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THE EFFECT OF CALCIUM CARBONATE AND CALCINED CLAY MICRO
FILLER MATERIALS ON THE ELECTRICAL CHARACTERISTICS OF
POLYVINYL CHLORIDE FOR CABLE INSULATION
MOHD ASYRAF REDUAN AZMI
UNIVERSITI TEKNOLOGI MALAYSIA
iii
To my beloved parents
Azmi Che Mat
Azlina Ibrahim
Thank You
iv
ACKNOWLEDGEMENT
I would like to convey my highest gratitude and appreciation to
Associate
Professor Dr. Mohd Muhridza Bin Yaacob for his continuous supervision,
encouragement and support to guide me in the whole process of completing this project.
Secondly, I really want to take this opportunity to express my thankfulness to
University Technology of Mara (UiTM) especially to the faculty of Electrical
Engineering, for the sponsorship and also the encouragement for me to pursue higher
education.
Next, I would like to thank Mr. Anuar Kamaruddin, the lab assistant at IVAT
(Institut Voltan Arus Tinggi), UTM for his expertise and time to guide me on the
experimental setup.
Last but not least, million of thanks to IRM (Industrial Resins Malaysia) Sdn
Bhd, especially En. Khalid Johari for his assistant and guidance in terms of PVC
samples preparation and also training. Without him, the preparation of PVC samples
will be jeopardized.
v
ABSTRACT
Polyvinyl Chloride (PVC) is widely used as cable insulation for low voltage
application.
In order to strengthen the electrical properties of the material, some
additives have to be added. In this project, various fillers were compounded with PVC.
The main parameters that have been studied were dielectric strength, and the dispersion
of PVC molecules. The polymer structure of PVC was altered after undergo high
voltage stress and it can be related to the breakdown voltage value. The type of fillers
that were used in this experiment is Calcium Carbonate NCC-P 1T, Neolite SP, and
Calcined Clay. Firstly the density of each test objects was measured using density meter
and the value obtained must within the SIRIM specification.
Then the dielectric
strength test was done under AC stress to observe the breakdown properties. It is
observed from the tests that when the density or Specific Gravity (SG) of test sample
increased, the breakdown voltage also increased.
But after the highest value, the
dielectric strength started to show degradation characteristic event though the density is
kept increasing. This phenomenon occurred to all formulation of filler materials. The
experimental results also show that PVC compounded with 10 wt% of Calcium
Carbonate Neolite SP produces the highest breakdown voltage and excellent dispersion.
PVC cost also can be reduced by the addition of filler material. The analysis depicted
that PVC combined with 10 wt% of CaC03 Neolite SP provides the best profile of cost
saving.
vi
ABSTRAK
Polyvinyl Chloride (PVC) digunakan secara meluas sebagai penebat bagi kabel
elektrik voltan rendah.
Untuk meningkatkan keupayaan elektrik bahan tersebut,
beberapa bahan tambahan perlu ditambah. Dalam kajian ini, PVC yang digunakan
sebagai penebat telah dicampur dengan beberapa agen tambahan. Beberapa ujikaji
seperti ukuran ketumpatan, ketahanan elektrik, dan ujikaji molekul PVC telah dilakukan
bagi melihat kesan pencampuran.
Di antara agen-agen tambahan yang digunakan
bersama PVC ialah seperti batu kapur (Kalsium Karbonat) dan tanah liat. Spesimenspesimen dikelaskan melalui nilai kandungan agen tambahan. Struktur polimer PVC
berubah selepas dikenakan voltan tinggi dan perbezaan ini mempunyai kaitan dengan
kejatuhan nilai voltan .
Ujikaji ketumpatan dilaksanakan terlebih dahulu bagi
memastikan campuran PVC dan agen tambahan sentiasa berada dalam piawaian SIRIM.
Spesimen yang dihasilkan daripada pelbagai formula telah diuji ketahanan elektrik
menggunakan arus ulang-alik (AC).
Kemudian, struktur polimer sampel-sampel
tersebut dianalisa melalui mikroskop elektron. Daripada kajian ini juga, didapati apabila
ketumpatan sesuatu sampel bertambah, ketahanan elektrik juga meningkat. Akan tetapi
pada sesuatu tahap tertentu, apabila ketumpatan bahan di naikkan, ketahanan elektrik
akan turun. Fenomena ini berlaku kepada semua formulasi bahan tambahan. Melalui
ujikaji ini, pencampuran PVC dengan 10 wt% Kalsium Kabonat Neolite SP mempunyai
ketahanan elektrik yang tertinggi dan kebolehan untuk menyerap yang terbaik ke dalam
polimer PVC berbanding dengan formulasi bahan-bahan tambahan yang lain. Kos
untuk menghasilkan penebat kabel juga dapat dikurangkan dengan kaedah pencampuran
ini. Campuran PVC dengan 10 wt% CaC03 Neolite SP telah memberikan profile terbaik
bagi penjimatan kos.
vii
TABLE OF CONTENTS
CHAPTER
1
TITLE
PAGE
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENTS
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENTS
vii
LIST OF TABLES
x
LIST OF FIGURES
xii
LIST OF ABBREVATIONS
xv
LIST OF SYMBOLS
xvi
LIST OF APPENDIXES
xvii
INTRODUCTION
1
1.1
Project Background
2
1.2
Problem Statement
2
1.3
Objective of Study
3
1.4
Scope of Study
3
1.5
Methodology
4
1.6
Thesis Structure
7
2
PVC AND FILLER MATERIAL APPLICATIONS
2.1
Introduction
9
2.2
Dielectric Strength
10
2.2.1 Specimen Size
12
viii
3
4
2.2.2 Breakdown voltage calculation
12
2.3
Density of test sample
12
2.4
Selection of fillers for experiment.
14
2.4.1
Calcium Carbonate
15
2.4.2
Calcined Clay
18
EXPERIMENTAL PROCEDURES
3.1
Introduction
21
3.2
Safety Procedure
21
3.2.1
General Safety:
22
3.2.2
Special Rules of Caution
23
3.3
Materials for Experiment
24
3.4
Polyvinyl Chloride Cable (MH-66 grade)
25
3.5
Fillers
26
3.6
Test Samples Preparation
27
3.7
Definition of Specific Gravity (SG)
33
3.8
Experiments Description and Lab Apparatus
34
3.8.1
AC Dielectric Breakdown Voltage Test
34
3.8.2
Polymer Dispersion Analysis
36
3.9
IEEE Standard Techniques for High-Voltage Testing
38
3.10
Experimental Procedures
38
3.11
AC Dielectric Breakdown Voltage Test
38
3.12
Test Samples Density Measurement Procedures
40
3.13
Polymer Dispersion Analysis procedure
40
EXPERIMENTAL WORK
4.1
Introduction
41
4.2
Results of Specimen Density Measurement
41
4.2.1
PVC + Calcium Carbonate NCC-P 1T
42
4.2.2
PVC + Calcium Carbonate Neolite SP
43
4.2.3 PVC + Calcined Clay
44
ix
4.3
Results for AC Dielectric Breakdown Voltage Test
45
4.4
Polymer Structure Dispersion Micrograph Results
46
4.5
Analysis of AC Dielectric Breakdown Voltage
50
and Molecule Dispersion
5
4.5.1
AC Dielectric Breakdown Voltage Analysis
50
4.5.2
Polymer Dispersion Micrograph Analysis
56
DISCUSSION
5.1
Effect of filler on the test samples density
58
5.2
PVC Compound with various concentration
59
of CaC03 NCC-P 1T
5.3
PVC Compound with various concentration
60
of CaC03 Neolite SP (Micro filler)
5.4
PVC Compound with various concentration of
61
Calcined Clay Polestar 501(Micro filler)
5.5
PVC Cost Analysis
61
5.5.1 Proposal for Cost Reduction
62
5.5.2
62
Price for PVC and Fillers
5.5.3 Study case 1
63
5.5.4 Study case 2
64
5.5.5 Study case 3
64
5.5.6
66
Cost Analysis for Weekly, Monthly, and
Annual Production
CONCLUSION AND RECOMMENDATION
6.1
Conclusion
68
6.2
Recommendation and future works
69
REFERENCES
70
Appendices A1-D1
72
x
LIST OF TABLES
TABLE
TITLE
PAGE
2.1
General electrical properties of CaCO3
17
2.2
General electrical properties of Calcined clay
20
3.1
Physical Properties of PVC MH-66
25
3.2
Specifications for NCCP-1T, Neolite SP,
26
and Polestar 501
3.3
List of Plasticizer and lubricants
28
3.4
Overall formulations for every type of fillers
29
4.1
Formulation PVC+ CaC03 (1T)
42
4.2
Formulation PVC+ CaC03 (NSP)
43
4.3
Formulation PVC+ Calcined Clay
44
4.4
Overall result of breakdown voltage
45
5.1
Price of Raw Materials for Cable Insulation
62
5.2
Estimation of saving for 100g sample
65
xi
LIST OF TABLES
TABLE
5.3
TITLE
Production Cost for weekly, Monthly and Annual
PAGE
66
xii
LIST OF FIGURES
FIGURE
TITLE
PAGE
1.1
Flow chart of the research
7
2.1
Milled calcium carbonate
16
2.2
Ultra fine ground Calcium Carbonate
16
2.3
SEM micrograph of Chalk
16
2.4
SEM micrograph of Kaolin
18
2.5
SEM micrograph of Calcinated Clay
19
3.1
Flow chart of Sample Preparation Process
27
3.2
Metler Toledo weighing meter
30
3.3
Sample mixing Process.
