UNIVERSITI TEKNIKAL MALAYSIA MELAKA
OPTIMIZATION OF MIXING PARAMETERS TO PRODUCE
PP/ENR BLEND VIA RESPONSE SURFACE METHODOLOGY
This report submitted in accordance with requirement of the Universiti Teknikal
Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering
(Engineering Material)
by
FAISAL FARIS BIN RAHIM
B050910134
870116565273
FACULTY OF MANUFACTURING ENGINEERING
2012
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA
TAJUK: Optimization of mixing parameters to produce PP/ENR blend via response surface methodology.
SESI PENGAJIAN: 2011/12 Semester 2 Saya FAISAL FARIS BIN RAHIM mengaku membenarkan Laporan PSM ini disimpan di Perpustakaan Universiti Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut:
1. Laporan PSM adalah hak milik Universiti Teknikal Malaysia Melaka dan penulis. 2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan
untuk tujuan pengajian sahaja dengan izin penulis. 3. Perpustakaan dibenarkan membuat salinan laporan PSM ini sebagai bahan
pertukaran antara institusi pengajian tinggi.
4. **Sila tandakan (√)
SULIT
TERHAD
TIDAK TERHAD
(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia yang termaktub di dalam
AKTA RAHSIA RASMI 1972)
(Mengandungi maklumat TERHAD yang telah ditentukan
oleh organisasi/badan di mana penyelidikan dijalankan)
Alamat Tetap:
No.100 Jalan TC 1/5
Taman Cemerlang, Gombak
53100 Kuala Lumpur
Tarikh: 1/06/2012
Disahkan oleh:
PENYELIA PSM
Tarikh: _______________________
** Jika Laporan PSM ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh laporan PSM ini perlu dikelaskan sebagai
SULIT atau TERHAD.
I hereby, declared this report entitled “Optimizing of mixing parameters to
produce PP/ENR blend via response surface methodology” is the results of my
own research except as cited in references.
Signature : ………………………………………….
Author’s Name : Faisal Faris Bin Rahim
Date : 1st June 2012
DECLARATION
This report is submitted to the Faculty of Manufacturing Engineering of
Universiti Teknikal Malaysia Melaka (UTeM) as a partial fulfillment of the
requirements for the degree of Bachelor of Manufacturing Engineering
(Engineering Material). The member of the supervisory committee is as
follow:
………………………………
(Official Stamp of Principal Supervisor)
APPROVAL
i
ABSTRAK
Termoplastik elastomer semakin mendapat perhatian kerana ciri-cirinya yang
menyerupai getah tervulkan dan mudah difabikat seperti termoplastik. Kajian ini
merupakan satu usaha untuk meneroka potensi polipropilena (PP) apabila
digabungkan dengan getah asli terepoksida ENR. Polipropilena (PP) dan getah asli
terepoksida(ENR) disediakan melalui kaedah penyebatian lebur menggunakan
pencampur dalaman dan pematangan sulfur. Parameter pencampur seperti nisbah,
suhu percampuran, masa percampuran dan kelajuan pemutar dioptimumkan dengan
kaedah metodologi permukaan sambutan dengan bantuan perisian Expert 6.0.10.
Suhu pencampuran dan terma interaksi telah dikenalpasti sebagai faktor tidak
signifikan dengan nilai P lebih daripada 0.0500. Beberapa ujian dan analisis
termasuk ujian ketumpatan, indeks kecairan aliran, ujian tegangan, ujian kekerasan,
kemikroskopan elektron imbasan (SEM) dan pemeteran kalori pengimbasan
kebezaan (DSC) dijalankan untuk mencirikan sifat-sifat PP/ENR. ENR berupaya
meningkatkan keliatan dan kebolehlenturan polipropilena. Nilai kiraan optimum
untuk pembolehubah yang dikaji (nisbah, suhu, kelajuan pemutar dan masa
pencampuran) untuk memaksimumkan pemanjangan sebelum putus telah
dikenalpasti sebagai ENR 16.33%, suhu 170oC, kelajuan pemutar 50rpm dan masa
pencampuran 6 minit dengan pemanjangan yang dijangkakan sebelum terputus pada
11.7171%, berbanding 9% PP tulen.
