix with nanoparticles of both n- and p- conductivity types, thus providing

access to peculiar morphologies, such as interpenetrating networks, p-n nano

junctions or fractal p-n interfaces, not achievable by traditional microelectronics

technology. The peculiarities in the conduction mechanism through a network of

semiconductor nanoparticle chains provide the basis for the manufacture of highly

sensitive gas and vapor sensors. These sensors combine the properties of the

polymer matrix with those of the nanoparticles. It allows the fabrication of sensor

devices selective to some definite components in mixtures of gases or vapors.

Magnetic phenomena, such as super paramagnetism, observed in polymer-

nanocomposites containing Fe3O4 nanoparticles in some range of concentrations,

particle sizes, shapes and temperatures, provide a way to determine the limits to

magnetic media storage density.

Over the last decades, the polymer nanocomposites application have gained their

commercial footing, due in large part to the efforts of resin manufacturers,

compounding and master batch producers who now offer user friendly products.

56 Chapter 1

Nanocomposites differ from traditional plastic composites in that they provide

these properties with minimal impact on articles weight and they do so without

providing penalties. Lastly in packaging nanocomposites deliver with good clarity,

a combination not possible using traditional composites approaches.

The first commercial application of polymer nanocomposites was the use of

clay/nylon-6 nanocomposites as timing belt covers for cars [347]. Also

nanocomposites were used as a step assistant component and in the doors of

automobiles [348]. More recently, clay/PP nanocomposites were used for

structural seat backs and for automotive fuel lines and fuel system components. In

addition to automotive applications, polymer nanocomposites have been used to

improve barrier resistance in beverage applications such as barrier liner materials

for enclosure applications [349], for drink packaging applications [350] and

polyethylene terephthalate (PET) bottle applications [351].

1.10. Polystyrene based nanocomposites

Polystyrene is a polymer made from the monomer styrene, a liquid hydrocarbon

that is commercially manufactured from petroleum. At room temperature,

polystyrene is normally a solid thermoplastic, but can be melted at higher

temperature for molding or extrusion, then resolidified. Pure solid polystyrene is a

colorless, hard plastic with limited flexibility. It can be cast into molds with fine

detail. Polystyrene can be transparent or can be made to take on various colors. It

is economical and is used for producing plastic model assembly kits, plastic

cutlery, CD "jewel" cases, and many other objects where a fairly rigid, economical

plastic of any of various colors is desired.

PS is a strong and brittle plastic that can easily be injected, extruded or blow

moulded for making it a very useful and versatile manufacturing material. The

nanocomposites of PS can be prepared by several routes like in-situ

polymerization [352], bulk polymerization [242], solution blending [353] and melt

blending [199, 302, 354]. A brief look into the reports available in literature about

polystyrene nanocomposites are listed below (Table 1.22):

Introduction 57

No. Nanocomposite Procedure Result Ref.

1. sPS/MMT Solution intercalation technique by mixing pure s-PS and organophilic clay with adsorbed cetyl pyridium chloride

Nearly exfoliated structure 355

2. PS/Smectite Dispersed in styrene, sonication,

Intercalated 229, 230

3. PS/clay Monomer intercalation in OMLS and polymerization with initiator AIBN

Fully intercalated 356

4. PS/MMT Monomer intercalation in OMLS and polymerization with initiator AIBN

Well intercalated, structural affinity between monomer and surfactant is important

357-359

5. PS/MMT Living free radical polymerization

Exfoliated 360

6. PS/MMT Three different alkyl ammonium salt modified clay

Thermal stability, HRR decreased considerably

361

7. PS/MMT Melt intercalation, Heated at 650C,

New peaks in WAXS 158, 159

8. PS/CNT Solution mixing at room temperature, annealing at 1800C

Percolated filler network structure

362

9. PS/MMT Melt intercalation using mini extruder at 2000C

Intercalated structure 363

10. PS/clay Melt intercalation Onset of degradation increased to 500C more

364

11. PS/MMT Melt intercalation 365

12. PS/Synthetic mica

Melt intercalation Particle network formation via interparticle interaction and self-assembly

366

13. PS/Alumina Polymer in solution Increase in Young’s modulus

214

14. sPS/clay Melt intercalation, Higher TS and YM 180

15. PS/clay Free radical polymerization, exfoliation,

Better mechanical properties

365

16. PS/clay Solvent and sonication Relationship between rheology and dispersion

366

58 Chapter 1

17. PS/TiO2 Melt compounding at 2000C in a brabender plasticoder

Decrease in Tg and increase in free volume

367

18. PS/OMLS Free radical bulk polymerization, exfoliated structure

Stress relaxation remains constant, die swell reduced, shows yield like behavior

368

19. PS/clay Melt compounding, exfoliated structure

Linear viscoelastic behavior for low conc. of clay, reduction in mechanical performance

369

20. PS/carbon nanofiber

Melt blending and solvent casting

Storage and loss modulus increases w. r. to filler conc., modeling

370

21. PS/MMT Solvent casting, intercalated structure

Storage and loss modulus increases w. r. to filler conc., more solid like behavior for PNC’s

371

22. PS/clay Emulsion polymerization, partially exfoliated

Higher Tg and dynamic modulus

372

23. PS/clay Melt mixing at 2100C, intercalated and exfoliated

Relation between rheology and microstructure

373

24. PS/graphite Anionic in-situ polymerization, good dispersion

High Tg, high thermal stability, increase in dielectric constant

374

25. PS/Au Sputter coating of Au nanoparticles on PS thin films

Critical deposition time for shape determination of particle w.r.t. morphology

375

26. PS/Biphenyl clay

Bulk polymerization and melt blending at 1900C

Easy preparation, more thermally stable and reduction heat release rate

376

27. PS/clay with phosphate

Solution blending in CHCl3

Improvement in fire retardancy though loss in mechanical properties

377

28. PS/MMT 4 OMMTs dispersed in styrene by ultrasonication at RT, irradiation

Exfoliated and intercalated, enhanced thermal properties

378

29. HIPS/TiO2 Pre treatment of fillers, Injection molding at 2200C

Notched impact strength, tensile strength and modulus increased and decreased upon more addition, HDT and flame retardancy improved

379

30. PS/Bentoite Melt blending at 2000C, injection molding

Improved tensile strength, impact and thermal properties

380

Introduction 57

No. Nanocomposite Procedure Result Ref.

1. sPS/MMT Solution intercalation technique by mixing pure s-PS and organophilic clay with adsorbed cetyl pyridium chloride

Nearly exfoliated structure 355

2. PS/Smectite Dispersed in styrene, sonication,

Intercalated 229, 230

3. PS/clay Monomer intercalation in OMLS and polymerization with initiator AIBN

Fully intercalated 356

4. PS/MMT Monomer intercalation in OMLS and polymerization with initiator AIBN

Well intercalated, structural affinity between monomer and surfactant is important

357-359

5. PS/MMT Living free radical polymerization

Exfoliated 360

6. PS/MMT Three different alkyl ammonium salt modified clay

Thermal stability, HRR decreased considerably

361

7. PS/MMT Melt intercalation, Heated at 650C,

New peaks in WAXS 158, 159

8. PS/CNT Solution mixing at room temperature, annealing at 1800C

Percolated filler network structure

362

9. PS/MMT Melt intercalation using mini extruder at 2000C

Intercalated structure 363

10. PS/clay Melt intercalation Onset of degradation increased to 500C more

364

11. PS/MMT Melt intercalation 365

12. PS/Synthetic mica

Melt intercalation Particle network formation via interparticle interaction and self-assembly

366

13. PS/Alumina Polymer in solution Increase in Young’s modulus

214

14. sPS/clay Melt intercalation, Higher TS and YM 180

15. PS/clay Free radical polymerization, exfoliation,

Better mechanical properties

365

16. PS/clay Solvent and sonication Relationship between rheology and dispersion

366

58 Chapter 1

17. PS/TiO2 Melt compounding at 2000C in a brabender plasticoder

Decrease in Tg and increase in free volume

367

18. PS/OMLS Free radical bulk polymerization, exfoliated structure

Stress relaxation remains constant, die swell reduced, shows yield like behavior

368

19. PS/clay Melt compounding, exfoliated structure

Linear viscoelastic behavior for low conc. of clay, reduction in mechanical performance

369

20. PS/carbon nanofiber

Melt blending and solvent casting

Storage and loss modulus increases w. r. to filler conc., modeling

370

21. PS/MMT Solvent casting, intercalated structure

Storage and loss modulus increases w. r. to filler conc., more solid like behavior for PNC’s

371

22. PS/clay Emulsion polymerization, partially exfoliated

Higher Tg and dynamic modulus

372

23. PS/clay Melt mixing at 2100C, intercalated and exfoliated

Relation between rheology and microstructure

373

24. PS/graphite Anionic in-situ polymerization, good dispersion

High Tg, high thermal stability, increase in dielectric constant

374

25. PS/Au Sputter coating of Au nanoparticles on PS thin films

Critical deposition time for shape determination of particle w.r.t. morphology

375

26. PS/Biphenyl clay

Bulk polymerization and melt blending at 1900C

Easy preparation, more thermally stable and reduction heat release rate

376

27. PS/clay with phosphate

Solution blending in CHCl3

Improvement in fire retardancy though loss in mechanical properties

377

28. PS/MMT 4 OMMTs dispersed in styrene by ultrasonication at RT, irradiation

Exfoliated and intercalated, enhanced thermal properties

378

29. HIPS/TiO2 Pre treatment of fillers, Injection molding at 2200C

Notched impact strength, tensile strength and modulus increased and decreased upon more addition, HDT and flame retardancy improved

379

30. PS/Bentoite Melt blending at 2000C, injection molding

Improved tensile strength, impact and thermal properties

380

Introduction 59

31. PS/Magadite ATRP synthesis Improved thermal and nanomechanical properties

381

32. sPS/clay Premixing at 2000C, Brabender mixer at 2800C

More enhanced overall crystallization, enhanced mechanical and dynamic mechanical properties

382

33. PS/clay Co-rotating twin-screw extruder at 2000C

Effects of melt compounding variables, matrix resin molecular weight and filler content on mechanical, thermal, fire and flammability properties

383-385

34. PS/Mg(OH)2 ATRP, transesterification Structurally well defined hybrids

386

35. PS/M6A Premixing, Brabender mixer at 2000C and compression molding

Intercalated structure, enhanced storage and loss moduli from rheology

387

36. PS/silicate ATRP Intercalated, well defined molecular weights and distributions

388,389

37. PS/clay Twin screw extruder High throughput methods for nanocomposites extrusion, NMR characterization and flammability property screening

390

38. PS/BaTiO3 Solution mixing, hot compression molding

Improvement in dielectric properties

391

39. PS/carbon nanofibers

Melt mixing, Brabender rheometer, 2050C

Functionalised CNFs, good dispersion, storage and tensile moduli improved

392

40. PS/CdS Solution mixing in toluene, ultrasonication

AFM and X-ray reflectivity revealed the tendency of fillers to aggregate parallel to surface

393

41. PS/o-MMT In-situ bulk polymerization

Greater thermal stability, partially exfoliated structure

394

42. PS/clay In-situ thermal polymerization

Enhanced anticorrosion properties, thermal and glass transition

395

43. PS/clay Solution free radical polymerization

Higher Tg, higher degradation temperature and decrease in dielectric loss and constant

396, 397

44. PS/clay Melt intercalation, in-situ polymerization and masterbatch methods

Intercalated and exfoliated structures, mechanical properties showed enhancement

398

60 Chapter 1

45. PS/clay Emulsion polymerization at 750C

Enhanced thermal and mechanical properties

399

46. PS/clay Bulk polymerization Enhancement in degradation temp to 500 peak HRR reduced to 27-58%

353, 361

47. PS/clay Haake Rheocod melt mixer at 2000C

Flammability compared between synthetic and natural clays

400

48. PS/clay Injection molding at 2000C

Homogenous dispersion of clays, high degradation temp, increase in Tg, dispersion in organic solvents

401

49. PS/clay In-situ intercalative free radical polymerization

Microstructure depends on the type of clay, thermal stability improved

402

50. PS/clay Solution (800C) and melt mixing (1900C) methods

Tg is not influenced by the intercalation of clay

403

51. PS/clay Melt blending twin-screw extruder at 1800C

Improvement in tensile and storage moduli

404

52. PS/clay Melt blending in Brabender at 1850C

Considerable reduction in PHRR, increase in modulus

405

53. PS/clay Premixing, melt blending at 2000C

Intercalated structure, reduction in PHRR

406

54. PS/clay Solution casting with chloroform

Higher thermal stability, shift from liquid like to solid like in rheology

407

55. PS/clay Solvent blending with sonication in chlorobenzene

Exfoliated structure 408

56. PS/MMT Suspension polymerization at 800C

Exfoliated structure, better thermal and mechanical properties

409

57. PS/MWCNT Melt mixing at 1950C in a mini-extruder

Good dispersion, enhanced thermal properties, pi-cation interaction between CNT and compatibiliser

410

58. PS/SWNT Solution mixing at RT in dichlorobenzene

Good dispersion, enhanced electrical conductivity and low percolation threshold, linear transfer of stress from PS to CNT

411

Introduction 59

31. PS/Magadite ATRP synthesis Improved thermal and nanomechanical properties

381

32. sPS/clay Premixing at 2000C, Brabender mixer at 2800C

More enhanced overall crystallization, enhanced mechanical and dynamic mechanical properties

382

33. PS/clay Co-rotating twin-screw extruder at 2000C

Effects of melt compounding variables, matrix resin molecular weight and filler content on mechanical, thermal, fire and flammability properties

383-385

34. PS/Mg(OH)2 ATRP, transesterification Structurally well defined hybrids

386

35. PS/M6A Premixing, Brabender mixer at 2000C and compression molding

Intercalated structure, enhanced storage and loss moduli from rheology

387

36. PS/silicate ATRP Intercalated, well defined molecular weights and distributions

388,389

37. PS/clay Twin screw extruder High throughput methods for nanocomposites extrusion, NMR characterization and flammability property screening

390

38. PS/BaTiO3 Solution mixing, hot compression molding

Improvement in dielectric properties

391

39. PS/carbon nanofibers

Melt mixing, Brabender rheometer, 2050C

Functionalised CNFs, good dispersion, storage and tensile moduli improved

392

40. PS/CdS Solution mixing in toluene, ultrasonication

AFM and X-ray reflectivity revealed the tendency of fillers to aggregate parallel to surface

393

41. PS/o-MMT In-situ bulk polymerization

Greater thermal stability, partially exfoliated structure

394

42. PS/clay In-situ thermal polymerization

Enhanced anticorrosion properties, thermal and glass transition

395

43. PS/clay Solution free radical polymerization

Higher Tg, higher degradation temperature and decrease in dielectric loss and constant

396, 397

44. PS/clay Melt intercalation, in-situ polymerization and masterbatch methods

Intercalated and exfoliated structures, mechanical properties showed enhancement

398

60 Chapter 1

45. PS/clay Emulsion polymerization at 750C

Enhanced thermal and mechanical properties

399

46. PS/clay Bulk polymerization Enhancement in degradation temp to 500 peak HRR reduced to 27-58%

353, 361

47. PS/clay Haake Rheocod melt mixer at 2000C

Flammability compared between synthetic and natural clays

400

48. PS/clay Injection molding at 2000C

Homogenous dispersion of clays, high degradation temp, increase in Tg, dispersion in organic solvents

401

49. PS/clay In-situ intercalative free radical polymerization

Microstructure depends on the type of clay, thermal stability improved

402

50. PS/clay Solution (800C) and melt mixing (1900C) methods

Tg is not influenced by the intercalation of clay

403

51. PS/clay Melt blending twin-screw extruder at 1800C

Improvement in tensile and storage moduli

404

52. PS/clay Melt blending in Brabender at 1850C

Considerable reduction in PHRR, increase in modulus

405

53. PS/clay Premixing, melt blending at 2000C

Intercalated structure, reduction in PHRR

406

54. PS/clay Solution casting with chloroform

Higher thermal stability, shift from liquid like to solid like in rheology

407

55. PS/clay Solvent blending with sonication in chlorobenzene

Exfoliated structure 408

56. PS/MMT Suspension polymerization at 800C

Exfoliated structure, better thermal and mechanical properties

409

57. PS/MWCNT Melt mixing at 1950C in a mini-extruder

Good dispersion, enhanced thermal properties, pi-cation interaction between CNT and compatibiliser

410

58. PS/SWNT Solution mixing at RT in dichlorobenzene

Good dispersion, enhanced electrical conductivity and low percolation threshold, linear transfer of stress from PS to CNT

411

Introduction 61

59. PS/MWNT Solution mixing at RT in toluene with surface grafted NTs

micromechanical properties of glassy polymer could be enhanced dramatically by adding surface grafted MWNTs, crazing

412

60. PS-b-PI/ clay/CNT

Solution casting with toluene

Exfoliated and intercalated structures, strong interfacial adhesions between CNTs and matrix

413

61. PS/CNTs In-situ polymerization Increase in wear resistance, decrease in friction coefficient, improvement in tribological properties

414

62. HIPS/EVA/

TiO2

Premixing and melt compounding

Regulated rheological properties, improvement in mechanical and surface properties

415

63. PS/clay Bulk polymerization and melt blending

Reduction in PHRR and total heat released due to the Br2 addition

416

64. PS/Graphite In-situ polymerization Improvement in electrical and mechanical properties

417

65. PS/PPE/

Graphite

Solution blending with sonication

Increase in mechanical, electrical properties, no shift in Tg

418

66. PS/graphite Brabender plasticoder at 2200C

Intercalated structure, improvement in thermal and fire properties

419

67. PS/LS Swelling of clay, Compounding in a DACA microcompounder at 2000C

Fully exfoliated structure, unique rheological behavior, hairy platelets to show inter particle interaction