31
3.4
Two roll mill machine
31
3.5
Samples in thin layer form
32
3.6
LabTech Hot Press Machine
32
3.7
Metler Toledo Density Meter
34
xiii
3.8
Digital Measurement Instruments
35
3.9
High Voltage Test Sample
35
3.10
Rod Plane Electrode Configuration
36
3.11
JEOL-JFC-1600 Auto fine coater
37
3.12
JEOL JSM-5610 Scanning Electron Microscope
37
4.1
SG measurement for PVC+ CaC03 (1T)
42
4.2
SG measurements for PVC+ CaC03 (NSP)
43
4.3
SG Measurements for PVC+ Calcined Clay
44
4.4
Pure PVC sample (F0) at 10,000 magnifications
46
4.5
Pure PVC sample (F0) at 20,000 magnifications
47
4.6
10 wt% CaC03 NCC-P 1T (F2) before AC
dielectric test
47
4.7
10 wt% CaC03 NCC-P 1T (F2) after AC
48
dielectric test
4.8
10 wt% CaC03 Neolite SP (F7) before AC
dielectric test
48
xiv
4.9
10 wt% CaC03 Neolite SP (F7) after AC dielectric test
49
4.10
15wt% Calcined Clay Polestar 501 (F13) before AC
49
dielectric test
4.11
15 wt% Calcined Clay Polestar 501 (F13) after AC
50
dielectric test
4.12
Comparison of PVC and PVC+CaC03 1T Dielectric AC Test
51
4.13
Comparison of PVC and PVC+CaC03 Neolite SP Dielectric
52
AC Test
4.14
Comparison of PVC and PVC+Calcined Clay Dielectric
53
AC Test
4.15
Overall Dielectric AC Test Breakdown Voltage
53
4.16
Comparison of breakdown voltage between previous
55
study and current experiment.
5.1
Filler with the highest breakdown voltage and cost
65
xv
LIST OF ABBREVIATIONS
LV
Low Voltage
MV
Medium Voltage
EHV
Extra High Voltage
PVC
Polyvinyl Chloride
XLPE
Cross-linked Polyethylene
PE
Polyethylene
SG
Specific Gravity
BS
British Standard
IEC
International Electro technical Commission
Vol
Volume
DC
Direct Current
AC
Alternate Current
SEM
Scanning Electron Microscope
NSP
Neolite SP
IRM
Industrial Resin Malaysia
SIRIM Malaysian Standard
xvi
LIST OF SYMBOLS
C
Carbon
o
Celcius
C
cm
Centimeter
F
Farad
g
Gram
H
Hydrogen
m
Mass
mm
Milimeter
R
Resistor
t
Time
V
Volume
V
Voltage
µ
Micro
wt
Weight
ρ
Density
xvii
LIST OF APPENDICES
APPENDIX
TITLE
PAGE
A-1
Datasheet of PVC MH 66
72
B-1
Datasheet of NCC-P 1T
73
C-1
Datasheet of Neolite SP
74
D-1
Datasheet of Polestar 501
75
CHAPTER 1
INTRODUCTION
1.1
Project Background
Minerals used as fillers in plastic compounds have traditionally been used to
reduce material costs by replacing a portion of the polymer with a less expensive
material. However, nowadays many functional fillers or mineral modifiers are required
to modify processing characteristics or finished part properties.
Fillers penetrate and infiltrate materials. But, there are hardly any cases in which
the surrounding material penetrates the filler's outside boundary. Their impregnating
and quenching activity can be translated into their ability to react or interact with the
surrounding material [1]. Thus, the word filler adequately describes the filler's potential
to perform in multi component systems.
Few types of additives used in Polyvinyl Chloride (PVC) formulations are
mainly plasticizers, stabilizers, lubricants and fillers. Fillers have vital roles in
modifying the properties of various polymers and reducing the cost of their composites.
2
The effect of fillers on properties of composites depends on their level of degree of
dispersion, aggregate size, surface characteristics, loading, and shape, particle size [2].
Low electrical strength could lead to failure of cable due to over voltage.
According to the thermoplastic industry, 70% of the total production is
accounted for by the large volume and low cost commodity resins such as PVC [1].
Hence, PVC is the most commonly used insulating materials for low and medium
voltage, which is around 3.3 kV. Due to high loss and dielectric constant characteristics,
Polyvinyl Chloride is inapplicable for high voltage appliance.
Consequently, the
breakdown voltage strength and the dispersion of PVC polymer become one of the focal
point of studies.
1.2
Problem statement
The insulator in electric cable provides isolation between conducting area and
the outer surface. Other than that, it provides protection to equipment and human. The
ideal case of insulator is, it will not breakdown or “ruptured” in the sense where the
property’s is inversed. But in practice, this condition never sustained because every
material have its own breakdown voltage limit.
Referring to previous statement; since PVC is widely used as an insulator in
electrical cable, this project will focus on the effect of fillers when compounded with
PVC and the testing related to dielectric strength. Furthermore, imperative study on the
cost reduction also will be done since when filler’s is used, the amount of PVC material
also decreased.
3
1.3
Objective of Study
The objectives of this project are:
1. To examine breakdown Dielectric strength test of pure PVC, and PVC
compounded with various type of fillers when alternating current is been
applied. Then verify whether the results shown better performance from
previous test.
2. The test sample will be further analyzed by using Scanning Electron
Microscope (S.E.M) for its density and dispersion.
3. Analysis and detail discussion about the electrical characteristics of PVC
when mixed with filler materials.
1.4
Scopes of Study
There are six scopes in this study.
1. Test samples preparation. PVC is amalgam with various types of fillers such
as Calcium Carbonate 1T (normal grade), Neolite SP Calcium Carbonate
(micro-filler) and Calcined Clay (micro-filler).
4
2. Measure the specific gravity (SG) or density using Metller Toledo density
meter. All the results have to be within the Malaysia Standard for electric
cable specification (1.45(+/-) 0.5 SG)
3. Analyzed the characteristic of test specimens which are blended with different
level of filler concentration (5wt%, 10wt%, 15wt%, 20wt%, and 25wt%)
under AC voltage stress.
4. To examine the filler’s dispersion on the PVC specimens using SEM
5. Comparison of breakdown voltage (AC Dielectric Test) results with previous
test by Lim [2].
6. Cost comparison of PVC and PVC compound with filler for cable
manufacturers.
1.5
Methodology
Generally this research work consists of laboratory experimental testing on the
density measurement, dielectric strength, and filler’s dispersion.
There are several
research methodologies for this laboratory work in order to obtain the result:-
1. Literature reviews to understand and identify the properties and functions of
Calcium Carbonate and Calcined Clay as a filler material for PVC.
5
2. Understand the principle operation and function of electrical characteristics
which will be tested.
3. Samples preparation
4. Measure the specific gravity using Mettler Toledo Density meter.
The
density value obtained must comply with SIRIM specification.
5. Examined the dielectric strength by applying AC and DC stress to test
samples.
6. Analyzed the dispersion of fillers in PVC polymer using SEM
7. Detail discussion and conclusion for every experiment results.
The methodology is shown in figure 1.1.
6
Start
Literature review on
Dielectric strength of CaC03
and Calcined Clay
Verify Specimens for its
dispersion using S.E.M
Understand properties for
each filler.
Milling and Hot press PVC
with fillers to produce test
samples.
Experimental work
Verify the density of each
test samples.
Test specimens under
Alternating Current.
Discussion and
summarization from the
experiment
Cost Analysis for PVC when
compounded with filler
material
Thesis writing
Verify Electrical
Characteristics i.e Dielectric
Breakdown Voltage
End
Figure 1.1
Flow chart of the research
7
1.6
Thesis Structure
There are 6 chapters for this report. The details for each report are listed as
below.
Chapter 1: Introduction
Chapter 2: PVC and Filler Material Applications
Chapter 3: Experimental Procedures
Chapter 4: Results and Analysis
Chapter 5: Discussions
Chapter 6: Conclusion and Recommendation
Chapter 1 provides overall outline of the project which are consists of objectives,
scopes of study, and methodology.
Chapter 2 describes the theory for every testing involved and explanation on filler
materials.
Chapter 3 described the process of samples preparation and the experiment procedures
Chapter 4 summarized the results from experiments such as density measurement,
dielectric strength, and the dispersion of molecules in PVC sample.
8
Chapter 5 contains detail observation and description from every test result. Also
included, the case study of the cost for PVC cable and PVC compounded with filler
materials.
Chapter 6 concludes the project according to the results achieved and suggested
recommendations for future works.
CHAPTER 2
PVC AND FILLER MATERIAL APPLICATIONS
2.1
Introduction
Polyvinyl chloride commonly abbreviated PVC, is a widely used thermoplastic
polymer. In terms of revenue generated, it is one of the most valuable products of the
chemical industry. Around the world, over 50% of PVC manufactured is used in
construction. As a building material, PVC is cheap, durable, and easy to assemble PVC
is commonly utilized as the insulation on electric wires. In order to make it usable for
this purpose, it has to be plasticized.
