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BIODEGRADABLE POLYMER NANOCOMPOSITES
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ORGANICALLY MODIFIED MONTMORILLONITE CLAY

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Ajay Kathuria

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BIODEGRADABLE POLYMER NANOCOMPOSITES FROM POLY(ALKYLENE
DICARBOXYLATE) AND ORGANICALLY MODIFIED MONTMORILLONITE
CLAY
By

Ajay Kathuria

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

2007

 

ABSTRACT

BIODEGRADABLE POLYMER NANOCOMPOSITES FROM POLY(ALKYLENE

DICARBOXYLATE) AND ORGANICALLY MODIFIED MONTMORILLONITE

CLAY
By
Ajay Kathuria

Packaging is a major consumer of plastics. After use. packaging plastics are
discarded, and they end-up as municipal solid waste (MSW). Limited land-fill
sites and environmental concerns related to the use of conventional plastics have
forced scientists to develop biodegradable materials for packaging applications.
Poly(alkylene dicarboxylate) is a class of aliphatic polyester type biodegradable
polymers among which poly(butlylene succinate) (PBS) and po|y(butylene
succinate-co-butylene adipate) (PBSA) are commercially available biodegradable
polymers. The reinforcement of these polyesters with organically modified clay
can help to improve their mechanical. thermo-mechanical, and barrier properties.
The effects of the clay content as well as melt processing cycle time on the
mechanical, thermo-mechanical, and barrier properties of the resulting
nanocomposites were studied. The storage modulus of PBSA improved by 90 %
with 5wt.% organo-clay reinforcement. The thermal behavior of the resulting
nanocomposites was studied using Differential Scanning Calorimetry (DSC) and
Dynamic Mechanical Analysis (DMA). The morphology of the resulting
nanocomposites was evaluated using Transmission Electron Microscopy (TEM)

and X-Ray Diffraction (XRD) studies.

 

ACKNOWLEDGEMENTS

I would like to thank my advisor, Dr. Amar K. Mohanty, for all his support,
mentoring, and guidance. His high motivation and new ideas always helped me
to gain knowledge and insight into biopolymers. I would like to thank my other
committee members: Dr. Bruce Harte and Dr. Farhang Pourboghrat. They were
very supportive in the completion of this work and were the source of invaluable

advice through our engaging discussions.

The research was made possible through funding received from Center for Food
and Pharmaceutical Packaging Research (CFPPR) at School of Packaging,
MSU. I am grateful to my colleagues, especially Dr. Mohanty's research group for
sharing their knowledge and expertise and helping me in performing my
experiments. I would also like to thank the faculty and staff of the School of
Packaging, my friends and fellow graduate students who have provided me with
a wonderful, friendly atmosphere throughout my Master’s program and research

period.

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

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

iii

 

TABLE OF CONTENTS

LIST OF TABLES ............................................................................... vi
LIST OF FIGURES ............................................................................. vii
Chapter 1: INTRODUCTION .................................................................. 1
Chapter 2: BACKGROUND AND LITERATURE REVIEW .......................... 14
Chapter 3: MATERIALS AND METHODS .............................................. 24
3.1 Materials ....................................................................... 24

3.1.1 Poly (butylene succinate)(PBS) ................................ 24

3.1.2 Poly(butylenes succinate-co-adipate)(PBSA) ............... 26

3.1.3 Organically Modified Montmorillonite (OMMT) Clay ....... 26

3.2 Methods ........................................................................ 28

3.3 Equipments and Preparation .............................................. 29

3.3.1 DSM Microcompounder ........................................... 29

3.3.2 Dynamic Mechanical Analysis .................................... 29

3.3.3 Tensile Properties ................................................... 29

3.3.4 Film Preparation ..................................................... 30

3.3.5 Measurement of Water Permeability ........................... 30

3.3.6 Measurement of 02 Gas Permeability .......................... 31

3.3.7 Differential Scanning Calorimetry ................................ 31

3.3.8 Izod Impact Tester ................................................... 31

3.3.9 X-Ray Diffraction ..................................................... 31

3.3.10 Transmission Electron Microscope (TEM) ................... 32

Chapter 4: RESULTS AND DISCUSSION .............................................. 34
4.1 Results ......................................................................... 34

4.1.1 Tensile Properties of PBSA Cloisite 25A ............................... 37

4.1.2 Dynamic Mechanical Analysis ................................... 44

4.1.3 Barrier Properties of PBSA Nanocomposites ................. 46

4.1.4 Water Vapor Barrier ................................................. 48

4.1.5 Oxygen Gas Barrier ................................................ 51

4.1.6 Notched Izod Impact Strength .................................... 53

4.1.7 XRD Analysis ......................................................... 55

4.1.8 Differential Scanning Calorimetry ................................ 57

4.1.9 Tensile Properties of PBS Nanocomposites .................. 62

4.2.10 Storage Modulus ................................................... 67

4.2.11 Permeability ......................................................... 71

4.2.12 Water Vapor Permeability ........................................ 71

4.2.13 Oxygen Permeability .............................................. 74

4.2.14 Differential Scanning Calorimetry .............................. 76
4.2.15 XRD Analysis ........................................................ 78
4.2.16 TEM Studies ......................................................... 80

Chapter 5: CONCLUSION AND RECOMMENDATION FOR FUTURE
WORK ............................................................................ 82

Table 2.1:
Table 3.1:
Table 3.2:
Table 4.1:
Table 4.2:

Table 4.3:

Table 4.4:
Table 4.5:
Table 4.6:

Table 4.7:

LIST OF TABLES

Material Properties of PBS and PBSA19
Properties of PBS 1020 and PBSA 3020 ................................ 25
Characteristics of Organically Modified Montmorillonite Clay.. .....27
Processing Conditions Used in Nanocomposites Fabrication ....... 35
Barrier Properties of PBSA Nanocomposites ........................... 51

Interlayer Spacing or d-Spacing of Clay and PBSA

Nanocomposites .............................................................. 55
Enthalpy of Melting of PBSA Nanocomposites ......................... 57
Barrier Properties of PBS Nanocomposites ............................. 74
Enthalpy of Melting of PBS Nanocomposites ........................... 76
Interlayer Spacing of PBS Nanocomposites ............................ 78

vi

Figure 1.1:

Figure 1.2:
Figure 1.3:

Figure 2.1:
Figure 2.2:
Figure 3.1:
Figure 3.2:

Figure 3.3:

Figure 3.4:

Figure 3.5:
Figure 4.1:
Figure 4.2:
Figure 4.3:
Figure 4.4:

Figure 4.5:
Figure 4.6:

Figure 4.7:

LIST OF FIGURES

Organically Modified Clay ...................................................... 8

Schematic Representation of Different Methods of Nanocomposites
Preparation ....................................................................... 1 1

Different Kinds of Polymer Clay Nanocomposites Morphologies

After Reference [59] ............................................................ 12
Structure of Poly(alkylene dicarboxylate) ................................. 16
Classification of Biodegradable Polymers ................................ 18
Structure of Poly(butylene succinate) ..................................... 25
Structure of Poly(butylene succinate-co-adipate) ...................... 26

Structure of the Organic Modifier Used for Cation Exchange
Reaction of Cloisite 25A ...................................................... 27

PBSA Film Prepared by Compression Molding ......................... 30

Schematic Representation of Steps Followed for This Research
Work ............................................................................... 33

Comparison of Percentage Elongation of PBSA and PBSA-3%
Cloisite 25A Nanocomposites ............................................... 39

Comparison of Percentage Elongation of PBSA and PBSA-5%
Cloisite 25A Nanocomposites ............................................... 40

Comparison of Tensile Strength of PBSA and PBSA -3% Cloisite

25A Nanocomposites .......................................................... 42
Comparison of Tensile Strength of PBSA and PBSA -5% Cloisite
25A Nanocomposites .......................................................... 43
Storage Modulus of PBSA Cloisite 25A Nanocomposites ............ 45
Permeability Mechanism ...................................................... 47

Water Vapor Permeability of PBSA and PBSA Cloisite 25A
Nanocomposites ................................................................ 49

Figure 4.8:

Figure 4.9:

Figure 4.10:

Figure 4.11:
Figure 4.12:
Figure 4.13:
Figure 4.14:

Figure 4.15:
Figure 4.16:
Figure 4.17:
Figure 4.18:
Figure 4.19:

Figure 4.20:
Figure 4.21:

Figure 4.22:

Figure 4.23:

Figure 4.24

Figure 4.25:

Schematic Representation of Permeation Process: Nano-
composites Vs. Conventional Composites ............................... 50

Oxygen Gas Permeability of PBSA Cloisite 25A ........................ 52

Izod Impact Strength of PBSA and PBSA Cloisite 25A
Nanocomposites ................................................................ 54

X-Ray Diffractogram of PBSA Cloisite 25A Nanocomposites ....... 56

Thermographs of PBSA Cloisite 25A Nanocomposites ............... 58
TEM Photomicrographs of PBSA-3% Cloisite 25A ..................... 59
TEM Photomicrographs of PBSA-5% Cloisite 25A ..................... 60

Comparison of Percentage Elongation of PBS and PBS-3% Cloisite
25A Nanocomposites .......................................................... 63

Comparison of Percentage Elongation of PBS and PBS-5% Cloisite
25A Nanocomposites .......................................................... 64

Comparison of Tensile Strength of PBS and PBS-3% Cloisite 25A
Nanocomposites ................................................................ 65