420

68. PS/CoFe2O4 In-situ precipitation Good mechanical and thermal properties, ferromagnetic behavior at RT

421

69. PS/Fe3O4 In-situ precipitation Particles of 2-20nm, special applications

422

70. PS/MMT Monomers in CO2, thermal polymerization

Intercalated and exfoliated structure, enhanced thermal properties

423

71. PS/MMT Twin-screw extruder at various speeds

Solid state NMR to investigate nanodispersion

424

72. PS/clay Bulk polymerization Higher thermal stability and higher dynamic modulus

425, 426

62 Chapter 1

73. PS/MMT Radiation polymerization Intercalated structure, higher thermal stability, positive shift in Tg

427

74. PS/MMT Extrusion Self assembly 428

75. PS/clay Emulsion polymerization Intercalated structure, pronounced shear thinning behavior w.r.to clay content

429

76. PS/MMT Emulsion polymerization and zwitter ion as clay modfier

Exfoliated structure, improved modulus, higher Tg and better thermal stability

430

77. PS/ZnO Melt blending in HAAKE at 1600C

Antistatic and flexural properties improved, higher Tg, aggregation for higher loading

431

78. PS/Ni Ultrasound irradiation Super paramagnetic composites

432

79. PS/PbS Solution mixing, sonication

Higher Tg, high thermal properties

433

80. PS/clay Polymerization techniques as well as melt blending

Structure depend upon the method preparation

434

81. PS/TiO2 In-situ polymerization Polystyrene bonded to TiO2 435

82. PS/TiO2 Sol-gel and phase inversion process

Microvoids restricted, inorganic network structure formed between PS and TiO2, improved permeability and porosity

436

83. PS/ZnO Solution casting Improved thermal stability and Tg, increase in modulus

437

84. PS/clay In-situ grafting polymerization

Exfoliated structure, higher thermal stability, swelling degree inceased

438

Table 1.22. Examples of PS nanocomposites with their preparation technique and major results

1.11. Ethylene-vinyl acetate based nanocomposites

Ethylene-vinyl acetate (also known as EVA or sometimes simply as "acetate") is

the copolymer of ethylene and vinyl acetate. It is a polymer that approaches

elastomeric materials in softness and flexibility, yet can be processed like other

thermoplastics. The material has good clarity and gloss, barrier properties, low-

Introduction 61

59. PS/MWNT Solution mixing at RT in toluene with surface grafted NTs

micromechanical properties of glassy polymer could be enhanced dramatically by adding surface grafted MWNTs, crazing

412

60. PS-b-PI/ clay/CNT

Solution casting with toluene

Exfoliated and intercalated structures, strong interfacial adhesions between CNTs and matrix

413

61. PS/CNTs In-situ polymerization Increase in wear resistance, decrease in friction coefficient, improvement in tribological properties

414

62. HIPS/EVA/

TiO2

Premixing and melt compounding

Regulated rheological properties, improvement in mechanical and surface properties

415

63. PS/clay Bulk polymerization and melt blending

Reduction in PHRR and total heat released due to the Br2 addition

416

64. PS/Graphite In-situ polymerization Improvement in electrical and mechanical properties

417

65. PS/PPE/

Graphite

Solution blending with sonication

Increase in mechanical, electrical properties, no shift in Tg

418

66. PS/graphite Brabender plasticoder at 2200C

Intercalated structure, improvement in thermal and fire properties

419

67. PS/LS Swelling of clay, Compounding in a DACA microcompounder at 2000C

Fully exfoliated structure, unique rheological behavior, hairy platelets to show inter particle interaction

420

68. PS/CoFe2O4 In-situ precipitation Good mechanical and thermal properties, ferromagnetic behavior at RT

421

69. PS/Fe3O4 In-situ precipitation Particles of 2-20nm, special applications

422

70. PS/MMT Monomers in CO2, thermal polymerization

Intercalated and exfoliated structure, enhanced thermal properties

423

71. PS/MMT Twin-screw extruder at various speeds

Solid state NMR to investigate nanodispersion

424

72. PS/clay Bulk polymerization Higher thermal stability and higher dynamic modulus

425, 426

62 Chapter 1

73. PS/MMT Radiation polymerization Intercalated structure, higher thermal stability, positive shift in Tg

427

74. PS/MMT Extrusion Self assembly 428

75. PS/clay Emulsion polymerization Intercalated structure, pronounced shear thinning behavior w.r.to clay content

429

76. PS/MMT Emulsion polymerization and zwitter ion as clay modfier

Exfoliated structure, improved modulus, higher Tg and better thermal stability

430

77. PS/ZnO Melt blending in HAAKE at 1600C

Antistatic and flexural properties improved, higher Tg, aggregation for higher loading

431

78. PS/Ni Ultrasound irradiation Super paramagnetic composites

432

79. PS/PbS Solution mixing, sonication

Higher Tg, high thermal properties

433

80. PS/clay Polymerization techniques as well as melt blending

Structure depend upon the method preparation

434

81. PS/TiO2 In-situ polymerization Polystyrene bonded to TiO2 435

82. PS/TiO2 Sol-gel and phase inversion process

Microvoids restricted, inorganic network structure formed between PS and TiO2, improved permeability and porosity

436

83. PS/ZnO Solution casting Improved thermal stability and Tg, increase in modulus

437

84. PS/clay In-situ grafting polymerization

Exfoliated structure, higher thermal stability, swelling degree inceased

438

Table 1.22. Examples of PS nanocomposites with their preparation technique and major results

1.11. Ethylene-vinyl acetate based nanocomposites

Ethylene-vinyl acetate (also known as EVA or sometimes simply as "acetate") is

the copolymer of ethylene and vinyl acetate. It is a polymer that approaches

elastomeric materials in softness and flexibility, yet can be processed like other

thermoplastics. The material has good clarity and gloss, barrier properties, low-

Introduction 63

temperature toughness, stress-crack resistance, hot-melt adhesive and heat

sealing properties and resistance to UV radiation.

As the level of vinyl acetate in the copolymer increases so the level of crystallinity

found in polythene alone reduces from about 60% to 10%. Common grades can

contain from 2% to 50% vinyl acetate. Clarity, flexibility, toughness and solvent

solubility increase with increasing vinyl acetate content. Of particular note is the

retention of flexibility of EVA rubber grades down to (-700C) and because they are

copolymers, problems due to plasticiser migration are not experienced. Good

resistance to water, salt and other environments can be obtained but solvent

resistance decreases with increasing vinyl acetate content. The copolymers can

accept high filler and pigment loadings. Being thermoplastic EVA can be moulded

by extrusion, injection, blow moulding, calendaring and rotational moulding.

Crosslinking with peroxides can produce thermoset products.

EVA has little or no odor and is competitive with rubber and vinyl products in many

electrical applications. EVA foam is used as padding in equipment for various

sports such as hockey, boxing, and mixed martial arts. EVA is also used in

biomedical engineering applications as a drug delivery device. While the polymer

is not biodegradable within the body, it is quite inert and causes little or no

reaction following implantation.

Ethylene vinyl acetate copolymer (EVA) is a widely used material, particularly as a

zero-halogen material in the cable industry. It is frequently formulated with large

quantities of inorganic filler material, such as aluminium trihydroxide (ATH). Since

the nanoclay incorporation is also believed to assist the formation of a protective

layer, researchers have studied the decomposition behavior of EVA

nanocomposite using nanofillers [439,440]. According to Hull et al [441]

incorporation of clay reduced the rate of decomposition significantly. There is

significant improvement in flame retardancy even though clay is not dispersed

properly, which suggests that the clay particles are able to reinforce the protective

layer formed. A delayed heat release results from delayed evolution of

degradation products combined with the barrier effect of dispersed nanolayers.

Furthermore, the nanocomposite provides physical integrity to the material burning

64 Chapter 1

in configurations (e.g. vertical upward combustion) in which fire dripping of flamed

material could occur which represents an additional hazard due to fire propagation

to surrounding materials [442,443].

An account of the EVA nanocomposites in recent literature is enlisted below in

Table 1.23.

No. Nanocomposite Procedure Result Ref.

1. EVA/Flurohectorite Melt mixing in a Brabender plasticoder at 1200C

Improved fire retardancy 441

2. EVA/LS Melt mixing in a twin-screw microcompounder at 1200C

In air degradation delays and in nitrogen degradation is more

443

3. EVA/MMT Melt intercalation, intercalated structure

Deacetylation accelerated in N2, significant delay in weight loss in air

365, 444,

445

4. EVA/OMLS Melt blending, exfoliated structure

Remarkable difference in dynamic and steady shear properties

446

5. EVA/OMLS Melt compounding, intercalated structure

With concentration of the nanoparticles and of the contact surface, Newtonian viscosity, non-Newtonian behavior and isothermal and non-isothermal elongational viscosity increases

447

6. EVA/MMT Melt mixing in a Brabender plasticoder at 1200C

Exfoliated structure, reduced effect of oxygen on thermooxidation, dramatic increase in storage and loss modulus

448

7. EVA/MWCNT Melt mixing in a Brabender internal mixer at 1400C

Possibility to delay both the ignition time and reduce the flammability (HRR) established

449

8. EPDM/EVA/Clay Solution mixing of three components in toluene

Intercalated structure, remarkable improvement in mechanical and thermal properties compared to pure EPDM/EVA

450

Introduction 63

temperature toughness, stress-crack resistance, hot-melt adhesive and heat

sealing properties and resistance to UV radiation.

As the level of vinyl acetate in the copolymer increases so the level of crystallinity

found in polythene alone reduces from about 60% to 10%. Common grades can

contain from 2% to 50% vinyl acetate. Clarity, flexibility, toughness and solvent

solubility increase with increasing vinyl acetate content. Of particular note is the

retention of flexibility of EVA rubber grades down to (-700C) and because they are

copolymers, problems due to plasticiser migration are not experienced. Good

resistance to water, salt and other environments can be obtained but solvent

resistance decreases with increasing vinyl acetate content. The copolymers can

accept high filler and pigment loadings. Being thermoplastic EVA can be moulded

by extrusion, injection, blow moulding, calendaring and rotational moulding.

Crosslinking with peroxides can produce thermoset products.

EVA has little or no odor and is competitive with rubber and vinyl products in many

electrical applications. EVA foam is used as padding in equipment for various

sports such as hockey, boxing, and mixed martial arts. EVA is also used in

biomedical engineering applications as a drug delivery device. While the polymer

is not biodegradable within the body, it is quite inert and causes little or no

reaction following implantation.

Ethylene vinyl acetate copolymer (EVA) is a widely used material, particularly as a

zero-halogen material in the cable industry. It is frequently formulated with large

quantities of inorganic filler material, such as aluminium trihydroxide (ATH). Since

the nanoclay incorporation is also believed to assist the formation of a protective

layer, researchers have studied the decomposition behavior of EVA

nanocomposite using nanofillers [439,440]. According to Hull et al [441]

incorporation of clay reduced the rate of decomposition significantly. There is

significant improvement in flame retardancy even though clay is not dispersed

properly, which suggests that the clay particles are able to reinforce the protective

layer formed. A delayed heat release results from delayed evolution of

degradation products combined with the barrier effect of dispersed nanolayers.

Furthermore, the nanocomposite provides physical integrity to the material burning

64 Chapter 1

in configurations (e.g. vertical upward combustion) in which fire dripping of flamed

material could occur which represents an additional hazard due to fire propagation

to surrounding materials [442,443].

An account of the EVA nanocomposites in recent literature is enlisted below in

Table 1.23.

No. Nanocomposite Procedure Result Ref.

1. EVA/Flurohectorite Melt mixing in a Brabender plasticoder at 1200C

Improved fire retardancy 441

2. EVA/LS Melt mixing in a twin-screw microcompounder at 1200C

In air degradation delays and in nitrogen degradation is more

443

3. EVA/MMT Melt intercalation, intercalated structure

Deacetylation accelerated in N2, significant delay in weight loss in air

365, 444,

445

4. EVA/OMLS Melt blending, exfoliated structure

Remarkable difference in dynamic and steady shear properties

446

5. EVA/OMLS Melt compounding, intercalated structure

With concentration of the nanoparticles and of the contact surface, Newtonian viscosity, non-Newtonian behavior and isothermal and non-isothermal elongational viscosity increases

447

6. EVA/MMT Melt mixing in a Brabender plasticoder at 1200C

Exfoliated structure, reduced effect of oxygen on thermooxidation, dramatic increase in storage and loss modulus

448

7. EVA/MWCNT Melt mixing in a Brabender internal mixer at 1400C

Possibility to delay both the ignition time and reduce the flammability (HRR) established

449

8. EPDM/EVA/Clay Solution mixing of three components in toluene

Intercalated structure, remarkable improvement in mechanical and thermal properties compared to pure EPDM/EVA

450

Introduction 65

9. EVA/clay Melt mixing in a Brabender

Intercalated structure, processable like pure EVA, increase in rigidity at low silicate content

451

10. EVA/LS/ATH Different compounding machines, 1600C

TGA in air shows delay in degradation, peak of heat release dramatically reduced, improved flame retardancy

452

11. EVA/cellulose whiskers

EVA dissolved in hot toluene stirred with whiskers suspension

Experimental and theoretical model predictions complement each other

453

12. EVA/clay Melt blending in rubber mill at 1200C and hot pressing at 1400C

Intercalated or partially exfoliated structure, E’ and thermal properties increase,

454

13. EVA/clay Melt mixing in Haake Rheocord mixer at 1400C

Exfoliated structure due to hydrogen bonding, effect of grafting of MAH studied

455

14. EVA/organoclay Melt mixing in Brabender mixer at 1300C at 60 rpm

Purification of organoclays improved mechanical and rheological behavior

456

15. EVA/MMT Melt blending at 1000C using Haake mixer

Intercalated structure, Young’s modulus increased, compatibiliser improved mechanical properties

457

16. EVA/MMT Melt blending at 1300C

Exfoliated, improved mechanical properties

458

17. EVA/MMT Melt blending at 1450C in a two roll mill

Exfoliated structure, two step degradation in TGA, peak HRR reduced and weight loss delayed

459, 460

18. EVA/MMT Solution blending Improved mechanical properties, improvement in thermal characteristics, decrease in swelling indices

461-465

19. EVA/clay Melt blending at 1500C in Brabender mixer under the flow of N2

Mixed exfoliated and intercalated clay structure, pseudo solid like behavior due to a 3D tactoid formation in polymer matrix, improved thermal properties

466-468

20. EVA/Na+MMT Melt blending at 1600C in Brabender mixer

Better fire performance for nanostructured composites

469

66 Chapter 1

21. EVA/clay Melt intercalation using twin-screw extruder at 1600C

Significant intercalation of clay, lower clay content showed exfoliation and higher modulus and tensile strength

470

22. EVA/MWNT/Clay Melt extrusion of a pre-blended nanotube/ EVA mixture using a Brabender at 1300C

Reduction in peak of heat release rate due to the formation of graphitic carbon, improved fire retardancy due to CNTs

471

23. EVA/OMMT Premixing, twin screw extrusion at 1200C

Mixed intercalated/exfoliated, enhanced linear viscoelastic response, occurrence of 3D network formation

472-474

24. EVA/clay Melt-blended at 1600C with a Brabender mixer and extruder

Exfoliated structure at low content, improved thermal properties

475

25. EVA/MMT/CTAB Melt mixing in twin-roll mill at 1200C or 1400C

Interlayer spacing increased, mechanical properties improved, thermally more stable w.r.t. mixing time

476

26. EVA/Rectorite Premixing, co-rotating twin-screw extruder, 1400C, injection molding

Intercalated structure, crystalline structure changes for higher loading, fractional free volume increases with loading, deacylation accelerated and main chain degradation delayed in air, reduces damping

477

27. Various nanocomposites including EVA

Various methods Nanodispersion decreases flame retardancy, combining nanoparticles with traditional flame retardants and surface treatment gives good results

478

28. PE/EVA/clay Premixing of blend, extrusion through twin-screw extruder at 1800C, hot press, irradiation at RT

Gel fraction, mechanical properties and morphology evolution estimated, effect of dosage analysed

479, 480

29. EVA/MMT Two-roll mill at 1300C for 7 min, one-pot process

Intercalated-exfoliated morphology, tensile and thermal properties improved

481

30. EVA/Mg(OH)2 Rubber mill at 1300C, hot pressing at 1500C

Drastic improvement for LOI due to good dispersion and compact char

482

Introduction 65

9. EVA/clay Melt mixing in a Brabender

Intercalated structure, processable like pure EVA, increase in rigidity at low silicate content

451

10. EVA/LS/ATH Different compounding machines, 1600C

TGA in air shows delay in degradation, peak of heat release dramatically reduced, improved flame retardancy

452

11. EVA/cellulose whiskers

EVA dissolved in hot toluene stirred with whiskers suspension

Experimental and theoretical model predictions complement each other

453

12. EVA/clay Melt blending in rubber mill at 1200C and hot pressing at 1400C

Intercalated or partially exfoliated structure, E’ and thermal properties increase,

454

13. EVA/clay Melt mixing in Haake Rheocord mixer at 1400C

Exfoliated structure due to hydrogen bonding, effect of grafting of MAH studied

455

14. EVA/organoclay Melt mixing in Brabender mixer at 1300C at 60 rpm

Purification of organoclays improved mechanical and rheological behavior

456

15. EVA/MMT Melt blending at 1000C using Haake mixer

Intercalated structure, Young’s modulus increased, compatibiliser improved mechanical properties