PVC has played an important role in electrical insulation in electrical
components and equipments. Sometimes, in the manufacture of PVC cable jacketing,
the additives for the formation and their compatibility may affect on the electrical
properties of the cable. Therefore the response of dielectric properties of PVC to
imposed alternating electric field (AC) of various strengths and frequencies become
point of interest.
Meanwhile filler material are widely used as a reinforcement material to increase
the mechanical, electrical, and other properties such as stiffness, dielectric strength fire
retardant and to prevent electrical discharge cause by void. Filler used as means to
lower cost of plastic part.
They also contributed to the unique properties for
sophisticated demand. In fact, many types of filler now cost more than the polymers
10
that they are added to. But such conditions make economic sense because of the value
that the filler brings to the formulation [3].
The electrical and mechanical properties of composites are significantly
dependent on the filler’s aspect ratio, interaction between fillers and polymer matrix and
also the surface area. The usage of fillers in PVC needs to carefully study because
fillers have its own aspect ratio. For example, a very high aspect ratio does not always
improve the electrical and mechanical properties but maybe decrease it.
2.2
Dielectric Strength
In physics, the term dielectric strength has the following meanings:
1.
Of an insulating material, the maximum electric field strength that it can
withstand intrinsically without breaking down or without experiencing failure of
its insulating properties.
2.
For a given configuration of dielectric material and electrodes, the minimum
electric field that produces breakdown.
The theoretical dielectric strength of a material is an intrinsic property of the
bulk material and is dependent on the configuration of the material or the electrodes
with which the field is applied [3]. At breakdown, the electric field frees bound
electrons. If the applied electric field is sufficiently high, free electrons may become
accelerated to velocities that can liberate additional electrons during collisions with
neutral atoms or molecules in a process called avalanche breakdown. Breakdown occurs
quite abruptly (typically in nanoseconds), resulting in the formation of an electrically
11
conductive path and a disruptive discharge through the material. For solid materials, a
breakdown event severely degrades, or even destroys, its insulating capability [4].
Besides, dielectric strength defined by ASTM D 149, measures the dielectric
breakdown of an insulating material by short time or step by step test in volts per 0.001
in thickness.
Mineral fillers, which do not destroy when high temperatures been
applied, basically improved this property; whereas organic fillers which are repellent or
tightly bound free water on their surfaces will reduce it.
According to IEC 80243 Standard [5], there are three basic procedures that can
be used to determine the dielectric strength of an insulator. These procedures are the
short-time method, the slow rate-of-rise method and the step-by-step method. Each of
these three methods has the same basic set-up, which consists of the test specimen
placed between two electrodes in air or oil.
For the most common test, the short-time method, voltage is applied across the
two electrodes and raised from zero to dielectric breakdown at a uniform rate.
Breakdown is when an electrical burn-through punctures the sample, or decomposition
occurs in the specimen. The rate of voltage rise is determined by the time it takes the
sample to reach dielectric breakdown.
The slow-rate-of rise method starts at 50% of the breakdown voltage as
determined by the short-time-method and is increased at a uniform rate.
The step-by-step method starts at 50% of the short-time-test then voltage is
increased at equal increments for a specified time period until breakdown. The test is
sometimes performed in oil to prevent arcing from the electrode to the ground.
12
2.2.1 Specimen size
The recommended specimen type for this test is a 4 inch plaque or larger. Any
specimen thickness can be used; however the most common thickness is between 0.8 to
3.2 mm (0.032 to 0.125 inch). Specimens over 2 mm thick are typically tested in oil to
decrease the chance of flashover before breakdown.
2.2.2
Breakdown voltage calculation
Dielectric strength is calculated by dividing the breakdown voltage by the
thickness of the sample. The data is expressed in Volts/mil. The location of the failure is
also recorded. A higher dielectric strength represents a better quality of insulator.
2.3
Density of test sample
In physics, density is mass (m) per unit volume (V) — the ratio of the amount of
matter in an object compared to its volume. In the common case of a homogeneous
substance, density is expressed as in equation 2.1.
(2.1)
13
Where, in SI Units:
ρ (rho) is the density of the substance, measured in kg·m–3
m is the mass of the substance, measured in kg
V is the volume of the substance, measured in m3
In some cases the density is expressed as a specific gravity or relative density, in
which case it is expressed in multiples of the density of some other standard material,
usually water or air. According to Wypych [2], the density of fillers range from 0.03 to
19.4 g/cm3. Fillers can be used either to increase or to decrease the density of a product.
Because the density of filler can be as high as 10 g/cm3 or as low as 0.03 g/cm3, there
may be a large difference between the density of the filler and the polymer. Thus a
broad range of product densities can be obtained. There are high density products
(above 3 g/cm3) such as materials used in appliances or casings for electronic devices.
More common are densities below 2 g/cm3, glass fiber filled composites being a typical
example. The effective density of the polymer can be decreased by filling foam with
hollow polymer spheres. In this example, the density of a material can be lower than
0.1 g/cm3.
14
2.4
Selection of Fillers for Experiment
Minerals used as fillers in plastic compounds have traditionally been used to
reduce material costs by replacing a portion of the polymer with a less expensive
material. Many functional fillers or mineral modifiers are required to modify processing
characteristics or finished part properties. Fillers penetrate and infiltrate materials. But,
there are hardly any cases in which the surrounding material penetrates the filler's
outside boundary. Their impregnating and quenching activity can be translated into
their ability to react or interact with the surrounding material [2]. Thus, the word filler
adequately describes the filler's potential to perform in multi component systems. Few
types of additives used in PVC formulations are mainly plasticizers, stabilizers,
lubricants and fillers. Fillers have vital roles in modifying the properties of various
polymers and reducing the cost of their composites. The effect of fillers on properties of
composites depends on their level of degree of dispersion, aggregate size, surface
characteristics, loading, and shape, particle size. Low electrical strength could lead to
failure of cable due to over voltage [6].
Hence, based on observation and initial study; 3 types of fillers are used for this
experiment.
They are Calcium Carbonate NCC-P 1T (Normal grade), Calcium
Carbonate Neolite SP (Micro-filler) and Calcined Clay Polestar 501 (Micro-filler).
15
2.4.1 Calcium Carbonate
Calcium carbonate, mined in the form of limestone, marble or chalk, has long
been used as a filler to reduce costs in PVC applications, such as wire and cable and
flooring. And it is reported by Harry [5], calcium carbonate is among the most abundant
minerals, in the world. This mineral is very stable in terms of chemical and mechanical
properties. However, in the last 10 to 15 years, calcium carbonate producers have
developed products with surface coatings to improve dispersion and finer particle sizes
to improve polymer properties. In PVC applications such as window profiles, calcium
carbonate can improve gloss and provide some impact resistance, potentially allowing
formulators to reduce elastometric impact modifier levels [7].
Furthermore, calcium carbonate is the most widely used filler or extender
pigment in the plastics industry [8].
Polyvinyl chloride, polyolefins, phenolics,
polyesters, and epoxies are all resins with calcium carbonate can be compounded. This
broad range implementation can be attributed to both economic and performance
considerations.
Three major technological processes are used in the production of calcium
carbonate filler. These are milling, precipitation, and coating. More than 90% calcium
carbonate is processed by milling. Two methods are used: dry and wet. The milling
technology was developed for reproducibility and to obtain the required particle size
distribution. In addition to general grades, ultra fine grades are also produced by the
milling process. If the wet milling process is used, the material is frequently delivered to
the customer in the form of slurry which makes subsequent processes more economical
and environmentally friendly. Figures 2.1 to 2.3 show SEM micrograph of milled
calcium carbonate. In this process, the crystalline structure of the rock has an important
influence on the morphology of the filler [3].
16
Figure 2.1
Figure 2.2
Milled calcium carbonate
Ultra fine ground calcium carbonate
Figure 2.3
SEM micrograph of Chalk
17
Table 2.1 represents the general electrical properties of Calcium Carbonate.
Table 2.1:
Parameter
Dielectric
constant
General electrical properties of CaCO3
Description
Value
1) Calcite, series to optic axis
104 Hz, 17-22oC
8.5
2) Calcite, parallel to optic axis
104 Hz, 17-22oC
8
3) Dolomite, series to optic
axis 108 Hz, 17-22oC
8
4) Dolomite, parallel to optic
axis 108 Hz, 17-22oC
Volume
resistivity
at 20oC
Surface
Resistivity
at 20oC
Specific
resistance
aqua slurry
at 23oC
6.8
Marble
109-1011 ohm-cm
1) Marble, 50% relative
humidity
3 to 8 x 109 ohmcm
2) Marble, 90% relative
humidity
1 to 3 x 107 ohmcm
1) 5g CaCO3(calcite)/100ml
water
17E3 - 25E3
ohms
2) 5g CaCO3 MgCO3
(dolomite)/100ml water
3E3 - 5E3 ohms
3) pH, calcite
9 - 9.5
4) pH, dolomite
9 - 9.5
5) Volume resistivity for
electrical
insulating PVC compound at
50oC
4 x 1014 ohm-cm
18
2.4.2
Calcined Clay
Calcined clay is derived from Kaolin. Kaolin is the common term for the
mineral kaolinite, which is one of many hydrous Alumino Silicates comprising a class
called clay. According to Harry [9], clay is a rock term applying to soft, earthy ores that
are plastic when mixed with water. All clays originated as the weathered products of
granite, which were reacted and deposited under various hydrothermal conditions to
become a very usual component of the earth’s surface above and below water.