ii
ABSTRACT
Thermoplastic elastomers have become important because they have combination
properties of vulcanized rubbers and can be rapidly fabricated as thermoplastic. This
research is an effort to explore the potential of polypropylene (PP) when
incorporated with ENR. Polypropylene (PP) and epoxidized rubber (ENR) were
prepared by melt blending with internal mixer and sulfur curing. Mixer parameter
such as the ratio, mixing temperature, mixing time, and rotor speed were optimized
with response surface methodology with the assistance of Design Expert 6.0.10
software. The mixing temperature and its interaction terms were identified as
insignificant factors with a P value greater than 0.0500. Testing and analysis
including density test, melt flow index (MFI), tensile test, hardness test, impact test,
scanning electron microscopy (SEM) and differential scanning calorimetry (DSC)
were performed to characterize the properties of PP/ENR. The ENR is proven to
increase toughness and flexibility of polypropylene. The optimum calculated values
of the tested variables (ratio, temperature, rotor speed and mixing time) for the
maximum elongation to break was found to be at ENR of 16.33%, temperature of
170oC, rotor speed of 50 rpm and a mixing time of 6 min with a predicted elongation
to break of 11.7171%, compared to 9% of pure PP.
iii
ACKNOWLEDGEMENT
I would like to offer my unreserved gratitude and praises to Almighty Allah for His
generous blessing and the undying strength bestowed upon me during the course of
this research.
Special thanks to my supervisor, Dr. Noraiham Mohamad who guide, assist and
advice me all the way through this project.
Thanks to all my friends, who always give me the moral support and been there
whenever I am in need.
iv
TABLE OF CONTENT
Abstrak i
Abstract ii
Acknowledgement iii
Table of Content iv
List of Tables viii
List of Figures xi
List of Abbreviations xiv
List of Symbols xv
1. INTRODUCTION 1
1.1 Background 1
1.2 Problem Statement 2
1.3 Objective 3
1.4 Scope 3
1.5 Chapter Overview 3
2. LITERATURE REVIEW 5
2.1 Polymer Blends 5
2.1.1 Thermoset Elastomer (TSE) 7
2.1.2 Thermoplastic Elastomer (TPE) 8
2.1.2.1 Thermoplastic 9
2.1.2.2 Elastomer 10
2.1.2.3 Current Development of Thermoplastic Elastomer 12
2.2 Compounding Process 14
2.2.1 Melt Blending 15
2.2.1.1 Internal Mixer 15
2.2.1.2 Twin-Screw Extruder 16
2.2.1.3 Two Roll Mill 17
2.2.1.4 Injection Molding 18
v
2.2.2 Compressing Molding 19
2.3 Vulcanization/Curing Process 20
2.3.1 Sulfur Vulcanization 20
2.3.2 Peroxide Vulcanization 23
2.3.3 Mixed Vulcanization 24
2.4 Fabrication 24
2.4.1 Hot Press 24
2.4.2 Cold Press 25
2.4.3 Isostatic Press 25
2.5 Testing and Analysis 26
2.5.1 Physical Test 26
2.5.1.1 Density Test 26
2.5.1.2 Melt Flow Index (MFI) 26
2.5.2 Mechanical Test 27
2.5.2.1 Tensile Test 27
2.5.2.2 Izod Impact Test 28
2.5.2.3 Hardness Test 29
2.5.3 Morphological Study 31
2.5.3.1 Scanning Electron Microscopy (SEM) 31
2.5.4 Thermal Analysis 32
2.5.4.1 Differential Scanning Calorimetry 32
2.6 Optimization 32
2.6.1 Response Surface Methodology (SEM) 33
3. METHODOLOGY 38
3.1 Introduction 38
3.2 Raw Material 40
3.3 Characterization of Raw Material 40
3.3.1 Polypropylene 40
3.3.2 Epoxidized Natural Rubber 41
3.3.3 Sulfur 42
vi
3.4 Optimization of Internal Mixer Parameter using Response Surface
Methodology (RSM) 44
3.4.1 Design of Experiment 44
3.4.1.1 Screening Factor 44
3.5 Blending of PP/ENR Blends in Internal Mixer 46
3.6 Pelletizing 48
3.7 Hot Pressing 50
3.8 Testing and Analysis 52
3.8.1 Physical Test 52
3.8.1.1 Density Test 52