457

16. EVA/MMT Melt blending at 1300C

Exfoliated, improved mechanical properties

458

17. EVA/MMT Melt blending at 1450C in a two roll mill

Exfoliated structure, two step degradation in TGA, peak HRR reduced and weight loss delayed

459, 460

18. EVA/MMT Solution blending Improved mechanical properties, improvement in thermal characteristics, decrease in swelling indices

461-465

19. EVA/clay Melt blending at 1500C in Brabender mixer under the flow of N2

Mixed exfoliated and intercalated clay structure, pseudo solid like behavior due to a 3D tactoid formation in polymer matrix, improved thermal properties

466-468

20. EVA/Na+MMT Melt blending at 1600C in Brabender mixer

Better fire performance for nanostructured composites

469

66 Chapter 1

21. EVA/clay Melt intercalation using twin-screw extruder at 1600C

Significant intercalation of clay, lower clay content showed exfoliation and higher modulus and tensile strength

470

22. EVA/MWNT/Clay Melt extrusion of a pre-blended nanotube/ EVA mixture using a Brabender at 1300C

Reduction in peak of heat release rate due to the formation of graphitic carbon, improved fire retardancy due to CNTs

471

23. EVA/OMMT Premixing, twin screw extrusion at 1200C

Mixed intercalated/exfoliated, enhanced linear viscoelastic response, occurrence of 3D network formation

472-474

24. EVA/clay Melt-blended at 1600C with a Brabender mixer and extruder

Exfoliated structure at low content, improved thermal properties

475

25. EVA/MMT/CTAB Melt mixing in twin-roll mill at 1200C or 1400C

Interlayer spacing increased, mechanical properties improved, thermally more stable w.r.t. mixing time

476

26. EVA/Rectorite Premixing, co-rotating twin-screw extruder, 1400C, injection molding

Intercalated structure, crystalline structure changes for higher loading, fractional free volume increases with loading, deacylation accelerated and main chain degradation delayed in air, reduces damping

477

27. Various nanocomposites including EVA

Various methods Nanodispersion decreases flame retardancy, combining nanoparticles with traditional flame retardants and surface treatment gives good results

478

28. PE/EVA/clay Premixing of blend, extrusion through twin-screw extruder at 1800C, hot press, irradiation at RT

Gel fraction, mechanical properties and morphology evolution estimated, effect of dosage analysed

479, 480

29. EVA/MMT Two-roll mill at 1300C for 7 min, one-pot process

Intercalated-exfoliated morphology, tensile and thermal properties improved

481

30. EVA/Mg(OH)2 Rubber mill at 1300C, hot pressing at 1500C

Drastic improvement for LOI due to good dispersion and compact char

482

Introduction 67

31. NR/EVA/MMT Haake internal mixer at 1250C, hot pressed

Partial exfoliation of clay, modulus, tensile strength, Tg

and thermal properties improved

483

32. EVA/Bentonite Banbury twin-screw compounder at 80°C using 70 rpm for 40 min, compression molded at 110°C

Orientation and exfoliation of clay studied by WAXS and SAXS

484

33. PA6/EVA/clay Melt mixing by blender and twin-screw extruder

Higher PA-6 show better fire properties but less mechanical response

485

34. PP-EP/EVA/clay Co-rotating twin screw extruder, 1300 and 1900C for EVA and PP, injection molding 1300C

Ordered intercalated structure, improved thermal degradation, flame retardancy of the composites increased

486

35. EVA/clay/MWNT Brabender internal mixer at 1400C, for 12 min with a speed of 45 rpm

Synergistic effect on adding clays and nanotubes, mechanical, thermal and flame retardant properties enhanced

487

36. EVA/hectorite and EVA/Magadiite

Melt blending the polymer with 3 wt% clay in a Brabender Plasticorder at 120-1300C, for 20 min at 60 rpm

Thermal degradation studied elaborately, multiple degradation pathways proposed

488

37. EVA/clay 4 different internal mixers for melt blending

Elastic modulus increased to 100%, remarkable improvement in thermo-oxidation

489

Table 1.23. Examples of EVA nanocomposites with their preparation technique and major results

1.12. Purpose and objectives of the present work

From the ongoing discussion it can be concluded that the area of polymer

nanocomposites is topic of this era. Their preparation, characterisation, properties and

application will be beneficial to the mankind in a long way. So far no studies have

been reported both in polystyrene and EVA nanocomposites based on nanocalcium

68 Chapter 1

phosphate. In the previous sections of PS and EVA based nanocomposites majority of

the researchers chose either layered silicates or clay as the nanofiller. This is mainly

because of the layered structure of the systems. There are some reports regarding the

usage of mineral fillers as the reinforcement also.

Previously our laboratory was working mainly on polymer blends and composites

and their characterisation and application studies [490-494]. Recently we also

entered into the nanocomposites. We were mainly working on the

nanocomposites of natural rubber latex and its blends with carboxylated styrene

butadiene rubber latex. The preparation, characterisation and analysis of the

above composites are well documented [495-497]. Nowadays we were looking for

new polymer matrices and new nanomaterials. In this study we tried to synthesis

nanoparticles of calcium phosphate by the polymer induced crystallization

technique, which is known to be economical and high yielding. The prepared

nanoparticles were incorporated into two polymer matrices such as PS and EVA.

The various physico chemical properties were studied in detail. To the best of our

knowledge no research group has carried out similar work in PS and EVA

matrices.

The specific objectives of the current study are

• To synthesise nanoparticles of calcium phosphate via the polymer

induced crystallization technique and to characterize them by various

techniques

• To prepare PS based nanocomposites with nanocalcium phosphate and

characterize them by different techniques

• To analyse the mechanical, dynamic mechanical, thermal, rheological and

surface properties of the composites

• To prepare nanocomposites of EVA with nanocalcium phosphate and

characterize them by different techniques

• To analyse the mechanical, dynamic mechanical, thermal, rheological,

transport and surface properties of the composites

Introduction 67

31. NR/EVA/MMT Haake internal mixer at 1250C, hot pressed

Partial exfoliation of clay, modulus, tensile strength, Tg

and thermal properties improved

483

32. EVA/Bentonite Banbury twin-screw compounder at 80°C using 70 rpm for 40 min, compression molded at 110°C

Orientation and exfoliation of clay studied by WAXS and SAXS

484

33. PA6/EVA/clay Melt mixing by blender and twin-screw extruder

Higher PA-6 show better fire properties but less mechanical response

485

34. PP-EP/EVA/clay Co-rotating twin screw extruder, 1300 and 1900C for EVA and PP, injection molding 1300C

Ordered intercalated structure, improved thermal degradation, flame retardancy of the composites increased

486

35. EVA/clay/MWNT Brabender internal mixer at 1400C, for 12 min with a speed of 45 rpm

Synergistic effect on adding clays and nanotubes, mechanical, thermal and flame retardant properties enhanced

487

36. EVA/hectorite and EVA/Magadiite

Melt blending the polymer with 3 wt% clay in a Brabender Plasticorder at 120-1300C, for 20 min at 60 rpm

Thermal degradation studied elaborately, multiple degradation pathways proposed

488

37. EVA/clay 4 different internal mixers for melt blending

Elastic modulus increased to 100%, remarkable improvement in thermo-oxidation

489

Table 1.23. Examples of EVA nanocomposites with their preparation technique and major results

1.12. Purpose and objectives of the present work

From the ongoing discussion it can be concluded that the area of polymer

nanocomposites is topic of this era. Their preparation, characterisation, properties and

application will be beneficial to the mankind in a long way. So far no studies have

been reported both in polystyrene and EVA nanocomposites based on nanocalcium

68 Chapter 1

phosphate. In the previous sections of PS and EVA based nanocomposites majority of

the researchers chose either layered silicates or clay as the nanofiller. This is mainly

because of the layered structure of the systems. There are some reports regarding the

usage of mineral fillers as the reinforcement also.

Previously our laboratory was working mainly on polymer blends and composites

and their characterisation and application studies [490-494]. Recently we also

entered into the nanocomposites. We were mainly working on the

nanocomposites of natural rubber latex and its blends with carboxylated styrene

butadiene rubber latex. The preparation, characterisation and analysis of the

above composites are well documented [495-497]. Nowadays we were looking for

new polymer matrices and new nanomaterials. In this study we tried to synthesis

nanoparticles of calcium phosphate by the polymer induced crystallization

technique, which is known to be economical and high yielding. The prepared

nanoparticles were incorporated into two polymer matrices such as PS and EVA.

The various physico chemical properties were studied in detail. To the best of our

knowledge no research group has carried out similar work in PS and EVA

matrices.

The specific objectives of the current study are

• To synthesise nanoparticles of calcium phosphate via the polymer

induced crystallization technique and to characterize them by various

techniques

• To prepare PS based nanocomposites with nanocalcium phosphate and

characterize them by different techniques

• To analyse the mechanical, dynamic mechanical, thermal, rheological and

surface properties of the composites

• To prepare nanocomposites of EVA with nanocalcium phosphate and

characterize them by different techniques

• To analyse the mechanical, dynamic mechanical, thermal, rheological,

transport and surface properties of the composites

Introduction 69

1.13. References

1. A Kelly, Compos Sci Technol 23 (1985) 171

2. A Kelley, C Zweben, editors, Comprehensive composite materials, vols.

1–6. Elsevier; (2000)

3. ET Thostenson, J Amer Cer Soc 12 (2004) 14.

4. Nanotechnology: Shaping the World Atom by Atom. National Science and

Technology Council Interagency Working Group on Nanoscience,

Engineering and Technology (1999). Available from: http://www.nano.gov.

5. ET Thostenson, Ph.D. Dissertation, University of Delaware (2004)

6. ET Thostenson, WZ Li, DZ Wang, ZF Ren, TW Chou, J Appl Phys 91

(1998) 6034

7. ET Thostenson, TW Chou, J Phys D 36 (2003) 573

8. Jpn Tokkyo Koho 1204305 (1983)), Unitika Ltd, Fujiwara, T Sakamoto

Chem Abstr 86 (1997) 141002.

9. Nanoscience and nanotechnologies: opportunities and uncertainties, The

Royal Society & The Royal Academy of Engineering, London, (2004)

10. LA Utracki, Clay-Containing Polymeric Nanocomposites, Rapra Tech Ltd,

London (2004)

11. M Okamoto, Advance in Polymeric Nanocomposites, CMC Publishers,

Tokyo (2004)

12. TJ Pinavaia, G Beall, Polymeric Clay Nanocomposites, Wiley, New York

(2000)

13. A Okada, A Usuki, T Kurauchi, O Kamigaito, ACS Sym Ser N. 585, Am

Chem Soc (1995) 55

14. A Okada, M Kawasumi, T Kurauchi, O Kamigaito, ACS Polym Prepr 28

(1987) 447

70 Chapter 1

15. U. S. 4739007 (1988), Toyota Chuo Kenkyuusho, A Okada, A Fukushima,

M Kawasumi, S Inagaki, A Usuki, S Sugiyama, T Kurauchi, O Kamigaito,

Chem Abstr 107 (1987) 60084

16. M Takayanagi, A Kobunshi (1984), Chem Abstr 101 (1984) 231305

17. M Takayanagi, T Ogata, M Mohkawa, T Kai, J Macromol Sci Phys B17

(1980) 591

18. H van Olphen, An Introduction to Clay Colloid Chemistry, 2nd edition,

Wiley-Interscience, New York (1977)

19. HZ Friedlander, J Polym Sci 2 (1964) 475

20. A Blumstein, J Polym Sci 3A (1965) 2653

21. HGG Dekking, J Appl Polym Sci 11 (1967) 23

22. LW Zhong, Mater Today 7 (2004) 26

23. T Naganuma, Y Kagawa Compos Sci Technol 62 (2002) 1187

24. RP Singh, M Zhang, D Chan J Mater Sci 37 (2002) 781

25. L Lopez, BMK Song, HT Hahn, Proceedings of the 14th international

conference on composite materials (ICCM-14), San Diego (2003) 138

26. CM Thompson, HM Herring, TS Gates, JW Connell, Compos Sci Technol

63 (2003) 1591

27. BJ Ash, RW Siegel, LS Schadler, Macromolecules 37 (2004) 1358

28. J Karger-Kocsis, Z Zhang, JF Palta Calleja, G Michler, editors, Mechanical

properties of polymers based on nanostructure and morphology, New

York (2004)

29. JJ Luo, IM Daniel, Compos Sci Technol 63 (2003) 1607

30. V Krikorian, DJ Pochan, Chem Mater 15 (2003) 4317

31. F Gao, Mater Today 7(2004) 50

32. SS Ray, M Okamoto, Progr Polym Sci 28 (2003) 1539

Introduction 69

1.13. References

1. A Kelly, Compos Sci Technol 23 (1985) 171

2. A Kelley, C Zweben, editors, Comprehensive composite materials, vols.

1–6. Elsevier; (2000)

3. ET Thostenson, J Amer Cer Soc 12 (2004) 14.

4. Nanotechnology: Shaping the World Atom by Atom. National Science and

Technology Council Interagency Working Group on Nanoscience,

Engineering and Technology (1999). Available from: http://www.nano.gov.

5. ET Thostenson, Ph.D. Dissertation, University of Delaware (2004)

6. ET Thostenson, WZ Li, DZ Wang, ZF Ren, TW Chou, J Appl Phys 91

(1998) 6034

7. ET Thostenson, TW Chou, J Phys D 36 (2003) 573

8. Jpn Tokkyo Koho 1204305 (1983)), Unitika Ltd, Fujiwara, T Sakamoto

Chem Abstr 86 (1997) 141002.

9. Nanoscience and nanotechnologies: opportunities and uncertainties, The

Royal Society & The Royal Academy of Engineering, London, (2004)

10. LA Utracki, Clay-Containing Polymeric Nanocomposites, Rapra Tech Ltd,

London (2004)

11. M Okamoto, Advance in Polymeric Nanocomposites, CMC Publishers,

Tokyo (2004)

12. TJ Pinavaia, G Beall, Polymeric Clay Nanocomposites, Wiley, New York

(2000)

13. A Okada, A Usuki, T Kurauchi, O Kamigaito, ACS Sym Ser N. 585, Am

Chem Soc (1995) 55

14. A Okada, M Kawasumi, T Kurauchi, O Kamigaito, ACS Polym Prepr 28

(1987) 447

70 Chapter 1

15. U. S. 4739007 (1988), Toyota Chuo Kenkyuusho, A Okada, A Fukushima,

M Kawasumi, S Inagaki, A Usuki, S Sugiyama, T Kurauchi, O Kamigaito,

Chem Abstr 107 (1987) 60084

16. M Takayanagi, A Kobunshi (1984), Chem Abstr 101 (1984) 231305

17. M Takayanagi, T Ogata, M Mohkawa, T Kai, J Macromol Sci Phys B17

(1980) 591

18. H van Olphen, An Introduction to Clay Colloid Chemistry, 2nd edition,

Wiley-Interscience, New York (1977)

19. HZ Friedlander, J Polym Sci 2 (1964) 475

20. A Blumstein, J Polym Sci 3A (1965) 2653

21. HGG Dekking, J Appl Polym Sci 11 (1967) 23

22. LW Zhong, Mater Today 7 (2004) 26

23. T Naganuma, Y Kagawa Compos Sci Technol 62 (2002) 1187

24. RP Singh, M Zhang, D Chan J Mater Sci 37 (2002) 781

25. L Lopez, BMK Song, HT Hahn, Proceedings of the 14th international

conference on composite materials (ICCM-14), San Diego (2003) 138

26. CM Thompson, HM Herring, TS Gates, JW Connell, Compos Sci Technol

63 (2003) 1591

27. BJ Ash, RW Siegel, LS Schadler, Macromolecules 37 (2004) 1358

28. J Karger-Kocsis, Z Zhang, JF Palta Calleja, G Michler, editors, Mechanical

properties of polymers based on nanostructure and morphology, New

York (2004)

29. JJ Luo, IM Daniel, Compos Sci Technol 63 (2003) 1607

30. V Krikorian, DJ Pochan, Chem Mater 15 (2003) 4317

31. F Gao, Mater Today 7(2004) 50

32. SS Ray, M Okamoto, Progr Polym Sci 28 (2003) 1539

Introduction 71

33. M Alexandre, P Dubois, Mater Sci Eng R Rep 28 (2000) 1

34. A Yasmin, JL Abot, IM Daniel, Proceedings of the 14th international

conference on composite materials (ICCM-14), San Diego (2003) 138

35. A Okada, A Usuki, Mater Sci Eng C 3 (1995) 109

36. J Tsai, CT Sun, J Compos Mater 38 (2004) 567

37. H Miyagawa, LT Drzal, Proceedings of the 14th international conference

on composite materials (ICCM-14), San Diego (2003) 512

38. T Ogasawara, Y Ishida, T Ishikawa, Proceedings of the 11th US-Japan

conference on composite materials, Yonezawa, Yamagata, Japan (2004)