Comparison of Tensile Strength of PBS and PBS-5% Cloisite 25A
Nanocomposites ................................................................ 66

Graph of Storage Modulus of PBS Cloisite 25A

Nanocomposites ................................................................ 68
Storage Modulus of PBS Cloisite 25A Nanocomposites .............. 69
Tan Delta of PBS Cloisite 25A Nanocomposites ........................ 70
Water Vapor Permeability of PBS-3% Cloisite 25A and PBS-5%
Cloisite 25A Processed at 5 Minute Cycle Time ........................ 73
Oxygen Gas Permeability of PBS-3% Cloisite 25A and PBS-5%

Cloisite 25A Processed at 5 Minute Cycle Time ........................ 75
Thermographs of PBS Cloisite 25A Nanocomposites ................ 77

XRD Analysis of PBS-3% Cloisite 25A and PBS—5% Cloisite
25A Processed at 5 Minute Cycle Time .................................. 79

viii

Figure 4.26: TEM Photomicrographs of PBS-3% Cloisite 25A Processed at
5 Minute Cycle Time ........................................................... 80

Figure 4.27: TEM Photomicrographs of PBS-5% Cloisite 25A Processed at
5 Minute Cycle Time ........................................................... 81

Chapter 1

Introduction

Plastics have played a significant role in the development of modern
civilization. Plastics have very diverse applications in various fields with
substantial contributions in the fields of construction, consumable goods,
manufacturing etc. Lightweight plastics used in the automobile, train, and aviation
sectors help in reducing energy consumption. Plastics can be divided into two
categories: namely, therrnosets and thermoplastics. Thermosets are the plastics
which cannot be reformed or remolded whereas therrnoplastics can be remolded
again and again. Thennoplastics and therrnosets have their own set of benefits
and applications. Thermoplastics have various advantages over thermosets, for
example high impact strength, fracture resistance, etc.'[1] Thermoplastics have
dominated packaging applications because of their desirable tailormade
properties. The good chemical resistance of petroleum- based therrnoplastics
make them an ideal choice for food, chemical, and pharmaceutical packaging.[2]
The ease of plastic processing (when compared to metals and glass) and their
versatility also played a vital role towards their domination in the packaging
industry. Plastics are also known for their light weight, durability, and ease with
which they can be easily shaped into various forms. They possess good thermal
and electrical insulation characteristics. Plastics processing requires less energy
than glass or metals processing and plastics are resilient to corrosion. Market

forces such as low cost and convenience also encouraged the use of plastics in

the last couple of decades”. Most of the commercially available plastics are
conventional petroleum-derived plastics such as polyethylene (PE),
polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), etc.
Conventional petroleum-derived plastics have remarkable properties for a vast
range of applications, but they pose serious environmental challenges because
of their persistent nature and problems related to disposability. Incineration as an
end of the carbon cycle of plastics produces C02 and other harmful gases such
as carbon monoxide. Recycling of the used plastic goods and plastic waste has
not been able to contain the municipal solid waste. Per the 1998 US census, the
United States generated 22.4 million tons of plastic waste. Limited petroleum
resources and rising crude petroleum prices are also affecting the economics of
the plastic and packaging industry. Agricultural raw materials like corn and
sugarcane, if utilized for the production of the monomers, can provide impetus to
the rural economy by generating additional rural employment. Bio-based material
can be helpful in catapulting the economy in the next orbit of economic growth. In
today’s fast-changing global political landscape, bio-based materials are
strategically important to reduce the dependency of various nations on
petroleum-based resources which are concentrated in certain geographies of the
world. The scientific and industrial communities around the world are working in
tandem for the development of alternative eco-friendly, biodegradable, and

sustainable packaging materials. [3, 4]

Biodegradable plastics are the polymers that can decompose with the aid
of microbial or enzymatic action when subjected to suitable composting
conditions. Biodegradable polymers present a challenging opportunity. A lot of
scientific research is focused on the development [5-10] and commercialization
of biodegradable polymers. They can be obtained from renewable resources like
corn, starch, wood cellulose, etc. However, they can also be derived from the
petrochemicals resources. Due to comparatively higher cost, small-scale, and
certain properties limitations biodegradable polymers in general are not prevalent
in the mainstream of plastic industry. Although biodegradable polymers have
started making inroads into the commercial applications, there is lot of potential
in the improvement of their properties for large scale or mass level applications.
Some of the widely available biodegradable polymers are polylactic acid (PLA),
polyhydroxybutyrate (PHB), poly (alkylene dicarboxylate), poly (butylene adipate

terephthalate) (PBAT), poly (e-caprolactone), thermoplastic starch, etc.

Poly(alkylene dicarboxylate) is a class of biodegradable aliphatic polyester
prepared by polycondensation reaction of glycols and dicarboxylic acids.[11]
Poly(alkylene dicarboxylate)s are commercially prepared by Showa High
Polymers Co. Ltd., Japan under the trademark “Bionolle." These polymers are
quite similar to the polyolefin family of polymers, but they possess poor melt
viscosity. Poly(alkylene dicarboxylate) polymers have relatively poor water and
gas barriers as compared to polyolefins. Bionolle has excellent processability. It

can be processed into melt blow, multifilament, monofilament, nonwoven, flat,

and split yarn in the field 'of textiles and also into injection-molded plastics
products, thus being a promising polymer for various potential applications
including packaging. Bionolle can be processed on polyolefin machines at
temperatures of 100-230°C. Some examples of its potential applications include
shampoo bottles, beverage bottles, food trays, shopping bags, cups, drug
bottles, etc. Bionolle can take between 2 to 6 months to degrade under
composting conditions. Bionolle has a promising future since succinic acid used
for the production of some of the polymers of this class can be derived from
biobased materials.“" Various chemical companies are in the process of
developing the technology to produce succinic acid from biobased resources at
bulk level. Therefore, the poly(alkylene dicarboxylate) class of polymers can be

categorized into the green and sustainable class of polymeric materials.

Polymer composites are prepared by a combination of two or more
materials such as reinforcement, matrix, fillers which differ in the form on macro-
scale. The constituents retain their identities. They do not dissolve or merge into
each other, although they act in concert. Normally, the components can be
physically identified and exhibit an interface between each other. Some of the
common reinforcements are glass fibers, silica, minerals, and natural fibers. A lot
of research has been done on glass fiber composites [12-17]. Glass fibers have
been commercially used in the automobile industry and for structural
applications. Natural fibers such a kenaf, jute, flax, hemp, and sisal have

attracted a lot of attention [18] because they are widely available, and they are

renewable in nature. Natural fibers have advantages over glass fibers such as
low cost, low density, ease of separation, and abundant presence. Natural fibers
are biodegradable in nature. Fabrication of polymer composites using natural
fibers such as flax, hemp, or jute is a good technique to improve the physical,
mechanical, and thermo-mechanical properties of polymers [19—23]. The
improvement in the properties of composites depends upon the amount of stress
transfer from the polymer matrix to the filler [24]. The size of filler, amount of the
filler [25], compatibility of the filler with the polymer matrix, distribution of the filler
[26], and its intimate contact with the polymer matrix play an important role in the
stress transfer. Conventional fibers or fillers also help to reduce the cost of the
end product. As compared to conventional fillers, a small amount of nano fillers
such as nano talc, layered silicates show a lot of improvement due to their high

aspect ratio and nano level interactions.

Nano means one billionth, and nanotechnology refers to one billionth of a
meter. As defined by The Royal Society, London "Nanotechnologies are design,
characterization, production and applications of structures, devices and systems
by controlling shape and size at nanometer scale." [27] The materials having
atleast one dimension in the range of 1 to 100 nanometers are categorized as
nano materials. Nano material can be classified into three categories: (i) nano
materials having all three dimensions in the nano range (for example, spherical
silica); (ii) nano materials having all two dimensions in the nano range (for

example, carbon nano tube); and (iii) nano materials having one dimensions in

the nano range (for example layered silicate). Carbon nano tubes, organically
modified layered silicates, nano-talc, and cellulose whiskers are popular nano
materials. Layered silicates are popular for the production of polymer
nanocomposites because they improve the barrier properties of polymer which is
crucial for food and pharmaceutical packaging applications. The interactions
between layered silicates and polymer matrix have attracted a lot of attention in
the scientific community [28-32]. The nano-reinforcement of the polymer matrix
with organically modified layered silicates is an exciting area to improve the
mechanical and thermo mechanical properties of the polymer. Organically
modified layered silicates (organo-clay) can reduce the flame retardancy [33-37]
and increase the heat deflection temperature (HDT) of the nanocomposites as
compared to virgin polymers [38-41]. Montmorillonite, hectorite, and saponite
organo-clays belong to the smectite group of the clay minerals. These clays are
popular because of good intercalation capabilities. Montmorillonite clay has been
extensively used for various polymer-nanocomposite studies. The main
constituent of montmorillonite is organic ash called bentonite. Each platelet of
montmorillonite clay consists of Al octahedral sheet sandwiched between two Si
tetrahedral sheets. lsomorphic substitution in the sheets creates deficit of positive
charge which is balanced by the Na+ charge present in the interlayer or d-
spacing region. Clay in its natural state is hydrophilic in nature because of the
presence of hydroxyl groups in the structure while the majority of the polymer
matrix are hydrophobic in nature because of the presence of long hydro-carbon

chains. Therefore clay in its natural state is not compatible with the polymers. To

make clay compatible with the polymer matrix organically modified clays have
been investigated [42-47]. The organic modification involves the replacement or
substitution of Na+ ions present in gallery or d-spacing. Organic modification
reduces the surface energy of the clay and increases the interlayer spacing (d-
spacing) between the clay platelets [48]. Organic modification of the clay also
increases the interfacial interaction between the polymer matrix and the clay
platelets [49]. These organically modified clays are also called nanoclay because
of the separation of the clay platelets. Each clay platelet being 1 nanometer thick

can be classified into the nano-material category.