3.8.1.2 Melt Flow Index (MFI) 53
3.8.2 Mechanical Test 55
3.8.2.1 Tensile Test 55
3.8.2.2 Hardness Test 56
3.8.2.3 Izod Impact Test 58
3.8.3 Morphological Study 59
3.8.3.1 Scanning Electron Microscopy (SEM) 59
3.8.4 Thermal Analysis 60
3.8.4.1 Differential Scanning Calorimetry (DSC) 60
4. RESULT AND DISCUSSION 61
4.1 Introduction 61
4.2 Raw Material Characterization 62
4.2.1 Density 62
4.2.2 Melt Flow Index 62
4.3 Optimization of Physical and Mechanical Properties 63
4.3.1 Density Analysis 63
4.3.2 Hardness 70
4.3.3 Melt Flow Index 76
4.3.4 Impact Strength 82
4.3.5 Tensile Properties 89
4.3.5.1 Tensile Strength 90
4.3.5.2 Elongation to Break 95
vii
4.3.5.3 Young Modulus 101
4.4 Analysis 107
4.4.1 Scanning Electron Microscopy (SEM) 107
4.4.2 Differential Scanning Calorimetry (DSC) 110
4.5 Determination of the optimum formulation of PP/ENR using the
Response Surface Methodology (RSM) 111
5. CONCLUSION AND RECOMMENDATION 114
5.1 Conclusion 114
5.2 Recommendation 115
REFERENCES 116
APPENDIX
viii
LIST OF TABLES
Table 2.1: Basic recipe for the sulfur vulcanization system 21
Table 2.2: Sulfur vulcanization system 23
Table 2.3: Compounding formulation for ENR 23
Table 2.4: 23 Factorial Design Matrix Used for the Screening Factors 35
Table 2.5: Levels of Variables Chosen for Trial 36
Table 2.6: Full Factorial Central Composite Design for the Optimization
of Machine Parameters in the ENRAN Composite Preparation 36
Table 2.7: Levels of Variables Chosen for Trial in the
Optimization Experiments 36
Table 3.1 General properties of polypropylene 40
Table 3.2 Thermal properties of polypropylene 41
Table 3.3: Properties of sulfur 43
Table 3.4: Properties of zinc oxide 43
Table 3.5: Properties of stearic acid 44
Table 3.6: Combination of parameters internal mixer machine for 24 factorial
designs for screening factor 45
Table 3.7: Level of variables for the screening factor 45
Table 3.8: Composition of ENR vulcanization 46
Table 3.9: Design matrix of process parameter PP/ENR blends 47
Table 3.10: Level of variables 48
Table 3.11: The standard test conditions sample weight and
testing time for materials. 55
Table 4.1: Density Average of PP and ENR 62
Table 4.2: Melt Flow Rate of PP and ENR 63
Table 4.3: Density Average with Mixing Parameters and Ratios 64
Table 4.4: ANOVA for the Selected Factorial Models 66
Table 4.5: Observed Responses and Predicted Values 67
Table 4.6: Regression Coefficients and P Values as
ix
Calculated from the Models 68
Table 4.7: Hardness with Mixing Parameters and Ratios 70
Table 4.8: ANOVA for the Selected Factorial Models 72
Table 4.9: Observed Responses and Predicted Values 73
Table 4.10: Regression Coefficients and P Values as
Calculated from the Models 74
Table 4.11: Melt flow rate with Mixing Parameters and Ratios 77
Table 4.12: ANOVA for the Selected Factorial Models 79
Table 4.13: Observed Responses and Predicted Values 80
Table 4.14: Regression Coefficients and P Values as
Calculated from the Models 80
Table 4.15: Impact strength with Mixing Parameters and Ratios 83
Table 4.16: ANOVA for the Selected Factorial Models 85
Table 4.17: Observed Responses and Predicted Values 86
Table 4.18: Regression Coefficients and P Values as
Calculated from the Models 87
Table 4.19: Tensile strength with Mixing Parameters and Ratios 90
Table 4.20: ANOVA for the Selected Factorial Models 91
Table 4.21: Observed Responses and Predicted Values 92
Table 4.22: Regression Coefficients and P Values as
Calculated from the Models 92
Table 4.23: Elongation to break with Mixing Parameters and Ratios 96
Table 4.24: ANOVA for the Selected Factorial Models 98