269

39. H Fukushima. LT Drzal, Proceedings of the 14th international conference

on composite materials (ICCM-14), San Diego (2003) 532

40. W Zheng, SC Wong, Compos Sci Technol 63 (2003) 225

41. W Zheng, XH Lu, SC Wong, J Appl Polym Sci 91 (2004) 2781

42. JH Song, H Huh, HT Hahn, Proceedings of the 14th international

conference on composite materials (ICCM-14), San Diego (2003) 512

43. VI Merkulov, DH Lowndes, YY Wei, G Eres, E Voelkl, Appl Phys Lett 76

(2000) 3555

44. M Endo, YA Kim, T Hayashi, Y Fukai, K Oshida, M Terrones, Appl Phys

Lett 80 (2002) 1267

45. M Endo, YA Kim, M Ezaka, K Osada, T Yanagisawa, T Hayashi, Nano

Lett 3 (2003) 723

46. CY Wei, D Srivastava, Appl Phys Lett 85 (2004) 2208

47. IC Finegan, GG Tibbetts, DG Glasgow, J Mater Sci 38 (2003) 3485

48. IC Finegan, GG Tibbetts, RF Gibson, Compos Sci Technol 63 (2003)

1629

72 Chapter 1

49. HM Ma, JJ Zeng, ML Real, S Kumar, DA Schiraldi, Compos Sci Technol

63 (2003) 1617

50. J Sandler, AH Windle, P Werner, V Altstadt, MV Es, MSP Shaffer, J Mater

Sci 38 (2003) 2135

51. S Iijima, Nature 354 (1991) 56

52. PG Collins, P Avouris, Scient Am 283 (2000) 62

53. RA Vaia, HD Wagner, Mater Today 7 (2004) 33

54. WA Curtin, BW Sheldon. Mater Today 7 (2004) 44

55. NH Tai, MK Yeh, JH Liu, Carbon 42 (2004) 2774

56. FH Gojny, MHG Wichmann, U Kopke, B Fiedler, K Schulte, Compos Sci

Technol 64 (2004) 2363

57. T Ogasawara, Y Ishida, T Ishikawa, R Yokota, Compos Part A 35 (2004)

67

58. ET Thostenson, TW Chou, J Phys D 35 (2002) L77

59. MD Frogley, D Ravich, HD Wagner, Compos Sci Technol 63 (2003) 1647

60. NASA Tech Briefs, 3 (2004) 46

61. TW Chou, Microstructural design of fiber composites, Cambridge

University Press (1992)

62. HR Shetty, TW Chou, Metall Trans A 16 (1985) 853

63. ET Thostenson, TW Chou, Carbon 42 (2004) 3015

64. CY Li, TW Chou, Mech Mater 36 (2004) 1047

65. TW Chou, RL McCullough, RB Pipes, Compos Scient Am 254 (1986) 193

66. Y Dzenis, Science 304 (2004) 1917

67. F Ko, Y Gogotsi, A Ali, N Naguib, HH Ye, GL Yang, Adv Mater 15 (2003)

1161

Introduction 71

33. M Alexandre, P Dubois, Mater Sci Eng R Rep 28 (2000) 1

34. A Yasmin, JL Abot, IM Daniel, Proceedings of the 14th international

conference on composite materials (ICCM-14), San Diego (2003) 138

35. A Okada, A Usuki, Mater Sci Eng C 3 (1995) 109

36. J Tsai, CT Sun, J Compos Mater 38 (2004) 567

37. H Miyagawa, LT Drzal, Proceedings of the 14th international conference

on composite materials (ICCM-14), San Diego (2003) 512

38. T Ogasawara, Y Ishida, T Ishikawa, Proceedings of the 11th US-Japan

conference on composite materials, Yonezawa, Yamagata, Japan (2004)

269

39. H Fukushima. LT Drzal, Proceedings of the 14th international conference

on composite materials (ICCM-14), San Diego (2003) 532

40. W Zheng, SC Wong, Compos Sci Technol 63 (2003) 225

41. W Zheng, XH Lu, SC Wong, J Appl Polym Sci 91 (2004) 2781

42. JH Song, H Huh, HT Hahn, Proceedings of the 14th international

conference on composite materials (ICCM-14), San Diego (2003) 512

43. VI Merkulov, DH Lowndes, YY Wei, G Eres, E Voelkl, Appl Phys Lett 76

(2000) 3555

44. M Endo, YA Kim, T Hayashi, Y Fukai, K Oshida, M Terrones, Appl Phys

Lett 80 (2002) 1267

45. M Endo, YA Kim, M Ezaka, K Osada, T Yanagisawa, T Hayashi, Nano

Lett 3 (2003) 723

46. CY Wei, D Srivastava, Appl Phys Lett 85 (2004) 2208

47. IC Finegan, GG Tibbetts, DG Glasgow, J Mater Sci 38 (2003) 3485

48. IC Finegan, GG Tibbetts, RF Gibson, Compos Sci Technol 63 (2003)

1629

72 Chapter 1

49. HM Ma, JJ Zeng, ML Real, S Kumar, DA Schiraldi, Compos Sci Technol

63 (2003) 1617

50. J Sandler, AH Windle, P Werner, V Altstadt, MV Es, MSP Shaffer, J Mater

Sci 38 (2003) 2135

51. S Iijima, Nature 354 (1991) 56

52. PG Collins, P Avouris, Scient Am 283 (2000) 62

53. RA Vaia, HD Wagner, Mater Today 7 (2004) 33

54. WA Curtin, BW Sheldon. Mater Today 7 (2004) 44

55. NH Tai, MK Yeh, JH Liu, Carbon 42 (2004) 2774

56. FH Gojny, MHG Wichmann, U Kopke, B Fiedler, K Schulte, Compos Sci

Technol 64 (2004) 2363

57. T Ogasawara, Y Ishida, T Ishikawa, R Yokota, Compos Part A 35 (2004)

67

58. ET Thostenson, TW Chou, J Phys D 35 (2002) L77

59. MD Frogley, D Ravich, HD Wagner, Compos Sci Technol 63 (2003) 1647

60. NASA Tech Briefs, 3 (2004) 46

61. TW Chou, Microstructural design of fiber composites, Cambridge

University Press (1992)

62. HR Shetty, TW Chou, Metall Trans A 16 (1985) 853

63. ET Thostenson, TW Chou, Carbon 42 (2004) 3015

64. CY Li, TW Chou, Mech Mater 36 (2004) 1047

65. TW Chou, RL McCullough, RB Pipes, Compos Scient Am 254 (1986) 193

66. Y Dzenis, Science 304 (2004) 1917

67. F Ko, Y Gogotsi, A Ali, N Naguib, HH Ye, GL Yang, Adv Mater 15 (2003)

1161

Introduction 73

68. L Viculis, J Mack, A Ali, R Luoh, G Yang, R Kaner, Proceedings of the

14th international conference on composite materials (ICCM-14), San

Diego (2003) 138

69. FK Ko, M Gandhi, C Karatzas, Proceedings of the 19th American society

for composites annual technical conference, Atlanta, Georgia, (2004)

70. H Mahfuz, A Adnan, VK Rangari, S Jeelani, BZ Jang, Compos Part A 35

(2004) 519

71. S Kumar, TD Dang, FE Arnold, AR Bhattacharyya, BG Min, XF Zhang,

Macromolecules 35 (2002) 9039

72. DT Colbert, RE Smalley, in E Osawa, editor, Perspectives of fullerene

nanotechnology, Kluwer Academic Publishers (2002) 3

73. DA Walters, MJ Casavant, XC Qin, CB Human, PJ Boul, LM Ericson,

Chem Phys Lett 338 (2001) 14

74. B Wang, Z Liang, KR Shankar, K Bareeld, C Zhang, L Kramer,

Proceedings of the 14th international conference on composite materials

(ICCM-14), San Diego (2003) 422

75. The MicroJetReactor for Producing Nanoparticles, Synthesechemie

GmbH, home.t-online.de/home/penth/ebesch.htm

76. Kava Technology (2004), www.kavatechnology.com/index.html

77. EL Mayes, J Mag Soc Jap 26 (2002) 932

78. KL Choy, In Innovative Processing of Films and Nanocrystalline Powders,

World Scientific Publishing, Singapore (2002)

79. MS Dresselhaus, Carbon nanotubes–Synthesis, Structure, Properties and

Applications, Springer-Verlag, Berlin/Heidelberg (2001)

80. M Boutonnet, J Kizling, P Stenius, G Maire, Colloids Surfaces, 5 (1982) 209

74 Chapter 1

81. R Leung, M Jeng, P Hou, DO Shah, In DT Wasan, ME Ginn, DO Shah

(Eds) Surfactants in Chemical Process Engineering, Marcel Dekker, New

York, Surfactant Sci Ser 28 (1988) 315

82. M Boutonnet, AN Khan-Lodhi, T Towey, Structure and Reactivity in

Reversed Micelles (MP Pileni, ed) Elsevier, Amsterdam and New York,

(1989) 198

83. P Barnickel, A Wokaun, W Sager, J Colloid Interface Sci 148 (1992) 80

84. I Lisiecki, MP Pileni, J Phys Chem 99 (1995) 5077

85. JP Chen, KM Lee, CM Sorensen, KJ Klabunde, GC Hadjipanavis, J Appl

Phys 75 (1994) 5876

86. ZJ Chen, XM Qu, FQ Tang, L Jiang, Colloids Surfaces B Biointerfaces 7

(1996) 173

87. AJI Ward, EC O'Sulivan, JC Rang, J Nedeljkovic, RC Patel, J Colloid

Interface Sci 161 (1993) 316

88. J Eastoe, B Warne, Curr Opin Colloid Interface Sci 1 (1996) 800

89. K Kandori, K Kon-No, A Kitahara, J Colloid Interface Sci 122 (1987) 78

90. K Kandori, K Kon-No, A Kitahara J Dispersion Sci Technol 9 (1988) 61

91. SY Chang, L Liu, SA Asher, J Am Chem Soc 116 (1994) 6739

92. E Joselevich, I Willner, J Phys Chem, 98 (1994) 7628

93. V Chhabra, V Pillai, BK Mishra, A Morrone, DO Shah, Langmuir 11

(1995) 3307

94. T Kawai, A Fujino, K Kon-No, Colloids Surfaces A 100 (1996) 245

95. V Pillai, P Kumar, MS Multani, DO Shah, Colloid Surf A 80 (1993) 695

96. LM Qi, J Ma, H Chen, Z Zhao, J Phys Chem B 101 (1997) 3460

97. W Cai, L Zhang, J Phys Condensed Matter 9 (1997) 7257

Introduction 73

68. L Viculis, J Mack, A Ali, R Luoh, G Yang, R Kaner, Proceedings of the

14th international conference on composite materials (ICCM-14), San

Diego (2003) 138

69. FK Ko, M Gandhi, C Karatzas, Proceedings of the 19th American society

for composites annual technical conference, Atlanta, Georgia, (2004)

70. H Mahfuz, A Adnan, VK Rangari, S Jeelani, BZ Jang, Compos Part A 35

(2004) 519

71. S Kumar, TD Dang, FE Arnold, AR Bhattacharyya, BG Min, XF Zhang,

Macromolecules 35 (2002) 9039

72. DT Colbert, RE Smalley, in E Osawa, editor, Perspectives of fullerene

nanotechnology, Kluwer Academic Publishers (2002) 3

73. DA Walters, MJ Casavant, XC Qin, CB Human, PJ Boul, LM Ericson,

Chem Phys Lett 338 (2001) 14

74. B Wang, Z Liang, KR Shankar, K Bareeld, C Zhang, L Kramer,

Proceedings of the 14th international conference on composite materials

(ICCM-14), San Diego (2003) 422

75. The MicroJetReactor for Producing Nanoparticles, Synthesechemie

GmbH, home.t-online.de/home/penth/ebesch.htm

76. Kava Technology (2004), www.kavatechnology.com/index.html

77. EL Mayes, J Mag Soc Jap 26 (2002) 932

78. KL Choy, In Innovative Processing of Films and Nanocrystalline Powders,

World Scientific Publishing, Singapore (2002)

79. MS Dresselhaus, Carbon nanotubes–Synthesis, Structure, Properties and

Applications, Springer-Verlag, Berlin/Heidelberg (2001)