Calcined clay has the formula Al2O3.SiO2.2H2O and consists of alternating silica
and hydrous alumina sheets. Particles larger than about 13 um esd (equivalent spherical
diameter) are stacks of platelets equal in three dimensions, and below about 2 um esd
they are entirely hexagonal platelets and fragments. The clay may be pulverized after
some of these drying process depending requirements. The morphology of kaolin is
shown in figure 2.4. The figure clearly depicted a typical platy structure.
Figure 2.4
SEM micrograph of Kaolin
19
The process of calcinations alters the original properties of the material. When kaolin is
heated at 450oC, the clay structure is modified to an improvised electrical resistance and
brightness. The process of calcinations is conducted in kilns at temperatures between
850 and 1500oC. Figure 2.5 shows the SEM of calcinated clay which is distinct from
dried clay by having round edges which is result of high temperature treatment.
Figure 2.5
SEM Micrograph of Calcinated Clay
Table 2.2 represents electrical characteristics for compressed powders of
calcined clay [5]. These data consists of brief comparison of fillers for their bulk
electrical properties. The importances of these data are the improvement obtained when
Calcined clay is surfeit to obtain hydrophobic.
20
Table 2.2: General electrical properties of Calcined clay
Insulator Material
Volume resistivity
(ohm-cm)
Dry
Humid
Dielectric
Strength
volts/mil
Dielectric
constant
Ke@1 mc
Kaolin, water
leached
1013
106
70-120a
2.6
Kaolin, Calcined
1013
108
60-100a
1.3
Kaolin, Calcined
hydrophobic
surface
1013
1012
80-150a
1.3
CHAPTER 3
EXPERIMENTAL PROCEDURES
3.1
Introduction
In this chapter, materials, experimental setup, procedures and apparatus will be
discussed. Experimental procedure is one of the important parts when conducting a
research. Basically, the procedures that had being laid out were based on the safety
requirement and BS/IEC standard on testing cable.
3.2
Safety Procedure
The following general safety procedures and regulations are intended to reduce
the risk of injury to persons and damage to material during work in the laboratories or
workshops, especially in high voltage environment. But these general safety procedures
or instructions alone do not represent a complete list of necessary precautions, where the
following procedures only for general precaution to prevent the user from electrical
22
shock as well as for equipments safety. Since the voltage in this experimental work is
exceeded 1000V to be generated, it is considered as high voltage testing. So, it is
necessary that respective safety regulation is carefully followed. The following general
safety procedures of safety requirement are defined in the subsection 3.2.1 and 3.2.2.
3.2.1
General Safety
The general safety requirements are as follow;
1. No connections shall be attempted or carried out on a live system and no
unauthorized person should be allowed within testing room while an
experiment is in progress.
2. Only necessary equipment is present in the work area. These shall be
arranged as neatly and clearly as possible. Exposed parts must be grounded
for protection. Since the testing involved with high voltage, the room
screening and grounding becomes more important.
3. Each connection must have an emergency cut-off switch (breaker). This must
be clearly indicated, have satisfactory trip capacity and be easily accessible
from the work area.
4. Before apparatus (instruments, breakers, wires, etc.) is connected and power
is applied it should be ensured that each piece of equipment is suitable for the
particular connection with respect to voltage rating, loading capacity and
insulation.
23
3.2.2
Special Rules of Caution
The rules of caution as stated as below;
1. Those who work in the laboratories or workshops should be aware of the
risks involved and should thus work with consideration and caution, having
regard for their safety as well as that of others.
2. All persons present in the laboratories and workshops must exercise caution
around connections that may be live. Never touch equipment or connections
unless you have personally verified that the circuits are dead.
3. Never take automatic protective devices for granted. Always maintain a
sense of personal responsibility and caution.
4. Test objects connected to condensers may not be touched until the
condensers have been short-circuited and grounded as condensers can
maintain charge for a long time. Since this experimental works involved the
high voltage charging condenser (capacitor) it is necessary to discharge it to
the ground before any disconnection or no testing is carried out.
5. Persons conducting electrical tests and experiments should not wear
necklaces, bracelets, or similar metallic objects. These increase the risk of
contact with sources of electric current. Serious burns can result if current is
transmitted through the metal objects. Even strong or high-frequency
magnetic fields can be hazardous in this context.
6. Each person is responsible for maintaining order at his or her workstation.
Objects that are not being used, such as tools, clothing and instruments
should not be allowed to mess the work area.
24
7. Power should be switched off at the breaker when one is leaving the
laboratory. The person in charge of a specific connection should check that
supply voltage or switches are turned off when work is completed.
8. Extreme caution should be exercised when carrying out measurement with an
oscilloscope. The ground rule is that the chassis of the oscilloscope should be
connected to zero potential (neutral) and that voltage probes be used with
voltages exceeding 250 V. In the case of special measurements where the
oscilloscope is subjected to high voltages (with respect to ground) it shall be
clearly marked with warning signs and be mechanically isolated so as to
prevent any unintentional contact with the apparatus.
As mentioned, this experimental is involving the high voltage; so, the safety
procedures that were mentioned are compulsory to comply during this experimental
work is carried out.
3.3
Materials for Experiment
PVC samples compounded with fillers were the main materials for this study.
Furthermore, the materials density also had been taken into considerations and at the end
of this experiment the relationship between AC breakdown voltage and materials density
will be discussed.
25
3.4
Polyvinyl Chloride Cable (MH-66 grade)
PVC's major benefit is its compatibility with many different kinds of additives,
making it a highly versatile polymer. PVC can be plasticized to make it flexible for use
in electric cable insulation of low, medium and high voltage applications. Its
compatibility with additives allows for the possible addition of flame retardants although
PVC is intrinsically fire retardant because of the presence of chlorine in the polymer
matrix. PVC has excellent electrical insulation properties, making it ideal for cabling
applications. Its good impact strength and weatherproof attributes make it ideal for
construction products. PVC can be clear or colored, rigid or flexible, formulation of the
compound is the key to PVC's "added value".
In the process of preparing the samples, dry blend PVC of MH-66 grade were
used as the main raw materials.
This material was provided by Industrial Resins
Malaysia (IRM) Sdn. Bhd. For further reference, the complete data sheet was attached
in appendix A-1. MH-66 is the most widely raw material used in cable insulator
production. It has good chemical stability, corrosion resistance and water resistance. It
can be dissolved in acetone, hydrochloric ether, ester and some alcohol. It can offer
good solubility, good electrical insulation, thermo plasticity and membrane forming
capacity.
Table 3.1 represents the specifications of PVC MH-66.
Table 3.1: Physical Properties of PVC MH-66
Tensile Strength
2.60
N/mm²
Notched Impact Strength
2.0 - 45
Kj/m²
Thermal Coefficient of expansion
80
x 10-6
Max Continues Use Temp
60
Density
1.38
o
C
g/cm
26
3.5
Fillers
Three types of fillers were compared in this project. All of the fillers were supplied by
PTS Research Lab, Industrial Resins Malaysia. Table 3.2 lists the specifications given
by respective manufacturers for every filler.
Table 3.2: Specifications for NCCP-1T, Neolite SP and Polestar 501
Grades
Property
Unit
NCCP-1T
Farmosa
Plastic
Corporation
Manufacturer
Chemical
Analysis
Neolite SP
Takehara Chemical
Calcined
Clay
Polestar
501
Imerys
Si02,Al203,
Fe03 and
Ti02
97.9
98
Specific Gravity
2.7
2.7
2.63
Mohs's
Hardness
3
3
n/a
pH Value
9.1
9
6.7-8.0
0.8-25
0.85
1.3
Avg Particle
Size
CaC03
um
27
3.6
Test Samples Preparation
For this project, the PVC sample of dry blend PVC of MH-66 grade
(without filler) was studied in comparison with PVC compounded with various level of
filler concentration, i.e 5%wt, 10%wt, 15%wt, 20%, and 25%wt. Three types of mixing
have been prepared.
1. PVC compounded with Calcium Carbonate NCC-P 1T (normal grade)
2. PVC compounded with Calcium Carbonate Neolite SP (micro-filler)
3. PVC compounded with Calcined Clay Polestar 501 (micro-filler)
To prepare the samples for every experiment, three stages of process are involved. The
stages are listed as figure 3.1.
1st stage:
Measurement and mixing
2nd stage:
Milling
3rd stage:
Molding and Hot press
3rd stage:
Density Measurement
Figure 3.1
Flow chart of Sample Preparation Process
28
a) 1st stage: Measurement and Mixing.
This is the very 1st stage in preparing the sample. For each of the filler, 5 samples will
be prepared.
Another materials need to be added are plasticizer DOP
(DIOCTYL PHTHALATE) and lubricants which consists of PbST (PLUMBUM
STERIDE) and TS (TRIBASIC LEAD SULPHATE). The overall formulation mixture
is shown in table 3.3.
Table 3.3: List of Plasticizer and lubricants
Material
Amount (g)
1
PVC @ PVC + Filler material
100
2
DOP-Plasticizer
50
3
PbST-Lubricant
1
4
TS-Lubricant
3
Each of the material is weight accurately using Metler Toledo SAG Precision Weighing.
