Design, Synthesis and Characterization of Polymeric Films and Membranes by Ikilem Gocek A dissertation submitted to the Graduate Faculty of Auburn University in partial fulfillment of the requirements for the Degree of Doctor of Philosophy Auburn, Alabama August 9, 2010 Keywords: High temperature PEMFC, PBI, PP, membrane, synthesis, modeling Copyright 2010 by Ikilem Gocek Approved by Sabit Adanur, Chair, Professor of Polymer and Fiber Engineering Peter Schwartz , Professor of Polymer and Fiber Engineering Carol Warfield, Professor of Consumer Affairs ii Abstract Solid polymer electrolyte membranes play a vital role in polymer electrolyte membrane fuel cells. Although these membranes have been used successfully, there is still a need to improve their proton conductivity, lower their cost and increase their operation temperature. Polybenzimidazole, a high temperature resistant polymer, was synthesized and polymer electrolyte membrane was fabricated with a novel method including ultrasonic generator and ultrasonic nozzle. A computer model was developed by using COMSOL Multiphysics program. Polypropylene (PP) films were fabricated by using single screw extruder in order to find out how the machine parameters affect the mechanical properties of the product. Nanoclay reinforced PP films were produced by using single screw extruder after compatibilizer, nanoclay and PP were mixed in a twin screw extruder. Tensile, tear and burst strength tests were performed on these films. With the increasing temperature and winding speed, the thickness of the films decreases; however, with the increasing screw motor speed film thickness increases. With the increasing temperature tear strength becomes higher in machine direction (MD); however tear strength decreases in cross direction (CD). With the increasing screw motor speed tear strength of the films did not show any specific trend in MD; however, tear strength of the films in CD increases. With the increasing winding speed the tear strength of the films decreases in MD; however, the data did not show any specific trend in CD. When the molecular orientation increases because of lower temperatures, tensile strength should increase according to the literature. However in this iii work, as the temperature increased, tensile strength increased in MD. With increasing screw motor speed tensile strength of the films increases in MD; however, tensile strength of the films decreases in CD. With increasing winding speed the tensile strength of the films increases in MD; however, tensile strength of the films decreases in CD. Nanoclay reinforced films having only 1% nanoclay content have more homogeneous nanoclay dispersion than the films having 3% nanoclay content. The films having 5% nanoclay content have better nanoclay dispersion compared to the other films. Screw speed was increased for the films having 5% nanoclay content. Since the screw speed was increased, shear stress increased. This caused the polymer and the nanoclay mix more homogeneously. According to the differential scanning calorimetry (DSC) results the melting points of the nanoclay reinforced films slightly increase as their nanoclay contents increase from 1% to 5%. Tensile tests showed that as the nanoclay contents increase, the extension of the films decreases. Nanoclay reinforced films having only 1% nanoclay content have higher tensile strength than the films having 3% nanoclay content. No specific result could be obtained about the effect of the compatibilizer content on tensile strength of the nanoclay reinforced films. Nanoclay reinforced films having only 1% nanoclay content have higher tear strength than the films having 3% nanoclay content. Since the screw speed was increased for the films having 5% nanoclay content in order to obtain a film structure, the films, having 5% nanoclay content, gained higher tear strength. Burst strength results show that as the nanoclay content of the nanoclay reinforced films increases from 1% to 5%, the extension of the films decreases. Nanoclay reinforced films having only 1% nanoclay content have higher burst strength than the films having 3% nanoclay content. iv Acknowledgments I would like to express my gratitude to my advisor Dr. Sabit Adanur, for giving me with the opportunity to pursue my doctor of philosophy degree. I would like to give my appreciation to my committee members, Dr. Peter Schwartz and Dr. Carol Warfield for their contribution. I really appreciate Dr. Ram Gupta for his guidance and for being an outside reader for my dissertation. This study would not have been possible without the help of several people that I would like to thank: Mr. William David Clark for helping me to produce my samples with twin screw and single screw extruders, Dr. Ramsis Farag for teaching how to perform tensile, tear and burst strength tests, and how to operate the testing machines, Dr. Miller for helping in SEM analysis, and Dr. Edward Davis for giving information and helping while operating the twin screw extruder and single screw extruder machines. I also appreciate the help of Mr. Jeff Thomson, and Mr. Steve Howard in several steps of this study. The financial support from the U.S. Department of Commerce is gratefully acknowledged. I would also like to express my most sincere thanks to my parents, Nuket and Riza Gocek, and my sister for always supporting me. v Table of Contents Abstract ......................................................................................................................................... ii Acknowledgments........................................................................................................................ iv List of Tables ............................................................................................................................. viii List of Figures .............................................................................................................................. ix List of Abbreviations ................................................................................................................. xiii Chapter 1 Introduction .................................................................................................................. 1 1.1. Fuel Cell ................................................................................................................... 1 1.2. Fuel Cell Membranes ............................................................................................... 4 Chapter 2 Literature Review ....................................................................................................... 6 2.1. Perfluorosulfonic Membranes .................................................................................. 6 2.2. Membranes for HTPEMFCs ................................................................................... 11 2.3. Composite Membranes .......................................................................................... 12 Chapter 3 Membrane Production Using Single Screw Extruder .............................................. 15 3.1. Machine Set Up and Operation ................................................................................ 15 3.2. Effect of Processing Parameters .............................................................................. 20 3.2.1. Introduction ................................................................................................... 20 3.2.2. Experimental ................................................................................................. 22 3.2.3. Results and Discussion .................................................................................. 24 3.2.4. Conclusions ................................................................................................... 38 vi Chapter 4 Nanoclay Reinforced Membrane Structures Using Twin and Single Screw Extruders ....................................................................................................................... 41 4.1. Introduction ............................................................................................................ 41 4.2. Experimental ............................................................................................................ 45 4.2.1. Materials and Equipments Used .................................................................... 45 4.2.2. Manufacturing and Testing ........................................................................... 50 4.3. Results and Discussion ............................................................................................ 54 4.3.1. Morphology Analysis .................................................................................... 54 4.3.2. DSC Analysis ................................................................................................ 61 4.3.3. Tensile Strength Analysis .............................................................................. 67 4.3.4. Tear Strength Analysis .................................................................................. 74 4.3.5. Burst Strength Analysis ................................................................................. 81 Chapter 5 Development of PBI Membrane ................................................................................ 91 5.1. Materials Used ......................................................................................................... 91 5.1.1. Polymer and Dopant ...................................................................................... 91 5.1.2. Synthesis of PBI ............................................................................................ 92 5.2. Machines Used ......................................................................................................... 93 5.2.1. Ultrasonic Generator ..................................................................................... 93 5.2.2. Ultrasonic Nozzle .......................................................................................... 94 5.2.3. Dispensing Robot .......................................................................................... 98 5.3. Membrane Fabrication ........................................................................................... 99 5.3.1. Programming of Dispensing Robot ............................................................... 99 5.3.2 Manufacturing Process of the Membrane .................................................... 104 vii Chapter 6 Model of Membrane Behaviour ............................................................................... 105 6.1. Assumptions of the Model ................................................................................... 105 6.2. Model Definition .................................................................................................. 106 6.3. Governing Equations ........................................................................................... 107 6.3.1. Anode .......................................................................................................... 107 6.3.2. Membrane .................................................................................................... 110 6.3.3. Cathode ........................................................................................................ 113 6.4. Solutions of the Governing Equations ................................................................. 116 6.5. Results and Discussions ....................................................................................... 116 Chapter 7 Conclusions and Recommendations ......................................................................... 121 References ............................................................................................................................... 124 Appendices .............................................................................................................................. 129 Appendix A: SEM Micrographs of Nanoclay Reinforced Films ......................... 129 Appendix B: Programs Written for the Dispensing Robot .................................... 138 viii List of Tables Table 2.1 Properties of some commercial membranes ............................................................... 10 Table 3.1 Machine parameters changed during manufacturing process of the films ................. 23 Table 3.2 Thickness test results .................................................................................................. 28 Table 4.1 Properties of Nylon 6/clay nanocomposites ............................................................... 45 Table 4.2 Nanoclay added films and their contents .................................................................... 51 Table 4.3 Thickness of the nanoclay reinforced films ................................................................ 53 Table 4.4 Tensile stress values .................................................................................................... 67 Table 4.5 Calculated tear strength values ................................................................................... 75 Table 4.6 Load and extension values from burst strength tests .................................................. 82 ix List of Figures Figure 1.1 PEM fuel cell configuration and basic operation principles ....................................... 4 Figure 2.1 Nafion??s chemical structure ...................................................................................... 7 Figure 2.2 Electro-osmotic drag in a PEMFC. BP (bipolar plates), GD (gas diffusion layers), CL (catalyst layers) and Mem (membrane) ............................................................................ 8 Figure 2.3 Structures of some PBIs ............................................................................................ 11 Figure 3.1 Schematic of a plastic extruder.................................................................................. 16 Figure 3.2 Schematic of the extrusion film die ........................................................................... 16 Figure 3.3 Wayne single screw extruder ..................................................................................... 17 Figure 3.4 Hopper of the single screw extruder .......................................................................... 17 Figure 3.5 Barrel of the single screw extruder ............................................................................ 18 Figure 3.6 Cast film die of the single screw extruder ................................................................. 18 Figure 3.7 Air blowing and drawing unit of the single screw extruder ...................................... 19 Figure 3.8 Winding unit of the single screw extruder ................................................................ 19 Figure 3.9 Control panel of the single screw extruder ................................................................ 20 Figure 3.10 DSC of the PP films (heating rate: 10 ?C/min) ....................................................... 25 Figure 3.11 Effect of temperature on crystallinity ...................................................................... 26 Figure 3.12 Effect of screw motor speed on crystallinity ........................................................... 27 Figure 3.13 Effect of winding speed on crystallinity .................................................................. 28 Figure 3.14 Effect of temperature on film thickness .................................................................. 29 Figure 3.15 Effect of screw motor speed on film thickness ....................................................... 30 x Figure 3.16 Effect of winding speed on film thickness .............................................................. 31 Figure 3.17 Effect of temperature on tear strength of the films.................................................. 32 Figure 3.18 Effect of screw motor speed on tear strength of the films ....................................... 33 Figure 3.19 Effect of winding speed on tear strength of the films ............................................. 34 Figure 3.20 Effect of temperature on tensile strength of the films ............................................. 35 Figure 3.21 Effect of screw motor speed on tensile strength of the films .................................. 36 Figure 3.22 Effect of winding speed on tensile strength of the films ......................................... 37 Figure 3.23 Burst strength of the films ....................................................................................... 38 Figure 4.1 Polymer-clay nanocomposite morphologies ............................................................. 42 Figure 4.2 Intercalated and exfoliated states of TEM micrograph of a montmorillonite poly (L- lactic acid) ....................................................................................................................... 43 Figure 4.3 Schematic representation of intercalated and exfoliated nanocomposites ................ 44 Figure 4.4 Leistritz twin screw extrusion machine ..................................................................... 47 Figure 4.5 Control panel of the twin screw extruder .................................................................. 47 Figure 4.6 Polymer feeder and hopper of the twin screw extruder ............................................. 48 Figure 4.7 Barrel and filament die of the twin screw extruder ................................................... 48 Figure 4.8 Instron 5565 universal testing machine ..................................................................... 49 Figure 4.9 Tensile testing of the films ........................................................................................ 52 Figure 4.10 Tear testing of the films ........................................................................................... 