80. M Boutonnet, J Kizling, P Stenius, G Maire, Colloids Surfaces, 5 (1982) 209

74 Chapter 1

81. R Leung, M Jeng, P Hou, DO Shah, In DT Wasan, ME Ginn, DO Shah

(Eds) Surfactants in Chemical Process Engineering, Marcel Dekker, New

York, Surfactant Sci Ser 28 (1988) 315

82. M Boutonnet, AN Khan-Lodhi, T Towey, Structure and Reactivity in

Reversed Micelles (MP Pileni, ed) Elsevier, Amsterdam and New York,

(1989) 198

83. P Barnickel, A Wokaun, W Sager, J Colloid Interface Sci 148 (1992) 80

84. I Lisiecki, MP Pileni, J Phys Chem 99 (1995) 5077

85. JP Chen, KM Lee, CM Sorensen, KJ Klabunde, GC Hadjipanavis, J Appl

Phys 75 (1994) 5876

86. ZJ Chen, XM Qu, FQ Tang, L Jiang, Colloids Surfaces B Biointerfaces 7

(1996) 173

87. AJI Ward, EC O'Sulivan, JC Rang, J Nedeljkovic, RC Patel, J Colloid

Interface Sci 161 (1993) 316

88. J Eastoe, B Warne, Curr Opin Colloid Interface Sci 1 (1996) 800

89. K Kandori, K Kon-No, A Kitahara, J Colloid Interface Sci 122 (1987) 78

90. K Kandori, K Kon-No, A Kitahara J Dispersion Sci Technol 9 (1988) 61

91. SY Chang, L Liu, SA Asher, J Am Chem Soc 116 (1994) 6739

92. E Joselevich, I Willner, J Phys Chem, 98 (1994) 7628

93. V Chhabra, V Pillai, BK Mishra, A Morrone, DO Shah, Langmuir 11

(1995) 3307

94. T Kawai, A Fujino, K Kon-No, Colloids Surfaces A 100 (1996) 245

95. V Pillai, P Kumar, MS Multani, DO Shah, Colloid Surf A 80 (1993) 695

96. LM Qi, J Ma, H Chen, Z Zhao, J Phys Chem B 101 (1997) 3460

97. W Cai, L Zhang, J Phys Condensed Matter 9 (1997) 7257

Introduction 75

98. L Maya, M Paranthaman, T Thundat, ML Bauer, J Vac Sci Tech B

Microelectronics and Nanometer 14 (1996) 15

99. R Subramanian, PE Denney, J Singh, M Otooni, J Mater Sci 33 (1998)

3471

100. SL Che, K Takada, K Takashima, O Sakurai, K Shinozaki, N Mizutani, J

Mater Sci 34 (1999) 1313

101. K Okuyama, IW Lenggoro, N Tagami, S Tamaki, N Tohge, J Mater Sci 32

(1997) 1229

102. W Li, B Chang, S Qian, X Zou, B Qian, W Zhou, Science 274 (1996)

1701

103. CNR Rao, A Govindaraj, R Sen, BC Satishkumar, Mater Res Innovations

2 (1998) 128

104. G Xiong, X Wang, L Lu, X Yang, Y Xu, J Sol Stat Chem 141(1998) 70

105. YD Jiang, M Phil Thesis, Georgia Institute of Technology (1999)

106. E Matijevic, WP Hsu, J Colloidal and Interface Science 118 (1987) 506

107. YX Huang, CJ Guo, Powder Technology, 72 (1992) 101

108. AS Pathak, D Kulkarni, SK Date, P Pramanik, Nanostruct Mater 8 (1997) 101

109. LL Hench, JK West, Chem Rev 90 (1990) 33

110. U Schubert, J Chem Soc Dalton Trans 33 (1996) 43

111. HH Huang, GL Wilkes, JG Carlson, Polymer 30 (1989) 2001

112. N Varnier, O Hovnanian, A Larbot, P Bergez, L Cot, J Charpin Mater Res

Bullet 29 (1994) 4779

113. C Wang, JY Ying, Chem Mater 11 (1999) 3113

114. W Chang, G Skandan, SC Danforth, BH Kear, H Hahn, Nanostruct Mater 4

(1994a) 507

76 Chapter 1

115. W Chang, G Skandan, H Hahn, SC Danforth, BH Kear, Nanostruct Mater 4

(1994b) 345

116. M Kitamura, M Nishioka, J Oshinowo, Y Arakawa, Jpn J Appl Phys Part 1

34 (1995) 4376

117. F Heinrichsdorff, A Krost, N Kirstaedter, M-H Mao, M Grundmann, D

Bimberg, AO Kosogov, P Werner, Jpn J Appl Phys Part 1 36 (1997) 4129

118. S Ishida, Y Arakawa, K Wada, Appl Phys Lett 72 (1998) 800

119. K Tachibana, T Someya, Y Arakawa, Appl Phys Lett 74 (1999) 383

120. T Seto, K Okuyama, A Hirota, J Aerosol Sci 26 (1995) 5601

121. Y Liu, W Zhu, OK Tan, Y Shen, Mater Sci Eng B B47 (1997) 171

122. Y Liu, W Zhu, OK Tan, X Yao, J Mater Sci Mater in Electronics 7 (1996)

279

123. MK Akhtar, SE Pratsinis, SVR Mastrangelo, J Mater Res 9 (1994) 1241

124. WZ Zhu, M Yan, Mater Chem Phys 53 (1998) 262

125. JP Dekker, PJ van der Put, HJ Veringa, J Schoonman, J Am Ceram Soc

80 (1997) 629

126. M Yudasaka, R Kikuchi, Y Ohki, E Ota, S Yoshimura, Appl Phys Lett 70

(1997) 1817

127. LC Qin, D Zhou, AR Krauss, DM Gruen, Appl Phys Lett 72 (1998) 3437

128. G Che, BB Lakshmi, CR Martin, ER Fisher, Langmuir 15 (1999) 750

129. AG Sutugin, NA Fuchs, J Colloid Interface Sci 27 (1968) 216

130. RC Flagan, MM Lunden, Mat Sci Eng A204 (1995) 113

131. RS Windeler, SK Friedlander, KEJ Lehtinen, Aerosol Sci Tech 27 (1997) 174

132. H Huang, S Yang, G Gu, J Phys Chem B 102 (1998) 3420

Introduction 75

98. L Maya, M Paranthaman, T Thundat, ML Bauer, J Vac Sci Tech B

Microelectronics and Nanometer 14 (1996) 15

99. R Subramanian, PE Denney, J Singh, M Otooni, J Mater Sci 33 (1998)

3471

100. SL Che, K Takada, K Takashima, O Sakurai, K Shinozaki, N Mizutani, J

Mater Sci 34 (1999) 1313

101. K Okuyama, IW Lenggoro, N Tagami, S Tamaki, N Tohge, J Mater Sci 32

(1997) 1229

102. W Li, B Chang, S Qian, X Zou, B Qian, W Zhou, Science 274 (1996)

1701

103. CNR Rao, A Govindaraj, R Sen, BC Satishkumar, Mater Res Innovations

2 (1998) 128

104. G Xiong, X Wang, L Lu, X Yang, Y Xu, J Sol Stat Chem 141(1998) 70

105. YD Jiang, M Phil Thesis, Georgia Institute of Technology (1999)

106. E Matijevic, WP Hsu, J Colloidal and Interface Science 118 (1987) 506

107. YX Huang, CJ Guo, Powder Technology, 72 (1992) 101

108. AS Pathak, D Kulkarni, SK Date, P Pramanik, Nanostruct Mater 8 (1997) 101

109. LL Hench, JK West, Chem Rev 90 (1990) 33

110. U Schubert, J Chem Soc Dalton Trans 33 (1996) 43

111. HH Huang, GL Wilkes, JG Carlson, Polymer 30 (1989) 2001

112. N Varnier, O Hovnanian, A Larbot, P Bergez, L Cot, J Charpin Mater Res

Bullet 29 (1994) 4779

113. C Wang, JY Ying, Chem Mater 11 (1999) 3113

114. W Chang, G Skandan, SC Danforth, BH Kear, H Hahn, Nanostruct Mater 4

(1994a) 507

76 Chapter 1

115. W Chang, G Skandan, H Hahn, SC Danforth, BH Kear, Nanostruct Mater 4

(1994b) 345

116. M Kitamura, M Nishioka, J Oshinowo, Y Arakawa, Jpn J Appl Phys Part 1

34 (1995) 4376

117. F Heinrichsdorff, A Krost, N Kirstaedter, M-H Mao, M Grundmann, D

Bimberg, AO Kosogov, P Werner, Jpn J Appl Phys Part 1 36 (1997) 4129

118. S Ishida, Y Arakawa, K Wada, Appl Phys Lett 72 (1998) 800

119. K Tachibana, T Someya, Y Arakawa, Appl Phys Lett 74 (1999) 383

120. T Seto, K Okuyama, A Hirota, J Aerosol Sci 26 (1995) 5601

121. Y Liu, W Zhu, OK Tan, Y Shen, Mater Sci Eng B B47 (1997) 171

122. Y Liu, W Zhu, OK Tan, X Yao, J Mater Sci Mater in Electronics 7 (1996)

279

123. MK Akhtar, SE Pratsinis, SVR Mastrangelo, J Mater Res 9 (1994) 1241

124. WZ Zhu, M Yan, Mater Chem Phys 53 (1998) 262

125. JP Dekker, PJ van der Put, HJ Veringa, J Schoonman, J Am Ceram Soc

80 (1997) 629

126. M Yudasaka, R Kikuchi, Y Ohki, E Ota, S Yoshimura, Appl Phys Lett 70

(1997) 1817

127. LC Qin, D Zhou, AR Krauss, DM Gruen, Appl Phys Lett 72 (1998) 3437

128. G Che, BB Lakshmi, CR Martin, ER Fisher, Langmuir 15 (1999) 750

129. AG Sutugin, NA Fuchs, J Colloid Interface Sci 27 (1968) 216

130. RC Flagan, MM Lunden, Mat Sci Eng A204 (1995) 113

131. RS Windeler, SK Friedlander, KEJ Lehtinen, Aerosol Sci Tech 27 (1997) 174

132. H Huang, S Yang, G Gu, J Phys Chem B 102 (1998) 3420

Introduction 77

133. WA Saunders, PC Sercel, RB Lee, HA Atwater, KJ Vahala, RC Flagan, J

Escorcia-Aparcia Appl Phys Lett 63 (1993) 1549

134. RP Camata, HA Atwater, KJ Vahala, RC Flagan, Mat Res Soc Symp Proc

405 (1996) 259

135. W Mahoney, RP Andres, Mat Sci Eng A204 (1995) 160

136. W Mahoney, MD Kempe, RP Andres, Mat Res Soc Symp Proc 400 (1996) 65

137. RS Windeler, Thesis, University of California, Los Angeles (1995)

138. T Yoshida, S Takeyama, Y Yamada, K Mutoh, Appl Phys Lett 68 (1996)

1772

139. MS El-Shall, W Slack, W Vann, D Kane, D Hanley, J Phys Chem 98

(1994) 3067

140. S Yatsuya, T Kamakura, K Yamauchi, K Mihama, Jap J Appl Phys 25

(1986) L42

141. M Hirasawa, H Shirakawa, H Hamamura, Y Egashira, H Komiyama, J

Appl Phys 82 (1997) 1404

142. B Wunderlich, Macromol Phys, 2 (1976) 47

143. EP Chang, R Kirsten, EL Sagowski, Polym Eng Sci 18 (1978) 932

144. JJ Bickerman, CC Davis, H Schonhorn, Plastic polymer science and

technology, Ed. M D Baijal, Wiley, New York (1982) 395

145. E Morales, JR White, J Mater Sci 23 (1988) 3612

146. PD Calvert, S Mann, J Mater Sci 23 (1988) 3801

147. KA Mauritz, E Baer, AJ Hopfinger, J Polym Sci Macromol Rev D 13 (1978) 1

148. SK Peneva, JM Schultz, J Polym Sci Polym Phys 25 (1987) 185

149. J Peterman, G Broza, J Mater Sci 22 (1987) 1108

78 Chapter 1

150. A Lowenstam, S Weiner, in Biomineralization, Oxford University Press,

London (1989)

151. MA Crenshaw, in Biological mineralisation and deminerlisation, Ed. GH

Nancollas, Springer, Berlin (1982) 243

152. S Radhakrishnan, SG Joshi, Intern J Polym Mater 11 (1987) 281

153. S Radhakrishnan, JM Schultz, J Crystal Growth 116 (1992) 378

154. C Saujanya, S Radhakrishnan, J Mater Sci 32 (1997) 1069

155. S Mishra, S Sonawane, A Mukherji, HC Mruthyunjaya, J Appl Polym Sci

100 (2006) 4190

156. RA Vaia, EP Giannelis, Macromolecules 30 (1997) 7990

157. RA Vaia, EP Giannelis, Macromolecules 30 (1997) 8000

158. RA Vaia, H Ishii, EP Giannelis, Chem Mater 5 (1993) 1694

159. FL Beyer, NCB Tan, A Dasgupta, ME Galvin, Chem Mater 14 (2002) 2983

160. RA Vaia, S Vasudevan, W Krawiec, LG Scanlon, EP Giannelis, Adv Mater

7 (1995) 154

161. Z Shen, GP Simon, YB Cheng, Polymer 43 (2002) 4251

162. LM Liu, ZN Qi, XG Zhu, J Appl Polym Sci 71(1999) 1133

163. DL VanderHart, A Asano, JW Gilman, Chem Mater 13 (2001) 3781

164. TD Fornes, PJ Yoon, H Keskkula, DR Paul, Polymer 42 (2001) 9929

165. TD Fornes, PJ Yoon, DL Hunter, H Keskkula, DR Paul, Polymer 43 (2002)

5915

166. N Hasegawa, H Okamoto, M Kato, A Usuki, N Sato, Polymer 44 (2003)

2933

167. A Usuki, M Kato, A Okada, T Kurauchi, J Appl Polym Sci 63 (1997) 137

Introduction 77

133. WA Saunders, PC Sercel, RB Lee, HA Atwater, KJ Vahala, RC Flagan, J

Escorcia-Aparcia Appl Phys Lett 63 (1993) 1549

134. RP Camata, HA Atwater, KJ Vahala, RC Flagan, Mat Res Soc Symp Proc

405 (1996) 259

135. W Mahoney, RP Andres, Mat Sci Eng A204 (1995) 160

136. W Mahoney, MD Kempe, RP Andres, Mat Res Soc Symp Proc 400 (1996) 65

137. RS Windeler, Thesis, University of California, Los Angeles (1995)

138. T Yoshida, S Takeyama, Y Yamada, K Mutoh, Appl Phys Lett 68 (1996)

1772

139. MS El-Shall, W Slack, W Vann, D Kane, D Hanley, J Phys Chem 98

(1994) 3067

140. S Yatsuya, T Kamakura, K Yamauchi, K Mihama, Jap J Appl Phys 25

(1986) L42

141. M Hirasawa, H Shirakawa, H Hamamura, Y Egashira, H Komiyama, J

Appl Phys 82 (1997) 1404

142. B Wunderlich, Macromol Phys, 2 (1976) 47

143. EP Chang, R Kirsten, EL Sagowski, Polym Eng Sci 18 (1978) 932

144. JJ Bickerman, CC Davis, H Schonhorn, Plastic polymer science and

technology, Ed. M D Baijal, Wiley, New York (1982) 395

145. E Morales, JR White, J Mater Sci 23 (1988) 3612

146. PD Calvert, S Mann, J Mater Sci 23 (1988) 3801

147. KA Mauritz, E Baer, AJ Hopfinger, J Polym Sci Macromol Rev D 13 (1978) 1

148. SK Peneva, JM Schultz, J Polym Sci Polym Phys 25 (1987) 185

149. J Peterman, G Broza, J Mater Sci 22 (1987) 1108

78 Chapter 1

150. A Lowenstam, S Weiner, in Biomineralization, Oxford University Press,

London (1989)

151. MA Crenshaw, in Biological mineralisation and deminerlisation, Ed. GH

Nancollas, Springer, Berlin (1982) 243

152. S Radhakrishnan, SG Joshi, Intern J Polym Mater 11 (1987) 281

153. S Radhakrishnan, JM Schultz, J Crystal Growth 116 (1992) 378

154. C Saujanya, S Radhakrishnan, J Mater Sci 32 (1997) 1069

155. S Mishra, S Sonawane, A Mukherji, HC Mruthyunjaya, J Appl Polym Sci

100 (2006) 4190

156. RA Vaia, EP Giannelis, Macromolecules 30 (1997) 7990

157. RA Vaia, EP Giannelis, Macromolecules 30 (1997) 8000

158. RA Vaia, H Ishii, EP Giannelis, Chem Mater 5 (1993) 1694

159. FL Beyer, NCB Tan, A Dasgupta, ME Galvin, Chem Mater 14 (2002) 2983

160. RA Vaia, S Vasudevan, W Krawiec, LG Scanlon, EP Giannelis, Adv Mater

7 (1995) 154

161. Z Shen, GP Simon, YB Cheng, Polymer 43 (2002) 4251

162. LM Liu, ZN Qi, XG Zhu, J Appl Polym Sci 71(1999) 1133

163. DL VanderHart, A Asano, JW Gilman, Chem Mater 13 (2001) 3781

164. TD Fornes, PJ Yoon, H Keskkula, DR Paul, Polymer 42 (2001) 9929

165. TD Fornes, PJ Yoon, DL Hunter, H Keskkula, DR Paul, Polymer 43 (2002)

5915

166. N Hasegawa, H Okamoto, M Kato, A Usuki, N Sato, Polymer 44 (2003)

2933

167. A Usuki, M Kato, A Okada, T Kurauchi, J Appl Polym Sci 63 (1997) 137

Introduction 79

168. M Kawasumi, N Hasegawa, M Kato, A Usuki, A Okada, Macromolecules

30 (1997) 6333

169. N Hasegawa, M Kawasumi, M Kato, A Usuki, A Okada, J Appl Polym Sci

67 (1998) 87

170. PH Nam, P Maiti, M Okamoto, T Kotaka, N Hasegawa, A Usuki, Polymer

42 (2001) 9633

171. X Liu, Q Wu, Polymer 42 (2001) 10013

172. PH Nam, P Maiti, M Okamaoto, T Kotaka, Proceedings Nanocomposites,

Chicago, Illinois, USA, ECM Publication (2001)

173. E Manias, A Touny, L Wu, B Lu, K Strawhecker, JW Gilman, TC Chung,

Polym Mater Sci Eng 82 (2000) 282

174. KH Wang, MH Choi, CM Koo, YS Choi, IJ Chung, Polymer 42 (2001)

9819

175. A Usuki, A Tukigase, M Kato Polymer 43 (2002) 2185

176. CH Davis, LJ Mathias, JW Gilman, DA Schiraldi, JR Shields, P Trulove,

TE Sutto, HC Delong, J Polym Sci Part B Polym Phys 40 (2002) 2661

177. SS Ray, P Maiti, M Okamoto, K Yamada, K Ueda, Macromolecules 35

(2002) 3104

178. SS Ray, K Okamoto, K Yamada, M Okamoto, Nano Lett 2 (2002) 423

179. C-M Chan, J Wu, J-X Li, Y-K Cheung, Polymer 43 (2002) 2981

180. CI Park, OO Park, JG Lim, HJ Kim, Polymer 42 (2001) 7465

181. ZS Petrovic, I Javni, A Waddon, G Banhegyi, J Appl Polym Sci 76 (2000)

133

182. MZ Rong, MQ Zhang, YX Zheng, HM Zeng, R Walter, K Friedrich,

Polymer 42 (2001) 167

183. J-X Li, J Wu, CM Chan, Polymer 41 (2000) 6935

80 Chapter 1

184. A Tidjani, CA Wilkie, Polym Degrad Stab 74 (2001) 33.

185. Q Huaili, Z Chungui, Z Shimin, C Guangming, Y Mingshu, Polym Degrad

Stab 81 (2003) 497

186. M Zanetti, P Bracco, L Costa, Polym Degrad Stab 85 (2004) 657

187. AAS Curvelo, AJF De Carvalho, JAM Agnelli, Carbohydr Polym 45 (2001)

183

188. HM Park, X Lee, CZ Jin, CY Park, WJ Cho, CS Ha, Macromol Mater Eng

287 (2002) 533

189. RC Willemse, Material GreenTech 2002, Amsterdam, The Netherlands

(2002)

190. P Nadege, M Alexandre, P Degee, C Calberg, R Jerome, Cloots R, e-

Polymers (2001) 09

191. X Zheng, CA Wilkie, Polym Degrad Stab 82 (2003) 441

192. P Aranda, E Ruiz-Hitzky, Chem Mater 4 (1992) 1395

193. DJ Greenland, J Colloid Sci 18 (1963) 647

194. CW Francis, Soil Sci 115 (1973) 40

195. X Zhao, K Urano, S Ogasawara, Colloid Polym Sci 267 (1989) 899

196. G Jimenez, N Ogata, H Kawai, T Ogihara, J Appl Polym Sci 64 (1997) 2211

197. N Ogata, G Jimenez, H Kawai, T Ogihara, J Polym Sci Part B Polym Phys

35 (1997) 389

198. M Kawasumi, N Hasegawa, A Usuki, A Okada, Mater Sci Eng C 6 (1998) 135

199. HG Jeon, HT Jung, SW Lee, SD Hudson, Polym Bull 41 (1998) 107

200. J Wu, MM Lerner, Chem Mater 5 (1993) 835

201. HJ Choi, SG Kim, YH Hyun, MS Jhon, Macromol Rapid Commun 22

(2001) 320

Introduction 79

168. M Kawasumi, N Hasegawa, M Kato, A Usuki, A Okada, Macromolecules

30 (1997) 6333

169. N Hasegawa, M Kawasumi, M Kato, A Usuki, A Okada, J Appl Polym Sci

67 (1998) 87

170. PH Nam, P Maiti, M Okamoto, T Kotaka, N Hasegawa, A Usuki, Polymer

42 (2001) 9633

171. X Liu, Q Wu, Polymer 42 (2001) 10013

172. PH Nam, P Maiti, M Okamaoto, T Kotaka, Proceedings Nanocomposites,

Chicago, Illinois, USA, ECM Publication (2001)