Then all of them will be blended together inside aluminum mug. Based on table above,
a list of specific formulation has been constructed and will be used through out this
project. Table 3.4 shows all formulations for this experiment.
29
Table 3.4: Overall formulations for every type of fillers
Formulation
PVC GP
(MH-66)
(100% wt)
F0
F1
F2
F3
F4
F5
F6
F7
F8
F9
F10
F11
F12
F13
F14
F15
100
95
90
85
80
75
95
90
85
80
75
95
90
85
80
75
Calcium
Calcium Calcined Clay
(micro filler)
Carbonate 1T Carbonate
(100% wt)
( Normal grade) Neolite SP
(100% wt)
(micro filler)
(100% wt)
0
5
10
15
20
25
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
5
10
15
20
25
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
5
10
15
20
25
Noted that, 100% wt is defined as the total weight of PVC and filler material
only. This assumption is made because this project is about what is the effect when
filler material is added and at the same time reduced the usage of Polyvinyl Chloride.
30
Figure 3.2 shows the mixing and weighing process done at Industrial Resins
Malaysia laboratory. Measurement is done by using Digital Metler Toledo weighing
meter. The process of weighing was done in great details because any miscalculation
will lead to imprecise results for the AC dielectric breakdown test and polymer
dispersion.
Figure 3.2
Metler Toledo weighing meter
After the measurement process is done, the next step is to mix completely the
formulation inside an aluminum mug. This procedure is repeated for 3 to 5 minutes.
Then all the specimens will be cooled at room temperature (310 C) for 5 minutes. These
steps are represented as in figure 3.3.
31
Figure 3.3
Sample mixing Process
b) 2nd stage: Milling and Hot Press procedures.
All of the specimens with different fillers and concentrations were blended using
Two-roll Mill machine. The temperature of the milling machine is set at
185 0C.
Specimens in the powder form will be poured between the roll mil and the process took
around 3-4 minutes. This is shown in figure 3.4.
Figure 3.4
Two roll mill machine
32
c) 3rd stage: Molding and Hot Press
After the milling process, the specimens will be in the form of thin layer as
represents in figure 3.5 and the structures are not even. So for the experiments purpose,
the samples have to be in uniform thickness (1 mm2). This can be achieved by placing
them into 1mm2 metal frame and. Then the metal molding is inserted in the LabTech
Engineering Limited Hot Press machine as in figure 3.6. Samples are pressed at the
temperature of 187 0C for 10 minutes and cooling for 5 minutes.
Figure 3.5
Figure 3.6
Samples in thin layer form
LabTech Hot Press Machine
33
d) 4th stage: Test Specimens Density Measurement
For electric cable manufacturer in Malaysia, the value of Specific Gravity (SG)
according to the Malaysian Standard must be within 1.45(+/-) 0.5. If the SG beyond the
upper limit, the cable will be too rigid and easily broken when bending. On the other
hand, when SG value is less than 1.40, the cable is too soft and prone to impact. This
tolerance is based on the climate and general purpose usage in Malaysia. Hence, for
other country in Europe, the SG specification might vary.
3.7
Definition of Specific Gravity (SG)
SG is a special case of relative density defined as the ratio of the density of a
given substance, to the density of water when both substances are at the same
temperature. Substances with a specific gravity greater than 1 are denser than water, and
those with a specific gravity of less than 1 are less dense than water.
SG = ρsubstance
ρwater
(3.1)
Metler Toledo Density meter is used to calculate the SG value of test samples as shown
in figure 3.7. Specimen will be measured in air by placing the specimen on the top plate
of density meter.
Then the specimen is immersed into the water to obtain the volume.
After that automatic calculation will be done to determine the density
34
Figure 3.7
3.8
Metler Toledo Density Meter
Experiments Description and Lab Apparatus
Two main experiments had been done in these studies, which are the
AC dielectric breakdown voltage and microstructure analysis using Scanning Electron
Micrograph. In this section, detail explanations are described about the experiments and
equipments involved.
3.8.1
AC Dielectric Breakdown Voltage Test
In this test, several important equipments have been used. As in figures 3.8 and
3.9, they are Haefely Operating Terminal OT 276 and Digital Measuring Instrument
DMI 551, step-up transformer, two capacitors (100 microfarad and 68 Pico farad), rod
35
plane electrode and a discharge rod. The step-up transformer is capable to generate a
voltage from 1kV to 1000kV.
Figure 3.8
Digital Measurement Instruments
Figure 3.9
High Voltage Test Sample
36
Meanwhile, the specimen (30mm x 30mm x 1mm) is located in between the Rod Plane
electrode is illustrated in figure 3.10
Figure 3.10
Rod Plane Electrode Configuration
3.8.2 Polymer Dispersion Analysis
The polymer dispersion of all samples are tested after the Dielectric test is
completed. Hence, a scanning electron microscope (SEM) (JEOL, Japan JSM-5610) is
utilized to observe in great detail the condition of the test samples. In this experiment,
the condition of the samples before dielectric test also been observed using SEM. The
purpose is to do comparison of the molecule structure before and after the breakdown.
Before the SEM observation, all of the PVC’s compounded with filler were coated with
a thin layer of gold.
The function of coater is to eliminate astigmatism effect
(High efficiency observation) and protect polymer from melting during SEM test.
37
The equipment used for coating is JEOL-JFC-1600 Auto fine coater which is shown in
figure 3.11.
Figure 3.11
JEOL-JFC-1600 Auto fine coater
Microstructure analysis is done using Scanning Electron Micrograph as in figure 3.12.
Figure 3.12
JEOL JSM-5610 Scanning Electron Microscope
38
3.9
IEEE Standard Techniques for High-Voltage Testing
In this project, all of the experiments procedures are based on the IEEE standard. This
standard establishes standard methods to measure high-voltage and basic testing
techniques, so far as they are generally applicable, to all types of apparatus for
alternating voltages, direct voltages, lightning impulse voltages, switching impulse
voltages, and impulse currents. This revision implements many new procedures to
improve accuracy, provide greater flexibility, and address practical problems associated
with high-voltage measurements. This particular standard also known as IEEE Standard
4-1995 [14].
3.10
Experimental Procedures
Besides complying with the general safety procedures in section 3.2.1, there are
additional operational procedures for each work involved. These procedures have to be
followed to ensure good and precise results.
3.11
AC Dielectric Breakdown Voltage Test
The breakdown voltage test in done according to the following steps;
39
1. Prepare the specimens for dielectric strength testing.
2. Connect the test circuit for the alternating current generation as shown in
figure 3.9.
3. Place the specimen between rod-plane electrodes.
4. Make sure there is tight joint between specimen and electrodes as air gap will
effected the result.
5. Take out the discharge rod.
6. Close the entrance door properly.
7. Switch on the Digital Measuring Instrument DMI 551 and Operating Terminal
OT 276.
8. Make sure the screen of Digital Measuring Instrument DMI 551 shows the AC
RMS reading. If not, press the “Display” button to show the reading.
9. Release the emergency button of 0T 276 and set the interlock key switch form
0 to 1 position.
10. Press the “READY” button of the operating terminal so that the light of
green and red color buttons illuminate. The high voltage supply is ready to be
“energized”.
11. Press the green color button. The red color button light will illuminate and
green color will switch off.
12. Press ‘^’ button on the OT 276. The screen of DMI 551 will display the
increment of AC RMS reading.
13. Observe the increment of AC RMS reading while pressing ‘^’ button.
14. Once the reading of AC RMS drop, the final value before it drops is taken as
the breakdown voltage.
15. Press ‘v’ button instantly on the operating terminal to step down the high
voltage.
16. Press ‘READY’ button after the voltage has reached zero.
17. Interlock key is set from ‘1’ to ‘0’ position.
18. Place discharge rod on the AC generation circuit.
*Repeat step 3 until 18 for other samples.2
40
3.12
Test Samples Density Measurement Procedures
The procedures of density measurement for test samples are listed as below;
1. Samples are placed in order for the measurement.
2. For the measuring weight, place the specimen on top of the density meter plate.
Record the reading.
3. For the volume, immersed the sample into water container.
Record the
reading.
4. Enter the data’s into the density meter to acquire the desired value.
*Repeat step 2 until 4 for other samples.
3.13
Polymer Dispersion Analysis Procedure
The procedures for polymer dispersion analysis are stated as below;
1. Samples are prepared for SEM examination.
2. Main power of SEM machine switched ON and let it operates for 15 minutes.
3. Coat the specimens using JEOL JFC-1600 Auto Fine Coater.
4. Place the samples firmly on the machine holder.
5. Monitor the dispersion of the PVC samples.
6. Select the best SEM magnification to obtain clear and fine image.
7. Save the image into PC.
*Repeat step 3 until 7 for other samples.
CHAPTER 4
RESULTS AND ANALYSIS
4.1
Introduction
In this chapter, the results of test samples density measurement, AC dielectric
breakdown voltage test and SEM analysis are presented in the form of table, graph and
figure. The project procedures as explained in chapter 3 were implemented to fulfill the
objective of the study.
4.2
Results of Specimen Density Measurement
The results for density of every test samples are listed as follow.