52 Figure 4.11 Instron 5565 universal machine performing burst strength test .............................. 53 Figure 4.12 Nanoclay dispersion in Film 1 ................................................................................. 54 Figure 4.13 Nanoclay dispersion in Film 2 ................................................................................. 55 Figure 4.14 Nanoclay dispersion in Film 3 ................................................................................. 56 xi Figure 4.15 Nanoclay dispersion in Film 4 ................................................................................. 57 Figure 4.16 Nanoclay dispersion in Film 5 ................................................................................. 57 Figure 4.17 Nanoclay dispersion in Film 6 ................................................................................. 58 Figure 4.18 Nanoclay dispersion in Film 7 ................................................................................. 59 Figure 4.19 Nanoclay dispersion in Film 8 ................................................................................. 59 Figure 4.20 Nanoclay dispersion in Film 9 ................................................................................. 60 Figure 4.21 DSC graph of Film 1 ............................................................................................... 61 Figure 4.22 DSC graph of Film 2 ............................................................................................... 62 Figure 4.23 DSC graph of Film 3 ............................................................................................... 62 Figure 4.24 DSC graph of Film 4 ............................................................................................... 63 Figure 4.25 DSC graph of Film 5 ............................................................................................... 64 Figure 4.26 DSC graph of Film 6 ............................................................................................... 64 Figure 4.27 DSC graph of Film 7 ............................................................................................... 65 Figure 4.28 DSC graph of Film 8 ............................................................................................... 66 Figure 4.29 DSC graph of Film 9 ............................................................................................... 66 Figure 4.30 Tensile stress-strain curve of Film 1, Film 2 and Film 3......................................... 69 Figure 4.31 Tensile stress-strain curve of Film 4, Film 5 and Film 6......................................... 70 Figure 4.32 Tensile stress-strain curve of Film 7, Film 8 and Film 9......................................... 72 Figure 4.33 Tear load-extension curve of Film 1, Film2 and Film 3.......................................... 77 Figure 4.34 Tear load-extension curve of Film 4, Film 5 and Film 6......................................... 78 Figure 4.35 Tear load-extension curve of Film 7, Film 8 and Film 9......................................... 79 Figure 4.36 Burst load-extension curve of Film 1, Film 2 and Film 3 ....................................... 84 Figure 4.37 Burst load-extension curve of Film 4, Film 5 and Film 6 ....................................... 85 xii Figure 4.38 Burst load-extension curve of Film 7, Film 8 and Film 9 ....................................... 87 Figure 4.39 Burst load-extension curve of Film 1, Film 4 and Film 7 ....................................... 88 Figure 4.40 Burst load-extension curve of Film 2, Film 5 and Film 8 ....................................... 89 Figure 4.41 Burst load-extension curve of Film 3, Film 6 and Film 9 ....................................... 90 Figure 5.1 Ultrasonic Broadband Generator ............................................................................... 94 Figure 5.2 Ultrasonic nozzle and its parts ................................................................................... 96 Figure 5.3 Ultrasonic nozzle cross-sectional view ..................................................................... 97 Figure 5.4 Dispenser robot and teach pendant ............................................................................ 98 Figure 5.5 Steps of program 1................................................................................................... 100 Figure 5.6 Steps of program 2................................................................................................... 102 Figure 6.1 Model geometry with its subdomains and boundary labels .................................... 106 Figure 6.2 Velocity field ........................................................................................................... 117 Figure 6.3 Total current density ................................................................................................ 117 Figure 6.4 Mass fraction of hydrogen on the anode side .......................................................... 118 Figure 6.5 Mass fraction of oxygen on the cathode side .......................................................... 118 Figure 6.6 Mass fraction of water on the anode side ................................................................ 119 Figure 6.7 Mass fraction of water on the cathode side ............................................................. 119 Figure 6.8 Total current density on the membrane ................................................................... 120 xiii List of Abbreviations AFC Alkaline Fuel Cell BP Bipolar Plates CL Catalyst Layer DSC Differential Scanning Calorimetry EW Equivalent Weight GDL Gas Diffusion Layer HPA Heteropoly Acid HTPEM High Temperature Polymer Electrolyte Membrane MCFC Molten Carbonate Fuel Cell MFI Melt Flow Index N Newton PAFC Phosphoric Acid Fuel Cell PBI Polybenzimidazole PEEK Polyetheretherketone PEM Polymer Electrolyte Membrane PEMFC Polymer Electrolyte Membrane Fuel Cell PES Polyethersulfone xiv PFSA Perfluorinated Sulfonic Acid Membranes PP Polypropylene PTA Phosphotungstic Acid PTFE Polytetraflouroethylene PWA Phosphotungstic Acid SEM Scanning Electron Microscope SOFC Solid Oxide Fuel Cell TPA Tungstophosphoric Acid 1 CHAPTER 1 INTRODUCTION 1.1. Fuel Cell Fuel cell converts the chemical energy in the fuel structure into electrical energy. This production goes on as long as the fuel is supplied [1]. There are five major types of fuel cells which are differentiated from each other by their electrolytes. These fuel cell types are [1, 2]: 1) Phosphoric acid fuel cell (PAFC) Concentrated phosphoric acid having a weight percentage of nearly 100 is used as the electrolyte. Silicon carbide (SiC) is used as the matrix to retain phosphoric acid. For anode and cathode, platinum is used as electrocatalyst. The range for operating temperature of phosphoric acid fuel cells is 150 to 220 ?C. 2) Polymer electrolyte membrane fuel cell (PEMFC) Polymer electrolyte membrane fuel cells are also called as proton exchange membrane fuel cells. As electrolyte, thin proton conductive polymer membranes usually having a thickness of less than 50 ?m are used for this kind of fuel cells. If 2 perfluorosulfonated acid polymers are used as electrolyte, the operating temperature can be in the range of 60 to 80 ?C. Polymer electrolyte membrane fuel cells can be used for automotive applications, small scale distributed stationary power generation and portable power applications [1,2]. 3) Alkaline fuel cell (AFC) Concentrated potassium hydroxide (KOH) having a weight percentage of 85 is used as the electrolyte for alkaline fuel cells for high temperature applications (above 200 ?C) and less concentrated KOH having a weight percentage of 35 to 50 is used as the electrolyte for lower temperature applications (below 120 ?C). Asbestos is used as a matrix to retain the electrolyte. Many types of electrocatalysts can be used for this kind of fuel cells. Nickel (Ni), silver (Ag), metal oxides and noble metals are some of the electrocatalysts that can be used for AFCs [1, 2]. 4) Molten carbonate fuel cell (MCFC) The electrolyte for molten carbonate fuel cells has the combination of alkali carbonates such as lithium (Li), sodium (Na) and potassium (K). Ceramic matrix of LiAlO2 retains these alkali carbonates. These fuel cells have an operating temperature range from 600 ?C to 700 ?C [1, 2]. 5) Solid oxide fuel cell (SOFC) As the electrolyte, Y2O3 stabilized ZrO2, which is a solid and non-porous metal oxide, is used for solid oxide fuel cells. The operating temperature is between 800 ?C and 1000 ?C [1, 2]. Polymer electrolyte membrane fuel cells are the subject of this study. 3 As mentioned before, polymer electrolyte membrane fuel cells (PEMFCs) have thin polymer membrane as the electrolyte, which is impermeable to gases and permeable to protons. Two porous, electrically conductive electrodes, which are made of carbon cloth or carbon fiber paper, take place at both sides of the membrane. Between the membrane and the electrodes, there is a layer containing catalyst particles (platinum supported on carbon). The surface of the catalyst is the place where the electrochemical reactions take place. Hydrogen is fed from the anode side and it splits into protons and electrons. These protons pass through the polymer membrane. The electrons pass through the electrically conductive electrodes, current collectors and outside circuit and reach to the other side of the membrane which is called as the cathode. The electrons meet with the protons and oxygen at the catalyst layer between the interface of the membrane and the cathode and forms water with electrochemical reaction. As a result of these electrochemical reactions, electron current occurs through an external circuit [1, 2]. The PEMFC configuration, components and principles of operation can be seen in Figure 1.1. 4 Figure 1.1 PEM fuel cell configuration and basic operation principles [2] 1.2. Fuel Cell Membranes Among the different types of fuel cells, polymer electrolyte membrane fuel cells (PEMFC) are one of the best candidates for clean power source for various applications. The polymer electrolyte membrane, which has the function of proton exchange, is the main part of the cell. The common membranes that are used for PEMFCs are perfluorinated polymers having sulfonic acid groups on side chains. However, at temperatures higher than 80 ?C, this kind of membranes require higher water content to provide enough proton conductivity which causes the fuel cell performance to drop. Operating the fuel cell at temperatures above 100 ?C provides various advantages such as improved impurities tolerance, more efficient heat 5 rejection and more useful waste heat [3]. Therefore, polymer electrolyte membranes that can operate at temperatures above 100 ?C are the subject of current research. To increase the fuel cell performance at high temperatures, the polymer electrolyte membrane must have better water retention characteristics to allow higher proton conductivity that improves fuel cell efficiency. In order to extend the fuel cell operation temperature range, novel membranes having different material properties such as higher thermal stability than Nafion? need to be produced. A material that is used for high temperature polymer electrolyte fuel cells is polybenzimidazole (PBI). Polybenzimidazoles are usually used after they are doped with acids because they gain high proton conductivity with no or low humidification after doping with acids. Especially phosphoric acid is used to dope polybenzimidazoles. Another approach to improve the proton transport and mechanical stability of perfluorinated sulfonic acid membranes (PFSA) such as Nafion? at high temperatures is to fill the membrane with inorganic materials. These inorganic materials are hygroscopic and help with water retention for operation of PEM fuel cells at higher temperatures and lower relative humidity. For this purpose, research is being done on Nafion? ? Silica and Nafion ? Titanya composite membranes. These inorganic materials help to develop self-humidifying polymer electrolyte membranes (PEM). All of the research that has been done proves that improving the characteristics of the membranes for high temperature applications helps to improve the performance of PEMFCs. Therefore, the attention must be focused on producing novel membrane structures or novel materials for high temperature PEMFCs. 6 CHAPTER 2 LITERATURE REVIEW 2.1. Perfluorosulfonic Membranes Commercial membranes for fuel cells are typically made of perfluorocarbon-sulfonic acid ionomer. This ionomer is a copolymer of tetrafluoroethylene and many perfluorosulfonate monomers. The most popular perfluorosulfonic membrane is Nafion? which is made by Dupont [2]. Hydrophobic perfluorinated polyethylene backbone and highly hydrophilic sulfonic acid terminated perfluoro vinyl ether pendant develops nanoscale domains where ionic transport occur [4]. Figure 2.1 shows the chemical structure of Nafion?. Typically x has the value of 7 and y has the value of 1. Nafion ? is used as a membrane for PEMFCs because of its high proton conductivity, chemical stability and longevity; however, it has some disadvantages that need to be improved. Firstly, Nafion? is an expensive material. Secondly, it does not perform well at operation conditions having high temperatures and low relative humidity which makes it require external humidification and water management [4]. 7 Figure 2.1 Nafion??s chemical structure [4]. Liquid water is needed for proton dissociation from the SO3H groups and proton transport in Nafion? since water molecules help to transfer protons. Membrane requirement for liquid water lowers the operating temperature below 80 ?C. Protons that pass through the humidified membrane carry the water molecules from anode side to cathode side which is called electro-osmotic drag. Electro-osmotic drag in PEMFC can be seen in Figure 2.2. However, there is also a back flow of water molecules from cathode side to anode side which is driven by the water concentration gradient. This phenomenon is called back diffusion. If there is an imbalance between these two forward and back flows, drying of anode catalyst layer, flooding of the catalyst layer, mechanical stresses in the membrane or delamination of the catalyst layer can occur. In addition, external systems for managing water through the membrane make the volume, weight, complexity and cost of the system higher. 8 Figure 2.2 Electro-osmotic drag in a PEMFC. BP (bipolar plates), GD (gas diffusion layers), CL (catalyst layers) and Mem (membrane) [4]. Different PFSA membranes are being developed to increase the PEMFC operating temperatures over 80 ?C. These membranes are modified perfluorinated or partially fluorinated and have shorter side chains as compared with Nafion?, which reduces the equivalent weight (EW) of the membrane. As the EW decreases to a certain level, proton conductivity increases; however, some problems develop with the durability and mechanical integrity because of the increased swelling of the membrane. The Dow Chemical Company produced short-side-chain membrane having an EW of 800-900. It is reported that this membrane has four times the power of Nafion? membrane operating at the same voltage since Nafion? has an EW of 1100 [4]. 9 Other companies produced similar kind of short-side-chain membranes as well. For example, Solvay Solexis, Inc., developed Hyflon Ion? which has 850-870 EW. Other Nafion?-like membranes are Flemion? produced by Asahi Glass Co. Ltd, Aciplex? produced by Asahi Chemical Co. Ltd., 3M membrane produced by 3M Inc. and Gore Select? produced by W.L. Gore and Associates, Inc. These short-side-chain membranes offer advantages at higher operating temperatures as compared with Nafion? since they have higher crystalllinity at a given EW and a higher glass transition temperature [4]. Properties of some commercial membranes can be seen in Table 2.1. 10 Table 2.1 Properties of some commercial membranes [5] Supplier and trade mark Equivalent weight (IEC; mequiv. g-1) Thickness (?m) Dupont Nafion? 120 1200 (0.83) 250 Nafion? 117 1100 (0.91) 175 Nafion? 115 1100 (0.91) 125 Nafion? 112 1100 (0.91) 50 Asahi Glass Flemion? T 1000 (1.00) 120 Flemion? S 1000 (1.00) 80 Flemion? R 1000 (1.00) 50 Asahi Chemicals Aciplex? S 1000-1200 (0.83-1.00) 25-100 Dow Chemical Dow? 800 (1.25) 125 Solvay Solexis, Inc. Hyflon? Ion 900 (1.11) 11 2.2. Membranes for HTPEMFCs Since the common perfluorosulfonic acid membranes cannot be used for high temperature applications, different polymers and systems are used for high temperature polymer electrolyte membrane fuel cells [6]. This kind of membranes are aromatic hydro-carbon based membranes. Many novel polymers having aromatic backbones can be used for HTPEMFCs such as polyetheretherketone (PEEK), polyethersulfone (PES) and polybenzimidazole (PBI) [4]. The most preferred polymer for HTPEMFC membrane is polybenzimidazole (PBI). PBI has good chemical and mechanical stability in the temperature range of 120 to 200 ?C. The structure of PBI can be seen in Figure 2.3. Figure 2.3 Structures of some PBIs [7] 12 As it is mentioned before, for HTPEMFC applications, PBI is used after it is doped with phosphoric acid, H3PO4. Phosphoric acid is a weak acid and it generates a hydrogen bonded network to increase conductivity without humidification after PBI is doped with it. As the doping level, temperature and humidification increase after PBI is doped with phosphoric acid, the protonic conductivity of the membrane also increases. Doping level is an important parameter for the doping process of PBI. The doping level can be defined as the number of molecules of phosphoric acid per repeat unit of PBI. For PBI, the optimum doping level is 5. As the doping level drops below this value, the conductivity is affected negatively and as the doping level exceeds this value, mechanical strength decreases. 