173. E Manias, A Touny, L Wu, B Lu, K Strawhecker, JW Gilman, TC Chung,

Polym Mater Sci Eng 82 (2000) 282

174. KH Wang, MH Choi, CM Koo, YS Choi, IJ Chung, Polymer 42 (2001)

9819

175. A Usuki, A Tukigase, M Kato Polymer 43 (2002) 2185

176. CH Davis, LJ Mathias, JW Gilman, DA Schiraldi, JR Shields, P Trulove,

TE Sutto, HC Delong, J Polym Sci Part B Polym Phys 40 (2002) 2661

177. SS Ray, P Maiti, M Okamoto, K Yamada, K Ueda, Macromolecules 35

(2002) 3104

178. SS Ray, K Okamoto, K Yamada, M Okamoto, Nano Lett 2 (2002) 423

179. C-M Chan, J Wu, J-X Li, Y-K Cheung, Polymer 43 (2002) 2981

180. CI Park, OO Park, JG Lim, HJ Kim, Polymer 42 (2001) 7465

181. ZS Petrovic, I Javni, A Waddon, G Banhegyi, J Appl Polym Sci 76 (2000)

133

182. MZ Rong, MQ Zhang, YX Zheng, HM Zeng, R Walter, K Friedrich,

Polymer 42 (2001) 167

183. J-X Li, J Wu, CM Chan, Polymer 41 (2000) 6935

80 Chapter 1

184. A Tidjani, CA Wilkie, Polym Degrad Stab 74 (2001) 33.

185. Q Huaili, Z Chungui, Z Shimin, C Guangming, Y Mingshu, Polym Degrad

Stab 81 (2003) 497

186. M Zanetti, P Bracco, L Costa, Polym Degrad Stab 85 (2004) 657

187. AAS Curvelo, AJF De Carvalho, JAM Agnelli, Carbohydr Polym 45 (2001)

183

188. HM Park, X Lee, CZ Jin, CY Park, WJ Cho, CS Ha, Macromol Mater Eng

287 (2002) 533

189. RC Willemse, Material GreenTech 2002, Amsterdam, The Netherlands

(2002)

190. P Nadege, M Alexandre, P Degee, C Calberg, R Jerome, Cloots R, e-

Polymers (2001) 09

191. X Zheng, CA Wilkie, Polym Degrad Stab 82 (2003) 441

192. P Aranda, E Ruiz-Hitzky, Chem Mater 4 (1992) 1395

193. DJ Greenland, J Colloid Sci 18 (1963) 647

194. CW Francis, Soil Sci 115 (1973) 40

195. X Zhao, K Urano, S Ogasawara, Colloid Polym Sci 267 (1989) 899

196. G Jimenez, N Ogata, H Kawai, T Ogihara, J Appl Polym Sci 64 (1997) 2211

197. N Ogata, G Jimenez, H Kawai, T Ogihara, J Polym Sci Part B Polym Phys

35 (1997) 389

198. M Kawasumi, N Hasegawa, A Usuki, A Okada, Mater Sci Eng C 6 (1998) 135

199. HG Jeon, HT Jung, SW Lee, SD Hudson, Polym Bull 41 (1998) 107

200. J Wu, MM Lerner, Chem Mater 5 (1993) 835

201. HJ Choi, SG Kim, YH Hyun, MS Jhon, Macromol Rapid Commun 22

(2001) 320

Introduction 81

202. YH Hyun, ST Lim, HJ Choi, MS Jhon, Macromolecules 34 (2001) 8084

203. SK Lim, JW Kim, I Chin, YK Kwon, HJ Choi, Chem Mater 14 (2002) 1989

204. SD Burnside, EP Giannelis, Chem Mater 7 (1995) 1597

205. K Yano, A Usuki, A Okada, J Polym Sci Part A Polym Chem 35 (1997)

2289

206. R Magaraphan, W Lilayuthalert, A Sirivat, JW Schwank, Compos Sci

Technol 61 (2001) 1253

207. N Ogata, G Jimenez, H Kawai, T Ogihara, J Polym Sci Part B Polym Phys

35 (1997) 389

208. KE Strawhecker, E Manias, Chem Mater 12 (2000) 2943

209. A Wheeler, US Pat 2847 (1958) 391

210. N Ogata, S Kawakage, T Ogihara, J Appl Polym Sci 66 (1997) 573

211. J Ren, AS Silva, R Krishnamoorti, Macromolecules 33 (2000) 3739

212. CA Mitchell, R Krishnamoorti, J Polym Sci Part B Polym Phys 40 (2002)

1434

213. CJG Plummer, L Garamszegi, Y Leterrier, M Rodlert, JAE Manson, Chem

Mater 14 (2002) 486

214. PHT Vollenberg, D Heikens, Polymer 30 (1989) 1656

215. JK Pandey, RP Singh, Starch/Starke, 2004, in press.

216. HC Lee, TW Lee, YT Lim, OO Park, Appl Clay Sci 21 (2002) 287

217. A Blumstein, J Polym Sci A 3 (1965) 2665

218. BKG Theng, Formation and properties of clay–polymer complexes,

Elsevier, Amsterdam (1979)

82 Chapter 1

219. A Okada, M Kawasumi, A Usuki, Y Kojima, T Kurauchi, O Kamigaito, In:

DW Schaefer, JE Mark, editors, MRS Symposium Proceedings,

Pittsburgh, 171 (1990) 45

220. A Usuki, M Kawasumi, Y Kojima, A Okada, T Kurauchi, O Kamigaito, J

Mater Res 8 (1993) 1174

221. A Usuki, Y Kojima, M Kawasumi, A Okada, Y Fukushima, T Kurauchi, O

Kamigaito, J Mater Res 8 (1993) 1179

222. Y Kojima, A Usuki, M Kawasumi, A Okada, T Kurauchi, O Kamigaito, J

Polym Sci Part A Polym Chem 31 (1993) 1755

223. P Reichert, J Kressler, R Thomann, R Mulhaupt, G Stoppelmann, Acta

Polym 49 (1998) 116

224. PB Messersmith, EP Giannelis, Chem Mater 5 (1993) 1064

225. B Lepoittevin, N Pantoustier, M Devalckenaere, M Alexandre, D Kubies, C

Calderg, R Jerome, P Dubois, Macromolecules 35 (2002) 8385

226. Z Wang, TJ Pinnavaia, Chem Mater 10 (1998) 3769

227. TK Chen, YI Tien, KH Wei, J Polym Sci Part A Polym Chem 37 (1999)

2225

228. KJ Yao, M Song, DJ Hourston, DZ Luo, Polymer 43 (2002) 1017

229. M Okamoto, S Morita, H Taguchi, YH Kim, T Kotaka, H Tateyama,

Polymer 41 (2000) 3887

230. M Okamoto, S Morita, T Kotaka, Polymer 42 (2001) 2685

231. J Tudor, L Willington, D O’Hare, B Royan, Chem Commun (1996) 2031

232. T Sun, JM Garces, Adv Mater 14 (2002) 128

233. JS Bergman, H Chen, EP Giannelis, MG Thomas, GW Coates, J Chem

Soc Chem Commun 21 (1999) 2179

234. Y-H Jin, H-J Park, S-S Im, S-Y Kwak, S Kwak, Macromol Rapid Commun

23 (2002) 135

Introduction 81

202. YH Hyun, ST Lim, HJ Choi, MS Jhon, Macromolecules 34 (2001) 8084

203. SK Lim, JW Kim, I Chin, YK Kwon, HJ Choi, Chem Mater 14 (2002) 1989

204. SD Burnside, EP Giannelis, Chem Mater 7 (1995) 1597

205. K Yano, A Usuki, A Okada, J Polym Sci Part A Polym Chem 35 (1997)

2289

206. R Magaraphan, W Lilayuthalert, A Sirivat, JW Schwank, Compos Sci

Technol 61 (2001) 1253

207. N Ogata, G Jimenez, H Kawai, T Ogihara, J Polym Sci Part B Polym Phys

35 (1997) 389

208. KE Strawhecker, E Manias, Chem Mater 12 (2000) 2943

209. A Wheeler, US Pat 2847 (1958) 391

210. N Ogata, S Kawakage, T Ogihara, J Appl Polym Sci 66 (1997) 573

211. J Ren, AS Silva, R Krishnamoorti, Macromolecules 33 (2000) 3739

212. CA Mitchell, R Krishnamoorti, J Polym Sci Part B Polym Phys 40 (2002)

1434

213. CJG Plummer, L Garamszegi, Y Leterrier, M Rodlert, JAE Manson, Chem

Mater 14 (2002) 486

214. PHT Vollenberg, D Heikens, Polymer 30 (1989) 1656

215. JK Pandey, RP Singh, Starch/Starke, 2004, in press.

216. HC Lee, TW Lee, YT Lim, OO Park, Appl Clay Sci 21 (2002) 287

217. A Blumstein, J Polym Sci A 3 (1965) 2665

218. BKG Theng, Formation and properties of clay–polymer complexes,

Elsevier, Amsterdam (1979)

82 Chapter 1

219. A Okada, M Kawasumi, A Usuki, Y Kojima, T Kurauchi, O Kamigaito, In:

DW Schaefer, JE Mark, editors, MRS Symposium Proceedings,

Pittsburgh, 171 (1990) 45

220. A Usuki, M Kawasumi, Y Kojima, A Okada, T Kurauchi, O Kamigaito, J

Mater Res 8 (1993) 1174

221. A Usuki, Y Kojima, M Kawasumi, A Okada, Y Fukushima, T Kurauchi, O

Kamigaito, J Mater Res 8 (1993) 1179

222. Y Kojima, A Usuki, M Kawasumi, A Okada, T Kurauchi, O Kamigaito, J

Polym Sci Part A Polym Chem 31 (1993) 1755

223. P Reichert, J Kressler, R Thomann, R Mulhaupt, G Stoppelmann, Acta

Polym 49 (1998) 116

224. PB Messersmith, EP Giannelis, Chem Mater 5 (1993) 1064

225. B Lepoittevin, N Pantoustier, M Devalckenaere, M Alexandre, D Kubies, C

Calderg, R Jerome, P Dubois, Macromolecules 35 (2002) 8385

226. Z Wang, TJ Pinnavaia, Chem Mater 10 (1998) 3769

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2225

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229. M Okamoto, S Morita, H Taguchi, YH Kim, T Kotaka, H Tateyama,

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235. M Alexandre, P Dubois, T Sun, JM Graces, R Jerome, Polymer 43 (2002)

2123

236. J Heinemann, P Reichert, R Thomson, R Mulhaupt, Macromol Rapid

Commun 20 (1999) 423

237. TY Tsai, Polyethylene terephthalate–clay nanocomposites, In: TJ

Pinnavaia, GW Beall, editors, Polymer–clay nanocomposites, Wiley

(2000) 173

238. CH Davis, LJ Mathias, JW Gilman, DA Schiraldi, JR Shields, P Trulove,

TE Sutto, HC Delong, J Polym Sci Part B Polym Phys 40 (2002) 2661

239. Y Imai, S Nishimura, E Abe, H Tateyama, A Abiko, A Yamaguchi, T

Aoyama, H Taguchi, Chem Mater 14 (2002) 477

240. PB Messersmith, EP Giannelis, Chem Mater 6 (1994) 1719

241. T Lan, TJ Pinnavaia, Chem Mater 6 (1994) 2216

242. MS Wang, TJ Pinnavaia, Chem Mater 6 (1994) 468

243. Z Wang, T Lan, TJ Pinnavaia, Chem Mater 8 (1996) 2200

244. C Zilg, R Mulhaupt, J Finter, Macromol Chem Phys 200 (1999) 661

245. X Kornmann, R Thomann, R Mulhaupt, J Finter, LA Berglund, Polym Eng

Sci 42 (2002) 1815

246. F Yang, Y Ou, Z Yu, J Appl Polym Sci 69 (1998) 355

247. BJ Ash, J Stone, DF Rogers, LS Schadler, RW Siegel, BC Benicewicz, T

Apple, Mater Res Soc Symp Proc 661 (2000) 1211

248. BJ Ash, LS Schadler, RW Siegel, Mater Lett 55 (2002) 83

249. RW Siegel, SK Chang, BJ Ash, J Stone, PM Ajayan, RW Doremus, LS

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250. J Rong, Z Jing, H Li, M Sheng, Macromol Rapid Commun 22 (2001) 329

251. PB Messersmith, EP Giannelis, J Polym Sci A Polym Chem 33 (1995) 1047

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252. F Gao, J Mater Sci Lett 20 (2001) 1807

253. P Musto, Polymer 45 (2004) 1697

254. Y Kojima, A Usuki, M Kawasumi, A Okada, Y Fukushima, T Kurauchi, O

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255. LM Liu, ZN Qi, XG Zhu, J Appl Polym Sci 71 (1999) 1133

256. P Reichert, H Nitz, S Klinke, R Brandsch, R Thomann, R Mulhaupt,

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257. SS Ray, K Yamada, M Okamoto, K Ueda, Polymer 44 (2003) 857

258. C-M Chan, J Wu, J-X Li, Y-K Cheung, Polymer 43 (2002) 2981

259. JS Shelley, PT Mather, KL DeVries, Polymer 42 (2001) 5849

260. K Masenelli-Varlot, E Reynaud, G Vigier, J Varlet, J Polym Sci B Polym

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264. W Dong, X Zhang, Y Liu, H Gui, Q Wang, J Gao, Z Song, J Lai, F Huang,

J Qiao, Polym Int (in press)

265. VE Yudin, JU Otaigbe, S Gladchenko, BG Olson, S Nazarenko, EN

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266. M Avella, M E Errico, G Gentile, Macromol Symp 247 (2007) 140

267. DPN Vlasveld, W Daud, HEN Bersee, SJ Picken, Compos Part A 38

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268. H Akita, T Hattori, J Polym Sci B Polym Phys 37 (1999) 189

269. H Akita, H Kobayashi, J Polym Sci B Polym Phys 37 (1999) 209

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235. M Alexandre, P Dubois, T Sun, JM Graces, R Jerome, Polymer 43 (2002)

2123

236. J Heinemann, P Reichert, R Thomson, R Mulhaupt, Macromol Rapid

Commun 20 (1999) 423

237. TY Tsai, Polyethylene terephthalate–clay nanocomposites, In: TJ

Pinnavaia, GW Beall, editors, Polymer–clay nanocomposites, Wiley

(2000) 173

238. CH Davis, LJ Mathias, JW Gilman, DA Schiraldi, JR Shields, P Trulove,

TE Sutto, HC Delong, J Polym Sci Part B Polym Phys 40 (2002) 2661

239. Y Imai, S Nishimura, E Abe, H Tateyama, A Abiko, A Yamaguchi, T

Aoyama, H Taguchi, Chem Mater 14 (2002) 477

240. PB Messersmith, EP Giannelis, Chem Mater 6 (1994) 1719

241. T Lan, TJ Pinnavaia, Chem Mater 6 (1994) 2216

242. MS Wang, TJ Pinnavaia, Chem Mater 6 (1994) 468

243. Z Wang, T Lan, TJ Pinnavaia, Chem Mater 8 (1996) 2200

244. C Zilg, R Mulhaupt, J Finter, Macromol Chem Phys 200 (1999) 661

245. X Kornmann, R Thomann, R Mulhaupt, J Finter, LA Berglund, Polym Eng

Sci 42 (2002) 1815

246. F Yang, Y Ou, Z Yu, J Appl Polym Sci 69 (1998) 355

247. BJ Ash, J Stone, DF Rogers, LS Schadler, RW Siegel, BC Benicewicz, T

Apple, Mater Res Soc Symp Proc 661 (2000) 1211

248. BJ Ash, LS Schadler, RW Siegel, Mater Lett 55 (2002) 83

249. RW Siegel, SK Chang, BJ Ash, J Stone, PM Ajayan, RW Doremus, LS

Schadler, Scr Mater 44 (2001) 2061

250. J Rong, Z Jing, H Li, M Sheng, Macromol Rapid Commun 22 (2001) 329

251. PB Messersmith, EP Giannelis, J Polym Sci A Polym Chem 33 (1995) 1047

84 Chapter 1

252. F Gao, J Mater Sci Lett 20 (2001) 1807

253. P Musto, Polymer 45 (2004) 1697

254. Y Kojima, A Usuki, M Kawasumi, A Okada, Y Fukushima, T Kurauchi, O

Kamigaito, J Mater Res 8 (1993) 1185

255. LM Liu, ZN Qi, XG Zhu, J Appl Polym Sci 71 (1999) 1133

256. P Reichert, H Nitz, S Klinke, R Brandsch, R Thomann, R Mulhaupt,

Macromol Mater Eng 275 (2000) 8

257. SS Ray, K Yamada, M Okamoto, K Ueda, Polymer 44 (2003) 857

258. C-M Chan, J Wu, J-X Li, Y-K Cheung, Polymer 43 (2002) 2981

259. JS Shelley, PT Mather, KL DeVries, Polymer 42 (2001) 5849

260. K Masenelli-Varlot, E Reynaud, G Vigier, J Varlet, J Polym Sci B Polym

Phys 40 (2002) 272

261. B Cotterell, JYH Chia, K Hbaieb, Eng Fracture Mech 74 (2007) 1054

262. IA Guz, AA Rodger, AN Guz, JJ Rushchitsky, Compos Part A 38 (2007)

1234

263. YQ Rao, JM Pochan, Macromolecules 40 (2007) 290

264. W Dong, X Zhang, Y Liu, H Gui, Q Wang, J Gao, Z Song, J Lai, F Huang,

J Qiao, Polym Int (in press)

265. VE Yudin, JU Otaigbe, S Gladchenko, BG Olson, S Nazarenko, EN

Korytkova, VV Gusarov, Polymer 48 (2007) 1306

266. M Avella, M E Errico, G Gentile, Macromol Symp 247 (2007) 140

267. DPN Vlasveld, W Daud, HEN Bersee, SJ Picken, Compos Part A 38

(2007) 730

268. H Akita, T Hattori, J Polym Sci B Polym Phys 37 (1999) 189

269. H Akita, H Kobayashi, J Polym Sci B Polym Phys 37 (1999) 209

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270. H Akita, H Kobayashi, T Hattori, K Kagawa, J Polym Sci B Polym Phys 37

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271. J-H Chang, YU An, J Polym Sci B Polym Phys 40 (2002) 670