Table 4.25: Observed Responses and Predicted Values 99
Table 4.26: Regression Coefficients and P Values as
Calculated from the Models 99
Table 4.27: Young Modulus with Mixing Parameters and Ratios 102
Table 4.28: ANOVA for the Selected Factorial Models 104
Table 4.29: Observed Responses and Predicted Values 105
Table 4.30: Regression Coefficients and P Values as
Calculated from the Models 105
Table 4.31: Glass Transition Temperature of samples 110
Table 4.32: Properties and characteristics processing of the need for
x
optimizing the formulation PP/ENR 111
Table 4.33: Optimum formulation with the processing characteristics and
properties generated for PP / ENR based on the degree of
desirability 112
xi
LIST OF FIGURES
Figure 2.1: Structure of Polypropylene 10
Figure 2.2: Structure of cis-Polyisoprene 11
Figure 2.3: Structure of Epoxidized Natural Rubber (ENR) 12
Figure 2.4: Schematic representation of the two-roll milling method 18
Figure 2.5: Schematic representation of the compressing molding 19
Figure 2.6: Schematic illustration of injection molding 20
Figure 2.7: The mechanism of peroxide vulcanization 24
Figure 2.8: Cold Compression Molding 25
Figure 2.9: Schematic illustration of how a tensile load produces an elongation
and positive linear strain 28
Figure 2.10: SEM micrographs of dynamically cured 60/40 ENR-30/PP
TPVs with sulphur system 31
Figure 3.1: Flow chart of the research project 39
Figure 3.2: Polypropylene 41
Figure 3.3: Epoxidized Natural Rubber 42
Figure 3.4: Stearic Acid (a), Zinc Oxide (b) and Sulfur (c) 43
Figure 3.5: ENR vulcanization; scale: 20cent Malaysia Diameter 23mm 46
Figure 3.6: HAAKE RHEOMIX OS internal mixer machine 48
Figure 3.7: PP/ENR using crusher machine 49
Figure 3.8: Crusher machine 49
Figure 3.9: Pellet compound is placed in the mold. 50
Figure 3.10: Gotech (GT 7014 – A) hot press machine 51
Figure 3.11: Gotech (GT 7016 –H) Specimen cutter machine 51
Figure 3.12: Electronic densimeter. 53
Figure 3.13: Melt Flow Indexer MH-525 equipment 54
Figure 3.14: Autograph AG-IC floor universal testing machine. 56
Figure 3.15: Dog bone type specimen size for ASTM D-638 Type 1 56
Figure 3.16: Shore D Durometer 57
Figure 3.17: Izod impact test equipment 58
xii
Figure 3.18: Zeiss EVO-50 ESEM machine 59
Figure 3.19: DSC Perkin Elmer DSC-7 60
Figure 4.1: Half Normal Plot for Density 65
Figure 4.2: Effects of the ENR and temperature on the density
of the PP/ENR blend 68
Figure 4.3: Density of all samples 69
Figure 4.4: Half Normal Plot for Hardness 71
Figure 4.5: Effects of the ENR and temperature on the hardness
of the PP/ENR blend 74
Figure 4.6: Hardness of all samples 75
Figure 4.7: Half Normal Plot for Melt Flow Rate 78
Figure 4.8: Effects of the ENR and temperature on the melt flow rate
of the PP/ENR blend 81
Figure 4.9: Melt flow rate of all samples 82
Figure 4.10: Half Normal Plot for Impact Strength 84
Figure 4.11: Effects of the ENR and temperature on the impact strength
of the PP/ENR blend 87
Figure 4.12: Impact strength of all samples 88
Figure 4.13: (a) Dogbone for PP, (b) Dogbone for PP/ENR 70/30 and
(c) PP/ENR 40/60 89
Figure 4.14: Half Normal Plot for Tensile Strength 91
Figure 4.15: Effects of the ENR and temperature on the tensile strength
of the PP/ENR blend 94
Figure 4.16: Tensile strength of all samples 94
Figure 4.17: Half Normal Plot for Elongation to Break 97
Figure 4.18: Effects of the ENR and temperature on the elongation to break
of the PP/ENR blend 100
Figure 4.19: Elongation to break of all samples 100
Figure 4.20: Half Normal Plot for Hardness 103
