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Transcript
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