 

CH3
I +
H3C—N —CH2—CH —CH2 —CH2 ——CH2 —CH3
IIIT CH2
I»...

 

Fig 1.1: Organically Modified Clay

d-Spacing

 

Organically modified layered silicates are prepared by replacing the Na+ or
K“ ions in the silicate layer with quaternary alkylammonium or alkylphosphonium
cations. These cation exchange reactions increase the organophilicity of the clay
thus helping in improving the interfacial interactions of the layered silicates with
the polymer matrix. Organically modified layered silicates have a typical
thickness of 1 nanometer and an aspect ratio of 10 to 1000 [50, 51]. A high
aspect ratio of layered silicates increases the interfacial interactions which can
help in drastically improving the mechanical and thenno-mechanical properties.
The layered silicates, if dispersed or exfoliated (delaminated) properly in the
polymer matrix, can improve the water vapor, gas, and organic vapors barrier

properties of the polymer by creating a tortuous zig-zag path for the perrneants.

Nano-technology and nanocomposites are getting a lot of attention these
days but the science of nanocomposites is around 50 years old [52]. Toyota
motor company was the first to introduce the concept of polymer clay
nanocomposites for automotive applications using nylon 6 and organophilic clay
[53]. Since then, various researches have been carried out in the field of
polymer-layered silicate nanocomposites. The reinforcement of polymer with the
nanoclay can improve mechanical, thermomechanical, and barrier properties as
well as flame retardancy [54, 55]. Some researchers have also evaluated the
effect of nano-reinforcement on the biodegradation of the biodegradable

polymers. Kazauki et. al. [56] established that the preparation of nanocomposites

can help in increasing the'biodegradability of nanocomposites in composting
conditions.

Nanocomposites can be prepared by three different techniques: in situ
polymerization, solvent casting, and melt processing of the polymer with the
organo-clay [Fig. 1.2]. In situ polymerization and solvent casting techniques have
limited utilization because of the unavailability of suitable monomer or compatible
solvent solution for all the nanocomposites systems [57]. The melt processing
technique is more popular for the preparation of the polymer nanocomposites.
Important reasons for the popularity of melt processing are: low cost of
production and high volume capacity as compared to solvent casting and in situ
polymerization. We can obtain three different kinds of nanocomposite
morphologies depending on the degree of the dispersion of organo-clay in the
polymer matrix: agglomerated, intercalated, exfoliated, and flocculated
nanocomposites. Schematic representation of the polymer-clay nanocomposites
is shown in Fig. 1.3 [58]. Some of the factors which affect the polymer clay
nanocomposites are the processing conditions of the polymer-nanoclay,

interactions between nanoclay and the polymer matrix, clay loading, etc.

 

 

Different Methods of the Preparation of
Polymer-Clay Nanocomposites

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In-Situ Solvent Melt
Polymerization Casting Extrusion
Master Direct
batch Method
Process

 

 

 

 

 

 

Fig 1.2: Schematic representation of different methods of nanocomposites preparation

E + %

Layered silicates Polymer

I 7
/

 

KL
I
/

m \ \5

n /_—— \ \ /
$.72 \ /§\ 2 7
Agglomeration Intercalation Exfoliation

Fig. 1.3: Different kinds of polymer clay nanocomposites morphologies after
reference [58]

The aim of this study was to prepare biodegradable nanocomposites and
to improve the mechanical, thermo-mechanical, and barrier properties of the
biodegradable polymers. We investigated polymer clay nanocomposites using
PBS and PBSA matrices with commercially available organically modified
montmorillonite layered silicates by using the melt extrusion technique. PBS and
PBSA are biodegradable polymers, and clay is a natural resource. Therefore,

nanocomposites are biodegradable in nature.

 

Chapter 2

Background and Literature Review

The production and application of biodegradable polymers in the medical
field can be traced back to the 1970’s [59, 60]. Biodegradable polymers are being
used in various high value biomedical applications like drug delivery systems,
sutures, and orthopedic parts. However, high cost and limited properties restrict
the ecological application of biodegradable polymers. The price rise of
conventional plastic resin, technological advances, environmental concerns, and
public awareness of the problems associated with the conventional plastics have
provided impetus to the biodegradable plastics in last decade. Biodegradable
plastics are now acquiring center stage in the development of polymer science
and technology. The industrial community has developed different technologies
to prepare biodegradable polymers from renewable resources, petroleum-based
resources, or a combination of both renewable and non-renewable resources.
Degradation of the polymers is independent of its origin. It is the intrinsic property
of the chemical structure of the repeating unit in the polymeric structure.
Standard authorities around the world have set up different standards tests for
biodegradable polymers. The International Standard Organization (ISO-472-
1988) has characterized biodegradable plastics as plastics which go through
chemical changes under particular environment. These polymers experience
change in their properties. The changes in the property of biodegradable plastics

are 3 results of natural process prompted by microorganisms [61]. The American

Society of Testing Material (ASTM Subcommittee 020-96) has classified
biodegradable plastic as plastic in which the degradation of chemical structure

takes place as a result of micro-organisms such as bacteria, fungi and algae [62].

On the basis of origin we can divide biodegradable polymers into three
classes: renewable resource-based biodegradable polymers, petroleum-based
biodegradable polymers, and Petro-Bio mixed. Biopolymers can be derived from
renewable resources like corn, cellulose, and sugar. BionolleTM is a class of
aliphatic polyesters. It is available in a variety of grades such as poly(butylene
succinate)(PBS), poly(butylene succinate-co-adipate) (PBSA), poly(ethylene
succinate), poly(ethylene succinate-co-adipate). PBS and PBSA are
commercially available biodegradable polymers in this class of aliphatic
polyesters. Chemical Structure of Poly(alkylene dicarboxylate) is represented in

Figure 2.1.

O 0

|| ||

O‘LCHS’xO—Cfilgnc
n

Fig 2.1 Structure of poly(alkylene dicarboxylate)
PBS Where, X=4 and Y=2
PBSA Where, X=4 and Y=2 or 4

Figure 2.2 [62, 63] shows the classification of biodegradable polymers on the
basis of their origin. Fujimaki reported that food trays, cups, vessels, shampoo
bottles, cosmetic bottles, composting bags, shopping bags, shrink film, etc. are
some of the potential applications of Bionolle.TM [64] However barrier properties,
softness, and thermal stability obstructed its mass-level applications. The
improvement in the performance and properties of PBS and PBSA can help in
expediting the transition from conventional polymers to biodegradable polymers.
Different techniques can be employed to improve the properties of the polymers
such as blending, composite fabrication, etc. Composite fabrications are popular
techniques followed by engineers and scientists for the improvement in the
performance and properties of the polymers. Glass fiber reinforced composites
and wood fiber composites have traditionally been utilized by various industries.
However, nano-materials are gaining a lot of attention these days. The layered
silicate nanocomposites contain small amount of modified layered silicates (1-5
weight %) where as conventional composites have high percentage of the filler in

the polymer matrix, generally in the 20-40%. High aspect ratio of the layered

silicates leads to manifold increase in the interface area of the filler and matrix.
There is not much variation in the density of nanocomposites with respect to the
matrix as observed in the conventional composites due to the bulk addition of the
filler. Cost effectiveness due to low concentration of filler can be another

favorable reason to select nanocomposites over conventional composites.

Figure 2.2 Classification of Biopolymers [62, 63]

 

| BIOPOLYMERS |

Petro- based
Synthetic

 

        

   

  
   

Renewable
resource based

 

 

 

PLA Polyhydroxy Aliphatic Polyester POIYUFI'

Polymer alkanoates methylene

from com (PHAS) Aliphatic-aromatic terephthalate)
_ polyester. (Soronam)

Cellulosic (Bacterial

plastics bio-plastics) Polyesteramides

Soy based Polyvinyl alcohols

Plastics

 

 

 

 

 

 

 

 

 

Table-2.1 Material Properties of PBS and PBSA [73]

 

 

 

 

 

 

 

 

 

 

 

 

Property Unit PBS 1020 PBSA 3020 PP
Mass Density g/l 1260 1230 900
Hie-Singil'aeiili" °C 97 69 145
Melting Point °C 115 95 164
Degree. 5” % 35-45 20-35 56
Crystallrnrty
22:33:33: .C 7s 53
efiéléfltiifi" °C -32 45 5
Tensile Strength
at Break MPa 21 34 44
Ultimate Elongation % 320 400 800
Flexural Modulus MPa 580 340 1370
Structure - Linear Linear Linear

 

 

 

 

 

 

 

The addition of organically modified layered silicates in the polymer matrix
is an innovative novel technique to improve the mechanical, thermo-mechanical,
and barrier properties of the polymers. Nanocomposites are also known for better
heat deflection temperature as compared to virgin polymers. E. Manias et al [65]
studied the polypropylene-montmorillonite clay-based nanocomposites. They
observed around 40% improvement in the heat deflection temperature of PP
nanocomposites with the addition of 6% organo-clay as compared to virgin
polymer. Various research studies have been published on PBS-organoclay
nanocomposites and PBSA-organoclay nanocomposites. Bousmina et al [66]
have studied Cloisite 15A, Cloisite 93 A, and Cloisite 308 with a PBSA polymer
matrix. The nanocomposites were prepared by melt extrusion followed by
compression molding. They observed improvement in the mechanical properties.
The nanoclay particles reduced the crystallinity of the polymer. Improvement in
the thermal stability of the nanocomposites was found to be related to the degree
of the dispersion of the nanoparticles. Five different kind of organic modifiers:
dodecylamine (DA), octadecylamine (ODA), 12-aminolauric acid (ALA), N-
lauryldiethanolamine (LEA) and 1-[N,N-bis(2-hydroxy-ethyl)amino]-2-propanol
(HEA) were utilized by Someya et al [67] to study the effect of modification on
the properties of PBS and organically modified clay based nanocomposites. They
have reported that the higher degree of intercalation showed higher tensile
modulii and lower tensile strength. An increase in the tensile modulus can be

related to better dispersion. The decrease in tensile strength was attributed to the

20

‘

decrease in elongation at break. The nanoparticles increased the glass transition

temperature and promoted the crystallinity by acting as nucleating agents.