Figure 4.21: Effects of the ENR and temperature on the Young modulus
of the PP/ENR blend 106
xiii
Figure 4.22: Young modulus of all samples 106
Figure 4.23: (a) Scanning electron micrograph of unfilled PP at magnification
of 500x. (b) Scanning electron micrograph of PP/ENR 70/30
at magnification of 500x. (c) Scanning electron micrograph
of PP/ENR 40/60 at magnification of 500x. 108
Figure 4.24: (a) Scanning electron micrograph of unfilled PP at magnification
of 5000x. (b) Scanning electron micrograph of PP/ENR 70/30
at magnification of 5000x. (c) Scanning electron micrograph
of PP/ENR 40/60 at magnification of 5000x. 109
Figure 4.25: Fractional degrees of desire fulfilled the selection formula
for PP / ENR 113
xiv
LIST OF ABBREVIATIONS
ASTM - American Standard Test Method
ENR - epoxidized natural rubber
TPNR - thermoplastic natural rubber
NR - natural rubber
NBR - nitrile butadiene rubber
PP - polypropylene
RSM - response surface methodology
SEM - scanning electron microscopy
DSC - differential scanning calorimetry
FTIR - fourier transform infrared
EPR - ethylene propylene rubber
TPO - thermoplastic polyolefin
TPV - thermoplastic vulcanizate
TPE - thermoplastic elastomer
TSE - thermoset elastomer
IR - synthetic isoprene rubber
BR - polybutadiene rubber
SBR - styrene butadiene rubber
IIR - butyl rubber
CIIR - chloro butyl rubber
BIIR - bromo butyl rubber
DOE - design of experimental
rpm - rotation per minute
xv
LIST OF SYMBOLS
oC - Celsius
M/S - meter per second
% - percentage
kW - kilo watt
min - minute
kg - kilogram
mm - millimeter
μm - micrometer
s - second
nm - nanometer
g - gram
Hz - hertz
1
1.1 Background
Polyolefins are the largest group of thermoplastics, the two most important and
common types of polyolefins are polyethylene and polypropylene. They are very
popular due to their low cost and wide range of applications. Polyolefins are usually
processed by extrusion, injection molding, blow molding, and rotational molding
methods.
Polyolefin elastomers (POEs) are a relatively new class of polymers that emerged
with recent advances in metallocene polymerisation catalysts. Representing one of
the fastest growing synthetic polymers, POE’s can be substituted for a number of
generic polymers including ethylene propylene rubbers (EPR or EPDM), ethylene
vinyl acetate (EVA), styrene-block copolymers (SBCs), and poly vinyl chloride
(PVC). Polyolefin elastomers are compatible with most olefinic materials, are an
excellent impact modifier for plastics, and offer unique performance capabilities for
compounded products.
Thermoplastic elastomers based on natural rubber and thermoplastic blends are
classified as thermoplastic natural rubber (TPNR) blends. There are two types of
thermoplastic natural rubber. Blending of NR with thermoplastic (i.e., polyolefins)
to get co-continuous phase morphology is technologically classified as thermoplastic
polyolefin (TPO). The other class is known as thermoplastic vulcanizate (TPV),
which is prepared by blending NR with polyolefins and involve vulcanization
process. In type two, the rubber phase is vulcanized during the mixing process at
INTRODUCTION
CHAPTER 1
2
high temperature, and the process is known as dynamic vulcanization. Dynamic
vulcanization of epoxidized natural rubber (ENR) and polypropylene (PP) are also
performed by using either a sulfur based system or peroxide. The sulfur cured
system showed superior mechanical properties in term of tensile strength, elongation
at break and tension set compared to the peroxide system due to the polypropylene
degradation during dynamic vulcanization.