42
4.2.1
1st Formulation: PVC + Calcium Carbonate NCC-P 1T (Normal grade)
The overall results for NCC-P 1T is shown in table 4.1.
Table 4.1: Formulation PVC+ CaC03 (1T)
Caco3
Sample PVC (g)
(1T)
SG
f0
100
0
1.42
f1
95
5
1.43
f2
90
10
1.45
f3
85
15
1.48
f4
80
20
1.49
f5
75
25
1.50
The results also represented in the form of graph as shown in figure 4.1.
SG
SG of PVC COMBINED WITH CaCO3 (1T)
1.52
1.50
1.48
1.46
1.44
1.42
1.40
1.38
1.5
1.49
1.48
SG value
1.45
1.43
1.42
f0
f1
f2
f3
f4
f5
Formulation
Figure 4.1
SG Measurements for PVC+ CaC03 (1T)
43
4.2.2
2nd Formulation: PVC + Calcium Carbonate Neolite SP (Micro-filler)
The overall result for Neolite SP is shown in table 4.2.
Table 4.2: Formulation PVC+ CaC03 (NSP)
CaCo3
Sample PVC (g) (Neolite SP)
SG
f0
100
0
1.42
f6
95
5
1.44
f7
90
10
1.47
f8
85
15
1.48
f9
80
20
1.49
f10
75
25
1.50
The results for PVC compounds with NSP formulations also represented in the form of
graph as shown in figure 4.2.
SG
SG of PVC COMBINED WITH NEOLITE SP
1.52
1.5
1.48
1.46
1.44
1.42
1.4
1.38
1.47
1.50
1.49
1.48
SG value
1.44
1.42
f0
f6
f7
f8
f9
f10
Formulation
Figure 4.2
SG Measurements for PVC+ CaC03 (NSP)
44
4.2.3
3rd Formulation: PVC + Calcined Clay (Micro-filler)
The overall result for Calcined Clay is shown in table 4.3.
Table 4.3: Formulation PVC+ Calcined Clay
Calcined
Sample PVC (g)
Clay
SG
f0
100
0
1.42
f11
95
5
1.44
f12
90
10
1.45
f13
85
15
1.47
f14
80
20
1.48
f15
75
25
1.50
The results for PVC compounds with clay formulations also represented in the form of
graph as shown in figure 4.3.
SG
SG of PVC COMBINED with Calcined Clay
1.52
1.5
1.48
1.46
1.44
1.42
1.4
1.38
1.50
1.48
1.47
SG value
1.45
1.44
1.42
f0
f11
f12
f13
f14
f15
Formulation
Figure 4.3
SG Measurements for PVC+ Calcined Clay
45
4.3
Results for AC Dielectric Breakdown Voltage Test
The measurement for breakdown voltage is done for a test sample with the
dimension of 30mm x 30mm x 1mm when AC stress is applied at room temperature.
The breakdown is considered when the specimen damaged or punctured. For each
formulation, let say PVC compounded with 5% of CaC03 1T, three reading were taken.
Then the value of breakdown voltage is the averaged of three measurements. Table 4.4
represents overall results of dielectric breakdown voltage for PVC when combined with
three different fillers at various concentrations.
Table 4.4: Overall result of breakdown voltage
Formulation
Breakdown Voltage (kV)
F0
5.310
F1
6.218
F2
6.921
F3
6.822
F4
6.701
F5
6.678
F6
7.231
F7
8.295
F8
7.912
F9
7.612
F10
6.941
F11
7.102
F12
7.417
F13
7.982
F14
7.431
F15
6.813
46
From the table 4.4, every formulation obtained its own highest value of
breakdown voltage obtained respectively. They are F2 which is PVC compounded with
10% of CaC03 NCC-P 1T, F7 is PVC combined with 10% of CaC03 Neolite SP, and
F13 is the mixing of Calcined Clay at 15% concentration with PVC.
The first
formulation (F0) in the table is the PVC sample without filler. F0 is utilized as a
reference in this experiment.
4.4
Polymer Structure Dispersion Micrograph Results
The dispersion of the polymer structure is observed before and after the AC
dielectric stress. The outcome from this test provides the relation between polymer
structure (consists of various type of fillers) and their breakdown voltage values. SEM
images of pure PVC and PVC blends with different kind of fillers with the highest
breakdown voltage only are shown in figure 4.4 until figure 4.11.
Figure 4.4
Pure PVC sample (F0) at 10,000 magnifications
47
Figure 4.5
Figure 4.6
Pure PVC sample (F0) at 20,000 magnifications
10 wt% CaC03 NCC-P 1T (F2) before AC dielectric test
48
Figure 4.7
Figure 4.8
10 wt% CaC03 NCC-P 1T (F2) after AC dielectric test
10 wt% CaC03 Neolite SP (F7) before AC dielectric test
49
Figure 4.9
10 wt% CaC03 Neolite SP (F7) after AC dielectric test
Figure 4.10
15 wt% Calcined Clay (F13) before AC dielectric test
50
Figure 4.11
4.5
15 wt% Calcined Clay (F13) after AC dielectric test
Analysis of AC Dielectric Breakdown Voltage and Molecule Dispersion
This chapter will analyze all the results obtained from AC dielectric breakdown
voltage and the dispersion observation from SEM. Also, the experiment results for AC
stress done by Lim [10] are compared with the current studies.
4.5.1
AC Dielectric Breakdown Voltage Analysis
From table 4.4, a distinct improvement in terms of higher breakdown voltage is
obtained for certain formulation. And basically, it proved that when PVC sample is
51
compounded with filler material the density or specific gravity (SG) increased with the
breakdown voltage compared to the sample of pure PVC.
Figure 4.12 shows the
analysis for breakdown voltage test of Calcium Carbonate NCC-P 1T. The highest
value achieved is 6.921 kV at concentrations of 10 wt%. Meanwhile when the sample is
mixed with 5 wt% of CaCO3, the breakdown voltage is the lowest compare to the others.
The divergence of maximum and minimum breakdown voltage compare to the pure
PVC (0 wt% filler) is 1.611 kV and 0.908 kV respectively.
Comparison for Breakdown Voltage and SG value
(PVC+CaCo3 (1T))
6.921
B /V ( k V ) a n d S G
7
6
6.822
6.218
6.701
6.678
5.31
5
4
3
2
1.42
1.43
1.45
1.48
1.49
1.50
Breakdown
Voltage (kV)
SG
1
0
0
5
10
15
20
25
Filler content (wt%)
Figure 4.12
voltage
Comparisons of PVC and PVC+CaC03 1T Dielectric AC test breakdown
52
In figure 4.13, it can be clearly seen that at 10 wt% of Calcium Carbonate
Neolite SP (micro-filler) produced the highest breakdown voltage compare to the other
formulations. As the content of filler increased, the breakdown voltage declined steadily.
Furthermore from the concentration of 5 until 25 wt% is concerned, Neolite SP
performed better compare to other type of fillers.
B / V (k V ) a n d S G
Comparison for Breakdown Voltage and SG (PVC+CaC03(NSP))
9
8
7
6
5
4
3
2
1
0
8.295
7.231
7.912
7.612
6.941
5.31
1.42
0
1.44
5
1.47
10
1.48
15
1.49
20
1.50
Breakdown
Voltage (kV)
SG
25
Filler content (wt%)
Figure 4.13
Comparisons of PVC and PVC+CaC03 Neolite SP Dielectric AC Test
Breakdown Voltage
Figure 4.14 explained the result for Calcined Clay (micro-filler). From this type,
it produced the highest breakdown voltage (7.982 kV) when PVC is compounded with
15 wt% of clay. The deviation of maximum and minimum breakdown voltage compare
to the pure PVC (0 wt% filler) is 2.672kV and 1.503 kV respectively.
53
Comparison for Breakdown Voltage and SG value (PVC+Calcined Clay)
B/v (kV) and SG
8
7
6
5
7.982
7.417
7.102
7.431
6.813
5.31
4
3
2
Breakdown
Voltage (kV)
1.48
1.45
1.43
1.42
1.50
1.49
SG
1
0
0
5
10
15
20
25
Filler content (wt%)
Figure 4.14
Comparisons of PVC and PVC+ Calcined Clay Dielectric AC Test Breakdown
Voltage
The overall performance of dielectric test is illustrated in figure 4.15.
B re a k d o w n V o lta g e (k V /m m )
AC Dielectric Test:Breakdown voltage
8.5
8.295
8
7.5
7.231
7
7.417 7.982
7.102
6.921
6.5
6.218
6
5.5
7.912
7.612
7.431
Calcium Carbonate (NSP)
6.941
6.813
6.822
6.701
6.678
Calcined clay
Calcium Carbonate 1T
Pure PVC
5.31
5
0
5
10
15
20
25
Filler content(wt%)
Figure 4.15
Overall results of Dielectric AC Test Breakdown Voltage
54
This result agreed with the theory stated in the literature review chapter in terms
of the effect of filler material when combined with PVC sample. And generally, the
modified formulation of PVC specimen improved the ability to avoid early breakdown
as occurred at pure PVC sample. In addition, the chemical properties and particle size
of the filler play a major role in deciding the value of its breakdown voltage when AC
stress in been applied via the specimen.