2.3. Composite Membranes Some membranes have composite structures to enhance the physical, mechanical and chemical properties in order to achieve composite structure for membranes, different materials and techniques are used. Reinforcement of polymeric membranes, preparation of composite and hybrid membranes are some of the methods used. Sandwich membrane structures are also used with good results. A non-conductive polymer for enhancing the mechanical properties, a conductive and non-conductive inorganic phase for enhancing thermal stability in addition to conductivity and water uptake properties and a compound that can be easily oxidized for reducing the degradation of the conducting polymer are reinforcement types that are used for the production of polymeric membranes. A solution of a functionalized polymer can be impregnated into a non-conductive porous substrate in order to enhance the mechanical properties of the membrane. Organic polymers showing mechanical and chemical resistance are used as porous substrate. Porous 13 PTFE sheets as ultra thin membranes or micro PTFE fibrils can be used to reinforce the composite perfluorosulfonic acid membranes and develop thin membrane technology. Although PTFE has weak adhesion onto the conducting polymer, it enhances the electrical resistance of the membrane. At least 95% PTFE as the reinforcing polymer and a conductive fluoropolymer can be mixed as copolymer and extruded in the form of droplets that can be sputtered to produce membranes. Membranes that are produced by this method have lower resistance to current flow and higher power than a membrane that has porous substrate. On the other hand, the minimum thickness of 100 or 200 ?m is a disadvantage for these membranes for fuel cell applications [5]. Composite membranes can be produced from fluoropolymers that are doped with fillers or solid inorganic proton conductors such as zirconium hydrogen phosphates, hygroscopic oxides, heteropolyacids (HPA), phosphotungstic acid (PWA, PTA), etc. There are some other polymers used for high temperature PEMFC membranes. One of the most widely used polymers for this purpose is PBI. Polybenzimidazole (PBI) is a polymer that is used especially for intermediate temperature PEMFCs. When PBI is doped with phosphoric acid, it gains outstanding thermo-chemical stability, lower gas permeability and good proton conductivity. Therefore, PBI is used after it is doped. As poly(2,2-m-(phenylene)-5,5-bibenzimidazole) has a glass transition temperature of 425-435 ?C, it has excellent thermal stability to be used in high temperature PEMFCs [8]. Also AB-PBI, poly(2.5-benzimidazole) that is a kind of PBI, shows outstanding performance in PEMFCs. In a research to enhance the durability of H3PO4/PBI membrane for real commercial operations, the Nafion?-PBI composite membrane was produced from a blend solution of Nafion?-Na and PBI in N,N?-dimethylformamide (DMF) by using the casting method [9]. Other polymers such as sulfonated poly(arylene ether sulfone), sulfonated polybenzimidazole and PTFE can be used with various different fillers. Some other composite 14 membranes that have outstanding conductivities can be produced by using the blend of PVDF and poly(styrene) sulfonic acid [5]. In today?s novel high performance materials, an important topic is using nano-ordered composite materials that include organic polymers and inorganic components. The hybrid organic-inorganic membranes having nano-sized phases and interfaces are intriguing alternatives to polymeric membranes that can provide high temperature operations for fuel cells. Thermal stability can be enhanced by the inorganic component and proton conductivity can be provided by the organic component. Moreover, the inorganic phase enhances the chemical stability and the membrane proton conductivity at high temperatures by improving the water retention at higher temperatures [10]. There are some inorganic substances that are used for doping during production of PEMFC composite membranes in order to enhance the proton conductivity. These materials can be metal oxides such as TiO2, SiO2, ZrO2 and acids such as heteropoly acids (HPA), phosphoric acid, solid acid named as Cs2.5H0.5PM12O40 (CsPOM), etc. Noble metals such as platinum, palladium, rhodium, ruthenium and iridium and nanosized particles such as nanoclays can be used to improve the physical, chemical and mechanical characteristics of the membranes. Nafion?/silica composite membranes can be produced by the sol-gel acidocatalysation of tetraethoxysilane (TEOS) in a Nafion 115 membrane which has en equivalent weight of 1100. As the reaction time changes, the amount of TEOS that can be impregnated into the membrane changes. Due to the silica content, the water absorption of the composite membrane can be improved; however, the proton conductivity can be lowered. The silica particles cause the inhibition of proton transfer. 15 CHAPTER 3 MEMBRANE PRODUCTION USING SINGLE SCREW EXTRUDER 3.1. Machine Set Up and Operation Wayne single screw extrusion machine was used in the project. The extrusion machine consists of hopper, barrel with heading zones, metering pump, control panel for temperature and pressure control, 15.24 mm (6?) wide film die, cylinders to form and to draw the film, air blowing unit to cool the film, and winding unit. The machine has a capability of combining two films by introducing a second film at the winding stage to the film that is extruded from the die. The general structure of a single screw extruder can be seen in Figure 3.1 and a cast film die can be seen in Figure 3.2. Figures 3.3 - 3.9 show the main parts of the Wayne single screw extrusion machine which was used in this study in order to produce polypropylene and nanoclay reinforced polypropylene films. This machine was purchased recently and a considerable amount of fine was spent on setting up the machine and start producing membranes successfully. 16 Figure 3.1 Schematic of a plastic extruder [11]. Figure 3.2 Schematic of the extrusion film die. Side Plate Die Bottom Die Top Side Plate Adjusting Guide Adjusting Fingers 17 Figure 3.3 Wayne single screw extruder Figure 3.4 Hopper of the single screw extruder 18 Figure 3.5 Barrel of the single screw extruder Figure 3.6 Cast film die of the single screw extruder 19 Figure 3.7 Air blowing and drawing unit of the single screw extruder Figure 3.8 Winding unit of the single screw extruder 20 Figure 3.9 Control panel of the single screw extruder 3.2. Effect of Processing Parameters Polypropylene was used to study the effect of the processing parameters during film manufacturing. 3.2.1. Introduction Polypropylene (PP) finds various new uses in commercial film applications due to its product properties such as thickness, resistance to tear, tensile and burst, transparency, clarity, gloss and haze. Since PP has high tensile strength and elongation at break, low permeability and good chemical resistance as well as low price, it has been used in various packaging and other specialty applications [12]. 21 The characteristics of cast PP films show differences not only due to their chemical structures and the additives and resin modifiers added but also due to their processing parameters in extrusion process. Therefore, determining the effect of processing parameters and process conditions in cast film extrusion is important to obtain the exact properties of the films for their end uses. Cast film technology is the simplest technology to produce polymeric films in which the molten polymer is extruded through a slot die, fed by a single-screw extruder, onto a chilled roll in order to be cooled. Then, the solidified film is taken up from the chilled roll by a nip roll (take up roll) and transferred to a winding unit after the edges are trimmed. A limited amount of orientation is obtained in the film by this process; the orientation can be affected by the ratio between the die thickness and film thickness and by the ratio between the extrusion speed and the take up speed. Since the orientation can be easily determined in this method, cast film technology is a low cost and easy-to-handle process. Temperature, screw motor speed and winding speed are the processing parameters that have effect on cast films. The final molecular orientation in a product depends on the thermomechanical history (melt temperature, stress, strain) of the product during processes [13]. It was reported that lower die temperature reduces the mobility of the chains to be extended at high draw ratios at the die exit [12]. Increasing screw motor speed results in the shear rate increase. At a given melt temperature, the higher the shear rate the higher the shear stress, which results in more molecular orientation in a product [13]. The aim of this study is to determine the effects of processing parameters such as temperature, screw motor speed and winding speed on the physical and structural characteristics 22 and mechanical performance of unmodified and pure PP cast films such as thickness, crystallinity, tear strength, tensile strength and burst strength. 3.2.2. Experimental 3.2.2.1. Materials and Equipments Used Polypropylene pellets commercially named as ?30 Melt Copolymer Natural? with a density of 0.91 g/cm3 and an MFI of 34 g/10 min were bought from Premier Plastic Resins Company. No modifiers and additives were added while producing the PP cast films. Wayne single screw extrusion machine having a 15.24 cm cast film die was used to produce polypropylene (PP) cast films in combination with a chill roll and a nip (take up) roll. The die melt was quenched onto a chill roll. The film was taken up through a pair of nip rolls onto a winder. For tensile, tear and burst strength testing, Instron 5565 universal testing machine was used, which has 5 kN capacity and 0.001-1000 mm/min speed range. Thickness measurements were done using Testing Machines Inc., (TMI) micrometer. Crystallinity tests were performed on all film samples using a TA Instruments DSC Q-2000 differential scanning calorimetry (DSC). 3.2.2.2. Manufacturing and Testing Twelve PP films were produced by using cast film technology. The machine parameters such as temperature, screw speed and winding speed were changed during production to observe their effects on film final properties. The machine parameters that were changed during the manufacturing process can be seen in Table 3.1. The barrel temperatures were the same along the barrel from feed end to the die for each sample. 23 Table 3.1 Machine parameters changed during manufacturing process of the films Sample Temperature (?C) Screw Motor Speed (RPM) Winding Speed (m/s) Film1 190 400 0.1 Film2 205 400 0.1 Film3 215 400 0.1 Film4 220 400 0.1 Film5 225 400 0.1 Film 6 220 300 0.1 Film7 220 500 0.1 Film8 220 600 0.1 Film 9 220 400 0.12 Film 10 220 400 0.13 Film 11 220 400 0.15 Film 12 220 400 0.16 Thickness, tensile, tear and burst strength tests were performed on the samples. The effect of temperature on film thickness, tear, tensile and burst strength was investigated on films 1,2,3,4 and 5; the screw motor speed effect was investigated on films 4, 6, 7 and 8 and the winding speed effect was investigated on films 9, 10, 11 and 12. The tests were performed both in machine direction (MD) and cross direction (CD). For tensile tests, ?ASTM D 882-02 Standard Test Method for Tensile Properties of Thin Plastic Sheeting? test method was used. The nominal width of the specimens was 25.4 mm. The grip separation (gauge length) was 50 mm; the test specimens were 50 mm longer than the grip 24 separation. The rate of grip separation (cross head speed) was 500 mm/min. Five specimens were tested from each sample for the tensile tests [14]. For tear tests, ?ASTM D 1938-06 Standard Test Method for Tear-Propagation Resistance (Trouser Tear) of Plastic Film and Thin Sheeting by a Single-Tear Method? was used. The nominal width of the specimens was 25.4 mm; the length of the test specimens was 80 mm. The grip separation (gauge length) was 50 mm. The rate of grip separation was 250 mm/min. Five specimens were tested from each sample for the tear tests [15]. For burst strength tests, ?ASTM D 6797-02 Standard Test Method for Bursting Strength of Fabrics Constant-Rate-of-Extension (CRE) Ball Burst Test? was used. The specimens have the dimensions of 125 x 125 mm. The CRE machine was started with a speed of 305 mm/min. and the speed was kept constant till the specimens bursted. Five specimens were tested from each sample for the burst tests [16]. For thickness tests, 10 measurements were taken from each sample. For crystallinity tests, samples were heated from -50 ?C to 350 ?C at a temperature increase of 10 ?C/min. 3.2.3. Results and Discussion 3.2.3.1. DSC Analysis and Crystallization DSC tests were performed on all of the films. Since the melting peaks of all samples did not change much, it was concluded that the change of the crystal thickness was negligible (Figure 3.10). Therefore, the main difference in the crystalline structure of the PP films is thought to be caused by the orientation of the crystal blocks [17]. 25 60 80 100 120 140 160 180 200 220 240 -2 .4 -2 .2 -2 .0 -1 .8 -1 .6 -1 .4 -1 .2 -1 .0 -0 .8 -0 .6 -0 .4 -0 .2 H e a t F l o w ( W / g ) Te m pe r a ture ( ?C ) ? H: F il m 1( 74. 62 J/ g ) F il m 2( 77. 82 J/ g ) F il m 3( 90. 25 J/ g ) F il m 4( 75. 17 J/ g ) F il m 5( 76. 20 J/ g ) F il m 6( 67. 34 J/ g ) F il m 7( 77. 26 J/ g ) F il m 8( 78. 96 J/ g ) F il m 9( 77. 48 J/ g ) F il m 10( 94. 13 J/ g ) F il m 11( 79. 79 J/ g ) F il m 12( 80. 78 J/ g ) Figure 3.10 DSC of the PP films (heating rate: 10 ?C/min) Films 1, 2, 3, 4 and 5 were analyzed to examine the effect of temperature on crystallinity. Although the areas under the curves of DSC graphs and ?H values (a parameter that can be used for defining crystallinity) fluctuate (Figure 3.10), they show a slightly increasing trend. As the temperature is increased during PP film production process, the crystallinity of the films increases slightly as shown in Figure 3.11. 26 190 195 200 205 210 215 220 225 230 74 76 78 80 82 84 86 88 90 92 ? H ( J / g ) Te m pe r a ture ( ?C ) F il m 1 F il m 2 F il m 3 F il m 4 F il m 5 y = 0. 0809x + 61. 693 R ? = 0. 0319 Figure 3.11 Effect of temperature on crystallinity Films 4, 6, 7 and 8 were analyzed to examine the effect of screw motor speed on crystallinity. As the screw motor speed increases, ?H value increases (Figure 3.12). 27 300 350 400 450 500 550 600 66 68 70 72 74 76 78 80 ? H ( J / g ) S c r e w Mot or S pe e d ( R P M) F il m 6 F il m 4 F il m 7 F il m 8 y = 0. 037x + 58. 055 R ? = 0. 8631 Figure 3.12 Effect of screw motor speed on crystallinity Films 9, 10, 11 and 12 were analyzed to examine the effect of winding speed on crystallinity. Although the areas under the curves of DSC graphs and ?H values fluctuate (Figure 3.13), this is not enough to reach a conclusion about the winding speed and crystallinity relation. 28 0.11 0.12 0.13 0.14 0.15 0.16 0.17 76 78 80 82 84 86 88 90 92 94 96 ? H ( J / g ) W indi ng S pe e d ( m /s ) F il m 9 F il m 10 F il m 11 F il m 12 y = - 18. 941x + 85. 715 R ? = 0. 0038 Figure 3.13 Effect of winding speed on crystallinity 3.2.3.2. Thickness Analysis The results of thickness tests for all of the 12 PP film samples can be seen in Table 3.2. Table 3.2 Thickness test results Film # 1 2 3 4 5 6 7 8 9 10 11 12 Thickness (mm) 0.0355 0.0356 0.0321 0.0345 0.0356 0.0224 0.0484 0.0522 0.0332 0.0267 0.0221 0.0209 One of the extrusion machine parameters in film manufacturing process is temperature. Therefore, thicknesses of the films 1, 2, 3, 4 and 5 were measured to analyze the effect of temperature on thickness (Figure 3.14). As the temperature increases, the thickness of the films decreases since the viscosity of the films decreases with increasing temperature. 29 370 380 390 400 410 420 430 440 450 0.0340 0.0342 0.0344 0.0346 0.0348 0.0350 0.0352 0.0354 0.0356 T h i c k n e s s ( m m ) Te m pe r a ture ( ? C) y = - 4E- 05x + 0. 0427 R ? = 0. 9313 F il m 1 F il m 2 F il m 3 F il m 4 F il m 5 Figure 3.14 Effect of temperature on film thickness Another extrusion machine parameter in film manufacturing process is the screw motor speed. Thicknesses of the films 4, 6, 7 and 8 were measured to analyze the effect of screw motor speed on thickness (Figure 3.15). As the screw motor speed increases, the thickness of the films also increases since the screw transfers more polymer from the barrel to the die. 30 300 350 400 450 500 550 600 0.020 0.025 0.030 0.035 0.040 0.045 0.050 0.055 T h i c k n e s s ( m m ) S c r e w Mot or S pe e d ( R P M) F il m 6 F il m 4 F il m 7 F il m 8 y = 0 . 0 0 0 1 x - 0 . 0 0 7 1 R? = 0 . 9 5 6 4 Figure 3.15 Effect of screw motor speed on film thickness To analyze the effect of winding speed on thickness, thicknesses of the films 9, 10, 11 and 12 were measured (Figure 3.16). As the winding speed increases, the thickness of the films drops since the increase in winding speed stretches the films and makes them thinner. 31 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.020 0.022 0.024 0.026 0.028 0.030 0.032 0.034 T h i c k n e s s ( m m ) W indi ng S pe e d ( m /s ) F il m 9 F il m 10 F il m 11 F il m 12 y = - 0 . 2 2 3 8 x + 0 . 0 5 7 3 R? = 0 . 9 5 3 3 Figure 3.16 Effect of winding speed on film thickness 3.2.3.3. Tear Strength Analysis Tear strength of the films 1, 2, 3, 4 and 5 were measured to determine the effect of temperature on tear strength (Figure 3.17). As the temperature increases, tear strength of the films increases in MD. Since the polymer chains become more oriented in MD as the temperature decreases, tear strength becomes higher with increasing temperature. As the temperature increases, tear strength of the films decreases in CD since the polymer chains are less oriented in MD and less force is needed to tear the polymer chains in CD. 32 190 195 200 205 210 215 220 225 230 0.8 1.0 1.2 1.4 1.6 1.8 F il m 5 F il m 5 F il m 4 F il m 4 F il m 3 F il m 3 F il m 2 F il m 2 F il m 1 T e a r S t r e n g t h ( N ) Te m pe r a ture ( ? C) MD dire c ti on C D dire c ti on F it ted C ur v e ( MD) F it ted C ur v e ( C D) F il m 1 y = 0 . 