1.2 Problem Statement
Polypropylene (PP) is well-known of its outstanding dielectric properties under high
voltage and high frequency condition up to 30 kHz (Khachen et al., 1992). Due to
that, it is a suitable material for electrical insulator whether in interior or exterior
cables. However, PP is less flexible when the thickness of the cable is increases. The
epoxidized natural rubber (ENR) is a potential candidate to increase the flexibility of
polypropylene. Malaysia is known as the world’s major natural rubber producer.
ENR being a derivative of natural rubber is more readily available, and it has unique
properties offering high strength due to their ability to undergo strain crystallization,
along with increased glass transition temperatures and solubility parameter. These
properties are reflected in vulcanizates with increased oil resistance, enhanced
adhesive properties, high degree of damping and reduce gas permeation (Gelling,
1991). Response surface methodology (RSM) is reported to be an effective tool for
optimizing a process, as highlighted by various workers (Yadav et al., 2007). RSM
could save cost and time by reducing number of experiments required. The
application of RSM to design optimization is aimed at reducing the cost of
expensive analysis methods and their associated numerical noise. Originally, RSM
was developed to model experimental responses (Box and Draper, 1987), and then
migrated into the modeling of numerical experiments.
3
1.3 Objective
The main objectives on this research are:
i. To produce PP/ENR blend via melt blending using internal mixer.
ii. To determine the optimum formula and mixer parameter using response
surface methodology
iii. To characterize the properties of PP/ENR blend through testing and analysis.
1.4 Scope
This research is focusing on optimization of formulation and mixer parameter to
produce PP/ENR blend. Firstly, the experiment was designed using RSM. Then,
samples were prepared in different combination of process parameters in an internal
mixer followed by various physical and mechanical testing. Some analysis such as
thermal and morphology were performed to support the data.
1.5 Chapter Overview
There are five chapters in this report;
i. Chapter 1 is the introduction of the research. That consists of research
background, a problem statement, and objectives of the project, scope and
chapter overview.
ii. Chapter 2 is the literature review and covers the fundamental of polymer
blends, thermoplastic elastomer and also a general overview of the current
development of polymer blends.
4
iii. Chapter 3 is the methodology of this research, response surface methodology
and it discuss the raw material specification, equipment and experimental
procedures used in this study.
iv. Chapter 4 is the results and discussions of laboratory and field research work
described in this study.
v. Chapter 5 is formulate procurement review and list of potential research and
also proposed future work.
5
2.1 Polymer Blends
Basic principles of polymer blends are either homogeneous or heterogeneous (He et
al., 2004). In homogeneous blends, the final properties are often an arithmetic
average of the properties of the blend components. In heterogeneous blends, the
properties of all blend components are present. A deficiency in the properties of one
component can be camouflaged to a certain extent by strengths of the others (He et
al., 2004). Polymer blending is a convenient route for the development of new
polymeric materials, able to yield materials with property profiles superior to those
of the individual components (He et al., 2004). Blending of polymers is an effective
way to obtain materials with specific properties. Most polymers are immiscible,
therefore, blending usually leads to heterogeneous morphologies (Willemse et al.,
1997). Most polymer pairs are immiscible, and therefore, their blends are not formed
spontaneously. Moreover, the phase structure of polymer blends is not equilibrium
and depends on the process of their preparation. Five different methods are used for
the preparation of polymer blends are melt mixing, solution blending, latex mixing,
partial block or graft copolymerization, and preparation of interpenetrating polymer
networks (Anonymous, 2005).
Polymer blend constitute of 36 wt% of the total polymer consumption, and their
pertinence continues to increase (Utracki, 2002). About 65% of polymer alloy and
blend are produced by polymer manufacturer, 25% by compounding companies and
the remaining 10% by the transformer (Utracki, 2002).
LITERATURE REVIEW
CHAPTER 2