Chen et. al. [68, 69] have studied PBS and PBSA with Cloisite 25A and
twice functionalized organoclay nanocomposites. Twice functionalized clay (TFC)
was prepared by the reaction of glycidoxypropyl trimethoxy silane (GPS) with the
silanol groups on Cloisite 25A. These studies evaluated the mechanical
properties, morphology, and viscoelastic properties. The improvement in
mechanical properties was observed up to 5 wt.% of Cloisite 25A and TFC. They
observed better dispersion of the twice functionalized clay (TFC) than the Cloisite
25A which indicated better interactions between TFC and the polymer matrix.
Okamato et. al. [56] studied PBS with montmorillonite clay modified with
octadecylammonium cation, octadecyl trimethyl ammonium cation, and saponite
clay modified hexadecyltiit 3;“ fi cation. They studied the
mechanical, thermomechanical, oxygen barrier properties and biodegradability of
the nanocomposites film. The biodegradability of nanocomposites was conducted
under soil field and in the composting conditions. After 35 days, it was observed
that the nanocomposites film degraded faster than the neat film in the
composting condition. The films’ surface showed signs of degradability after 6
months under soil field conditions. The rate of degradation of the films was
independent of the type of montmorillonite clay modification. In the case of
modified saponite clay, the degradation rate was high, which may be because of

the presence of an alkylphOSphonium surfactant. Oxygen gas permeability

21

 

decreased for all the PBS-organoclay compositions. The oxygen barrier
properties improved by approx. 45% for PBS and 3.6% octadecylammonium

modified montmorillonite clay.

Ray et. al. [70] also published a study on PBS-C13—mmt nanocomposites.
They observed remarkable improvement in the mechanical properties. The
morphological studies revealed that the clay platelets were intercalated and
randomly distributed in the polymer matrix. Research has been conducted on
PBS/glass fiber composites [71] prepared by electron beam irradiation in the
presence of cross linking agent. The polymer matrix was found to be degradable,
and the glass fiber needed to be collected from the composting facilities for

recycling purposes.

Jo Ann Ratto et. al. [72] studied blends of PBSA and starch composites.
The starch composition was varied from 5 to 30% in the PBSA matrix. The
mechanical and thermo-mechanical properties along with the biodegradability of
the extrusion blown PBSA/ starch film were evaluated. The tensile strength and
toughness of the film decreased with the increase in the starch content in the
PBSA matrix. Biodegradability of the PBSA films increased with the addition of
the starch in the PBSA matrix. The biodegradability of the composites was

supported by the respirometric test and scanning electron microscopic studies.

22

The objective of this research was to prepare biodegradable PBS and
PBSA-organo—clay nanocomposites with improved mechanical,
thermomechanical, and barrier properties for packaging applications. Organically
modified montmorillonite clay based nanocomposites were fabricated by melt
extrusion followed by the injection molding process. The effect of temperature,
clay content, and cycle time of compounding on the mechanical properties and
thermo-mechanical properties of the resulting nanocomposites were studied. The
oxygen and water vapor permeability of the compression-molded
nanocomposites films were evaluated and compared with other conventional
polymers. The resulting nanocomposites properties were verified through

Transmission Electron Microscopy (TEM) and X- ray Diffraction (XRD) studies.

23

 

Chapter 3

Materials and Methods

3.1 Materials
3.1.1 Poly(butylene succinate):

Poly(butylene succinate) (“Bionolle 1020”) was supplied by Showa High
Polymers Co. Ltd., Japan under the tradename “Bionolle". It is prepared by
condensation polymerization of 1, 4 butanediol with succinic acid. “Bionolle 1020"
is an injection grade polymer having density of 1.25 9/00 and its melting point is
115°C [64,73]. PBS 1020 is biodegradable under composting conditions. The
plastic pellets were dried in the vacuum oven at 70°C for 24 hrs before
processing. The structure of PBS is shown in Fig. 3.1. PBS has a promising
future because both the monomers used in the condensation polymerization of
PBS (i.e., succinic acid and 1, 4 butanediol) can be obtained from the renewable
resources such as corn, sugarcane, etc. Table 3.1 represents various properties

of PBS 1020 and PBSA 3020.

24

/\/\/O

O
n

Fig 3.1 Structure of Poly(butylene succinate)

Table 3.1. Properties of PBS 1020 and PBSA 3020 [64, 73]

 

 

 

 

 

 

 

 

 

 

Property PBS 1020 PBSA 3020
Melting Point (°C) 114-115 93-95
Density (g/cc) 1.26 1.23
Tensile Elongation (%) 320 400
Tensile Strength at Break (MPa) 21 34
Crystallization Temperature (°C) 76 53
Glass Transition Temperature (°C) -32 ~45

 

 

25

 

3.1.2 Poly(butylene succiriate-co-adipate) (PBSA)

Poly(butylene succinate-co—adipate) (“BionolleTM 3020") is an injection
grade copolymer supplied by Showa High Polymer Co. Ltd, Japan. It is prepared
by condensation polymerization of 1, 4 butanediol with adipic acid and succinic
acid. The Chemical structure of PBSA is represented in Fig. 3.2. Its properties
are listed in Table 3.1. It has a density of 1.23 glcc and melting temperature of

95°C. [64' 7°] The pellets were dried at 65°C for 24 hrs before processing.

ii i
owe—cease
n

Figure 3.2. Structure of Poly(butylene succinate-co—adipate)
Where, X =4 and Y=2 or 4

3.1.3 Organically Modified Montmorillonite Clay. The organically modified
montmorillonite, Cloisite 25ATM, is a commercial product of Southern Clay
Products Inc., Texas. This clay is modified with dimetyl, hydrogenated tallow, 2-
ethylhexyl quaternary ammonium cation. The structure of the organic modifier is

shown in Figure 3.3.

26

 

Table 3.2. Characteristics of Organically Modified Montmorillonite Clay

 

 

XRD Extent of Specific
OMMT Clay Basal Spacing Modification Gravity
doo1(nm) [mqu1 009 clay] (glcc)
Cloisite 25 A“ 1.86 95 1.87

 

 

 

 

 

 

*Data obtained from Southern Clay Products Inc. Texas

CH3

+

HT CH2

CH3

Fig. 3.3: Structure of the organic modifier used for cation exchange reaction of
Cloisite 25A

27

3.2 Methods. There are two methods of nanocomposite preparation: direct
blending and masterbatch-based blending. The masterbatch melt blending
technique was used in this study to prepare PBS-Cloisite 25A and PBSA-Cloisite
25A nanocomposites. The DSM micro-compounding instrument was used to
fabricate the masterbatch and the desired nanocomposite compositions. There
were two steps used for the preparation of nanocomposites. In the first step, the
masterbatch of PBS or PBSA and Cloisite 25A was prepared using high weight%
of clay concentration. The masterbatch was extruded as strands and then
palletized in the pelletizer. In the second step, the desired compositions of the
polymer and organoclay were prepared from the masterbatch and neat polymer.
The main reason for using a two-step process for the preparation of
nanocomposites was to achieve better dispersion of organoclay in the polymer
matrix. The intercalation or exfoliation of clay in the polymer matrix was

necessary to obtain the novel properties.

PBS was processed at 160°C at a screw speed of 100 rpm. The
nanocomposites were injected with the help of an injection molder attached to
the micro-compounding instrument. The injection mold temperature was
maintained at 45°C. Injection pressure was set at 100 psi. The PBS-3% 25A and
PBS-5% 25A nanocomposites were prepared at 5 mins., 10 mins. and 15 mins.
of melt processing cycle time to evaluate the effect of processing conditions on

the performance of the resulting nanocomposites.

28

 

PBSA was processed at two processing temperatures: 125°C and 140°C.
The melt extrusion was followed by the injection molding technique. The mold
temperature was maintained at 40°C with injection pressure of 100 psi. The
process cycle time was varied from 5 mins. to 20 mins. at a screw speed of 100

rpm.
3.3 Equipments and Preparation

3.3.1 DSM Microcompounder. The DSM micro-compounding instrument
consists of two vertical screws having a length of 150 mm. The volume of micro-
compounding instrument is 15cc, and it has an L/D ratio of 18. The micro-
compounder is attached to an injection molding unit. The injection molding unit
has different designed standard molds to prepare samples for tensile testing,

DMA testing, XRD samples, etc.