0 0 1 5 x + 0 . 4 9 6 1 R ? = 0 . 9 4 8 5 y = -0 . 0 0 6 3 x + 2 . 8 9 0 5 R ? = 0 . 5 8 2 4 Figure 3.17 Effect of temperature on tear strength of the films To analyze the effect of screw motor speed on tear strength, tear strengths of the films 4, 6, 7 and 8 were measured (Figure 3.18). Although with increasing screw speed, the tear strength in MD is expected to decrease, the data do not show any specific trend. Therefore, no conclusion can be made from the data obtained. The shear rate increases with increasing screw motor speed. At a given melt temperature, higher shear rate gives higher shear stress, resulting in more molecular orientation in a product. The amount of molecular orientation is proportional to the magnitude of stress. Since the molecular orientation improves in MD, tear strength of the films increases in CD with increasing screw motor speed. 33 300 350 400 450 500 550 600 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 F il m 6 F il m 4 F il m 7 F il m 8 M D d i re ct i o n C D d i re ct i o n F i t t e d C u rv e (M D ) F i t t e d C u rv e (C D ) T e a r S t r e n g t h ( N ) S c r e w Mot or S pe e d ( R P M) y = 0. 0003x + 0. 7745 R ? = 0. 0473 y = 0. 0044x - 0. 2395 R ? = 0. 9996 F il m 6 F il m 4 F il m 7 F il m 8 Figure 3.18 Effect of screw motor speed on tear strength of the films To analyze the effect of winding speed on tear strength, tear strengths of the films 9, 10, 11 and 12 were measured (Figure 3.19). As the winding speed increases, the tear strength of the films drops in MD. The orientation in MD increases due to high draw ratio. Therefore, tear strength in MD decreases with increasing winding speed. Although the tear strength of films is expected to increase in CD with increasing winding speed, the data show no specific trend. 34 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 F il m 12 F il m 11 F il m 10 F il m 9 T e a r S t r e n g t h ( N ) W indi ng S pe e d ( m /s ) M D d i re ct i o n C D d i re ct i o n F i t t e d C u rv e (M D ) F i t t e d C u rv e (C D ) F il m 9 F il m 10 F il m 11 F il m 12 y = - 9. 3945x + 2. 0285 R ? = 0. 9813 y = - 6. 8702x + 2. 1375 R ? = 0. 3355 Figure 3.19 Effect of winding speed on tear strength of the films 3.2.3.4. Tensile Strength Analysis Tensile strength of the films 1, 2, 3, 4 and 5 were measured to determine the effect of temperature on tensile strength (Figure 3.20). At a given shear rate, lower melt temperature gives higher viscosity, resulting in higher shear rate. Lower melt temperature or higher shear rate gives rise to higher shear stress, resulting in more molecular orientation in MD. Therefore, as the molecular orientation increases due to lower temperatures, tensile strength increases. However, from Figure 3.20, it can be seen that as the temperature increases, tensile strength increases both in MD and CD. 35 190 195 200 205 210 215 220 225 230 19.5 20.0 20.5 21.0 21.5 22.0 22.5 F il m 5 F il m 4 F il m 3 F il m 2 F il m 1 T e n s i l e S t r e n g t h ( M P a ) Te m pe r a ture ( ? C) MD dire c ti on C D dire c ti on F it ted C ur v e ( MD) F it ted C ur v e ( C D) F il m 1 F il m 2 F il m 3 F il m 4 F il m 5 y = 0. 0586x + 8. 7274 R ? = 0. 4269 y = 0. 0229x + 16. 493 R ? = 0. 8134 Figure 3.20 Effect of temperature on tensile strength of the films To analyze the effect of screw motor speed on tensile strength, tensile strengths of the films 4, 6, 7 and 8 were measured (Figure 3.21). The shear rate increases with increasing screw motor speed. At a given melt temperature, higher shear rate gives higher shear stress, resulting in more molecular orientation in a product. Since the molecular orientation increases in MD, the tensile strength of the films increases in MD. Tensile strength of the films decreases with increasing screw motor speed in CD because of the orientation in MD. 36 300 350 400 450 500 550 600 17 18 19 20 21 T e n s i l e S t r e n g t h ( M P a ) S c r e w Mot or S pe e d ( R P M) MD dire c ti on C D dire c ti on F it ted C ur v e ( MD) F it ted C ur v e ( C D) y = 0. 0105x + 14. 462 R ? = 0. 5998 y = - 0. 0084x + 23. 852 R ? = 0. 732 F il m 6 F il m 4 F il m 7 F il m 8 F il m 6 F il m 4 F il m 7 F il m 8 Figure 3.21 Effect of screw motor speed on tensile strength of the films To analyze the effect of winding speed on tensile strength, tensile strengths of the films 9, 10, 11 and 12 were measured (Figure 3.22). As the winding speed increases, the tensile strength of the films increases in MD since the orientation in MD improves due to the increasing draw ratio. The tensile strength of films decreases in CD with increasing winding speed due to the orientation increase in MD. 37 0.11 0.12 0.13 0.14 0.15 0.16 0.17 11 12 13 14 15 16 17 F il m 12 F il m 11 F il m 10 T e n s i l e S t r e n g t h ( M P a ) W indi ng S pe e d ( m /s ) MD dire c ti on C D dire c ti on F it ted C ur v e ( MD) F it ted C ur v e ( C D) F il m 9 F il m 10 F il m 11 F il m 12 F il m 9 y = 26. 054x + 11. 351 R ? = 0. 8658 y = - 71. 293x + 23. 781 R ? = 0. 4625 Figure 3.22 Effect of winding speed on tensile strength of the films 3.2.3.5. Burst Strength Analysis During the burst strength tests, only Film 6 bursted. The tests were done by using Instron universal testing machine and there was not enough space in the machine?s bursting strength equipment for highly stretchable films to extend. The graphs of the other 11 films did not show any decreasing trend at 45 mm extension. This means that the graphs obtained did not have their maximum loads since they have an increasing trend. Therefore, the burst strength values, stress at the maximum load, could not be obtained for the other 11 films. As it is seen in Figure 3.23, the graphs of all of the films show a similar trend. For the same extension value, 45 mm, Film 11 gives the lowest load value (not considering Film 6) while Film 8 gives the highest load value. 38 0 10 20 30 40 50 - 10 0 10 20 30 40 50 60 70 L o a d ( N ) Exte nsi on ( m m ) F il m 1 F il m 2 F il m 3 F il m 4 F il m 5 F il m 6 F il m 7 F il m 8 F il m 9 F il m 10 F il m 11 F il m 12 Figure 3.23 Burst strength of the films The films exhibit early load peaks at the extension of nearly 0.4-0.8 mm range, but then their load values begin to decrease as the extension increases. The load values begin to increase from the extension range of 3.2-4.2 mm to the extension 45 mm. 3.2.4. Conclusions In this work, twelve different PP cast films were manufactured and analyzed to find the effects of machine parameters such as temperature, screw speed and winding speed on film properties such as crystallinity, thickness, tear strength, tensile strength and burst strength. These analyses were done in MD and CD directions for tear and tensile strength. 39 From the DSC analysis it was found that the position of the melting peak did not have a significant change. Because of this, it was assumed that the crystal thickness change was negligible. Therefore, the main difference in the crystalline structure of the PP films is considered to be caused by the orientation of the crystal blocks. The thickness analysis was done by considering temperature, screw motor speed and winding speed. It was found that when the temperature increases, the thickness of the films decreases since the viscosity of the films decreases with increasing temperature. As the screw motor speed increases, the screw transfers more polymer from the barrel to the die which results in increase of film thickness. Increase of winding speed causes the films to be stretched, making them thinner. Since the polymer chains become less oriented in MD as the temperature increases, tear strength becomes higher with increasing temperature. When the temperature increases, tear strength of the films decreases in CD since the polymer chains are less oriented in MD and less force is needed to tear the polymer chains in CD. Although it is expected that increasing screw speed decreases the tear strength in MD, tear strength of the films does not show any specific trend as the screw motor speed increases; as a result no conclusions can be made from the data obtained. Tear strength of the films increases in CD with increasing screw motor speed because the molecular orientation increases in MD. When the winding speed increases, the tear strength of the films decreases in MD because the orientation in MD increases due to high draw ratio. Therefore, when winding speed increases, tear strength in MD decreases. Although the tear strength of films should increase in CD with increasing winding speed, the data show no specific trend. 40 When the molecular orientation increases because of lower temperatures, tensile strength should increase according to the literature. However in this work, as the temperature increased, tensile strength increased in MD. When screw motor speed increases, the shear rate also increases. At a given melt temperature, higher shear rate gives higher shear stress which causes higher molecular orientation in the product. Molecular orientation increase in MD causes the tensile strength of the films to increase. Tensile strength of the films decreases with increasing screw motor speed in CD due to the orientation in MD. Increase in winding speed causes the tensile strength of the films to increase in MD since the orientation in MD increases because of the increasing draw ratio. The tensile strength of films decreases in CD with increasing winding speed because of the orientation increase in MD. Except Film 6, the films did not burst in burst strength tests. Therefore, burst stress at the maximum load could not be obtained for the other 11 films. 41 CHAPTER 4 NANOCLAY REINFORCED MEMBRANE STRUCTURES USING TWIN AND SINGLE SCREW EXTRUDERS 4.1. Introduction Polymer layered silicate (PLS) nanaocomposites have gained attention recently since the final composite product shows improvement on mechanical, barrier, thermal and some other properties as compared with its polymer matrix. Furthermore, silicate based nanoclays that these nanocomposites are made from are environmentally friendly, naturally abundant and economical [18]. Nanoclay reinforced composites are one type of nanoplatelet-reinforced composites. In their bulk state, clays exist as layered materials. These natural or organically modified clays have a stacked structure of parallel silicate layers in their pure state. In order to use nanoclays more efficiently, there must be a good layer separation and uniform dispersion throughout the polymer matrix phase. The morphology of nanoclay reinforced polymer composites can be seen in Figure 4.1 [18, 19]. 42 Figure 4.1 Schematics of the polymer-clay nanocomposite morphologies: a) conventional miscible b) partially intercalated and exfoliated c) fully intercalated and dispersed d) fully exfoliated and dispersed [19]. The interlayer spacing of a clay particle is minimum in the conventional miscible state. After insertion of polymer resin into the place between adjacent layers of a clay particle, the interlayer spacing gets larger. This state is called as intercalated state. The state is called as exfoliated state if fully separation of the layers of clay particle is achieved. Intercalated and exfoliated clay layers can be seen in Figure 4.2 and 4.3. For nanocomposites, the clay layers must be intercalated or exfoliated and must not be aggregated as tactoids [18, 19]. 43 Figure 4.2 Intercalated and exfoliated states of TEM micrograph of a montmorillonite poly (L-lactic acid) [19]. 44 Figure 4.3 Schematic representation of intercalated and exfoliated nanocomposites [18]. The most widely used clay materials are montmorillonite, saponite and synthetic mica. Properties that nanoclay materials provide for polymeric materials are improved stiffness, strength, toughness, thermal stability, reduced gas permeability and coefficient of thermal expansion [19]. Sometimes, agglomeration of the mineral in the polymeric matrix can occur because of the lack of affinity between hydrophilic silicate and hydrophobic polymer. In order to solve this problem, surface modification is performed for clay particles [19]. Many matrix polymers have been used for PLS nanocomposite production such as nylon, polystyrene and polypropylene which are synthetic, non-degradable, and polylactide and starch which are biopolymers [18]. 45 It has been proven that small amounts of montmorillonite nanoclay addition increases the tensile strength, tensile modulus, and heat degradation temperature (HDT) of Nylon 6/clay hybrid. Moreover, if the platelets are well dispersed in the polymeric matrix, the composites gain higher load transfer efficiency [19]. Properties of Nylon 6/clay nanocomposites can be seen in Table 4.1. Table 4.1 Properties of Nylon 6/clay nanocomposites [19] Sample Wt% clay montmorillonite Tensile strength (MPa) Tensile modulus (GPa) Charpy impact strength (kJ/m3) HDT at 18.5 kg cm-2 (?C) NCH-5 4.2 107 2.1 2.1 152 NCC-5 5.0 61 1.0 1.0 89 Nylon 6 0 69 1.1 1.1 65 Furthermore, thermal stability, fire resistance and gas barrier properties of nanoclay reinforced polymer composites can be increased by addition of nanometer scale reinforcement. Nanoclay/polypropylene composites are used as functional parts in automobiles. 4.2. Experimental 4.2.1. Materials and Equipments Used Polypropylene pellets commercially named as ?30 Melt Copolymer Natural? with a density of 0.91 g/cm3 and an MFI of 34 g/10 min were bought from Premier Plastic Resins Company. 46 Cloisite? 15A, which is an organically modified montmorillonite clay, was used as nanoclay (supplied by Southern Clay Products). Cloisite? 15A consists of organically modified nanometer scale, layered magnesium aluminum silicate platelets. Cloisite? 15A is a natural montmorillonite modified with a quaternary ammonium salt [20]. Fusabond? P M613-05 which was supplied by DuPont, was used as compatibilizer; it is a chemically modified polypropylene. Fusabond? P M613-05 has an MFI (190 ?C/1000 g) of 49 g/10 min and a melting point of 162 ?C (324 ?F) [21]. Leistritz Micro 27 twin screw extrusion machine having two co-rotating screws of 27 mm diameter was used for melt intercalation (Figures 4.4, 4.5, 4.6, and 4.7). This is a lab extruder that provides compounding and reaction processes for production settings [22]. PP pellets, Fusabond? P M613-05 compatibilizer and Cloisite? 15A nanoclay were mixed by using the twin screw extruder. The temperature profile of extrusion was the same from the feed zone to the die at 220 ?C. The mixtures were extruded at a screw speed of 200 RPM. Extruded strands of the molten composite were then water quenched and pelletized. 47 Figure 4.4 Leistritz twin screw extrusion machine Figure 4.5 Control panel of the twin screw extruder 48 Figure 4.6 Polymer feeder and hopper of the twin screw extruder Figure 4.7 Barrel and filament die of the twin screw extruder 49 Wayne single screw extrusion machine having a 15.24 cm wide cast film die was used to produce nanoclay reinforced polypropylene (PP) cast films in combination with a nip (take up) roll. The films were taken up through a pair of nip rolls onto a winder. For tensile, tear and burst strength testing, Instron 5565 universal testing machine was used, which has 5 kN capacity and 0.001-1000 mm/min speed range (Figure 4.8). Figure 4.8 Instron 5565 universal testing machine [23] Thickness measurements of nanoclay reinforced PP films were done using Testing Machines Inc., (TMI) 49-72 series micrometer. This micrometer has digital display and motorized automatic cycling [24]. For morphology analysis of nanoclay reinforced PP films, Carl Zeiss EVO 50 VP scanning electron microscope (SEM) operating at 20 kV was used [25]. Before phase morphology analysis of the nanoclay reinforced film specimens, gold sputtering was done for each specimen. The electrically conductive thin coating is representative 50 of the surface of the specimen. The coating inhibits charging, reduces thermal damage, and improves secondary electron emission, which are beneficial for scanning electron microscopy. For gold sputtering, EMS 550X sputter coating device, which has multi specimen holder and is capable of fully automatic control and high resolution fine coating, was used. It has a deposition rate of 0-25 nm/min [26]. 