Since CaC03 Neolite SP and Calcined Clay Polestar 501 are micro filler, they
exhibit the capability to withstand higher electrical stress compare to specimen
compounded with a normal grade of filler. This is because the filler which is very fine
can amalgam and filled the void that exists in PVC polymer. Among the three types of
filler, Neolite SP at 10 wt% concentration produced the highest breakdown voltage
which is 8.295 kV. For clay, the maximum value achieved is 7.982 kV at 15 wt%
combinations and lastly NCC-P 1T is 6.921 kV. The distinction between Neolite SP
(10 wt% filler content) and pure PVC is about 3 kV. From the theory as explained in
chapter 2, it has been shown that with the addition of filler material had increased the
dielectric strength of test samples. However, the breakdown voltage started to decrease
after it had reached the optimum value. This characteristic occurred when the content of
filler is kept increasing. It happened to all type of fillers and for CaC03 NCC-P 1T the
degradation of dielectric strength is gradual as compared to the other micro fillers.
From figure 4.16, by applying the new type of fillers it produced better dielectric
strength than CaC03 (FCC-200). FCC-200 is the filler that being used by Lim [10] in
her previous test. In this study, formulation of Neolite SP with 10% filler concentration
achieved the highest breakdown voltage.
compare with the result of FCC-200.
The improvement is about 3 kV when
55
Summarize of the highest B/V and its SG for each type of filler
9
8.295
1.5
7.982
8
6.921
7
1.48
5.95
1.47
6
B/V (kV)
1.46
1.46
SG
5
1.45
4
1.44
3
2
1.42
1
1.411
0
1.4
5
CaCo3 (FCC-200)
-Refer from previous
test [5]
Figure 4.16
10
CaCo3 (NCC-P 1T)
10
CaCo03 (Neolite SP)
15
Calcined Clay
Filler content (wt%)
Comparisons of breakdown voltage between previous study and current
experiment
Another observation from this graph is when the density of sample increased, the
break down voltage also increased accordingly. But at some level where the sample is
too dense, the filler molecules are likely to agglomerates with each other and do not
blend well with the PVC.
This phenomenon contributes to the behavior of poor
dielectric strength which occurred to every formulation.
56
4.5.2
Polymer Dispersion Micrograph Analysis
Figure 4.4 until 4.11 represents SEM images of the pure PVC and PVC with
various types of filler materials dispersed in PVC polymer structure. Whenever the
filler material blended well with the insulating polymer, the breakdown voltage of these
samples raised with the addition of fillers.
This attribute has been observed
experimentally. Besides, the agglomerations and bonding degree are greatly depends on
the size and chemical properties of filler. For SEM images, the filler particles appeared
in bright while PVC polymer is black in color.
According to figure 4.4, pure PVC sample has the “Terrain” surface type with
observable cavities. The non- uniform structure lead to possibility of low breakdown
voltage which is 5.31 kV.
For the sample of 10 wt% CaC03 NCC-P 1T (F2) before AC dielectric test as
illustrated in figure 4.6, CaC03 have a Trigonal Rhombohedral shape (Tri-direction
structure). Furthermore the filler molecules tend to agglomerate it selves and quite
poorly dissolved in PVC polymer. Also micro void exists in between PVC molecules.
Figure 4.7 shows the condition after the dielectric test with breakdown voltage of 6.921
kV. At this stage, the filler molecules are still dispersed in non-uniform structure and
micro void still can be observed
For the SEM of CaC03 Neolite SP 10 wt% before AC test, it is display in figure
4.8.
This micro filler tends to produce a spontaneous formation of stacked
superstructures calcite plates. Another interesting feature is it has an improved structure
of ultra fine molecules and thin structure in one direction. Since Neolite SP has an ultra
fine molecule, it can disperse and filled the void of PVC polymer very well. Hence, it
produced the highest breakdown voltage. The micrograph picture after the test is shown
in figure 4.9.
57
As for Calcined Clay, the highest breakdown voltage is achieved at the
concentration of 15 wt%. Before the test, the molecules of clay disperse quite well
when compare to normal filler but less than Neolite SP.
This characteristic is
accordance to the size of particle. Referring to the specification table of 3.2, the size
Calcined Clay is 1.3 um and Neolite SP is 0.85 um. In figure 4.11 which after the AC
stresses experiment, Calcined Clay still retain the original molecule shape.
CHAPTER 5
DISCUSSION
5.1
Effect of Filler on the Test Samples Density
From table 4.1 until 4.3 in chapter 4, it can be clearly observed that when the
amount of filler increased, the density of specific gravity (SG) also increased. This
condition occurred for all type fillers that being used in this study. When a specimen
has low density, it will be soft and easy to bend. But when the sample is high in density
it will more rigid and hard. This feature provides the capability of sustaining high
impact but lack of flexibility to bend and prone to break. Hence a good sample must
have both attributes.
For electric cable manufacturer in Malaysia, the value of Specific Gravity (SG)
according to the Malaysian Standard must be within 1.45(+/-) 0.5. So, this specification
also has been followed in this project as illustrated in figure 4.1 until 4.3. Another
interesting finding is when the density increased, the dielectric strength of test sample
also improved distinctively. At certain point where the highest breakdown voltage is
attained, it started to degrade when the density is too high. The probability of this
59
situation is the filler is unlikely to diffuse into PVC polymer structure but it tends to
bind with each other.
5.2
PVC Compound with various concentration of CaC03 NCC-P 1T
PVC samples compounded with various concentration CaC03 1T are tested with
AC Dielectric test.
Referring to figure 4.12, the density value increased with the
addition of filler material. The highest value of breakdown voltage for this type is 6.921
kV at the concentrations of 10 wt%. It means an enhancement of 30.34% from the
result of pure PVC. After this peak point, the dielectric strength started to fall gradually
form 6.921 to 6.678 kV and settled around this value. The divergence of maximum and
minimum breakdown voltage compare to the pure PVC (0 wt% filler) is 1.611 kV and
0.908 kV respectively. When evaluated with other type of fillers (Neolite SP and
Polestar 501), CaC03 1T stand the lowest in terms of breakdown voltage. Few factors
contributed to this result.
1. NCC-P 1T is a normal grade of filler; meanwhile the previous two materials
are micro filler.
2. Normal filler can’t disperse well into PVC polymer structure and this is shown
in SEM images of figure 4.6 and 4.7.
60
5.3
PVC Compound with various concentration of CaC03 Neolite SP
(Micro filler)
This type of filler gave the best result in terms of dielectric strength among the
other three materials. At 10 wt% concentration of Calcium Carbonate Neolite SP, the
breakdown value is 8.295 kV and it is the optimum condition from the other
concentrations. In this case, a significant improvement had been from pure PVC and
previous test done by Lim [11]. The percentages of increment are 56.21% and 28.27%
correspondingly. As the content of filler increased, the breakdown voltage declined
steadily. Furthermore from the concentration of 5 until 25 wt% is concerned, Neolite SP
performed better compare to other type of fillers.
On the other hand, Neolite SP capability to obtain the highest breakdown voltage is
depend from several factors:
1. The particles size of CaC03 Neolite SP is the smallest from NCC-P 1T and
Calcined Clay Polestar 501. According to the specification given in table 3.2,
the size is about 0.85 um.
2.
The above statement is also supported by the fact of SEM micrograph test
which shown the excellent dispersion in between PVC polymer voids.
In
addition, although the sample of 10 wt% filler concentration punctured after AC
stress test, the microstructure of Neolite SP remained uniformly distributed and
did not agglomerates together.
61
5.4
PVC Compound with various concentration of Calcined Clay Polestar 501
(Micro filler)
Figure 4.14 explained the result for Calcined Clay (micro-filler). For this filler
material, the highest breakdown voltage (7.982 kV) it can produced is when PVC
compounded with
15 wt% concentration of clay. The deviation of maximum and
minimum breakdown voltage compare to the pure PVC (0 wt% filler) is 2.672kV and
1.503 kV respectively. At low concentration of filler which is from 5 wt% until 10 wt%,
this organic filler performed a moderate dispersion and bonding strength into the PVC
matrix compared to Neolite SP but greater than NCC-P 1T. The adhesion and filler
diffusion is showed in SEM figure 4.10 and 4.11.
Based on the density results, with the addition of 10 wt% Neolite SP compared
to pure PVC it is proven that organic filler with micro size compounded and occupied
well into the free space exist in PVC polymer.
5.5
PVC Cost Analysis
Manufacturers of PVC materials are constantly searching methods to reduce cost.
One of the most common ways to decrease the formulation cost is the addition of filler,
mainly Calcium Carbonate.
It is vital due to electric cable manufacturer depends
heavily on this material to ensure their end product is competitive on price and also
electrical characteristics. The cost reduction proposal in this chapter is the initial step to
compensate the soaring price of PVC and solely based on the dielectric strength and the
62
dispersion properties. However, other properties such as mechanical and chemical
attributes must be considered before it can be applied to the industry.
5.5.1
Proposal for Cost Reduction
To reduce the cost of insulation for PVC cable, two proposals are stated.
1. Reduce the content of PVC by adding filler material, such as Calcium
Carbonate or Calcined Clay with correct amount.
2.
Although reducing the amount of PVC, the electrical characteristic such as
Breakdown voltage has to be maintained or increased.
5.5.2
Price for PVC and Fillers
Price quoted by Industrial Resins Malaysia as December 2007 [12].