3.3.2 Dynamic Mechanical Analysis. DMA 0800 from TA Instruments was
used to analyze the dynamic mechanical properties. The single cantilever mode
and multifrequency strain mode were used to measure the storage modulus, loss
modulus, and tan delta over the temperature range of -80°C to 70°C at a

frequency of 1 hz and an amplitude of 15 um.

3.3.3 Tensile Properties. The dog-bone tensile samples were prepared by
injection molding. The tensile properties such as % elongation at break and

tensile strength were measured using the Universal Testing Machine (UTS,

29

Model SFM-20) as per ASTM D-638 using a gauge length of 1 inch. A load cell of
1,000 lbs was utilized for the testing at a crosshead speed of 20 in./min. At least

five specimens were used for all property evaluations.

3.3.4 Film Preparation. Nanocomposite films
were prepared by compression molding
technique with the help of a compression
molding machine of an area 9" x 9". The PBSA
and PBS nanocomposites disc samples were

compressed at 120°C and 150°C, respectively,

 

using a force of 6,000 pounds for 2 minutes.
The compression-molded films were used for Fig 3.4: PBSA Film prepared

by compression molding
evaluating the permeability characteristics of

the .PBS and PBSA nanocomposites.

3.3.5 Measurement of Water Permeability. The water vapor transmission rate
was measured by using MOCON PERMATRAN-W 3/33 (MOCON Inc., US). The
permeability values of PBS and PBSA nanocomposites films were calculated
from the Water Vapor Transmission Rate (WVTR) data. The tests were carried
out at a temperature of 378°C and 100% relative humidity. In analyzing the data,
three specimens of each sample were exposed by using aluminum masks of

1cm2 area.

30

3.3.6 Measurement of Oz'Gas Permeability. The 02 gas transmission rate of
PBS and PBSA nanocomposites films were measured with the help of MOCON
OXTRAN-2/21 (MOCON Inc., US). The tests were performed using 100% 02 gas
concentration at a temperature of 23°C. The aluminum masks were used to

expose an area of 1 cm2 area of compression-molded nanocomposite films.

3.3.7 Differential Scanning Calorimetry.The glass transition, melting, and
crystallization temperatures of the PBS and PBSA nanocomposites were
measured using a 0100 (TA instruments) differential scanning calorimeter. The
tests were carried out at the temperature range of -80°C to 140°C at a scanning

rate of 10°C/min. The materials were scanned using a “heat-cool-heat” cycle.

3.3.8 Izod Impact Tester. A Monitor Izod Impact tester (Testing Machines Inc.,
USA, Model TMI® 43-02-01) was used with a 5-pound pendulum to measure the
notched Izod Impact strength of samples at ambient conditions according to the
ASTM 0256 standard. A TMI notching cutter (Model-22-05) was used to notch
the samples as per the standard. The notched samples were conditioned for at
least 48 hours at 23°C and 50% RH before testing. At least five specimens were

used for each sample in evaluating the notched Izod impact test.

3.3.9 X-Ray Diffraction. The XRD characterization of nanocomposites was used
to study the morphological characteristics of the resulting nanocomposites. The

Bragg’s equation n A = 2 d sine [where; A is the wave length of the light, d is the

 

distance between the clay‘platelets, 6 is the angle of incidence] was used to
calculate interlayer spacing between clay platelets of the organo-clay and the
clay platelets dispersed in the polymer matrix. Experiments were performed at a

wavelength of 0.01541838 nm.

3.3.10 Transmission Electron Microscopy (TEM). The morphological
behaviors of the nanoclay platelets in the PBS and PBSA nanocomposites were
observed using Transmission Electron Microscopy (TEM). Cryogenically
microtomed ultra thin film specimens of the nanocomposites with a thickness of
approximately 70 nm were used for the TEM observations. The microtoming was
carried out at —130°C using the ultramicrotomy with a cryogenic attachment and
diamond knife. A Joel 100 CX TEM with LaB6 filament in 100kV accelerating

voltage was used for observing the TEM images of nanocomposites.

32

 

Preparation of poly (alkylene dicarboxylate)
nanocomposites (PBS-Cloisite 25A or PBSA-
Cloisite 25A nanocomposites)

 

 

 

Second Step ' gfiyfiztron of the tensrle properties by varying the

 

 

 

Analyze the effect of organically modified layered
silicates on the barrier properties of the
nanocomposites

 

 

 

 

Evaluation of the thermo-mechanical properties of
optimum compositions using Dynamic Mechanical
Analysis, Therrno Mechanical Analysis etc.

 

 

 

 

 

V

Morphological study using TEM (Transmission
electron microscopy) and XRD (X-ray diffraction)
for the correlation between the properties and
morphology

 

 

 

 

Figure 3.5: Schematic representation of steps followed for this research work

33

 

Chapter 4

Results and Discussion

4.1 Results. PBS and PBSA are commercially available biodegradable
polyesters with promising futures because of their biodegradable and benign
nature. However, there are certain hurdles towards their commercialization such
as poor properties, high raw material costs, commercial availability at mass
scale, etc. Improvement in the barrier properties, processing properties, and
stiffness of PBS and PBSA can provide the impetus for commercial applications
of these polymers. Reinforcement of polymers with organically modified layered
silicates is a novel innovative technique to improve the mechanical, thenno-
mechanical, and barrier properties of the polymer resins. In this study, we
evaluated the properties of PBS and PBSA nanocomposites. The properties of
the polymer-based nanocomposites are dependent upon processing conditions
such as processing temperature, screw speed, etc. The PBS and PBSA were
processed at 160°C and140°C, respectively. The processing cycle time was
varied from 5 mins. to 20 mins. The processing conditions of PBS and PBSA
nanocomposites are represented in Table 4.1. It was observed that the increase
in process cycle time helped in improving the tensile properties of

nanocomposites.

34

Table 4.1. Processing Conditions Used in Nanocomposites Fabrication

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Processing Conditions
Parameter Unit PBS-Cloisite 25A PBSA-Cloisite 25A
Processing Temperature °C 160 140
Injection Mold Temperature °C 45 40
Screw Speed of Extruder Rpm 100 100
Injection Pressure Psi 100 100
Processing Time Min 3 to 15 Minutes 3 to 20 Minutes
Drying Temp. (Polymer) °C 65 65
Drying Time (Polymer) - Overnight Overnight
Drying Temp. (Clay) °C 80 80
Drying Time (Clay) Hour 6 6
35

Part I

PBSA 3020 - Cloisite 25A

Nanocomposites

36

 

4.1.1 Tensile Properties of PBSA-Cloisite 25A. The Elongation of PBSA-3%
Cloisite 25A and PBSA-5% Cloisite 25A are represented in Figures 4.1 and 4.2,
respectively. Some important factors that can affect the tensile properties of the
polymer clay nanocomposites are aspect ratio of the clay, polymer-organoclay
compatability, dispersion of clay in the polymer matrix, etc. The processing
conditions such as processing cycle time or residence time and screw speed are
also important as they can affect the dispersion of the clay platelets in the
polymeric matrix.

The optimum properties for PBSA-3% 25A and PBSA—5% 25A were
observed at 15 mins and 20 mins processing cycle time, respectively, under the
present experimental conditions. One of the general observations from these
tensile tests was the improvement of the consistency in the properties of the
PBSA-Cloisite25A nanocomposites with the increase in the cycle time that is
supported by lower values of standard deviation at a higher cycle. It was
observed that an increase in cycle time helped in improving % elongation at
break. This could be explained by the better dispersion of the organo-clay in the
polymer matrix which lead to better energy dissipation mechanism. At the lower
processing cycle time, the elongation values dropped drastically. This might be
attributed to the possible agglomeration of the clay. This was due to the fact that
the cracks were usually initiated and propagated through the agglomerates to
provoke the failure of the samples [74]. The d-spacing between the clay platelets
of Cloisite 25A was 1.8 nm [75]. The XRD of PBSA-3% 25A at 15 mins.

processing cycle time indicated exfoliation of the clay platelets whereas in the

37

case of PBSA-5% 25A, the d spacing increased to 3.2 nm. The increase in the
interlayer spacing of the clay platelets in the polymer matrix supports
intercalation of the polymer matrix in the clay platelets. These results were further

elucidated with the help of the TEM studies.

38

 

 

600 -

500 -

400 a

0)
O
O

200 —

Elongation at break(%)

100 -

 

 

 

 

 

 

 

 

Figure 4.1: Comparison of percentage elongation of PBSA and PBSA -3%
Cloisite 25A nanocomposites

A = PBSA (3 min processing time)

B = PBSA-3% Cloisite 25A (10 min processing time)
C = PBSA-3% Cloisite 25A (15 min processing time)
D = PBSA-3% Cloisite 25A (20 min processing time)

39

 

300 9

200 -

 

Elongation at break(%)
8
O

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 4.2: Comparison of percentage elongation of PBSA and PBSA -5%
Cloisite 25A nanocomposites

A = PBSA (3 min processing time)

B = PBSA-5% Cloisite 25A (10 min processing time)
C = PBSA-5% Cloisite 25A (15 min processing time)
D = PBSA-5% Cloisite 25A (20 min processing time)

40

The tensile strength of PBSA-3% 25A and PBSA-5% 25A at varying cycle times
are represented in Figures 4.3 and 4.4, respectively. The change in the
processing cycle time has no effect on the tensile strength of PBSA-3% and
PBSA-5% Cloisite 25A nanocomposites. The increase in the clay concentration
from 3% to 5wt.% did not affect the tensile strength of the nanocomposites.
Similar results for tensile properties were observed by Bousmina et. al. [66] for
PBSA-organoclay nanocomposites. Ray et. al. [70] worked on PBSA and various
organically modified montmorillonite clay, and they found that the yield strength is
independent of the organically modified clay. They related it to the decrease in

the crystallinity of the polymer with the addition of the nanoparticles.