4.2.2. Manufacturing and Testing Nine nanoclay reinforced PP films were produced using cast film technology. For the films having nanoclay content of 5%, the screw motor speed was 690 RPM; for the other films, the screw motor speed was 500 RPM. 500 RPM was not enough to produce films having 5% nanoclay content with smooth surface without defects. The contents of the nanoclay added films produced are given in Table 4.2. Their mechanical and physical properties were measured. For tensile tests, ?ASTM D 882-02 Standard Test Method for Tensile Properties of Thin Plastic Sheeting? was used. The nominal width of the specimens was 25.4 mm. The grip separation (gauge length) was 50 mm; the test specimens were 50 mm longer than the grip separation. The rate of grip separation (cross head speed) was 500 mm/min. Five specimens were tested from each sample for the tensile tests [14]. Instron 5565 universal testing machine is shown in Figure 4.9 during a tensile test. 51 Table 4.2 Nanoclay added films and their contents Compatibilizer (%) Nanoclay (%) Compatibilizer (g) Nanoclay (g) PP (g) Mixture (g) Film 1 10% 1% 100 10 890 1000 Film 2 10% 3% 100 30 870 1000 Film 3 10% 5% 100 50 850 1000 Film 4 15% 1% 150 10 840 1000 Film 5 15% 3% 150 30 820 1000 Film 6 15% 5% 150 50 800 1000 Film 7 20% 1% 200 10 790 1000 Film 8 20% 3% 200 30 770 1000 Film 9 20% 5% 200 50 750 1000 For tear tests, ?ASTM D 1938-06 Standard Test Method for Tear-Propagation Resistance (Trouser Tear) of Plastic Film and Thin Sheeting by a Single-Tear Method? was used. The nominal width of the specimens was 25.4 mm; the length of the test specimens was 80 mm. The grip separation (gauge length) was 50 mm. The rate of grip separation was 250 mm/min. Five specimens were tested from each sample for the tear tests [15]. Instron 5565 universal machine is shown in Figure 4.10 during a tear test. 52 Figure 4.9 Tensile testing of the films Figure 4.10 Tear testing of the films For burst strength tests, ?ASTM D 6797-02 Standard Test Method for Bursting Strength of Fabrics Constant-Rate-of-Extension (CRE) Ball Burst Test? was used. The specimens have the dimensions of 125 x 125 mm. The CRE machine was started with a speed of 305 mm/min. and the speed was kept constant till the specimens bursted. Five specimens were tested from each sample for the burst tests [16]. Instron 5565 universal machine is shown in Figure 4.11 during a burst strength test. 53 Figure 4.11 Instron 5565 universal machine performing burst strength test For thickness tests, 5 measurements were taken from each sample and the average was used. Table 4.3 shows the thickness of the nanoclay reinforced films. These thickness results were used in order to calculate tensile strength. Table 4.3 Thickness of the nanoclay reinforced films Film # Film 1 Film 2 Film 3 Film 4 Film 5 Film 6 Film 7 Film 8 Film 9 Thickness (mm) 0.128 0.130 0.162 0.092 0.138 0.162 0.114 0.142 0.20 54 4.3. Results and Discussion 4.3.1. Morphology Analysis As it is seen from Figure 4.12 and 4.13, Film 1 has more homogeneous nanoclay dispersion since it has only 1% nanoclay content. Film 2 has bigger nanoclay particles since it has lower nanoclay dispersion due to 3% nanoclay content. Figure 4.12 Nanoclay dispersion in Film 1 55 Figure 4.13 Nanoclay dispersion in Film 2 Although Film 3 has the highest nanoclay content (5%) as compared with Film 1 and Film 2, it has better nanoclay dispersion and has smaller nanoclay particles in its structure compared to Film 2 (Figure 3.36 and 3.37). Screw speed was increased for the films having 5% nanoclay content because the films could not be drawn with the same screw speed that was used for the films having 1% and 3% nanoclay content. Therefore, since the screw speed was increased, shear stress increased. This caused the polymer and nanoclay to mix more homogeneously, making the morphological structure of Film 3 more homogeneous. 56 Figure 4.14 Nanoclay dispersion in Film 3 As it is seen from Figure 4.15 and 4.16, Film 4 has more homogeneous nanoclay dispersion since it has only 1% nanoclay content; Film 5 has bigger nanoclay particles in its structure since it has lower nanoclay dispersion due to 3% nanoclay content. 57 Figure 4.15 Nanoclay dispersion in Film 4 Figure 4.16 Nanoclay dispersion in Film 5 58 Although Film 6 has the highest nanoclay content (5%) as compared with Film 4 and Film 5, it has better nanoclay dispersion and has smaller nanoclay particles in its structure compared to Film 5 (Figure 4.16 and 4.17). Screw speed was increased for the films having 5% nanoclay content, which increased shear stress. This caused the polymer and nanoclay to mix more homogeneously, making the morphological structure of Film 6 more homogeneous. Figure 4.17 Nanoclay dispersion in Film 6 As it is seen from Figure 4.18 and 4.19, Film 7 has more homogeneous nanoclay dispersion since it has only 1% nanoclay content; Film 8 has bigger nanoclay particles in its structure since it has lower nanoclay dispersion due to 3% nanoclay content. 59 Figure 4.18 Nanoclay dispersion in Film 7 Figure 4.19 Nanoclay dispersion in Film 8 60 Although Film 9 has the highest nanoclay content (5%) as compared with Film 7 and Film 8, it has better nanoclay dispersion and has smaller nanoclay particles in its structure compared to Film 8 (Figure 4.19 and 4.20) due to increased screw speed. Figure 4.20 Nanoclay dispersion in Film 9 If the films 1, 4, 7 having 1% nanoclay content, films 2, 5, 8 having 3% nanoclay content and films 3, 6, 9 having 5% nanoclay content are compared according to the increasing compatibilizer content from 10% to 20%, it could be seen that no conclusion can be drawn from the morphology analysis about the effect of compatibilizer content increase on the nanoclay dispersion and the homogeneity of the morphological structure of the films. 61 4.3.2. DSC Analysis Film 1, Film 2 and Film 3 have nanoclay contents of 1%, 3% and 5%, respectively. From Figures 4.21, 4.22 and 4.23 it can be seen that the melting points of films 1, 2 and 3 slightly increase as the nanoclay content increases. Figure 4.21 DSC graph of Film 1 62 Figure 4.22 DSC graph of Film 2 Figure 4.23 DSC graph of Film 3 63 Film 4, Film 5 and Film 6 have nanoclay contents of 1%, 3% and 5%, respectively. From Figures 4.24, 4.25 and 4.26 it can be seen that the melting points of films 4, 5 and 6 slightly increase as the nanoclay content increases. Figure 4.24 DSC graph of Film 4 64 Figure 4.25 DSC graph of Film 5 Figure 4.26 DSC graph of Film 6 65 Film 7, Film 8 and Film 9 have nanoclay contents of 1%, 3% and 5%, respectively. From Figures 4.27, 4.28 and 4.29 it can be seen that the melting points of films 7, 8 and 9 slightly increase as the nanoclay content increases. Figure 4.27 DSC graph of Film 7 66 Figure 4.28 DSC graph of Film 8 Figure 4.29 DSC graph of Film 9 67 4.3.3. Tensile Strength Analysis Tensile strength analysis was done to examine the effect of nanoclay and compatibilizer content of nanoclay reinforced PP films. The tensile strength of the films is shown in Table 4.4. Table 4.4 Tensile stress values FILM # TENSILE STRESS (MPa) SAMPLE 1 SAMPLE 2 SAMPLE 3 SAMPLE 4 SAMPLE 5 AVERAGE Film 1 6.89 7.55 6.99 5.38 8.47 7.056 Film 2 4.32 4.7 5.48 5.64 5.46 5.12 Film 3 6 6.97 7.08 7.43 6.7 6.836 Film 4 6.7 7.55 6.84 6.69 5.9 6.736 Film 5 4.56 4.65 4.47 4.96 4.46 4.62 Film 6 9.45 9.37 9.53 8.44 9.42 9.242 Film 7 5.03 5.71 6.11 7.59 7.84 6.456 Film 8 4.87 4.43 4.91 4.62 4.89 4.744 Film 9 6.06 5.97 5.75 5.94 5.89 5.922 68 Evaluation According to Nanoclay Content: - Condition of 10 wt % Compatibilizer Presence Tensile test results for Film 1, Film 2 and Film 3 are shown in Figure 4.30. Film 1 includes 1%, Film 2 includes 3% and Film 3 includes 5% nanoclay. In Figure 4.30, the strain value of Film 1 is nearly 560%. However, the strain values of Film 2 is 420% and the strain values of Film 3 is 60% (Figure 4.30). This shows that as the nanoclay content of the films, having 10% compatibilizer content, increases, the extension of the films decreases. As it is seen from Table 4.4, maximum tensile stress for films 1, 2 and 3 decreases first then increases as the nanoclay content increases from 1% to 5%. The increase in nanoclay content reduces the tensile strength. As explained earlier, nanoclay dispersion in Film 1 is better than nanoclay dispersion in Film 2. However, for Film 3, having the highest nanoclay content the screw speed was increased, resulting in higher tensile strength. It can be seen from morphology analysis that Film 3 has more homogeneous structure than Film 2. As a result, the tensile strength of Film 2 (3% nanoclay content) decreased as compared with Film 1 (1% nanoclay content), however, the tensile strength of Film 3 (5% nanoclay content) increased although it has higher nanoclay content as compared with Film 2. 69 0 100 200 300 400 500 600 -1 0 0 10 20 30 40 50 60 70 80 90 St re ss (MPa ) St ra i n (% ) F i l m 1 F i l m 2 F i l m 3 Figure 4.30 Tensile stress-strain curve of Film 1, Film 2 and Film 3 - Condition of 15 wt % Compatibilizer Presence Tensile test results for Film 4, Film 5 and Film 6 are shown in Figure 4.31. Film 4 includes 1%, Film 5 includes 3% and Film 6 includes 5% nanoclay. In Figure 4.31, the strain value of Film 4 is nearly 375%. However, the strain value of Film 5 is nearly 125% and the strain value of Film 6 is nearly 25%. This shows that as the nanoclay content of the films, having 15% compatibilizer content, increases, the extension of the films decreases. As it is seen from Table 4.4, maximum tensile stress for films 4, 5 and 6 decreases first then increases as the nanoclay content increases from 1% to 5%. The increase in nanoclay 70 content reduces the tensile strength. The results are similar to those with 10 wt% compatibilizer. As explained earlier, nanoclay dispersion in Film 4 is better than nanoclay dispersion in Film 5. However, for Film 6, having the highest nanoclay content the screw speed was increased, resulting in higher tensile strength. It can be seen from morphology analysis that Film 6 has more homogeneous structure than Film 5. As a result, the tensile strength of Film 5 (3% nanoclay content) decreased as compared with Film 4 (1% nanoclay content), however, the tensile strength of Film 6 (5% nanoclay content) increased although it has higher nanoclay content as compared with Film 5. Figure 4.31 Tensile stress-strain curve of Film 4, Film 5 and Film 6 -5 0 0 50 100 150 200 250 300 350 400 0 20 40 60 80 100 St re ss (MPa ) St ra i n (% ) F i l m 4 F i l m 5 F i l m 6 71 - Condition of 20 wt % Compatibilizer Presence Tensile test results for Film 7, Film 8 and Film 9 are shown in 4.32. Film 7 includes 1%, Film 8 includes 3% and Film 9 includes 5% nanoclay. In Figure 4.32, the strain value of Film 7 is nearly 500%. However, the strain value of Film 8 is nearly 220% and the strain value of Film 9 is nearly 25%. This shows that as the nanoclay content of the films, having 20% compatibilizer content, increases, the extension of the films decreases. As it is seen from Table 4.4, maximum tensile stress for films 7, 8 and 9 decreases first then increases as the nanoclay content increases from 1% to 5%. The increase in nanoclay content reduces the tensile strength. The results are similar to those with 10 wt% and 15 wt% compatibilizer. As explained earlier, nanoclay dispersion in Film 7 is better than nanoclay dispersion in Film 8. However, for Film 9, having the highest nanoclay content the screw speed was increased, resulting in higher tensile strength. It can be seen from morphology analysis that Film 9 has more homogeneous structure than Film 6. As a result, the tensile strength of Film 7 (3% nanoclay content) decreased as compared with Film 8 (1% nanoclay content), however, the tensile strength of Film 9 (5% nanoclay content) increased although it has higher nanoclay content as compared with Film 8. 72 0 100 200 300 400 500 -2 0 0 20 40 60 80 St re ss (MPa ) St ra i n (% ) F i l m 7 F i l m 8 F i l m 9 Figure 4.32 Tensile stress-strain curve of Film 7, Film 8 and Film 9 Evaluation According to Compatibilizer Content: - Condition of 1 wt % Nanoclay Presence Film 1 includes 10%, Film 4 includes 15% and Film 7 includes 20% compatibilizer. As seen from Figure 4.30, the strain value of Film 1 is 550%. However, the strain values of Film 4 is 375% and the strain values of Film 7 is 500% (Figure 4.31 and 4.32). The compatibilizer content of the nanoclay reinforced films, having 1% nanoclay content, increases, the strain of the films decreases first then increases. 73 As it is seen from Table 4.4, tensile stress for films 1, 4 and 7 decreases, as the compatibilizer content increases from 10% to 20%. - Condition of 3 wt % Nanoclay Presence Film 2 includes 10%, Film 5 includes 15% and Film 8 includes 20% compatibilizer. From Figure 4.30, the strain value of Film 2 is 420%. However, the strain value of Film 5 is 120% and the strain value of Film 8 is 220% (Figure 4.31 and 4.32). As the compatibilizer content of the nanoclay reinforced films, having 3% nanoclay content, increases, the strain of the films decreases first then increases. As it is seen from Table 4.4, tensile stress for films 2, 5 and 8 firstly decreases, then increases as the compatibilizer content increases from 10% to 20%. For Film 5 (15% compatibilizer content) the tensile strength decreased as compared with Film 2 (10% compatibilizer content), but for Film 8 (20% compatibilizer content) the tensile strength increased as compared with Film 5. - Condition of 5 wt % Nanoclay Presence Film 3 includes 10%, Film 6 includes 15% and Film 9 includes 20% compatibilizer. As seen from Figure 4.30, the strain value of Film 3 is 50%. However, the strain value of Film 6 is 25% and the strain value of Film 9 is 25% (Figure 4.31 and 4.32). As the compatibilizer content of the nanoclay reinforced films, having 5% nanoclay content, increases, the strain of Film 6 and Film 9 decreases nearly to the same values. 74 As it is seen from Table 4.4, tensile stress for films 3, 6 and 9 firstly increases then decreases as the compatibilizer content increases from 10% to 20%. For Film 6 (15% compatibilizer content) the tensile strength increased as compared with Film 3 (10% compatibilizer content), but for Film 9 (20% compatibilizer content) the tensile strength decreased as compared with Film 6. If all of these results considering the evaluation of compatibilizer content change are examined, no specific conclusion can be drawn about the effect of compatibilizer content on tensile strength of the films. 4.3.4. Tear Strength Analysis Tear strength analysis was done based on nanoclay and compatibilizer content of the reinforced PP films. To compare the tear strength of the films, the area under the load-extension curve was determined and this value was divided by the extension value. Calculated tear strength values can be seen in Table 4.5. The tear load (N) was used to compare the tear strength of the nanoclay reinforced PP films. 75 Table 4.5 Calculated tear strength values FILM # SAMPLE 1 SAMPLE 2 SAMPLE 3 SAMPLE 4 SAMPLE 5 AVERAGE Film 1 Area (Nmm) 43.94985 51.80483 43.06312 46.73279 49.26152 Extension (mm) 61.26669 71.98334 53.38326 61.41662 58.4834 Tear (N) 0.717353 0.719678 0.806678 0.760914 0.842316 0.769388 Film 2 Area (Nmm) 45.48238 50.08909 43.09892 43.10592 43.02687 Extension (mm) 72.02501 66.0332 64.04986 57.83327 64.20817 Tear (N) 0.63148 0.758544 0.672896 0.745348 0.670115 0.695677 Film 3 Area (Nmm) 62.63299 45.72679 53.51617 68.26655 45.18898 Extension (mm) 63.04992 49.28306 55.81651 62.40853 56.37492 Tear (N) 0.993387 0.92784 0.958787 1.093866 0.801579 0.955092 Film 4 Area (Nmm) 43.66039 40.15241 35.75421 37.94295 37.27858 Extension (mm) 72.28343 63.52534 65.3251 62.19165 61.69145 Tear (N) 0.604017 0.632069 0.547327 0.610097 0.604275 0.599557 Film 5 Area (Nmm) 41.15258 32.33616 42.86967 40.48964 48.41843 Extension (mm) 60.25837 64.10818 65.3251 73.03321 67.66686 Tear (N) 0.682935 0.5044 0.656251 0.5544 0.715541 0.622706 Film 6 Area (Nmm) 61.36684 52.12976 45.33582 63.19742 58.0279 Extension (mm) 73.16661 56.44162 46.20817 65.35012 59.42502 Tear (N) 0.838727 0.923605 0.981121 0.967059 0.976489 0.9374 Film 7 Area (Nmm) 75.60466 62.22934 74.50421 76.11081 64.46762 Extension (mm) 71.44169 68.50009 72.09998 73.61652 64.17499 76 Tear (N) 1.058271 0.908456 1.033346 1.033882 1.00456 1.007703 Film 8 Area (Nmm) 46.81317 50.85026 53.44458 58.28861 49.8039 Extension (mm) 66.01655 58.60016 72.55827 72.43325 75.13343 Tear (N) 0.709113 0.86775 0.736575 0.804722 0.662873 0.756206 Film 9 Area (Nmm) 43.94985 51.80483 43.06312 46.73279 49.26152 Extension (mm) 61.26669 71.98334 53.38326 61.41662 58.4834 Tear (N) 0.717353 0.719678 0.806678 0.760914 0.842316 0.769388 Evaluation According to Nanoclay Content: - Condition of 10 wt % Compatibilizer Presence Tear test results for Film 1, Film 2 and Film 3 can be seen in Figure 4.33. Film 1 includes 1%, Film 2 includes 3% and Film 3 includes 5% nanoclay. As it is seen from Table 4.5, tear strength of films 1, 2 and 3 decreases first, then increases as the nanoclay content increases from 1% to 5%. The increase in nanoclay content reduces the tear strength since nanoclay dispersion cannot be achieved as good as in the films having lower nanoclay content. Besides, as it can be seen from morphology analysis nanoclay dispersion in Film 1 is better than Film 2. Therefore, for Film 1, the more evenly dispersed nanoparticles resist tearing force (load) making the tear strength higher. However, when Film 2 is tried to be torn, since the nanoclay dispersion is not as good as Film 1 and nanoclay particles are not evenly dispersed in the structure to resist the tearing force, it is seen that tear strength decreases compared to Film 1. For Film 3, having the highest nanoclay content, the situation is different. Since for 5% nanoclay content, the films could not be drawn with the same screw 77 speed that was used for the films having 1% and 3% nanoclay content, screw speed was increased. Since the screw speed was increased, shear stress increased. Increase in the shear stress made the polymer and nanoclay mix more homogeneously by making the films, having 5% nanoclay content, gain higher tear strength. Better nanoclay dispersion in Film 3 can be seen from SEM micrographs of morphology analysis. Because of this, for Film 2 (3% nanoclay content) the tear strength decreased as compared with Film 1 (1% nanoclay content), but for Film 3 (5% nanoclay content) the tear strength increased although it has higher nanoclay content as compared with Film 2. 0 10 20 30 40 50 60 0 .0 0 .5 1 .0 1 .5 2 .0 L o a d (N ) Ex t e n si o n (m m ) F i l m 1 F i l m 2 F i l m 3 Figure 4.33 Tear load-extension curve of Film 1, Film2 and Film 3 78 - Condition of 15 wt % Compatibilizer Presence Tear test results for Film 4, Film 5 and Film 6 are shown in Figure 4.34. Film 4 includes 1%, Film 5 includes 3% and Film 6 includes 5% nanoclay content. As it is seen from Table 4.5, tear strength for films 4, 5 and 6 increases as the nanoclay content increases from 1% to 5%. Since the difference of nanoclay dispersion is not much different in Film 4 and 5 according to SEM micrographs of morphology analysis, this small difference is thought to have little effect on tear strength of the films 4 and 5. For Film 6 (5% nanoclay content); since the screw speed was increased, the tear strength increased although it has higher nanoclay content as compared with Film 5. 