272. J Jordan, KI Jacob, R Tannenbaum, MA Sharaf, I Jasiuk, Mater Sci Eng A

393 (2005) 1

273. SS Ray, K Okamoto, M Okamoto, Macromolecules 36 (2003) 2355

274. M Okamoto, PH Nam, N Hasegawa, A Usuki, Macromol Mater Eng

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275. L Priya, JP Jog, J Polym Sci B Polym Phys 40 (2002) 1682

276. JH Park, SC Jana, Macromolecules 36 (2003) 2758

277. Y Kojima, A Usuki, M Kawasumi, A Okada, T Kurauchi, O Kamigaito, J

Polym Sci Part A Polym Chem 31 (1993) 983

278. D Acierno, E Amendola, P Russo, Macromol Symp 247 (2007) 156

279. S H Nair, K C Pawar, J P Jog, M V Badiger, J Appl Polym Sci 103 (2007)

2896

280. S Xie, S Zhang, F Wang, H Liu, M Yang, Polym Eng Sci 45 (2005) 1247

281. M Biswas, SS Ray, Adv Polym Sci 155 (2001) 167

282. EP Giannelis, Appl Organomet Chem 12 (1998) 675

283. JW Gilman, Appl Clay Sci 15 (1999) 31

284. GS Sur, HL Sun, SG Lyu, JE Mark, Polymer 42 (2001) 9783

285. JT Yoon, WH Jo, MS Lee, MB Ko, Polymer 42 (2001) 329

286. YT Vu, JE Mark, LH Pham, M Engelhardt, J Appl Polym Sci 82 (2001) 1392

287. C Aymonier, D Bortzmeyer, R Thomann, R Mulhaupt, Chem Mater 15

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86 Chapter 1

288. M Zanetti, G Camino, P Reichert, R Mulhaupt, Macromol Rapid Commun

22 (2002) 176

289. RD Davis, JW Gilman, DL VanderHart, Polym Degrad Stab 79 (2003) 111

290. KP Pramoda, L Tianxi, L Zhehui, H Chaobin, S Hung-Jue, Polym Degrad

Stab 81 (2003) 47

291. JW Gilman, T Kashiwagi, JET Brown, S Lomakin, SAMPE J 33 (1997) 40

292. JX Du, DY Wang, CA Wilkie, JQ Wang, Polym Degrad Stab 79 (2003) 319

293. D Acierno, E Amendola, G Callegaro, G Napolitano, Macromol Symp 247

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294. S Varghese, J Karger-Kocsis, KG Gatos, Polymer 44 (2003) 3977

295. A Harrane, M Belbachir, Macromol Symp 247 (2007) 379

296. D Lee, K Char, Polym Degrad Stab 75 (2002) 555

297. A Gu, G Liang, Polym Degrad Stab 80 (2003) 383

298. TJ Pinnavaia, GW Beall, Polymer clay nanocomposites, Chichester/New

York, Wiley, (2000) 158

299. S Fujiwara, T Sakamoto, Kokai patent application, SHO511976-109998

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300. F Dabrowski, ML Bras, S Bourbigot, JW Gilman, T Kashiwagi,

Proceedings of the Euro- fillers’99, Lyon-Villeurbanne, France (1999)

301. S Bourbigot, M LeBras, F Dabrowski, JW Gilman, T Kashiwagi, Fire Mater

24 (2000) 201

302. JW Gilman, CL Jackson, AB Morgan, R Harris Jr, E Manias, EP Giannelis,

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303. B Schartel, M Bartholmai, U Knoll, Polym Adv Technol 17 (2006) 772

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270. H Akita, H Kobayashi, T Hattori, K Kagawa, J Polym Sci B Polym Phys 37

(1999) 199

271. J-H Chang, YU An, J Polym Sci B Polym Phys 40 (2002) 670

272. J Jordan, KI Jacob, R Tannenbaum, MA Sharaf, I Jasiuk, Mater Sci Eng A

393 (2005) 1

273. SS Ray, K Okamoto, M Okamoto, Macromolecules 36 (2003) 2355

274. M Okamoto, PH Nam, N Hasegawa, A Usuki, Macromol Mater Eng

Submitted for publication.

275. L Priya, JP Jog, J Polym Sci B Polym Phys 40 (2002) 1682

276. JH Park, SC Jana, Macromolecules 36 (2003) 2758

277. Y Kojima, A Usuki, M Kawasumi, A Okada, T Kurauchi, O Kamigaito, J

Polym Sci Part A Polym Chem 31 (1993) 983

278. D Acierno, E Amendola, P Russo, Macromol Symp 247 (2007) 156

279. S H Nair, K C Pawar, J P Jog, M V Badiger, J Appl Polym Sci 103 (2007)

2896

280. S Xie, S Zhang, F Wang, H Liu, M Yang, Polym Eng Sci 45 (2005) 1247

281. M Biswas, SS Ray, Adv Polym Sci 155 (2001) 167

282. EP Giannelis, Appl Organomet Chem 12 (1998) 675

283. JW Gilman, Appl Clay Sci 15 (1999) 31

284. GS Sur, HL Sun, SG Lyu, JE Mark, Polymer 42 (2001) 9783

285. JT Yoon, WH Jo, MS Lee, MB Ko, Polymer 42 (2001) 329

286. YT Vu, JE Mark, LH Pham, M Engelhardt, J Appl Polym Sci 82 (2001) 1392

287. C Aymonier, D Bortzmeyer, R Thomann, R Mulhaupt, Chem Mater 15

(2003) 4874

86 Chapter 1

288. M Zanetti, G Camino, P Reichert, R Mulhaupt, Macromol Rapid Commun

22 (2002) 176

289. RD Davis, JW Gilman, DL VanderHart, Polym Degrad Stab 79 (2003) 111

290. KP Pramoda, L Tianxi, L Zhehui, H Chaobin, S Hung-Jue, Polym Degrad

Stab 81 (2003) 47

291. JW Gilman, T Kashiwagi, JET Brown, S Lomakin, SAMPE J 33 (1997) 40

292. JX Du, DY Wang, CA Wilkie, JQ Wang, Polym Degrad Stab 79 (2003) 319

293. D Acierno, E Amendola, G Callegaro, G Napolitano, Macromol Symp 247

(2007) 120

294. S Varghese, J Karger-Kocsis, KG Gatos, Polymer 44 (2003) 3977

295. A Harrane, M Belbachir, Macromol Symp 247 (2007) 379

296. D Lee, K Char, Polym Degrad Stab 75 (2002) 555

297. A Gu, G Liang, Polym Degrad Stab 80 (2003) 383

298. TJ Pinnavaia, GW Beall, Polymer clay nanocomposites, Chichester/New

York, Wiley, (2000) 158

299. S Fujiwara, T Sakamoto, Kokai patent application, SHO511976-109998

(1976)

300. F Dabrowski, ML Bras, S Bourbigot, JW Gilman, T Kashiwagi,

Proceedings of the Euro- fillers’99, Lyon-Villeurbanne, France (1999)

301. S Bourbigot, M LeBras, F Dabrowski, JW Gilman, T Kashiwagi, Fire Mater

24 (2000) 201

302. JW Gilman, CL Jackson, AB Morgan, R Harris Jr, E Manias, EP Giannelis,

M Wuthenow, D Hilton, SH Phillips, Chem Mater 12 (2000) 1866

303. B Schartel, M Bartholmai, U Knoll, Polym Adv Technol 17 (2006) 772

304. R Zong, Y Hu, N Liu, S Li, G Liao, J Appl Polym Sci 104 (2007) 2297

305. R Barbosa, EM Araújo, TJA Melo, EN Ito, Mater Lett (in press)

Introduction 87

306. S Zhang, TR Hull, AR Horrocks, G Smart, BK Kandola, J Ebdon, P

Joseph, B Hunt, Polym Degrad Stab xx (2007) 1

307. G Guo, CB Park, YH Lee, YS Kim, M Sain, Polym Eng Sci 47 (2007) 330

308. K Yano, A Usuki, A Okada, T Kurauchi, O Kamigaito, J Polym Sci Part A

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309. K Yano, A Usuki, A Okada, T Kurauchi, O Kamigaito, Polym Prepr (Jpn)

32 (1991) 65

310. SS Ray, K Yamada, M Okamoto, A Ogami, K Ueda, Chem Mater 15

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311. R Xu, E Manias, AJ Snyder, J Runt, Macromolecules 34 (2001) 337

312. RK Bharadwaj, Macromolecules 34 (2001) 1989

313. Y Lu, RC Larock, Biomacromolecules 7 (2006) 2692

314. T Ogasawara, Y Ishida, T Ishikawa, T Aoki, T Ogura, Compos Part A 37

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315. E Picard, A Vermogen, J-F G´erard, E Espuche, J Memb Sci (2007) in

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316. E Picard, H Gauthier, J-F Gérard, E Espuche, J Colloid Interface Sci 307

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317. C M Small, G M McNally, P McShane, IKenny, J Vinyl Addit Technol 13

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318. V Vladimirov, C Betchev, A Vassiliou, G Papageorgiou, D Bikiaris,

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319. P Maiti, AB Carl, EP Giannelis, Polym Mater Sci Eng 88 (2003) 59

320. Y Deng, A Gu, Z Fang, Polym Int 53 (2004) 85

321. C Guan, C-L Lu, Y-F Liu, B Yang, J Appl Polym Sci 102 (2006) 1631

88 Chapter 1

322. A Rahimi, S Gharazi, A Ershad-Langroudi, D Ghasemi, J Appl Polym Sci

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323. Y Peneva, E Tashev, L Minkova, Eur Polym J 42 (2006) 2228

324. W Chen, L Feng, B Qu, Solid State Commun 130 (2004) 259

325. K Asuka, B Liu, M Terano, Ki Nitta, Macromol Rapid Commun 27 (2006) 910

326. T Wang, CH Lei, AB Dalton, C Creton, Y Lin, KAS Fernando, YP Sun, M

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330. SS Ray, K Yamada, M Okamoto, K Ueda, Nano Lett 2 (2002) 1093

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332. TM Wu, CY Wu, Polym Degrad Stab 91 (2006) 2198

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336. R Krishnamoorti, EP Giannelis, Macromolecules 30 (1997) 4097

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Introduction 87

306. S Zhang, TR Hull, AR Horrocks, G Smart, BK Kandola, J Ebdon, P

Joseph, B Hunt, Polym Degrad Stab xx (2007) 1

307. G Guo, CB Park, YH Lee, YS Kim, M Sain, Polym Eng Sci 47 (2007) 330

308. K Yano, A Usuki, A Okada, T Kurauchi, O Kamigaito, J Polym Sci Part A

Polym Chem 31 (1993) 2493

309. K Yano, A Usuki, A Okada, T Kurauchi, O Kamigaito, Polym Prepr (Jpn)

32 (1991) 65

310. SS Ray, K Yamada, M Okamoto, A Ogami, K Ueda, Chem Mater 15

(2003) 1456

311. R Xu, E Manias, AJ Snyder, J Runt, Macromolecules 34 (2001) 337

312. RK Bharadwaj, Macromolecules 34 (2001) 1989

313. Y Lu, RC Larock, Biomacromolecules 7 (2006) 2692

314. T Ogasawara, Y Ishida, T Ishikawa, T Aoki, T Ogura, Compos Part A 37

(2006) 2236

315. E Picard, A Vermogen, J-F G´erard, E Espuche, J Memb Sci (2007) in

press

316. E Picard, H Gauthier, J-F Gérard, E Espuche, J Colloid Interface Sci 307

(2007) 364

317. C M Small, G M McNally, P McShane, IKenny, J Vinyl Addit Technol 13

(2007) 46

318. V Vladimirov, C Betchev, A Vassiliou, G Papageorgiou, D Bikiaris,

Compos Sci Technol 66 (2006) 2935

319. P Maiti, AB Carl, EP Giannelis, Polym Mater Sci Eng 88 (2003) 59

320. Y Deng, A Gu, Z Fang, Polym Int 53 (2004) 85

321. C Guan, C-L Lu, Y-F Liu, B Yang, J Appl Polym Sci 102 (2006) 1631

88 Chapter 1

322. A Rahimi, S Gharazi, A Ershad-Langroudi, D Ghasemi, J Appl Polym Sci

102 (2006) 5322

323. Y Peneva, E Tashev, L Minkova, Eur Polym J 42 (2006) 2228

324. W Chen, L Feng, B Qu, Solid State Commun 130 (2004) 259

325. K Asuka, B Liu, M Terano, Ki Nitta, Macromol Rapid Commun 27 (2006) 910

326. T Wang, CH Lei, AB Dalton, C Creton, Y Lin, KAS Fernando, YP Sun, M

Manea, JM Asua, JL Keddie, Adv Mater 18 (2006) 2730

327. JLH Chau, YM Lin, AK Li, WF Su, KS Chang, SLC Hsu, TL Li, Mater Lett

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328. JA Tetto, DM Steeves, EA Welsh, BE Powell, ANTEC (1999) 1628

329. SR Lee, HM Park, HL Lim, T Kang, X Li, WJ Cho, CS Ha, Polymer 43

(2002) 2495

330. SS Ray, K Yamada, M Okamoto, K Ueda, Nano Lett 2 (2002) 1093

331. SS Ray, M Okamoto, Macromol Mater Eng 288 (2003) 936

332. TM Wu, CY Wu, Polym Degrad Stab 91 (2006) 2198

333. U Hiroshi, K Mai, T Takashi, N Mitsuru, U Arimitsu, K Shiro, Chem Mater

15 (2003) 2492

334. SS Ray, K Okamoto, P Maiti, M Okamoto, J Nanosci Nanotechnol (2002)

2171

335. A Ammala, AJ Hill, KA Lawrence, T Tran, J Appl Polym Sci 104 (2007)

1377

336. R Krishnamoorti, EP Giannelis, Macromolecules 30 (1997) 4097

337. G Galgali, C Ramesh, A Lele, Macromolecules 34 (2001) 852

338. JW Kim, SG Kim, HJ Choi, MS Jhon, Macromol Rapid Commun 20 (1999) 450

339. RA Vaia, G Price, PN Ruth, HT Nguyen, J Lichtenhan, Appl Clay Sci 15

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VI Tomilo, YP Gomza, Polymer 46 (2005) 12226

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372. Y Wang, J Xu, SE Bechtel, KW Koelling, Rheol Acta 45 (2006) 919

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374. S Qutubuddin, X Fu, Y Tajuddin, Polym Bull 48 (2002) 143

375. YT Lim, OO Park, Rheol Acta 40 (2001) 220

376. M Xiao, L Sun, J Liu, Y Li, K Gong, Polymer 43 (2002) 2245

377. S Chattopadhyay, A Datta, Synth Metals 155 (2005) 365

378. G Chigwada, D Wang, DD Jiang, CA Wilkie, Polym Degrad Stab 91

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379. X Zheng, CA Wilkie, Polym Degrad Stab 81 (2003) 539

380. WA Zhang, DZ Chen, HY Xu, XF Shen, YE Fang, Eur Polym J 39 (2003)

2323

381. J Zhang, X Wang, L Lu, D Li, X Yang, J Appl Polym Sci 87 (2003) 381

382. MV Burmistr, KM Sukhyy, VV Shilov, P Pissis, A Spanoudaki, IV Sukha,

VI Tomilo, YP Gomza, Polymer 46 (2005) 12226

383. CP Li, CM Huang, MT Hsieh, KH Wei, J Polym Sci Part A: Polym Chem

43 (2005) 534

384. CI Park, WM Choi, MH Kim, OO Park, J Polym Sci Part B: Polym Phys 42

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385. S Tanoue, LA Utracki, A Garcia-Rejon, J Tatibouet, KC Cole, MR Kamal,

Polym Eng Sci, 44 (2004) 1046

386. S Tanoue, LA Utracki, A Garcia-Rejon, P Sammut, MT Ton-That, I Pesneau,

MR Kamal, J Lyngaae-Jørgensen, Polym Eng Sci, 44 (2004) 1061

387. S Tanoue, LA Utracki, A Garcia-Rejon, J Tatibouet, MR Kamal, Polym

Eng Sci, 45 (2005) 827

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388. MJ Chang, JY Tsai, CW Chang, HM Chang, GJ Jiang, J Appl Polym Sci

103 (2007) 3680

389. YT Lim, OO Park, Macromol Rapid Commun 21 (2000) 231

390. SD Argoti, S Reeder, H Zhao, DA Shipp, Polym Prepr 43 (2002) 267

391. H Zhao, SD Argoti, BP Farrell, DA Shipp, J Polym Sci Part A: Polym

Chem 42 (2004) 916

392. JW Gilman, S Bourbigot, JR Shields, M Nyden, T Kashiwagi, RD Davis,

DL Vanderhart, W Demory, CA Wilkie, AB Morgan, J Harris, RE Lyon, J

Mater Sci 38 (2003) 4451

393. P Badheka, V Magadala, NG Devaraju, BI Lee, ES Kim, J Appl Polym Sci

99 (2006) 2815

394. O Morales-Teyssier, S Sanchez-Valdes, LF Ramos-de Valle, Macromol

Mater Eng 291 (2006) 1547

395. M Mukherjee, N Deshmukh, SK Kulkarni, Appl Surface Sci 218 (2003) 323

396. FA Bottino, E Fabbri, IL Fragala, G Malandrino, A Orestano, F Pilati, A

Pollicino, Macromol Rapid Commun 24 (2003) 1079

397. JM Yeh, SJ Liou, CG Lin, YP Chang, YH Yu, CF Cheng, J Appl Polym Sci

92 (2004) 1970

398. HW Wang, KC Chang, JM Yeh, SJ Liou, J Appl Polym Sci 91 (2004) 1368

399. HW Wang, KC Chang, HC Chu, SJ Liou, JM Yeh, J Appl Polym Sci 92

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404. HA Essawy, AS Badran, AM Youssef, AA Abd El-Hakim, Macromol Chem