Table 5.1
represents the price of PVC and fillers that have been used through out this study.
Table 5.1: Price of Raw Materials for Cable Insulation
Material
Price/kg ($ USD)
Price/kg (RM)
PVC resins
1.1
3.542
NCC-P 1T
0.236
0.76
Neolite SP
0.497
1.6
Polestar 501
0.932
3
63
The usual cost of cable insulation is stated as below.
i.
From this experiment, 100g of PVC can produce a sample with a dimension of
21cm x 21cm x 0.1cm.
ii.
From table 5.1, the cost of PVC for 1 kg is $1.1 USD.
Hence,
For 100g of PVC = $1.1 USD/1000 x (100) = $0.11 USD
= RM 0.3542
So for cost reduction, three parameters are taken into consideration.
i. Cost analysis is done for every filler material that produced the highest
Breakdown voltage.
ii. Estimation are done base on 100g sample.
iii. Calculation for the optimize cost proposal.
5.5.3
Study case 1
The calculation for material cost using Calcium Carbonate NCC-P 1T as followed.
Highest Breakdown Voltage: 6.921 kV at formulation F2 (10% of filler concentration).
90g PVC
= $0.0011 USD/g
x 90g = $0.099
USD
10g CaC03 = $0.000236 USD/g x 10g =$0.00236 USD
Total
= $0.10136 USD = RM 0.3264
64
5.5.4
Study case 2
The calculation for material cost using Calcium Carbonate Neolite SP as followed.
Highest Breakdown Voltage: 8.295 kV at formulation F7 (10% of filler concentration)
90g PVC
= $0.0011 USD/g
x 90g = $0.099 USD
10g CaC03 = $0.000497 USD/g x 10g = $0.00497 USD
Total
5.5.5
= $0.10397 USD = RM 0.3348
Study case 3
The calculation for material cost using Calcined Clay Polestar 501 as followed.
Highest Breakdown Voltage: 7.982 kV at formulation F13 (15% of filler concentration)
85g PVC
= $0.0011 USD/g
15g Clay
= $0.0009317 USD/g x 15g = $0.01398 USD
Total
x 85g = $0.0935
USD
= $0.1075 USD = RM 0.3461
65
Figure 5.1 shows the cost for every filler material (100g) that obtained the
highest dielectric strength in their respective type. Also it can be clearly observed that
the cost of sample consist only PVC is the most expensive compare to the other
formulations.
Summarize of the highest B/V and its cost for each type of formulation
9
8.295
0.3542
8
0.3461
0.34
5.31
0.3348
5
0.33
4
RM
B/V(kV)
0.35
6.921
7
6
0.36
7.982
0.3264
0.32
3
2
0.31
1
0
0.3
f0
f2
PVC
NCC-P (1T)
Figure 5.1
f7
f13
Formulation
Filler with the highest breakdown voltage and cost
Formulation of F2 provides the most saving when compare to the pure PVC
which is about RM 0.0278. Meanwhile RM 0.0194 can be saved by F7 and followed by
F13 with RM 0.0081 worth of saving. The amount of saving is summarized in table 5.2.
Table 5.2: Estimation of saving for 100g sample
Material
PVC
PVC+NCC-P (1T)
F0 (100%
Formulation
PVC)
Breakdown
Voltage (kV)
5.31
Cost (100g per
sample)
RM 0.3542
Saving
(Price of PVC Propose
method)
N/A
F2 (90%
PVC+10%filler)
PVC+Neolite SP
F7
(90%PVC+10%
filler)
PVC+Polestar 501
F13
(85%PVC+15%
filler
6.921
8.295
7.982
RM 0.3264
RM 0.3348
RM 0.3461
RM 0.0278
RM 0.0194
RM 0.0081
66
5.5.6
Cost Analysis for Weekly, Monthly, and Annual Production
Table 5.3 stated the production cost for every type of formulation. The rate is
categorized in three sections which are weekly, monthly and annually.
All the
calculations are refer to IRM manufacturing profile as stated below:
1. IRM produced 30 tons of PVC resins per week.
2. For yearly calculation, only 11 months are calculated. 1 month is reserved for
maintenance and holiday.
Table 5.3: Production Cost for weekly, Monthly and Annual
Normal Production cost
PVC+NCC-P (1T)
F2
(90%PVC+10%filler)
PVC+Neolite SP
F7
(90%PVC+10% filler)
PVC+Polestar 501
F13
(85%PVC+15%filler
RM 1,062,600
RM 979,200
RM 1,004,400
RM 1,038,300
RM 31,878,000
RM 29,376,000
RM 30,132,000
RM 31,149,000
RM 350,658,000
RM 323,136,000
RM 331,452,000
RM 342,639,000
Material
Formulation
PVC
F0
(100% PVC)
New cost after PVC reduction
1
w
e
e
k
1
m
o
n
t
h
1
y
e
a
r
67
From table 5.3, referring to annual production cost, it is fairly to evaluate that by
reducing the amount of PVC in every formulation a lot of saving can be done. The
percentage of price reduction for PVC/CaC03 1T is 7.85%, for PVC/ CaC03 NSP is
5.48% and 2.29% for PVC/Calcined Clay. From the cost estimation, formulation F7
(PVC+Neolite SP with 10 wt% concentration) gave the best proposal of cost reduction
(RM 0.0194/100g) and also provide with the highest Breakdown voltage among other
formulations.
CHAPTER 6
CONCLUSION AND RECOMMENDATIONS
6.1
Conclusion
From this study, it can be clearly seen that by using Calcium Carbonate Neolite
SP (micro-filler) with SG of 1.47 obtained the highest breakdown voltage compare to
the other formulations.
The results also had shown distinct improvement compare to the previous
experiment [11]. It proves that micro-filler have the capability to compound itself better
compare to the normal filler in between PVC molecules matrix.
Indeed the size of filler particle play major role in determining the breakdown
boltage. Breakdown voltage increased fairly when SG increased. After the specimen
reached its peak breakdown voltage, it started to degrade afterwards although SG value
increasing.
The molecule dispersion properties also contributed to the value of
breakdown voltage.
As the conclusion of this study, the strength of cable insulation increased by the
addition of filler material.
69
6.2
Recommendation and future works
1. For future experiments, researcher can study more details on the formulation
of Neolite SP with SG value of 1.47, since it had obtained the highest
Breakdown Voltage.
2. In this project, the concentrations of filler are set at 5,10,15,20 and 25%. It is
highly recommended to further the research at the concentration of 5 until
15% because the critical percentage of filler is observed at 10%.
3. Another type of base polymer besides PVC such as XLPE or natural rubber
can be studied its characteristic when compound with filler materials.
4. From the cost estimation, formulation F7 (PVC+Neolite SP with 10 wt%
concentration) gave the best proposal of cost reduction (RM 0.0194) and also
provide with the highest Breakdown voltage among other formulations.
Although NCC-P (1T) provide the highest saving of cost, it is not preferred
due to its breakdown voltage margin is only 1.5 kV more than pure PVC.
REFERENCES
[1]
Marino Xanthos, “Functional fillers for plastics”, 1st edition, 2005
[2]
George Wypych, “Handbook of Fillers”, 2nd edition, 1998.
[3]
H.Zhang, “Electrical surface resistance, hydrophobicity, and diffusion
phenomena in PVC”, IEEE Trans on Electrical Insulation, Vol. 6, February 1999.
[4]
R.E Wetton, “Effect of physical aging of polymers on dielectric permittivity and
loss values over wide tempreature and frequency ranges”, Polymer laboratories,
UK
[5]
American Standard for Test Measurement (ASTM), “Dielectric Breakdown
Voltage Test”, ASTM D149.
[6]
Jaroslav Lelak, “Diagnostics of medium voltage PVC cables by dissipation
factor measurement at very low frequency”, IEEE International Symposium,
Boston, 2002.
[7]
John Murphy, ”Additives for Plastics Handbook”, Elsevier Advanced
Technology, 1996.
[8]
Charles H. Kline, “Reinforcement and Fillers for Plastics”, 1980
[9]
Harry S.Katz,”Handbook of Fillers for Platics”, Van Nostrand Reinhold
Company of Publication, 1987.
71
[10]
YS Lim, “Comparison between micro-filler and Nano- filler material on the
Dielectric Strength of PVC cable”, journal of Elektrika, UTM, September 2007.
[11]
MM Yaacob, YS Lim, ”The effect of filler material on the physical
characteristics of PVC cable”, IEM journal, University Technology of Malaysia,
Malaysia, 2006.
[12]
Industrial Resins Malaysia,”Annual Report on Manufacturing and Production”,
2007.
[13]
M.R Wertheimer, ”Dielectric permittivity, conductivity, and breakdown
characteristics of polymer-mica composites”, IEEE Trans on Electrical
Insulation, Vol. E1-12, April 1977.
[14]
IEEE Standards, ”IEEE Standard Techniques for High-Voltage Testing”, March,
1995.
71
72
APPENDIX A-1
DATASHEET OF PVC
73
APPENDIX B-1
DATASHEET OF CaC03 NCC-P 1T
74
APPENDIX C-1
DATASHEET OF CaC03 NEOLITE SP
75
APPENDIX D-1
DATASHEET OF CALCINED CLAY POLESTAR 501