0 10 20 30 40 50 60 70 -0 .2 0 .0 0 .2 0 .4 0 .6 0 .8 1 .0 1 .2 1 .4 L o a d (N ) Ex t e n si o n (m m ) F i l m 4 F i l m 5 F i l m 6 Figure 4.34 Tear load-extension curve of Film 4, Film 5 and Film 6 79 - Condition of 20 wt % Compatibilizer Presence Tear test results for Film 7, Film 8 and Film 9 are shown in Figure 4.35. Film 7 includes 1%, Film 8 includes 3% and Film 9 includes 5% nanoclay content. As it is seen from Table 4.5, tear strength for films 7, 8 and 9 firstly decreases then increases as the nanoclay content increases from 1% to 5%. The reasons are similar to the results explained before. -1 0 0 10 20 30 40 50 60 70 -0 .2 0 .0 0 .2 0 .4 0 .6 0 .8 1 .0 1 .2 1 .4 1 .6 1 .8 L o a d (N ) Ex t e n si o n (m m ) F i l m 7 F i l m 8 F i l m 9 Figure 4.35 Tear load-extension curve of Film 7, Film 8 and Film 9 80 Evaluation According to Compatibilizer Content: - Condition of 1 wt % Nanoclay Presence Film 1 includes 10%, Film 4 includes 15% and Film 7 includes 20% compatibilizer. As it is seen from Table 4.5, tear strength for films 1, 4 and 7 decreases first then increases as the compatibilizer content increases from 10% to 20%. For Film 4 (15% compatibilizer content), the tear strength decreased as compared with Film 1 (10% compatibilizer content), but for Film 7 (20% compatibilizer content) the tear strength increased as compared with Film 4. - Condition of 3 wt % Nanoclay Presence Film 2 includes 10%, Film 5 includes 15% and Film 8 includes 20% compatibilizer. As it is seen from Table 4.5, tear strength for films 2, 5 and 8 decreases first then increases as the compatibilizer content increases from 10% to 20%. For Film 5 (15% compatibilizer content), the tear strength decreased as compared with Film 2 (10% compatibilizer content), but for Film 8 (20% compatibilizer content), the tear strength increased as compared with Film 5. - Condition of 5 wt % Nanoclay Presence Film 3 includes 10%, Film 6 includes 15% and Film 9 includes 20% compatibilizer. As it is seen from Table 4.5, tear strength for films 3, 6 and 9 decreases as the compatibilizer content increases from 10% to 20%. 81 4.3.5. Bust Strength Analysis Burst strength analysis was done based on the nanoclay and compatibilizer content of the reinforced PP films. To compare the burst strength of the films, load values (N) at the time of burst were used. Load and extension values for burst strength tests are shown in Table 4.6. Evaluation According to Nanoclay Content: - Condition of 10 wt % Compatibilizer Presence Burst strength test results for Film 1, Film 2 and Film 3 are shown in Figure 4.36. Film 1 includes 1%, Film 2 includes 3% and Film 3 includes 5% nanoclay. As seen from Figure 4.36, the extension value of Film 1 is 45 mm. However, the extension value of Film 2 is 33 mm and the extension value of Film 3 is 20 mm. This shows that as the nanoclay content of the nanoclay reinforced films, having 10% compatibilizer content, increases, the extension of the films decreases. 82 Table 4.6 Load and extension values from burst strength tests FILM # SAMPLE 1 SAMPLE 2 SAMPLE 3 SAMPLE 4 SAMPLE 5 AVERAGE Film 1 Load (N) 53.5 52.26 51.81 53.51 55.62 53.34 Extension (mm) 44.6 44.6 43.7 43.7 44 44.06 Film 2 Load (N) 43.06 45.35 44.93 43.55 44.47 44.272 Extension (mm) 28.2 38.6 30.7 34.7 27.6 31.96 Film 3 Load (N) 52.35 53.69 55.34 53.69 50.28 53.07 Extension (mm) 14.3 15.5 17.2 17.1 14.9 15.8 Film 4 Load (N) 38.48 39.77 40.2 41.81 49.28 41.908 Extension (mm) 24.6 32.3 34.8 37.8 34.2 32.74 Film 5 Load (N) 34.61 36.45 37.79 38.5 39.67 37.404 Extension (mm) 17.3 27.9 25.4 27.2 24.4 24.44 Film 6 Load (N) 51.9 52.1 49.63 53.59 54.41 52.326 Extension (mm) 12.9 15 13.3 15.2 14 14.08 Film 7 Load (N) 47.53 47.04 46.75 44.54 48.49 46.87 Extension (mm) 44.1 44.8 43.4 44.3 43.6 44.04 Film 8 Load (N) 41.46 46.11 42.59 42.63 45.32 43.622 Extension (mm) 29 33.5 26.2 30.2 32.8 30.34 Film 9 Load (N) 60.07 59.58 56.91 63.51 56.99 59.412 Extension (mm) 16.7 15.6 17.6 17.1 16.9 16.78 83 As it is seen from Table 4.6, burst strength for films 1, 2 and 3 decreases first then increases as the nanoclay content increases from 1% to 5%. Although the burst strength for Film 1 cannot be determined since the film could not burst in the specified extension range that was determined according to the instruments available space for this test, it is obvious from the data that the maximum load that Film 1 can burst is over 60, which is higher than Film 2. The increase in the nanoclay content makes the films have lower burst strength since nanoclay dispersion cannot be achieved as good as in the films having lower nanoclay content. Moreover, nanoclay dispersion in Film 1 is better than Film 2. When Film 1 is tried to be bursted, the more evenly dispersed nanoparticles resist bursting force (load) making the burst strength higher. However, when Film 2 is tried to be bursted, since the nanoclay dispersion is not as good as Film 1 and nanoclay particles are not evenly dispersed in the film structure to resist the bursting force, the burst strength decreases compared to Film 1. For Film 3, screw speed was increased which made the polymer and the nanoclay mix more homogeneously; this increased the burst strength since the more the nanoclay particles are evenly dispersed the better they resist the bursting force. Better nanoclay dispersion in Film 3 can be seen from the SEM micrographs of morphology analysis. Because of this, for Film 2 (3% nanoclay content) the burst strength decreased as compared with Film 1 (1% nanoclay content), but for Film 3 (5% nanoclay content) the burst strength increased although it has higher nanoclay content as compared with Film 2. 84 0 10 20 30 40 50 0 10 20 30 40 50 60 L o a d (N ) Ex t e n si o n (m m ) F i l m 1 F i l m 2 F i l m 3 Figure 4.36 Burst load-extension curve of Film 1, Film 2 and Film 3 - Condition of 15 wt % Compatibilizer Presence Burst strength test results for Film 4, Film 5 and Film 6 can be seen in Figure 4.37. Film 4 includes 1%, Film 5 includes 3% and Film 6 includes 5% nanoclay. As seen from Figure 4.37, the extension value of Film 4 is 27.5 mm. However, the extension value of Film 5 is 27.5 mm and the extension value of Film 6 is 15 mm. This shows that as the nanoclay content of the nanoclay reinforced films, having 15% compatibilizer content, increases, the extension of the films decreases. As it is seen from Table 4.6, burst strength for films 4, 5 and 6 decreases first then increases as the nanoclay content increases from 1% to 5%. The increase in the nanoclay content makes the films have lower burst strength since nanoclay dispersion cannot be achieved as good 85 as in the films having lower nanoclay content. Also, as it can be seen from morphology analysis nanoclay dispersion in Film 4 is better than Film 5. Therefore, when Film 4 is tried to be bursted, the more evenly dispersed nanoparticles resist bursting force (load) making the burst strength higher. However, when Film 5 is tried to be bursted, since the nanoclay dispersion is not as good as Film 4 and nanoclay particles are not evenly dispersed in the film structure to resist the bursting force, burst strength decreases compared to Film 4. For Film 6, screw speed was increased which made the polymer and the nanoclay mix more homogeneously; this increased the burst strength since the more the nanoclay particles are evenly dispersed the better they resist the bursting force. Better nanoclay dispersion in Film 6 can be seen from the SEM micrographs of morphology analysis. Because of this, for Film 5 (3% nanoclay content) the burst strength decreased as compared with Film 4 (1% nanoclay content), but for Film 6 (5% nanoclay content) the burst strength increased although it has higher nanoclay content as compared with Film 5. 0 5 10 15 20 25 30 0 10 20 30 40 50 L o a d (N ) Ex t e n si o n (m m ) F i l m 4 F i l m 5 F i l m 6 Figure 4.37 Burst load-extension curve of Film 4, Film 5 and Film 6 86 - Condition of 20 wt % Compatibilizer Presence Burst strength test results for Film 7, Film 8 and Film 9 are shown in Figure 4.38. Film 7 includes 1%, Film 8 includes 3% and Film 9 includes 5% nanoclay content. As seen from Figure 4.38, the extension value of Film 7 is 45 mm. However, the extension value of Film 8 is 35 mm and the extension value of Film 9 is 18 mm ranges. This shows that as the nanoclay content of the nanoclay reinforced films, having 20% compatibilizer content, increases, the extension of the films decreases. As it is seen from Table 4.6, burst strength for films 7, 8 and 9 decreases first then increases as the nanoclay content increases from 1% to 5%. Although the burst strength for Film 7 cannot be determined since the film could not burst in the specified extension range that was determined according to the instruments available space for this test, it is obvious from the data that the maximum load that Film 7 can burst is over 47 which is higher than Film 8. The increase in the nanoclay content makes the films have lower burst strength since nanoclay dispersion cannot be achieved as good as in the films having lower nanoclay content. Moreover, nanoclay dispersion in Film 7 is better than Film 8. Therefore, when Film 7 is tried to be bursted, the more evenly dispersed nanoparticles resist bursting force (load) making the burst strength higher. However, when Film 8 is tried to be bursted, since the nanoclay dispersion is not as good as Film 7 and nanoclay particles are not evenly dispersed in the film structure to resist the bursting force, burst strength decreases compared to Film 7. For Film 9, screw speed was increased which made the polymer and the nanoclay mix more homogeneously; this increased the burst strength since the more the nanoclay particles are evenly dispersed the better they resist the bursting force. Better nanoclay dispersion in Film 9 can be seen from the SEM micrographs of morphology analysis. Because of this, for Film 8 (3% nanoclay content) the burst strength decreased as 87 compared with Film 7 (1% nanoclay content), but for Film 9 (5% nanoclay content) the burst strength increased although it has higher nanoclay content as compared with Film 8. 0 10 20 30 40 50 0 10 20 30 40 50 60 L o a d (N ) Ex t e n si o n (m m ) F i l m 7 F i l m 8 F i l m 9 Figure 4.38 Burst load-extension curve of Film 7, Film 8 and Film 9 Evaluation According to Compatibilizer Content: - Condition of 1 wt % Nanoclay Presence Film 1 includes 10%, Film 4 includes 15% and Film 7 includes 20% compatibilizer content. As seen from Figure 4.39, the extension value of Film 1 is 45 mm. However, the extension value of Film 4 is 30 mm and the extension value of Film 7 is 45 mm. This shows that 88 as the compatibilizer content of the nanoclay reinforced films, having 1% nanoclay content, increases, the extension of the films firstly decreases then increases. As it is seen from Table 4.6, burst strength for films 1, 4 and 7 firstly decreases then increases as the compatibilizer content increases from 10% to 20%. 0 10 20 30 40 50 0 10 20 30 40 50 60 L o a d (N ) Ex t e n si o n (m m ) F i l m 1 F i l m 4 F i l m 7 Figure 4.39 Burst load-extension curve of Film 1, Film 4 and Film 7 - Condition of 3 w % Nanoclay Presence Film 2 includes 10%, Film 5 includes 15% and Film 8 includes 20% compatibilizer content. As seen from Figure 4.40, the extension value of Film 2 is 32.5 mm. However, the extension value of Film 5 is 27.5 mm and the extension value of Film 8 is 35 mm ranges. This 89 shows that as the compatibilizer content of the nanoclay reinforced films, having 3% nanoclay content, increases, the extension of the films firstly decreases then increases. As it is seen from Table 4.6, burst strength for films 2, 5 and 8 firstly decreases then increases as the compatibilizer content increases from 10% to 20%. -5 0 5 10 15 20 25 30 35 0 10 20 30 40 50 L o a d (N ) Ex t e n si o n (m m ) F i l m 2 F i l m 5 F i l m 8 Figure 4.40 Burst load-extension curve of Film 2, Film 5 and Film 8 - Condition of 5 w % Nanoclay Presence Film 3 includes 10%, Film 6 includes 15% and Film 9 includes 20% compatibilizer content. As seen from Figure 4.41, the extension value of Film 3 is 18 mm. However, the extension value of Film 6 is 15 mm and the extension value of Film 9 is 18 mm. This shows that 90 as the compatibilizer content of the nanoclay reinforced films, having 5% nanoclay content, increases, the extension of the films firstly decreases then increases as the compatibilizer content increases from 10% to 20%. As it is seen from Table 4.6, burst strength for films 3, 6 and 9 firstly decreases then increases as the compatibilizer content increases from 10% to 20%. 0 5 10 15 20 0 10 20 30 40 50 60 L o a d (N ) Ex t e n si o n (m m ) F i l m 3 F i l m 6 F i l m 9 Figure 4.41 Burst load-extension curve of Film 3, Film 6 and Film 9 91 CHAPTER 5 DEVELOPMENT OF PBI MEMBRANE 5.1. Materials Used To increase the fuel cell performance at high temperatures, the polymer electrolyte membrane must have better water retention characteristics to allow higher proton conductivity that improves fuel cell efficiency. In order to extend the fuel cell operation temperature range, novel membranes having better material properties, such as higher thermal stability than Nafion?, need to be produced. A material that is used for high temperature polymer electrolyte fuel cells is polybenzimidazole (PBI). Polybenzimidazoles are usually used after they are doped with acids because they gain high proton conductivity with no or low humidification after doping with acids. Especially phosphoric acid is used to dope polybenzimidazoles. Therefore, PBI was synthesized to be used as fuel cell membrane. 5.1.1. Polymer and Dopant PBI is chosen as the polymer because of its outstanding characteristics that are needed for fuel cell membranes. PBI has excellent thermal stability. With some modifications using doping process, thermal stability of the PBI membranes can be increased. Since PBI reacts easily with acids, it is easy to dope it with phosphoric acid which is the most frequently used dopant for PBI 92 [27, 28]. PBI can keep its mechanical properties up to 300 ?C. As the temperature increases, the performance of the fuel cell increases, too. Therefore, polymers that can withstand high temperatures such as PBI are good candidates as electrolytes. By using PBI as a polymer for fuel cell membrane, temperature limitation that is imposed by the electrolyte materials can be overcome. As acid, phosphoric acid (H3PO4) was used for doping in this project. Doping is a process which includes immersing of a polymer film into an aqueous or aqueous-organic solution of an acid for a certain period [27]. By doping PBI with phosphoric acid, the proton conductivity can be increased. In addition, doping process eliminates the need for water to have high proton conductivity and helps to improve thermal stability. Therefore, phosphoric acid-doped PBI will not require humidification in high temperature fuel cell applications. 5.1.2. Synthesis of PBI To synthesize PBI polymer, 3.24 g (15.1 mmol) of 3, 3, 4, 4?-tetraaminobiphenyl and 2.51 g (15.1 mmol) of isophthalic acid were mixed in 180 g of polyphosphoric acid and 0.05 g of triphenyl phosphite. The reaction system consisted of a 250 ml four neck flask equipped with a calcium chloride drying tube and nitrogen inlet. Stirring was done by a heating/stirring mantle. The system was heated at 200 ?C for 10 hours. Then, the polymer was isolated by pouring down the reaction mixture into deionised (DI) water. The polymer was then filtered by using filter papers and applying vacuum. Then, the polymer obtained was neutralized with potassium hydroxide and filtered again. After neutralization process, the polymer powder was rinsed with deionised water and filtered. The polymer obtained was left overnight inside an oven at 50 ?C. As a last step the polymer was ground in order to have polymer powder [29]. 93 5.2 Machines Used 5.2.1. Ultrasonic Generator In this project, broadband ultrasonic generator was used in order atomize the solution with the help of an ultrasonic nozzle. The broadband ultrasonic generator can be seen in Figure 5.1. This generator, which is designed and manufactured by Sono-tek Corp., delivers a high frequency electrical energy required to operate ultrasonic atomizing nozzles that are also supplied by Sono-tek. One of the features of the ultrasonic generator is that it can operate over a frequency range of 25-120 kHz, which can be selected according to the nozzle used. The ultrasonic generator uses advanced phase-locked-loop control technology in order to lock onto a nozzle?s specific operating frequency automatically. It includes an output for connection to a remote alarm, an input for remote power control and an LCD power meter and power level control for setup and monitoring of nozzle operation. It has the capability of providing audible and visual alarms if a system malfunction occurs. The ultrasonic generator can be triggered on/off by an external control signal [30]. 