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409. TH Kim, ST Lim, CH Lee, HJ Choi, MS Jhon, J Appl Polym Sci 87 (2003)

2106

410. AB Morgan, JD Harris, Polymer 45 (2004) 8695

411. JM Hwu, TH Ko, WT Yang, JC Lin, GJ Jiang, W Xie, WP Pan, J Appl

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412. S Bellayer, JW Gilman, N Eidelman, S Bourbigot, X Flambard, DM Fox,

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413. TE Chang, A Kisliuk, SM Rhodes, WJ Brittain, AP Sokolov, Polymer 47

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414. CC Hsiao, TS Lin, LY Cheng, CCM Ma, ACM Yang, Macromolecules 38

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417. Z Wang, G Xie, X Wang, Z Zhang, J Appl Polym Sci 100 (2006) 4434

418. G Chigwada, P Jash, DD Jiang, CA Wilkie, Polym Degrad Stab 88 (2005)

382

419. GH Chen, DJ Wu, WG Weng, B He, Wl Yan, Polym Int 50 (2001) 980

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420. C Celik, SB Warner, J Appl Polym Sci 103 (2007) 645

421. FM Uhl, CA Wilkie, Polym Degrad Stab 76 (2002) 111

422. O Meincke, B Hoffmann, C Dietrich, C Friedrich, Macromol Chem Phys

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428. X Fu, S Qutubuddin, Polymer 42 (2001) 807

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431. TH Kim, LW Jang, DC Lee, HJ Choi, MS Jhon, Macromol Rapid Commun

23 (2002) 191

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437. Y Rong, HZ Chen, G Wu, M Wang, Mater Chem Phys 91 (2005) 370

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404. HA Essawy, AS Badran, AM Youssef, AA Abd El-Hakim, Macromol Chem

Phys 205 (2004) 2366

405. Y Li, H Ishida, Macromolecules 38 (2005) 6513

406. N Hasegawa, H Okamoto, M Kawasumi, A Usuki, J Appl Polym Sci 74

(1999) 3359

407. J Zhang, DD Jiang, D Wang, CA Wilkie, Polym Adv Technol 16 (2005) 800

408. D Wang, CA Wilkie, Polym Degrad Stab 80 (2003) 171

409. TH Kim, ST Lim, CH Lee, HJ Choi, MS Jhon, J Appl Polym Sci 87 (2003)

2106

410. AB Morgan, JD Harris, Polymer 45 (2004) 8695

411. JM Hwu, TH Ko, WT Yang, JC Lin, GJ Jiang, W Xie, WP Pan, J Appl

Polym Sci 91 (2004) 101

412. S Bellayer, JW Gilman, N Eidelman, S Bourbigot, X Flambard, DM Fox,

HC DeLong, PC Trulove, Adv Funct Mater 15 (2005) 910

413. TE Chang, A Kisliuk, SM Rhodes, WJ Brittain, AP Sokolov, Polymer 47

(2006) 7740

414. CC Hsiao, TS Lin, LY Cheng, CCM Ma, ACM Yang, Macromolecules 38

(2005) 4811

415. K Litina, A Miriouni, D Gournis, MA Karakassides, N Georgiou, E

Klontzas, E Ntoukas, A Avgeropoulos, Eur Polym J 42 (2006) 2098

416. Z Yang, B Dong, Y Huang, L Liu, FY Yan, HL Li, Mater Chem Phys 94

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417. Z Wang, G Xie, X Wang, Z Zhang, J Appl Polym Sci 100 (2006) 4434

418. G Chigwada, P Jash, DD Jiang, CA Wilkie, Polym Degrad Stab 88 (2005)

382

419. GH Chen, DJ Wu, WG Weng, B He, Wl Yan, Polym Int 50 (2001) 980

94 Chapter 1

420. C Celik, SB Warner, J Appl Polym Sci 103 (2007) 645

421. FM Uhl, CA Wilkie, Polym Degrad Stab 76 (2002) 111

422. O Meincke, B Hoffmann, C Dietrich, C Friedrich, Macromol Chem Phys

204 (2003) 823

423. D Lopez, I Cendoya, F Torres, J Tejada, C Mijangos, Polym Eng Sci 41

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424. L Jiang, W Sun, J Kim, Mater Chem Phys 101 (2007) 291

425. Z Dong, Z Liu, J Zhang, B Han, D Sun, Y Wang, Y Huang, J Appl Polym

Sci 94 (2004) 1194

426. S Bourbigot, DL Vanderhart, JW Gilman, WH Awad, RD Davis, AB

Morgan, CA Wilkie, J Polym Sci Part B Polym Phys 41 (2003) 3188

427. X Fu, S Qutubuddin, Mater Lett 42 (2000) 12

428. X Fu, S Qutubuddin, Polymer 42 (2001) 807

429. WA Zhang, XF Shen, MF Liu, YE Fang, J Appl Polym Sci 90 (2003) 1692

430. G Chen, S Liu, S Zhang, Z Qi, Macromol Rapid Commun 21 (2000) 746

431. TH Kim, LW Jang, DC Lee, HJ Choi, MS Jhon, Macromol Rapid Commun

23 (2002) 191

432. H Li, Y Yu, Y Yang, Eur Polym J 41 (2005) 2016

433. CCM Ma, YJ Chen, HC Kuan, J Appl Polym Sci 100 (2006) 508

434. RV Kumar, Y Koltypin, O Palchik, A Gedanken, J Appl Polym Sci 86

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435. PS Nair, T Radhakrishnan, N Revaprasadu, GA Kolawole, AS Luyt, V

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436. DY Wang, J Zhu, Q Yao, CA Wilkie, Chem Mater 14 (2002) 3837

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440. A Akelah, A Rehab, T Agag, M Betiha, J Appl Polym Sci 103 (2007) 3739

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365

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448. FP La Mantia, NT Dintcheva, Polym Test 25 (2006) 701

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Bian, M Guardasole, S Vaccaro, e-Polymers 014 (2006) 1

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Part B: Polym Phys 40 (2002) 2065

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Sci 87 (2003) 2216

465. M Pramanik, H Acharya, SK Srivastava, Macromol Mater Eng 289 (2004)

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44 (2006) 471

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M Rafailovich, BB Sauer, WJ Choi, SC Kim, Proceedings of the

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BB Sauer, JW Gilman, Macromolecules 38 (2005) 3765

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438. Y Yang, P Wang, Polymer 47 (2006) 2683

439. DW Chae, BC Kim, Polym Adv Technol 16 (2005) 846

440. A Akelah, A Rehab, T Agag, M Betiha, J Appl Polym Sci 103 (2007) 3739

441. TR Hull, D Price, Y Liu, CL Wills, J Brady, Polym Degrad Stab 82 (2003)

365

442. M Zanetti, G Camino, R Mulhaupt, Polym Degrad Stab 74 (2001) 413

443. JK Pandey, KR Reddy, AP Kumar, RP Singh, Polym Degrad Stab 88

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444. M Zanetti, G Camino, R Thomann, R Mulhaupt, Polymer 42 (2001) 4501

445. Mc Neill LS, Comprehensive Polymer Science, Oxford, Pergamon Press 6

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446. G Camino, R Sgobbi, S Colombier, C Scelza, Fire Mater 24 (2000) 85

447. V Pasanovic-Zujo, RK Gupta, SN Bhattacharya, Rheol Acta 43 (2004) 99

448. FP La Mantia, NT Dintcheva, Polym Test 25 (2006) 701

449. A Riva, M Zanetti, M Braglia, G Camino, L Falqui, Polym Degrad Stab 77

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450. S Peeterbroeck, F Laoutid, B Swoboda, J Lopez-Cuesta, N Moreau, JB

Nagy, M Alexandre, P Dubois, Macromol Rapid Commun 28 (2007) 260

451. H Acharya, SK Srivastava, AK Bhowmick, Polym Eng Sci 46 (2006) 837

452. FP La Mantia, SL Verso, NT Dintcheva, Macromol Mater Eng 287 (2002) 909

453. G Beyer, Fire Mater 25 (2001) 193

454. G Chauve, L Heux, R Arouini, K Mazeau, Biomacromolecules 6 (2005) 2025

455. W Zhang, D Chen, Q Zhao, Y Fang, Polymer 44 (2003) 7953

456. X Li, C Ha, J Appl Polym Sci 87 (2003) 1901

96 Chapter 1

457. F Bellucci, G Camino, A Frache, V Ristori, L Sorrentino, S Iannace, X

Bian, M Guardasole, S Vaccaro, e-Polymers 014 (2006) 1

458. CH Jeon, SH Ryu, YW Chang, Polym Int 52 (2003) 153

459. M Alexandre, G Beyer, C Henrist, R Cloots, A Rulmont, R Jerome, R

Dubois, Macromol Rapid Commun 22(2001) 643

460. Y Tang, Y Hu, SF Wang, Z Gui, Z Chen, W C Fan, Polym Degrad Stab 78

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461. Y Tang, Y Hu, J Wang, R Zong, Z Gui, Z Chen, Y Zhuang, W Fan, J Appl

Polym Sci 91 (2004) 2416

462. M Pramanik, SK Srivastava, BK Samantaray, AK Bhowmick, J Mater Sci

Lett 20 (2001) 1377

463. M Pramanik, SK Srivastava, BK Samantaray, AK Bhowmick, J Polym Sci

Part B: Polym Phys 40 (2002) 2065

464. M Pramanik, SK Srivastava, BK Samantaray, AK Bhowmick, J Appl Polym

Sci 87 (2003) 2216

465. M Pramanik, H Acharya, SK Srivastava, Macromol Mater Eng 289 (2004)

562

466. SK Srivastava, M Pramanik, H Acharya, J Polym Sci Part B: Polym Phys

44 (2006) 471

467. M Gelfer, C Burger, C Avila-Orta, L Yang, I Sics, BS Hsiao, B Chu, M Si,

M Rafailovich, BB Sauer, WJ Choi, SC Kim, Proceedings of the

International Symposium on Polymer Nanocomposites Science and

Technology, Boucherville, Quebec, Canada, (2003) 10

468. M Gelfer, HH Song, L Liu, C Avila-Orta, L Yang, M Si, B Hsiao, B Chu, M

Rafailovich, A H Tsou, Polym Eng Sci 42 (2002) 1841

469. MY Gelfer, C Burger, B Chu, BS Hsiao, AD Drozdov, M Si, M Rafailovich,

BB Sauer, JW Gilman, Macromolecules 38 (2005) 3765

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474. DS Chaudhary, R Prasad, RK Gupta, SN Bhattacharya, Thermochim Acta

433 (2005) 187

475. R Prasad, RK Gupta, F Cser, SN Bhattacharya, J Appl Polym Sci 101

(2006) 2127

476. BR Guduri, AS Luyt, J Appl Polym Sci 103 (2007) 4095

477. H Zou, Q Ma, Y Tian, S Wu, J Shen, Polym Compos 27 (2006) 529

478. P Fang, Z Chen, S Zhang, S Wang, L Wang, J Feng, Polym Int 55 (2006)

312

479. H Lu, Y Hu, Q Kong, Z Chen, W Fan, Polym Adv Technol 16 (2005) 688

480. H Lu, Y Hu, Q Kong, Y Cai, Z Chen, W Fan, Polym Adv Technol 15 (2004)

601

481. M Alexandre, G Beyer, C Henrist, R Cloots, A Rulmont, R Jerome, P

Dubois, Chem Mater 13 (2001) 3830

482. L Qiu, R Xie, P Ding, B Qu, Compos Struct 62 (2003) 393

483. J Sharif, W Yunus, K Dahlan, M Ahmad, J Appl Polym Sci 100 (2006) 353

484. F Cser, SN Bhattacharya, J Appl Polym Sci 90 (2003) 3026

485. Y Tang, Y Hu, J Xiao, J Wang, L Song, W Fan, Polym Adv Technol 16

(2005) 338

486. M Valera-Zaragoza, E Ramýrez-Vargas, FJ Medellýn-Rodrýguez, BM

Huerta-Martýnez, Polym Degrad Stab 91 (2006) 1319

98 Chapter 1

487. S Peeterbroeck, M Alexandre, JB Nagy, C Pirlot, A Fonseca, N Moreau, G

Philippin, J Delhalle, Z Mekhalif, R Sporken, G Beyer, P Dubois, Compos

Sci Technol 64 (2004) 2317

488. MC Costache, DD Jiang, C A Wilkie, Polymer 46 (2005) 6947

489. W Gianelli, G Camino, NT Dintcheva, SL Verso, FP La Mantia, Macromol

Mater Eng 289 (2004) 238

490. R Thomas, S Durix, C Sinturel, T Omonov, S Goossens, G Groeninckx, P

Moldenaers, S Thomas, Polymer 48 (2007) 1695

491. PA Sreekumar, K Joseph, G Unnikrishnan, S Thomas, Compos Sci

Technol 67 (2007) 453

492. S Jose, SP Thomas, S Thomas, J Karger-Kocsis, Polymer 47 (2006) 6328

493. B Francis, VL Rao, GV Poel, F Posada, G Groeninckx, R Ramaswamy, S

Thomas, Polymer 47(2006) 5411

494. VG Geethamma, S Thomas, J Adhes Sci Technol 18 (2006) 951

495. R Stephen, S Varghese, K Joseph, Z Oommen, S Thomas, J Memb Sci

282 (2006) 162

496. R Stephen, R Alex, T Cherian, S Varghese, K Joseph, S Thomas, J Appl

Polym Sci 101 (2006) 2355

497. R Stephen, C Ranganathaiah, S Varghese, K Joseph, S Thomas,

Polymer 47 (2006) 858

Introduction 97

470. S Duquesne, C Jama, M Le Bras, R Delobel, P Recourt, JM Gloaguen,

Compos Sci Technol 63 (2003) 1141

471. F Zhang, U Sundararaj, Polym Compos 25 (2004) 535

472. F Gao, G Beyer, Q Yuan, Polym Degrad Stab 89 (2005) 559

473. R Prasad, V Pasanovic-Zujo, RK Gupta, F Cser, SN Bhattacharya, Polym

Eng Sci 44 (2004) 1220

474. DS Chaudhary, R Prasad, RK Gupta, SN Bhattacharya, Thermochim Acta

433 (2005) 187

475. R Prasad, RK Gupta, F Cser, SN Bhattacharya, J Appl Polym Sci 101

(2006) 2127

476. BR Guduri, AS Luyt, J Appl Polym Sci 103 (2007) 4095

477. H Zou, Q Ma, Y Tian, S Wu, J Shen, Polym Compos 27 (2006) 529

478. P Fang, Z Chen, S Zhang, S Wang, L Wang, J Feng, Polym Int 55 (2006)

312

479. H Lu, Y Hu, Q Kong, Z Chen, W Fan, Polym Adv Technol 16 (2005) 688

480. H Lu, Y Hu, Q Kong, Y Cai, Z Chen, W Fan, Polym Adv Technol 15 (2004)

601

481. M Alexandre, G Beyer, C Henrist, R Cloots, A Rulmont, R Jerome, P

Dubois, Chem Mater 13 (2001) 3830

482. L Qiu, R Xie, P Ding, B Qu, Compos Struct 62 (2003) 393

483. J Sharif, W Yunus, K Dahlan, M Ahmad, J Appl Polym Sci 100 (2006) 353

484. F Cser, SN Bhattacharya, J Appl Polym Sci 90 (2003) 3026

485. Y Tang, Y Hu, J Xiao, J Wang, L Song, W Fan, Polym Adv Technol 16

(2005) 338

486. M Valera-Zaragoza, E Ramýrez-Vargas, FJ Medellýn-Rodrýguez, BM

Huerta-Martýnez, Polym Degrad Stab 91 (2006) 1319

98 Chapter 1

487. S Peeterbroeck, M Alexandre, JB Nagy, C Pirlot, A Fonseca, N Moreau, G

Philippin, J Delhalle, Z Mekhalif, R Sporken, G Beyer, P Dubois, Compos

Sci Technol 64 (2004) 2317

488. MC Costache, DD Jiang, C A Wilkie, Polymer 46 (2005) 6947

489. W Gianelli, G Camino, NT Dintcheva, SL Verso, FP La Mantia, Macromol

Mater Eng 289 (2004) 238

490. R Thomas, S Durix, C Sinturel, T Omonov, S Goossens, G Groeninckx, P

Moldenaers, S Thomas, Polymer 48 (2007) 1695

491. PA Sreekumar, K Joseph, G Unnikrishnan, S Thomas, Compos Sci

Technol 67 (2007) 453

492. S Jose, SP Thomas, S Thomas, J Karger-Kocsis, Polymer 47 (2006) 6328

493. B Francis, VL Rao, GV Poel, F Posada, G Groeninckx, R Ramaswamy, S

Thomas, Polymer 47(2006) 5411

494. VG Geethamma, S Thomas, J Adhes Sci Technol 18 (2006) 951

495. R Stephen, S Varghese, K Joseph, Z Oommen, S Thomas, J Memb Sci

282 (2006) 162

496. R Stephen, R Alex, T Cherian, S Varghese, K Joseph, S Thomas, J Appl

Polym Sci 101 (2006) 2355

497. R Stephen, C Ranganathaiah, S Varghese, K Joseph, S Thomas,

Polymer 47 (2006) 858