41

 

 

N
01

Tensile Strength (M Pa)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 4.3: Comparison of tensile strength of PBSA and PBSA-3%
Cloisite 25A nanocomposites

A = PBSA (3 min processing time)

B = PBSA-3% Cloisite 25A (10 min processing time)
C = PBSA-3% Cloisite 25A ( 15 min processing time)
D = PBSA-3% Cloisite 25A (20 min processing time)

42

 

 

 

 

 

 

 

 

 

 

 

 

 

 

E
g 25 ‘ _._.._.
s 20 - iiiéiiiiiiié
2’ 2222325232:
2 15: 55533355533:
2 1°: éaééiéiéiséz
2 5 — izisisisisiz
.3 233323232323

0 ......

A B c D

 

Figure 4.4: Comparison of tensile strength of PBSA and PBSA-5%
Cloisite 25A nanocomposites

A = PBSA (3 min processing time)

B = PBSA-5% Cloisite 25A (10 min processing time)
C = PBSA-5% Cloisite 25A (15 min processing time)
D = PBSA-5% Cloisite 25A (20 min processing time)

43

 

 

4.1.2 Dynamic Mechanical Analysis: The storage modulus, loss modulus, and
tan delta peak were analyzed with the help of the DMA. The storage modulus
and loss modulus of a viscoelastic material determine the energy stored and the
energy dissipated as heat. It helps in understanding the viscoelastic behavior and
stiffness of the polymeric material over a range of temperatures. The storage
modulus of PBSA and its nanocomposites is represented in Figure 4.5. The
DMA analysis of the PBSA-Cloisite 25A nanocomposites show that there is
approximately a 53-88% increase in the storage modulus with 3 and 5 wt. %
Cloisite 25A, respectively, as compared to the neat PBSA at 30°C. The increase
in the storage modulus of PBSA nanocomposites can be attributed to the
intercalation of the polymer in the clay platelets that reduces the mobility of
polymer chains [56]. There was no shift in the tan-delta peak with the addition of

the organo-clay in the polymer matrix.

44

 

 

§

 

 

 

 

 

 

 

 

 

 

 

’6
o. _. . I . ..
E 600 ,_ g:;:;:g:g:g:g:g:
g 33:3:3T'-':3:3:3: 22223232133?
3 2:222:2:2:2:2:: 222233222222:
0 40°“ ....... 1...... zzsrszzzsrsrszz 2:222:2zszszzrs:
2 313:3:3:3:3:3:3: :12323232323:3: 23:3:323z323:3:i
g, 1:3:3:3:1:3:3:3: 1321;321:155: 11235233313131
(5 200- f:f:f:f:§:f:f:f: :f:}:§:§:f:;:f: :;:;:;:f:;:;:;:1
3 -:-:-:':-:-:-:-: ;.;.;.;.;.;.;.; :-:-:-:~:-:-:-:i
.._, .............................................. j
(I) i:?:3:?:3:?:3:T: 23:11:223135: 2313;323:3513:
0 .............................................. I
A B C

 

Figure 4.5: Storage Modulus of PBSA Cloisite 25A nanocomposites
A = PBSA (3 min processing time)

B = PBSA-3% Cloisite 25A (15 min processing time)
C = PBSA-5% Cloisite 25A (20 min processing time)

45

 

4.1.3 Barrier Properties of PBSA Nanocomposites: Evaluation of the barrier
properties is crucial for determining the possible food and medical packaging
applications of the polymeric material. Poor oxygen gas and water vapor
permeability reduce the shelf life of the food or pharmaceutical product by
producing physical and chemical changes. Oxidation and loss of crispiness in the
food product as well as stability of the pharmaceutical product are some of the
common factors which determine the selection of the package system for a
particular product. The permeability through the polymer is a combination of
three phenomenons: absorbtion, permeation, and desorbtion. Figure 4.6 shows a
schematic representation of the permeability mechanism through a polymeric

material.

The permeability coefficient (P) of a polymer is defined as the product of a
diffusion coefficient (D) and a solubility coefficient (S). PBSA is polar in nature.

Therefore, it has a higher water solubility coefficient as compared to polyolefins.

46

High
Pressure

#
fl
_
fl
#
a
—a

Fig. 4.6: Permeability Mechanism

Adsorption

 

3W“

Diffusion

W

 

 

 

 

P=DxS

 

 

 

47

Desorption

lllllll

Low
Pressure

4.1.4 Water Vapor Barrier. The permeability of a polymer is the product of
diffusion and solubility. The high aspect ratio of the clay combined with the
dispersion of the clay and proper orientation of the clay platelets in the polymer
matrix help in reducing the diffusion of the water vapors and other permeants.
Morphology and chemical structure also affect the barrier properties of a
polymer. We used compression-molded PBSA nanocomposites films to evaluate
the water barrier properties. The water vapor permeability of PBSA and PBSA-
3% Cloisite 25A is represented in Figure 4.7. The water barrier of compression-
molded PBSA was found to be poor as compared to commercially available
polyethylene. The water vapor barrier of PBSA improved by 70% with the
addition of 3 wt.% Cloisite 25A. The improvement in water barrier can be related
to the tortuous zig- zag path created by the clay platelets which hindered the
diffusion process resulting in the improvement of the water barrier characterstics
of the polymer. A schematic representation of the tortuous zig-zag path is shown
in Figure 4.8. Ray et. al. [51] observed similar kinds of results for FLA-organically
modified clay-based nanocomposites. Processing of the films play an important
part in the morphology and the barrier characteristics. Therefore, the permeability
of the PBSA nanocomposite films can be improved by preparation of the cast

films using biaxial orientation.

48

 

 

 

g mil/100in2day mmhg

 

 

 

 

 

 

 

 

 

 

2 _
..... .T......
23:2:2:s:2:i.:2:s:2:s:2:
1.5 — 33332333233333333323333
1 ~ :ézé;:;é:é;é;ézé:ézéaéa
0.5 « §s§s§s§2§s§s§s§3§3§3§5§ .;.;.;.;.;L.:.:.:.:.
0 :;:;:;:;:;:;:;:;:;:;:;: :3:3:1:3:3:3:3:3:3:3:3:
A B

 

 

 

Fig 4.7: Water vapor permeability of PBSA Cloisite 25A
Nanocomposites

A = PBSA
B = PBSA-3% 25A

49

High Concentration of High Concentration of
Permeant Permeant

/—-—-\

 

 

 

 

 

V V V

 

Low Concentration of
Permeant

Low Concentration of
Permeant

Nanocomposites Conventional Composites

Fig 4.8: Schematic representation of permeation process: Nana-composites Vs.
Conventional composites

50

4.1.5 Oxygen Gas Barrier. The oxygen gas permeability coefficients of PBSA,
PBSA-3% Cloisite 25A are represented in Figure 4.9. The oxygen banter of
PBSA-3% Cloisite 25A improved by 56% as compared to the neat polymer. The
exfoliation of the clay in the PBSA-3% Cloisite 25A is responsible for the creation

of the tortuous zig—zag path as explained in Figure 4.8.

Table 4.2. Bam’er Properties of PBSA Nanocomposites

 

 

 

 

 

Water vapor permeability Oxygen permeability
Material
(9 mil/ 100 in2 day mmHg) (cc mil/ 100 in2 day atm)
PBSA 1.8 80
PBSA-3% Cloisite 25A 0.5 35.5

 

 

 

51

 

 

 

 

 

 

 

 

 

 

100 22
>‘ T
g 80 2323332325445232533232
5 so -- iiiiiiiiiiiiiiiiifiiiié
o .......................
O :3:3:3:3:3:3:3:3:3:3:3:
‘- 40 4 :f:f:f:f:f:§:f:f:f:f:f: 1-
E :-:-:-:-:-:-:-:-:-:-:' .......................
E :f:f:§:f:f:f:f:f:§:f:f: :§:§:§:§:§:J;?f:f:f:f:§:j
o 20 2 333:3:3:3:3:3:3:3:3:3:? 3:323:3:3:f:3:3:3:3:}:f
° :;;;;;;;;;;;;;;;;;;;;; 2:222:222252232222222
0 _i-2___ :-:-:-:-:-:-:-:-:~:-:-: #_ :.:-:-:-:-:-:-:-:-:-:-:
A B

 

Fig 4.9: Oxygen gas permeability of PBSA Cloisite 25A
Nanocomposites

A = PBSA
B = PBSA-3% Cloisite 25A

52

 

4.1.6 Notched Izod Impact Strength: Izod impact strength plays an important
role to select the polymer for particular applications. It helps us to understand the
effect of stress concentration at notch on the performance of the polymers. The
izod impact strength of PBSA, PBSA-3 wt.% Cloisite 25A and PBSA-5 wt.%
Cloisite 25A are represented in Figure 4.10. The impact strength of the PBSA
decreased with the addition of the clay in the PBSA matrix. The energy required
to break the PBSA specimens was 115 J/m. It was noted that the energy
required for the PBSA-3wt.% Cloisite 25A nanocomposites and PBSA-5wt.%
Cloisite 25A nanocomposites decreased to about 50 J/m. This indicates that
there was more stress concentration in the case of PBSA nanocomposites as

compared to the neat polymer.