94 Figure 5.1 Ultrasonic Broadband Generator [30] 5.2.2. Ultrasonic Nozzle Sono-tek ultrasonic nozzle that has a corrosion-resistant titanium and stainless steel construction was used as titanium has good acoustical properties, high tensile strength, and excellent corrosion resistance. This ultrasonic spraying system is chosen for the project because it is more precise, more controllable, and more environmentally friendly liquid atomization. This highly controllable spray produces reliable, consistent results by producing a tight and controllable drop size distribution which gives the flexibility to influence coating porosity. By the help of ultrasonic energy, it is possible to disperse agglomerated particles and obtain homogenous coatings. Ultrasonic nozzle provides not only 80% reduction in material consumption but also provides reduced wasteful overspray and atmospheric contamination due 95 to soft spray characteristics. It has a non-clogging design that saves time for cleaning the inside of the nozzle. Only the solvent of the polymer is enough to clean the nozzle. It has no moving parts so there is no chance to encounter with the problem of wearing out. This technique can be used for substrate coatings, moisturizing, spray drying, web coating, fine-line spraying, and many other industrial and R&D applications [30]. The ultrasonic nozzle and its parts can be seen in Figure 5.2. The ultrasonic atomizing nozzle technology is different from other spray nozzle technologies. As the ultrasonic atomizing nozzles are pressureless, they create a soft, low- velocity spray, typically in the order of 7.5-12.5 cm (3-5 inches) per second. Other atomization techniques using pressure to spray, produce drops with velocities well over 100 times that produced by ultrasonic atomization. This velocity differential means that pressure sprays generate on the order of 10,000 as much kinetic energy as do ultrasonically atomized sprays. This difference in spray energy creates some outcomes. In coating applications, the unpressurized, low-velocity spray decreases the amount of overspray by making the drops settle on the substrate rather than bouncing off it. Therefore, substantial material savings and decrease in emissions into the environment can be easily achieved [30]. 96 Figure 5.2 Ultrasonic nozzle and its parts [30] Also Sono-Tek ultrasonic nozzle system that we use has an optional dual liquid feed assembly installed. This dual liquid feed option gives us the opportunity to be able to mix two liquids right at the nozzle?s atomizing surface. Therefore, there is no need for premature mixing of components and it is also ideal for micro-encapsulation [30]. The ultrasonic nozzle cross- sectional view can be seen in Figure 5.3. 97 Figure 5.3 Ultrasonic nozzle cross-sectional view [30] The AccuMistTM system combines microspray ultrasonic atomizing nozzle with low pressure air for the formation of a soft, highly focused beam of small spray drops. 6894 Pa (1 psi) compressed air is inserted into the diffusion chamber of the air shroud that forms a uniformly distributed flow of air around the nozzle stem. The spray that is ultrasonically produced at the tip of the stem is immediately entrained in the low pressure air stream. The focusing mechanism on the air shroud allows complete control of spray width having a range of 2mm - 10mm.The spray envelope is bow-shaped. The width of the bow is controlled by moving the focus-adjust mechanism in and out [30]. Working Principle Of Ultrasonic Spray Nozzles Ultrasonic nozzles employ high frequency sound waves which are beyond the range of human hearing. Ultrasonic nozzles have disc-shaped ceramic piezoelectric transducers that convert electrical energy into mechanical energy. These piezoelectric transducers receive electrical input in the form of a high frequency signal from a power generator. Then they convert 98 this into vibratory motion at the same frequency. Two titanium cylinders exaggerate the motion and enhance the vibration amplitude at the atomizing surface. By the excitation of the piezoelectric crystals of the nozzles, a transverse standing wave along the length of the nozzle is produced. The ultrasonic energy that is produced by the crystals goes through a step transition and amplification as the standing wave as it traverses the length of the nozzle. In ultrasonic generators, power is controlled by adjusting the output level on the power supply and power levels are no more than 15 watts for ultrasonic atomization [30]. 5.2.3. Dispensing Robot In this project I&J4300-LF Benchtop Dispensing Robot, which is a programmable coating system, was used to automate the manual dispensing operations. By automating the dispensing operations using the desktop dispensing robot, more uniform surface of polymer electrolyte membrane, saving costs in material waste and time can be achieved [31]. Figure 5.4 Dispenser robot and teach pendant [31] 99 The I&J4300-LF model 3-axis desktop dispensing robot that was used in this project is a RoHS-compliant lead-free dispensing robot having an easy to use teaching pendant that is used to control the robot. The dispenser robot and its teach pendant are shown in Figure 5.4. Programming of the robot can be done by teach pendant, using the dispensing software that gives the user through step-by-step instructions to generate different shaped coated surfaces. It can also be programmed by a PC. This compact-sized desktop robot has a working area of 300 x 300mm (11.81" x 11.81"). 100 programs can be saved in the memory of the robot. It has a continuous path motion for precision xyz dispensing and also interpolates lines and arcs for three dimensional dispensing [31]. 5.3. Membrane Fabrication 5.3.1. Programming of Dispensing Robot In order to use the dispensing robot properly, it needs to be programmed according to the coating shape that is needed. Fifteen programs that can make different shapes with different time durations were written. Some of the programs that were used in this project are shown below. The other programs that were written are shown in APPENDIX B. 5.3.1.1. Program 1 This program makes the dispensing robot draw a square (Figure 5.5). 100 Figure 5.5 Steps of program 1 Steps of the program are as follows: 1) Set up ? Line speed ? Enter ? 55 ? Enter Set up ? XY move speed ? Enter ? 5 - Enter 2) Menu 2 ? Numerical move ? Enter X1=0 Y1=100 Z1=50 3) Enter (or point) ? Line start ? Enter 4) Menu 2 ? Numerical Move ? Enter X2=0 Y2=200 Z2=50 5) Enter (or point) ? Line passing ? Enter 6) Menu 2 ? Numerical move ? Enter X3=100 Y3=200 Z3=50 Line start Line end X1=0 X5=0 Y1=100 Y5=100 Z1=50 Z5=50 Line Passing X2=0 Y2=200 Z2= 50 Line Passing X4=100 Y4=100 Z4= 50 Line Passing X3=100 Y3=200 Z3= 50 101 7) Enter (or point) ? Line passing ? Enter 8) Menu 2 ? Numerical move ? Enter X4=100 Y4=100 Z4=50 9) Enter (or point) ? Line passing ? Enter 10) Menu 2 ? Numerical move ? Enter X5=0 Y5=100 Z5=50 11) Enter (or point) ? Line end ? Enter 12) Enter ? End Program ? Enter 13) Run 5.3.1.2. Program 2 This program makes the dispensing robot draw a square and then fill inside the square (Figure 5.6). 102 Figure 5.6 Steps of program 2 Steps of the program are as follows: 1) Set up ? Line Speed ? Enter ? 30 ? Enter Set up ? XY Move Speed ? Enter ? 30 ? Enter 2) Menu 2 ? Numerical Move ? Enter X1 = 100 Y1 = 100 Z1 = 50 3) Enter (or Point) ? Line Start ? Enter 4) Menu 2 ? Numerical Move ? Enter X2 = 100 Y2 = 200 Z2 = 50 Line Start X1=100 Y1=100 Z1=50 Line Passing X3=200 Y3=200 Z3=50 Line Passing X2=100 Y2=200 Z2=50 Line Passing X4=200 Y4=100 Z4=50 Line End X5=100 Y5=100 Z5=50 Line Start X6=100 Y6=100 Z6=50 Line End X7=200 Y7=200 Z7=50 103 5) Enter (or Point) ? Line Passing ? Enter 6) Menu 2 ? Numerical Move ? Enter X3 = 200 Y3 = 200 Z3 = 50 7) Enter (or Point) ? Line Passing ? Enter 8) Menu 2 ? Numerical Move ? Enter X4 = 200 Y4 = 100 Z4 = 50 9) Enter (or Point) ? Line Passing ? Enter 10) Menu 2 ? Numerical Move ? Enter X5 = 100 Y5 = 100 Z5 = 50 11) Enter (or Point) ? Line End - Enter 12) Enter (or Point) ? Brush Area ? Enter ? Select (1 - Rectangle) ? Width ? 5 ? Enter ? 1.X 2.Y:1 (Rectangle) ? Enter 13) Menu 2 ? Numerical Move ? Enter X6= 100 Y6=100 Z6=50 14) Enter (or Point) ? Line Start ? Enter 15) Menu 2 ? Numerical Move ? Enter X7=200 Y7=200 Z7=50 16) Enter (or Point) ? Line End ? Enter 17) Enter (or Point) ? End Program ? Enter 18) Run 104 5.3.2. Manufacturing Process of the Membrane Firstly, the PBI powder obtained was dissolved in N,N-dimethylacetamide (DMAc) by heating at 160 ?C under stirring [32]. The solution had 5wt% PBI with 1.5% of LiCl. Then, 5 wt% PBI solution was put into syringe of the ultrasonic nozzle and fed to the nozzle that was mounted on the dispensing robot. The solution was sprayed on the glass plate. The glass plate was heated to 60 ?C and the solvent was evaporated. The plate was immersed in deionised water in order to detach the membrane from the plate [32]. 105 CHAPTER 6 MODEL OF MEMBRANE BEHAVIOR 6.1. Assumptions of the Model The following assumptions are made for the model: 1) Ideal gas properties: All the gases in diffuser regions exhibit ideal gas behavior. 2) Ideal gas mixtures: Reactant gases are well mixed and behave as ideal gas mixture. 3) Incompressible flow 4) Laminar flow: Flow is laminar everywhere because of small gas pressure gradient and low Reynolds number. 5) Isotropic and homogeneous membrane and electrode structures: Both of the electrodes and membrane are made of homogeneous and isotropic materials. (Isotropic macro-homogeneous porous regions) 6) Negligible ohmic potential drop in solid components 7) Uniform temperature distribution: Temperature distribution across the cell is uniform. 8) Impermeable PEM: The PEM is impermeable to reactant gases and water. 9) Proton and electron transport: Protons can only transport through the electrolyte membrane and electrons through the solid phase. 106 10) Species on the anode and cathode sides: Two species (hydrogen and water) are considered on the anode side and three species (oxygen, water and nitrogen) are considered on the cathode side. 11) Steady state: Fuel cell is operating at the steady state. 12) Multi domain approach: For this model, multi domain approach is chosen by using separate governing equations in each subdomain. 13) Only gas phases present: Water is expected to exist only in vapor phase. At elevated temperatures no aqueous or liquid phases exist. 6.2. Model Definition For high temperature polymer electrolyte fuel cell membrane having a PBI based membrane, a two dimensional mathematical model was developed as shown in Figure 6.1. The model has three domains: a) An anode b) A PEM c) A cathode Figure 6.1 Model geometry with its subdomains and boundary labels Outlet Inlet Anode Cathode Membrane Outlet Inlet 107 6.3. Governing Equations The governing equations of all of the domains were obtained. 6.3.1. Anode 6.3.1.1. Flow Channels: Maxwell-Stefan Mass Balances (Conservation of Species) Two species such as H2 and H2O are taken into consideration in the anode side flow channels. The multicomponent diffusion and convection in flow channels are described by the Maxwell-Stefan equation. This equation solves for the fluxes in terms of mass fraction. The equation for the Maxwell-Stefan multicomponent diffusion is [33, 34, 35, 36]: (6.1) where: ?: mass fraction p: pressure (Pa) T: (cell) temperature (K) u: velocity vector (m/s) ?: density of the mixture of the gas phase (kg/m3) Dij : Maxwell-Stefan diffusion coefficient (m2/s) Ri: reaction rate (kg/(m3.s)) 108 x: mole fraction M: molecular (molar) mass (kg/mol) i or j: These subscripts represent each species of hydrogen and water. It is assumed that temperature-driven diffusion, which sets the source term R to zero, is insignificant. Therefore, the reaction rate is zero in the flow channel. Density of the mixture of the gas phase is a function of mixture components and is described by the equation: (6.2) where: R: universal gas constant (8.314 J/(mol.K)) On the anode side, the hydrogen transport equation is solved first. Then, mass fraction of water can be obtained by the equation: (6.3) 6.3.1.2. Gas Diffusion Layer and Catalyst Layer: Darcy?s Law And Mass Conservation Equation (Porous Media Fluid Flow) Continuity equation gives the gas velocity as below [33, 34, 35, 36]: (6.4) 109 u: gas velocity (m/s) The pressure gradient, viscosity of the fluid and structure of the porous media determine the velocity vector according to the Darcy?s Law for porous media: (6.5) where: kp: electrode?s permeability (m2) ?: gas?s viscosity (Pa.s) The mixture density of the gas phase is given by the ideal gas law: (6.6) The pressure at the outlets and inlets are: (6.7) (6.8) The velocity of gas is determined from the total mass flow that is given by the electrochemical reaction rate at the electrode boundary: (6.9) Gas flow velocity is determined by Darcy?s Law; the total mass conservation is preserved in the anode gas backing with this given boundary condition. 110 6.3.2. Membrane PBI membrane is lightweight and stable at higher temperatures (150-200?C). PBI membrane conducts the protons through the solid matrix. Its conductivity is less dependent on water content when it is compared with Nafion? membrane. Conductivity of PBI membrane can be improved by doping it with phosphoric or sulfuric acid. PBI has higher mechanical strength than Nafion?. Therefore, it leads to a reduction in membrane thickness and lower ionic resistance since the resistance is proportional to thickness of the membrane. PBI has lower permeability to hydrogen than Nafion?. Proton conduction in PBI may be based on Grotthuss mechanism. For Nafion?, proton migration happens by the vehicle mechanism in which the translational dynamics of the electrolyte species (H2O) is required. In vehicle mechanism, protons diffuse through the medium by the help of the solvated hydrogen ion species, H3O+. Therefore, the observed conductivity is directly related to the rate of the carrier diffusion. But in PBI case, the carriers show pronounced local dynamics however, reside on their sites. The H+ ions are transferred from one carrier to another by the help of hydrogen bonds (proton hoping). For PBI, there is no net transport of any carrier species across the membrane. Since the drag coefficient of water is virtually zero, it can be understood that liquid water is not carried across the membrane together with the protons. For PBI, there is no requirement for liquid water for the conduction of protons. Therefore, water management problems associated with Nafion? do not exist. In the PBI membrane, the protons are conducted through the solid matrix. Protons diffuse in a solid state across the membrane, under the influence of an electrolyte potential gradient via migration only. 111 Since the protons are in a solid state, a solid-fluid ?phase change? occurring during the electrochemical reactions exists. This phenomenon that only occurs in HTPEMFCs must be considered. This is achieved by considering a non-conservative form of the continuity equation [37, 38, 39, 40]: (6.10) where: Si: reaction rate source term (kg.m-3.s-1) Since the PBI membrane is assumed to be impermeable to gas flow and no fluid flow across the membrane exists, flow in the porous catalyst and diffuser regions are governed by Darcy?s Law and no equations can be used for membrane region. Because of the flow of electrical currents in both the solid and electrolyte regions, there are potential variations across each of the solid and electrolyte phases. Charge conservation is given by the equations below: (6.11) (6.12) Charge conservation equations can be modeled by using two Conductive Media DC Modules of COMSOL Multiphysics Software Package. The potential is specified at the gas channel/gas diffuser interfaces, while insulation conditions are specified at the catalyst layer/membrane interfaces and all other boundaries. j= spatial rate of reaction 112 ?j? is defined by the Butler-Volmer equation: (6.13) where: i0= exchange current density (A.m-2) ai= specific surface area (m2.m-3) R= gas constant (J.mol-1.K-1) F= Faraday constant (A.s.mol-1) The quantity given by equation (6.13) provides the coupling between all the variables since the source terms are given in terms of reaction rate. (6.14) (6.15) (6.16) (6.17) The only source term that is not shown in terms of j is the ohmic heating term; nevertheless, it does not depend on the local current densities. (6.18) 113 6.3.3. Cathode 6.3.3.1. Flow Channels: Maxwell-Stefan Mass Balances (Conservation of Species) Three species, O2, N2 and H2O, are taken into consideration in the cathode side flow channels. The multicomponent diffusion and convection in flow channels are described by the Maxwell-Stefan equation. This equation solves for the fluxes in terms of mass fraction. The equation for the Maxwell-Stefan multicomponent diffusion [2, 33-36, 41]: (6.19) where: ?: mass fraction p: pressure (Pa) T: (cell) temperature (K) u: velocity vector (m/s) ?: density of the mixture of the gas phase (kg/m3) Dij : Maxwell-Stefan diffusion coefficient (m2/s) Ri: reaction rate (kg/(m3.s)) x: mole fraction 114 M: molecular (molar) mass (kg/mol) i or j: These subscripts represent each species of oxygen, water and nitrogen. It is assumed that temperature-driven diffusion which sets the source term R to zero is insignificant. Therefore, the reaction rate is zero in the flow channel. Density of the mixture of the gas phase is a function of mixture components and is described by the equation: (6.20) where: R: universal gas constant (8.314 J/(mol.K)) The mass transport is described by using Darcy?s Law that describes the flow rate: (6.21) (6.22) On the cathode side, mass transport equations are solved for two species, because the third species can always be obtained from the mass balance equation: (6.23) where: 1: for oxygen, 2: for water, 115 3: for nitrogen 6.3.3.2. Gas Diffusion Layer And Catalyst Layer: Darcy?s Law And Mass Conservation Equation (Porous Media Fluid Flow) Continuity equation gives the gas velocity [1, 2, 33-36, 41]: (6.24) where: u: gas velocity (m/s) The pressure gradient, the viscosity of the fluid and the structure of the porous media determine the velocity vector according to the Darcy?s Law for porous media: (6.25) where: kp: electrode?s permeability (m2) ?: gas?s viscosity (Pa.s) The mixture density of the gas phase is given by the ideal gas relation: (6.26) The pressure at the outlets and inlets are: (6.27) 116 (6.28) The velocity of gas is determined from the total mass flow that is given by the electrochemical reaction rate at the electrode boundary: (6.29) Gas flow velocity is determined by the Darcy?s Law. The total mass conservation is preserved in the cathode gas backing with this given boundary condition. 