53

150 -
125 i
100 I

75 -‘

 

Impact strength (J/m)

257

 

 

PBSA/3% 25A PBSN5% 25A

 

0 l_____ _________
PBSA

Fig. 4.10: Izod impact strength of PBSA and PBSA Cloisite 25A
nanocomposites

54

4.1.7 XRD Analysis. X-ray diffraction (XRD) is widely used to analyze the
morphology of polymer—clay nanocomposites. XRD data provides interlayer
spacing or d-spacing between the clay platelets. PBSA-3% 25A (15 min. cycle
time) and PBSA-5% 25A (20 min. cycle time) have been analyzed at the
wavelength of 0.015418 nm. The interlayer spacing of Cloisite 25A, PBSA-3 wt.%
Cloisite 25A and PBSA-5wt.% Cloisite 25A are represented in Table 4.3. There
was no doo1 peak in PBSA-3 wt.% w/w 25A which would have indicated the
exfoliation of the clay in the polymer matrix. For PBSA-5 wt.% 25A, the interlayer
spacing between the clay platelets increased to 34 A from 18.6 A. The data
supports better dispersion of clay platelets in the polymer matrix at a low weight
percentage. The diffractograms of PBSA-3% Cloisite 25A and PBSA-5% 25A are

represented in Figure 4.11.

Table 4.3. lnterla yer Spacing or d Spacing of Clay and PBSA Nanocomposites

 

 

 

 

Material Interlayer Spacing (A)
Cloisite 25A* 18.6
PBSA-3% Cloisite 25A (15 min. cycle time) No Peak
PBSA-5% Cloisite 25A (20 min. cycle time) 32.1

 

 

 

 

* Data from the Southern Clay Products, Texas

55

CPS

8000 -

6000

40004

2000 :

 

 

 

2 Theta

Figure 4.11:X-Ray Diffractogram of PBSA Cloisite 25A
nanocomposites

A = PBSA-3% Cloisite 25A
B = PBSA-5% Cloisite 25A

56

4.1.8 Differential Scanning Calorimetry. The total heat of fusion (A Hm),
calculated by the integration of the area under the melting peak is shown in Table
4.4. The heat of fusion decreased significantly with the incorporation of 3 wt. %
Cloisite 25A as compared to the neat PBSA. The morphology of the clay platelets
in the polymer matrix also affects the overall crystallization. Krikorian et. al. [76]
observed that increased sperulite nucleation is achieved in the intercalated kind
of morphology. We observed the exfoliation kind of morphology in the PBSA - 3
wt.% Cloisite 25A system. TEM images and XRD indicate that a combination of
intercalation and exfoliation exist in the PBSA-5% Cloisite 25A nanocomposites
[76]. The intercalated portion might be responsible for the higher enthalpy of
PBSA-5% Cloisite 25A than PBSA-5% Cloisite 25A.

Table 4.4. Enthalpy of Melting of PBSA Cloisite 25A Nanocomposites

 

 

 

 

 

Material Enthalpy of melting (J/g) Standard Deviation
PBSA 50.6 1.1
PBSA-3% Cloisite 25A 36.6 0.8
PBSA-5% Cloisite 25A 39.7 4.4

 

 

 

57

 

 

 

 

 

 

 

 

 

 

 

20
B & c.
10 . f; (Overlapping)
3 JR: A
2 .— J '-
Z 0 l L"; 1
a ‘ _ w ..... ’-
é’ \
-10 2
-20 , . . T .
—80 -30 20 70 120 170
Temperature (°C)

Fig. 4.12 Thermographs of PBSA Cloisite 25A nanocomposites
A = PBSA

B = PBSA-3% Cloisite 25A
C = PBSA-5% Cloisite 25A

58

TEM images:-

 

Fig: 4.13: TEM Photomicrographs of PBSA—3% Cloisite 25A

59

 

Fig: 4.14: TEM Photomicrographs of PBSA-5% Cloisite 25A

60

Part II

PBS 1020 - Cloisite 25A

Nanocomposites

6l

4.1.9 Tensile Properties of PBS Nanocomposites. The properties of PBS-3%
25A and PBS-5% 25A nanocomposites were studied at processing cycle times of
5 mins., 10 mins. and 15 mins. The mechanical, thermo-mechanical, and barrier
properties of PBS nanocomposites were evaluated. The tensile properties of the
PBS and PBS nanocomposites were measured as per ASTM D-638. The tensile
properties of PBS-3% 25A are represented in Figure 4.15. The PBS 1020 has
300% elongation at break. The elongation of PBS improved by 20% due to the

reinforcement of the matrix with 3% Cloisite 25A at a different cycle time.

The increase in the cycle time has no effect on the elongation of PBS-3%
Cloisite 25A. This could be explained by the good polymer-nanoclay interaction.
The elongation of PBS-5% Cloisite 25A is represented in Figure 4.16. It was also
observed that the increase in the clay content from 3% wt.% to 5 wt.% did not
help in further improving the tensile properties. The tensile strength of the PBS
nanocomposites improved by 10% with the addition of 3% and 5 wt.% organically
modified clay. These results support that the 3% Cloisite 25A is optimum for this
particular polymer matrix-clay system, and the increase of the clay content to 5

wt. % did not affect the properties of the system.

62

 

 

 

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A B C D

 

 

 

Figure 4.15: Comparison of percentage elongation of PBS and PBS-3%
Cloisite 25A nanocomposites

A = PBS (3 min processing time)

B = PBS-3% Cloisite 25A (5 min processing time)
C = PBS-3% Cloisite 25A (10 min processing time)
D = PBS-3% Cloisite 25A (15 min processing time)

63

 

 

 

 

 

 

 

 

 

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Figure 4.16: Comparison of percentage elongation of PBS and PBS-5%
Cloisite 25A nanocomposites

A = PBS (3 min processing time)

B = PBS-5% Cloisite 25A (5 min processing time)
C = PBS-5% Cloisite 25A (10 min processing time)
D = PBS-5% Cloisite 25A (15 min processing time)

 

 

 

 

 

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Figure 4.17: Comparison of tensile strength of PBS and PBS-3%

Cloisite 25A nanocomposites

A = PBS (3 min processing time)

B = PBS-3% Cloisite 25A (5 min processing time)
C = PBS-3% Cloisite 25A (10 min processing time)
D = PBS—3% Cloisite 25A (15 min processing time)

65

 

 

 

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Figure 4.18: Comparison of tensile strength of PBS and PBS-5%
Cloisite 25A nanocomposites

A = PBS (3 min processing time)

B = PBS-5% Cloisite 25A (5 min processing time)
C = PBS-5% Cloisite 25A (10 min processing time)
D = PBS-5% Cloisite 25A (15 min processing time)

66

 

4.1.10 Storage Modulus. The storage modulus was measured with the help of
DMA 0800. The data is represented in Figure 4.19. The storage modulus of the
PBS increased with the increasing nano-clay content in the polymer matrix. The
modulus of the PBS matrix increased by 30% and 57% with loadings of 3% and 5
wt % clay, respectively. The organo-clay platelets can reduce the mobility of the
polymer chains as well as increase the reinforcement of the polymer matrix. The
increase in the storage modulus in the PBS clay nanocomposites has also been

reported by other researchers.

67

Storage Modulus (MPa)

5000 2

 

 

 

4000 2 '- A
‘\
3000 2
2000
I000 -
0 . . . . .
-100 -60 -20 20 60 I00

Temperature (°C)

Fig. 4.19: Graph of Storage Modulus of PBS Cloisite 25A
nanocomposites

A = Neat PBS

8 = PBS-3% Cloisite 25A processed for 5 minute
C = PBS-5% Cloisite 25A processed for 5 minute

68

 

 

 

 

 

 

 

 

 

 

 

 

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Figure 4.20: Storage modulus of PBS Cloisite 25A nanocomposites

A = PBS
8 = PBS-3% Cloisite 25A
C = PBS-5% Cloisite 25A

69

Tan Delta

0.12 -

0.1 ’

0.03 .
0.06 -'
0.04 «

0.02 i

 

 

 

 

 

20 70

Temperature (0 C)

Figure 4.21: Tan 6 of PBS Cloisite 25A nanocomposites

A=PBS (3 min processing time)
B=PBS-3% Cloisite 25A (5 min processing time) at 160°C
C=PBS-5% Cloisite 25A (5 min processing time) at 160°C

70

4.1.11 Permeability: Free volume of a polymer, orientation of polymer chains,
and the percentage crystallinity of the polymeric materials play an important part
in understanding the permeability of a packaging material. For the polymer-clay
nanocomposites system, the clay platelets hinder the crystallinity of the polymer
nanocomposites by reducing the flexibility of the chains because of the
intercalation of the polymer between the clay platelets. The high aspect ratio and
the tortuous path created by the layered silicates are some of the factors
responsible for reducing the permeability of the polymer. Therefore, the
dispersion of the clay in the polymer matrix plays a crucial role in reducing the
permeability. The permeability of compression molded films of PBS—3 wt.% 25A
and PBS-5 wt.% 25A nanocomposites were evaluated at the 5-minute
processing cycle time. The permeability of the nanocomposites decreased as
compared to the virgin polymer because layered silicate platelets hindered the
permeability by creating a “tortuous path” which decreased the transmission rate

of the water vapors and gases.

4.1.12 Water Vapor Permeability. The water vapor permeability of PBS, PBS-
3% 25A (5 mins.) and PBS-5% 25A (5 mins.) is represented in Figure 4.22. The
permeability of PBS-3% 25A decreased by 20% as compared to the neat PBS
polymer. The increase in the clay content from 3 wt. % to 5 wt. % did not help in
reducing the permeability of the polymer. The increase in the clay content to 5%

may have reduced the crystallinity process of the polymer-clay nanocomposites

71

that may have compensated for the barrier created by the increase in the layered
silicates.

The Neilson model is a two-dimensional model that predicts the
permeability of the polymer composites. This model assumes that the clay
platelets are dispersed parallel to the film surface. The mathematical equation for

the Neilson model is [29, 51]:
PN/Pp = Vp/ 1 + (U2W) VF

Where,

PM = Permeability of the composites
Pp = Permeability of the polymer
Vp= Volume fraction of the polymer
Vp= Volume fraction of the filler

W = Aspect ratio of the filler

Cloisite 25A has an aspect ratio of 200 (approx). We observed that water
vapor permeability values obtained for the PBS-3 wt. % nanocomposites match
the aspect ratio value of 150. The TEM images of the PBS-nanocomposite
support the aspect ratio of 150. However, no further increase was observed in
the permeability of the PBS nanocomposites with elevated clay content from 3
wt. % to 5 wt. %. This can be explained by the partial agglomeration of clay

platelets in the polymer matrix as observed in the TEM images.

72

 

 

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Fig 4.22: Water vapor permeability of PBS-3% 25A and PBS-5% 25A
processed at 5 min. cycle time

A=PBS

B = PBS-3% Cloisite25A
C = PBS-5% CloisiteZSA

73

4.1.13 Oxygen Permeability: The oxygen gas permeability of PBS, PBS-3%
25A, and PBS-5% 25A are represented in Figure 4.23. We observed around 5%
improvement in the oxygen barrier with the addition of 3 wt. % organo-clay. The
addition of 5 wt. % organo-clay in the polymer matrix increased the permeability
of the PBS-nanocomposites. This could be explained by the agglomeration of

clay in the polymer matrix at a high clay concentration.

Table 4.5. Barn'er Properties of PBS Cloisite 25A Nanocomposites

 

 

 

 

 

Water Vapor Permeability Oxygen Permeability
Material . . 2 . . 2
(9 mill 100m day mmhg) (cc "NV 100 In day atm)
PBS 0.62 30.82
PBS-3% Cloisite 25A 0.5 29.34
PBS-5% Cloisite 25A 0.49 42.9

 

 

 

 

 

74

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0 4L_ V.J.‘..::.:.:. ...... L ..... 1133 ;.:.:.:.:.:.:.:.

Fig: 4.23: Oxygen gas permeability of PBS and PBS nanocomposites
A = PBS (3 min processing time)

B = PBS-3% Cloisite 25A (5 min processing time)
C = PBS-5% Cloisite 25A (5 min processing time)

75

4.1.14 Differential Scanning Calorimetry. The total heat of fusion (A Hm)
calculated by the integration of the area under the melting peak and
crystallization onset temperatures are shown in Table 4.6. A decrease was
observed in the crystallization onset temperature in the presence of the Cloisite®
25A. The heat of fusion increases upon the incorporation of 3 wt. % Cloisite 25A
as compared to the neat PBS. However, the heat of fusion of PBS-3 wt. %
Cloisite 25A and PBS-5 wt. % Cloisite® 25A are almost similar. This can be
ascribed to the phenomenon that a small amount of clay can increase the rate of
crystallization; however, high organoclay loading reduces the rate of
crystallization. The morphology of the clay platelets in the polymer matrix also
affects the overall crystallization. Krikorian et. al [76] observed that increased
sperulite nucleation is achieved in the intercalated kind of morphology. A
combination of exfoliation and interaction morphology was observed in the PBS-
3% w/w Cloisite” 25A system; whereas TEM images and XRD support the
combination of intercalation and partial agglomeration in the PBS - 5% 25A

nanocomposites.

Table 4.6. Enthalpy of Melting of PBS Cloisite 25A Nanocomposites

 

 

 

 

Material Enthalpy of Melting (Jlg) Standard Deviation
PBS 53.3 4.8
PBS-3% Cloisite 25A 55.3 0.9
PBS-5% Cloisite 25A 55.6 2.2

 

 

 

 

 

76

Heat flow

 

20 .

10*

 

 

 

 

 

 

-20 T r r T r
-80 -30 20 70 120 170

Temperature (°C)

Fig. 4.24 Thermographs of PBS Cloisite 25A nanocomposites
A = PBS

B = PBS-3% Cloisite25A
C = PBS-5% Cloisite 25A

77

 

4.1.15 XRD Analysis: The X-ray diffraction of PBS-3% 25A (5-min. cycle time)
and PBS-5% 25A (5-min. cycle time) has been studied at the wavelength of
0.015418 nm. The gallery spacing (dam spacing) between the clay platelets of
PBS-3% 25A and PBS-5% 25A nanocomposites when calculated through
bragg’s equation is 35.4 and 34.6 A, respectively. The increase in the interlayer
spacing supports the intercalated morphology in the PBS-3 wt. % 25A and

PBSA-5 wt. % nanocomposites.

Table 4.7. Interlayer Spacing of PBS-3% 25A (5 mins.)

 

 

 

 

and PBS-5% 25A (5 mins.)
Material Interlayer Spacing (A)
Cloisite 25A* 18.6
PBS-3% Cloisite 25A 35.34
PBS-5% Cloisite 25A 34.65

 

 

 

 

* Data from the Southern Clay Products, Texas

78

CPS

 

 

 

 

4000 7
A

3000 e
B

2000 d

1000 r

0 ‘t—' ‘ — fi fi r
1 3 5 7 9

2 Theta

Fig. 4.25 XRD Analysis of PBS-3% Cloisite 25A and PBS-5%
Cloisite 25A Processed at 5-min. cycle time

A = PBS-3% Cloisite 25A
B = PBS-5% Cloisite 25A

79

4.1.16 TEM Studies: Figures 4.26 and 4.27 represent TEM photo micrographs of
PBS-3% wt.% Cloisite 25A and PBS-5 wt.% Cloisite 25A nanocomposites,
respectively. An exfoliated type of morphology was obtained in the PBS-3 wt.%
Cloisite 25A nanocomposites while a combination of intercalated and exfoliated

type of morphology was observed in PBS-5 wt.% Cloisite 25A.

 

Fig: 4.26: TEM Photomicrographs of PBS- 3% Cloisite 25A processed at

5 minute cycle time.

80

 

Fig: 4.27: TEM Photomicrographs of PBS- 5% Cloisite 25A processed at

5 minute cycle time.

81

Chapter 5
Conclusion and Recommendation

for Future Work

We have successfully developed biodegradable poly(butylene succinate)-
Cloisite 25A (OMMT) nanocomposites. The effect of variation in the processing
conditions, especially processing cycle time on the mechanical properties, was
studied. It was observed that the higher processing time can help in the

improvement of the mechanical properties of the polymer.

Significant improvement was observed in the storage modulus and
thenno-mechanical properties. The storage modulus of PBSA-5% Cloisite 25A
improved by 87% as compared to virgin PBSA. The storage modulus of PBS-5%
Cloisite 25A increased by 57% as compared to the neat polymer. The layered
silicates created a tortuous zig-zag path for the penneant which help with the
water and oxygen gas barrier properties of PBSA-Cloisite 25A and PBS-Cloisite
25A nanocomposites. The oxygen and water vapor barrier of PBSA improved by
52% and 76%, respectively, with 5% wt.% Cloisite 25A. A 20% improvement was

observed in the water vapor barrier properties of PBS nanocomposites. There

82

was XRD, and TEM revealed the intercalated and exfoliated kind of morphology

in the PBS and PBSA nanocomposites.

In conclusion:

Increase in the processing cycle time helped in the better dispersion and
exfoliation of the clay in the polymer matrix of PBSA-Cloisite 25A
nanocomposites.

The reinforcement of the PBS and PBSA with Cloisite-25A helped in
increasing the stiffness of the polymer.

PBS nanocomposites and PBSA nanocomposites possess better thermo-
mechanical properties as compared to respective virgin polymers.

Barrier properties of PBS-Cloisite 25A nanocomposites and PBSA-Cloisite
25A nanocomposites improved significantly because of the creation of a
tortuous zig-zag path by the clay platelets in the polymer matrix.

There was no significant difference in the properties of PBS-3 wt.%
Cloisite 25A and PBS-5 wt. % Cloisite 25A. Therefore, it is perhaps safe to
conclude that 3 wt% Cloisite 25A concentration can be the optimum
amount of clay in the PBS nanocomposites under the present
experimental set of conditions or parameters.

XRD, TEM, and properties correlation were well established.

The increase in the processing cycle time from 5 mins. to 15 mins. did not

have much impact on tensile properties of PBS-3% 25A.

83

Based on our studies, it is recommended that these studies be further
extended by utilizing the Twice F unctionalized Clay (T FC)

The stiffness of PBS and PBSA can be enhanced by preparing blends
with stiff materials such as SoronaT”.

The compression molding technique was used to prepare nanocomposites
films. Better PBS and PBSA nanocomposite properties can be obtained
through extrusion-blown film or biaxial cast film production because of
orientation of the polymeric chain. Therefore, this work can be extended
by producing nanocomposites film at blown film or cast film extruder.
Nano—reinforcement helps in improving processing conditions. Therefore,
the effect of nano-reinforcement on the processing properties of PBS and

PBSA can be evaluated.

84

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