6.4. Solutions of the Governing Equations COMSOL Multiphysics Software Package is used for solving the equations of the two dimensional mathematical model of the high temperature polymer electrolyte fuel cell membrane having a PBI based membrane since these governing equations are coupled equations to be solved simultaneously and contain nonlinearities that are hard to be solved analytically. 6.5. Results and Discussion Using the computational modeling, graphs were obtained to show the behavior of the fuel cell membrane in PEMFC. Figure 6.2 shows the gas velocity distribution. Figure 6.3 shows current density distribution. Figure 6.4 and 6.5 show mass fractions of hydrogen and oxygen, respectively. Figure 6.6 and 6.7 show mass fractions of water on the anode side and the cathode side, respectively. Figure 6.8 shows current density distribution on the membrane. 117 Figure 6.2 Velocity field Figure 6.3 Total current density 118 Figure 6.4 Mass fraction of hydrogen on the anode side Figure 6.5 Mass fraction of oxygen on the cathode side 119 Figure 6.6 Mass fraction of water on the anode side Figure 6.7 Mass fraction of water on the cathode side 120 Figure 6.8 Total current density on the membrane 121 CHAPTER 7 CONCLUSIONS AND RECOMMENDATIONS With the increasing temperature and winding speed, the thickness of the films decreases; however, with the increasing screw motor speed film thickness increases. With the increasing temperature tear strength becomes higher in machine direction (MD); however tear strength decreases in cross direction (CD). With the increasing screw motor speed tear strength of the films did not show any specific trend in MD; however, tear strength of the films in CD increases. With the increasing winding speed the tear strength of the films decreases in MD; however, the data did not show any specific trend in CD. As the temperature increased, tensile strength increased in MD. With increasing screw motor speed tensile strength of the films increases in MD; however, tensile strength of the films decreases in CD. With increasing winding speed the tensile strength of the films increases in MD; however, tensile strength of the films decreases in CD. Nanoclay reinforced films having only 1% nanoclay content have more homogeneous nanoclay dispersion than the films having 3% nanoclay content. Screw speed was increased for the films having 5% nanoclay content in order to obtain a film structure since for 5% nanoclay content, the films could not be drawn with the same screw speed that was used for the films having 1% and 3% nanoclay content. Therefore, since the screw speed was increased, shear stress increased. This caused the polymer and the nanoclay mix more homogeneously by making the morphological structure of the films having 5% nanoclay content more homogeneous. 122 According to the differential scanning calorimetry (DSC) results the melting points of the nanoclay reinforced films slightly increase as their nanoclay contents increase from 1% to 5%. Tensile tests showed that as the nanoclay contents of the nanoclay reinforced films increase, the extension of the films decreases. No specific result could be obtained about the effect of the compatibilizer content on tensile strength of the nanoclay reinforced films. Nanoclay reinforced films having only 1% nanoclay content have higher tear strength than the films having 3% nanoclay content. Since the screw speed was increased for the films having 5% nanoclay content in order to obtain a film structure, the films, having 5% nanoclay content, gained higher tear strength. Burst strength results show that as the nanoclay content of the nanoclay reinforced films increases from 1% to 5%, the extension of the films decreases. Nanoclay reinforced films having only 1% nanoclay content have higher burst strength than the films having 3% nanoclay content. The following is recommended for any future work on this subject: Composite membranes for fuel cell applications can be manufactured by adding some materials to the structure of the polymer electrolyte membrane such as: - Titanya Titanya is a metal oxide and an inorganic material having hygroscopic properties. By adding titanya into the structure of polymer electrolytes, water retention ability of the membranes can be enhanced. Titanium oxide is a good hydrophilic filler candidate to polymer electrolytes since it maintains the membrane hydration. Addition of titanium dioxide to the composite membrane structures will enhance water uptake, ion exchange capacity (IEC), conductivity and 123 electrochemical performance of membranes [41]. Therefore, it is possible to produce a self humidifying membrane by adding titanium dioxide nanoparticles to the membrane structure. - Phosphotungstic Acid Phosphotungstic acid, which has a molecular formula of H3PW12O40, is a heteropoly acid (HPA). It has different names, one of the other names is tungstophosphoric acid (TPA). Tungstophosphoric acid is thermally stable up to 400?C. It is the strongest of heteropolyacids which can be qualified as super acid. Phosphotungstic acid (PWA) is a very conductive material in the crystalline form having 29 water molecules per molecule. Because of the high number of water molecules in their reticular structure they exhibit very high proton conductivity. 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Sacca, A., Carbone, A., Passalacqua,E., D?Epifanio,A., Licoccia,S., Traversa,E., Sala,E., Traini,F., and Ornelas,R., ?Nafion-TiO2 hybrid membranes for medium temperature polymer electrolyte fuel cells (PEFCs)?, Journal of Power Sources, 2005, 152, 16?21. 129 APPENDICES APPENDIX A: SEM Micrographs of Nanoclay Reinforced Films Figure A-1 Nanoclay dispersion in Film 1 130 Figure A-2 Nanoclay dispersion in Film 2 131 Figure A-3 Nanoclay dispersion in Film 3 132 Figure A-4 Nanoclay dispersion in Film 4 133 Figure A-5 Nanoclay dispersion in Film 5 134 Figure A-6 Nanoclay dispersion in Film 6 135 Figure A-7 Nanoclay dispersion in Film 7 136 Figure A-8 Nanoclay dispersion in Film 8 137 Figure A-9 Nanoclay dispersion in Film 9 138 APPENDIX B: Programs Written for the Dispensing Robot Program 3 This program makes the dispensing robot draw a square by filling inside the square (Figure B-1). Figure B-1 Steps of program 3 Steps of the program are as follows: 1) Set up ? Line Speed ? Enter ? 10 ? Enter Set up ? XY Move Speed ? Enter ? 10 ? Enter 2) Enter (or Point) ? Brush Area ? Enter ? Select (1 - Rectangle) ? Width ? 1 ? Enter ? 1.X 2.Y:1 (Rectangle) ? Enter 3) Menu 2 ? Numerical Move ? Enter Line Start X1=125 Y1=125 Z1=50 Line End X2=175 Y2=175 Z2=50 139 X1= 125 Y1=125 Z1=50 4) Enter (or Point) ? Line Start ? Enter 5) Menu 2 ? Numerical Move ? Enter X2=175 Y2=175 Z2=50 6) Enter (or Point) ? Line End ? Enter 7) Enter (or Point) ? End Program ? Enter 8) Run 140 Program 4 This program makes the dispensing robot draw a square by filling inside the square two times calling the program 3 from its memory (Figure B-2). Steps of the program are as follows: 1) Enter (or Point) ? Call Program ? Enter ? Program 3 ? Enter 2) Enter (or Point) ? Call Program ? Enter ? Program 3 ? Enter 3) Enter (or Point) ? End Program ? Enter 4) Run Figure B-2 Steps of program 4 Line Start X1=125 Y1=125 Z1=50 Line End X2=175 Y2=175 Z2=50 141 Program 5 This program makes the dispensing robot draw a square by filling inside the square three times calling the program 3 from its memory (Figure B-3). Steps of the program are as follows: 1) Enter (or Point) ? Call Program ? Enter ? Program 3 ? Enter 2) Enter (or Point) ? Call Program ? Enter ? Program 3 ? Enter 3) Enter (or Point) ? Call Program ? Enter ? Program 3 ? Enter 4) Enter (or Point) ? End Program ? Enter 5) Run Figure B-3 Steps of program 5 Line Start X1=125 Y1=125 Z1=50 Line End X2=175 Y2=175 Z2=50 142 Program 6 This program makes the dispensing robot draw a square by filling inside the square four times calling the program 3 from its memory (Figure B-4). Figure B-4 Steps of program 6 Steps of the program can be seen below: 1) Enter (or Point) ? Call Program ? Enter ? Program 3 ? Enter 2) Enter (or Point) ? Call Program ? Enter ? Program 3 ? Enter 3) Enter (or Point) ? Call Program ? Enter ? Program 3 ? Enter 4) Enter (or Point) ? Call Program ? Enter ? Program 3 ? Enter 5) Enter (or Point) ? End Program ? Enter 6) Run Line Start X1=125 Y1=125 Z1=50 Line End X2=175 Y2=175 Z2=50 143 Program 7 This program makes the dispensing robot draw a square by filling inside the square five times calling the program 3 from its memory (Figure B-5). Figure B-5 Steps of program 7 Steps of the program can be seen below: 1) Enter (or Point) ? Call Program ? Enter ? Program 3 ? Enter 2) Enter (or Point) ? Call Program ? Enter ? Program 3 ? Enter 3) Enter (or Point) ? Call Program ? Enter ? Program 3 ? Enter 4) Enter (or Point) ? Call Program ? Enter ? Program 3 ? Enter 5) Enter (or Point) ? Call Program ? Enter ? Program 3 ? Enter 6) Enter (or Point) ? End Program ? Enter 7) Run Line Start X1=125 Y1=125 Z1=50 Line End X2=175 Y2=175 Z2=50 144 Program 8 This program makes the dispensing robot move by drawing a circle. Figure B-6 Steps of program 8 Steps of the program: 1) Set up ? Line speed ? Enter ? 30 ? Enter Set up ? XY move speed ? Enter ? 50 ? Enter 2) Menu 2 ? Numerical move ? Enter X1=150 Y1=150 Z1=50 3) Enter (or point) ? Circle ? Enter Diameter ? 200 ? Enter Over angle ? 0 ? Enter Z lift select ? (2 no) ? Enter 4) Enter (or point) ? End Program ? Enter 5) Run r 145 Program 9 This program makes the dispensing robot move by drawing two circles attached to each other. Arc Point Arc Point Figure B-7 Steps of program 9 Steps of the program: 1) Set up ? Line speed ? Enter ? 5 ? Enter Set up ? XY move speed ? Enter ? 100 - Enter 2) Menu 2 ? Numerical move ? Enter X1=0 Y1=100 Z1=50 3) Enter (or point) ? Line start ? Enter 4) Menu 2 ? Numerical Move ? Enter X2=50 Y2=25 Z2=50 Line Passing X7=100 Y7=100 Z7=50 Line Passing X3=100 Y3=100 Z3=50 Line Passing X5=200 Y5=100 Z5=50 Line Start X1=0 Y1=100 Z1=50 Line End X9=0 Y9=100 Z9=50 X6=150 Y6=175 Z6=50 X8=50 Y8=175 Z8=50 146 5) Enter (or point) ? Arc point ? Enter 6) Menu 2 ? Numerical move ? Enter X3=100 Y3=100 Z3=50 7) Enter (or point) ? Line passing ? Enter 8) Menu 2 ? Numerical move ? Enter X4=150 Y4=25 Z4=50 9) Enter (or point) ? Arc point ? Enter 10) Menu 2 ? Numerical move ? Enter X5=200 Y5=100 Z5=50 11) Enter (or point) ? Line passing ? Enter 12) Menu 2 ? Numerical move ? Enter X6=150 Y6=175 Z6=50 13) Enter (or point) ? Arc point ? Enter 14) Menu 2 ? Numerical move ? Enter X7=100 Y7=100 Z7=50 15) Enter (or point) ? Line passing ? Enter 16) Menu 2 ? Numerical move ? Enter X8=50 Y8=175 Z8=50 17) Enter (or point) ? Arc point ? Enter 18) Menu 2 ? Numerical move ? Enter X9=0 Y9=100 Z9=50 19) Enter (or point) ? Line end ? Enter 20) Enter ? End Program ? Enter 147 Program 10 This program makes the dispensing robot move by drawing a triangle. Line passing X2=100 Y2=50 Z2=10 Line start Line End X1=0 X4=0 Y1=250 Y4=250 Line passing Z1=10 Z4=10 X3=200 Y3=250 Z3=10 Figure B-8 Steps of program 10 Steps of the program: 1) Set up ? Line speed ? Enter ? 5 ? Enter Set up ? XY move speed ? Enter ? 500 - Enter 2) Menu 2 ? Numerical move ? Enter X1=0 Y1=250 Z1=10 3) Enter (or point) ? Line start ? Enter 4) Menu 2 ? Numerical Move ? Enter X2=100 Y2=50 Z2=10 5) Enter (or point) ? Line passing ? Enter 6) Menu 2 ? Numerical move ? Enter X3=200 Y3=250 Z3=10 148 7) Enter (or point) ? Line passing ? Enter 8) Menu 2 ? Numerical move ? Enter X4=0 Y4=250 Z4=10 9) Enter (or point) ? Line end ? Enter 10) Enter ? End Program ? Enter 11) Run 149 Program 11 This program makes the dispensing robot move by drawing a free style shape. Figure B-9 Steps of program 11 Steps of the program: 1) Set up ? Line Speed ? Enter ? 25 ? Enter Set up ? XY Move Speed ? Enter ? 20 - Enter 2) Menu 2 ? Numerical move ? Enter Arc Point X2=50 Y2=250 Z2=40 Line Start Line End X1=50 X9=50 Y1=150 Y9=150 Z1=40 Z9=40 Arc Point X8=50 Y8=50 Z8=40 Line Passing X3=150 Y3=250 Z3=40 Line Passing X7=150 Y7=50 Z7=40 Arc Point X4=250 Y4=250 Z4=40 Line Passing X5=250 Y5=150 Z5=40 Arc Point X6=250 Y6=50 Z6=40 150 X1=50 Y1=150 Z1=40 3) Enter (or point) ? Line start ? Enter 4) Menu 2 ? Numerical move ? Enter X2=50 Y2=250 Z2=40 5) Enter (or point) ? Arc Point ? Enter 6) Menu 2 ? Numerical move ? Enter X3=150 Y3=250 Z3=40 7) Enter (or Point) ? Line Passing ? Enter 8) Menu 2 ? Numerical move ? Enter X4=250 Y4=250 Z4=40 9) Enter (or Point) ? Arc Point ? Enter 10) Menu 2 ? Numerical move ? Enter X5=250 Y5=150 Z5=40 11) Enter (or Point) ? Line Passing ? Enter 12) Menu 2 ? Numerical move ? Enter X6=250 Y6=50 Z6=40 13) Enter (or Point) ? Arc Point ? Enter 14) Menu 2 ? Numerical move ? Enter X7=150 Y7=50 Z7=40 15) Enter (or Point) ? Line Passing ? Enter 16) Menu 2 ? Numerical move ? Enter X8=50 Y8=50 Z8=40 17) Enter (or Point) ? Arc Point ? Enter 151 18) Menu 2 ? Numerical move ? Enter X9=50 Y9=150 Z9=40 19) Enter (or Point) ? Line End - Enter 20) Enter (or point) ? End Program ? Enter 21) Run 152 Program 12 This program makes the dispensing robot move by drawing a free style shape. Figure B-10 Steps of program 12 Steps of the program: 1) Set up ? Line speed ? Enter ? 30 ? Enter Set up ? XY move speed ? Enter ? 50 ? Enter 2) Menu 2 ? Numerical move ? Enter X1=150 Y1=150 Z1=50 3) Enter (or point) ? Circle ? Enter Diameter ? 200 ? Enter Over angle ? 0 ? Enter Z lift select ? (2 No) ? Enter 4) Enter (or point) ? Call program ? Enter ? Program 5 ? Enter 5) Enter (or point) ? End Program ? Enter 6) Run r X1=150 Y1=150 Z1=50 153 Program 13 This program makes the dispensing robot move by drawing a free style shape and filling circular part of the shape. Figure B-11 Steps of program 13 Steps of the program: 1) Enter (or point) ? Call program ? Enter ? Program 6 ? Enter 2) Enter (or point) ? Brush area ? Enter ? Select (2 - Circle) ? Enter ? Width ? 5 ? Enter 3) Menu 2 ? Numerical move ? Enter X1=50 Y1=150 Z1=20 4) Enter (or point) ? Line start ? Enter 5) Menu 2 ? Numerical move ? Enter X2=150 Y2=150 Z2=20 6) Enter (or point) ? Line end ? Enter 7) Enter (or point) ? End Program ? Enter X1=50 Y1=150 Z1=20 154 Program 14 This program makes the dispensing robot move by drawing a free style shape and filling a part of the circular part and a part of the rectangular part of the shape. Figure B-12 Steps of program 14 Steps of the program: 1) Set up ? Line Speed ? Enter ? 50 ? Enter Set up ? XY Move Speed ? Enter ? 10 - Enter 2) Menu 2 ? Numerical move ? Enter Line Start Line End X2=0 X6=0 Y2=0 Y6=0 Z2=30 Z6=30 Line Start X7=0 Y7=0 Z7=30 Line Passing X3=0 Y3=300 Z3=30 X1=150 Y1=150 Z1=30 Line Passing X4=300 Y4=300 Z4=30 Line End X8=300 Y8=300 Z8=30 Line Start X9=75 Y9=150 Z9=30 Line Passing X5=300 Y5=0 Z5=30 Line End X10=150 Y10=150 Z10=30 155 X1=150 Y1=150 Z1=30 3) Enter (or point) ? Circle ? Enter Diameter ? 150 ? Enter Over Angle ? 0 ? Enter Z lift select ? (2 - No) - Enter 4) Menu 2 ? Numerical move ? Enter X2=0 Y2=0 Z2=30 5) Enter (or point) ? Line Start ? Enter 6) Menu 2 ? Numerical move ? Enter X3=0 Y3=300 Z3=30 7) Enter (or Point) ? Line Passing ? Enter 8) Menu 2 ? Numerical move ? Enter X4=300 Y4=300 Z4=30 9) Enter (or Point) ? Line Passing ? Enter 10) Menu 2 ? Numerical move ? Enter X5=300 Y5=0 Z5=30 11) Enter (or Point) ? Line Passing ? Enter 12) Menu 2 ? Numerical move ? Enter X6=0 Y6=0 Z6=30 13) Enter (or Point) ? Line End ? Enter 14) Enter (or Point) ? Brush Area ? Enter ? Select ? (4 ? Rect Band) ? Enter ? Width ? 5- Enter ? Band ? 50 ? Enter 15) Menu 2 ? Numerical move ? Enter 156 X7=0 Y7=0 Z7=30 16) Enter (or Point) ? Line Start ? Enter 17) Menu 2 ? Numerical move ? Enter X8=300 Y8=300 Z8=30 18) Enter (or Point) ? Line End ? Enter 19) Enter (or Point) ? Brush Area ? Enter ? Select ? (5 ? Circle Band) ? Enter ? Width ? 5 ? Enter ? Band ? 50 ? Enter 20) Menu 2 ? Numerical move ? Enter X9=75 Y9=150 Z9=30 21) Enter (or Point) ? Line Start ? Enter 22) Menu 2 ? Numerical move ? Enter X10=150 Y10=150 Z10=30 23) Enter (or Point) ? Line End ? Enter 24) Enter (or point) ? End Program ? Enter 25) Run 157 Program 15 This program makes the dispensing robot move by drawing a free style shape and filling a part of the circular part and a part of the rectangular part of the shape. Figure B-13 Steps of program 15 Steps of the program: 1) Enter (or Point) ? Call Program ? Enter ? Program 5 ? Enter 2) Set up ? Line Speed ? Enter ? 60 ? Enter Set up ? XY Move Speed ? Enter ? 40 - Enter STOP 1 Line End LineStart X5=50 X1=50 Y5=150 Y1=150 Z5=40 Z1=40 STOP 4 Line Passing X4=150 Y4=50 Z4=40 STOP 3 Line Passing X3=250 Y3=150 Z3=40 STOP 2 Line Passing X2=150 Y2=250 Z2=40 158 3) Menu 2 ? Numerical move ? Enter X1=50 Y1=150 Z1=40 4) Enter (or point) ? Line start ? Enter 5) Enter (or Point) ? Wait Point ? Enter ? 30 sec ? Enter 6) Menu 2 ? Numerical move ? Enter X2=150 Y2=250 Z2=40 7) Enter (or point) ? Line Passing ? Enter 8) Enter (or Point) ? Wait Point ? Enter ? 30 sec ? Enter 9) Menu 2 ? Numerical move ? Enter X3=250 Y3=150 Z3=40 10) Enter (or Point) ? Line Passing ? Enter 11) Enter (or Point) ? Wait Point ? Enter ? 30 sec ? Enter 12) Menu 2 ? Numerical move ? Enter X4=150 Y4=50 Z4=40 13) Enter (or Point) ? Line Passing ? Enter 14) Enter (or Point) ? Wait Point ? Enter ? 30 sec ? Enter 15) Menu 2 ? Numerical move ? Enter X5=50 Y5=150 Z5=40 16) Enter (or Point) ? Line End ? Enter 17) Enter (or point) ? End Program ? Enter 18) Run