DEVELOPMENT AND CHARACTERIZATION OF SULFONATED POLYSULFONE

MEMBRANE FOR PROTON EXCHANGE MEMBRANE FUEL CELL (PEMFC)

ROSMAWATI BT NAIM

A thesis submitted in fulfilment of the

requirements for the award of the degree of

Master of Engineering (Gas)

Faculty of Chemical and Natural Resources Engineering

Universiti Teknologi Malaysia

JULY 2004

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To my beloved husband; Zafizal bin Zolkafli, my family and my eternal friends,

Tengku Nur Radiatul Khalilah and Nur Airina Mazlan.

iv

ACKNOWLEDGEMENT

I would like to take this opportunity to express my sincere gratitude to my

research advisor, Prof. Dr. Ahmad Fauzi bin Ismail, for his encouragement, guidance and

inspiration throughout this work. I have exceedingly benefited from his vast knowledge,

lasting enthusiasm and exceptional personality. Thanks also go to my co-supervisor, Prof.

Dr. Hamdani Saidi who shares his precious time in guiding me and funding the research

project.

I would also like to acknowledge the valuable assistance of Mrs. Tan (Elemental

analysis, RRIM), Mr. Roslan (FTIR & TGA), Mr. Zainal (XRD), Mr. Ayob (SEM), Mrs.

Ambiga and Ms. Zainab (DSC) and Dr. Elias Saion (Proton conductivity, UPM). Not

forgotten En. Suhaimi bin Abdullah and Pn. Suhaila bt Sanip for their moral support and

being there whenever needed.

Of course, I greatly appreciate and cherish the friendships developed with my

former and present colleagues at Membrane Research Unit (MRU), FKKKSA who have

given me generous assistance and moral support in completing this research. Gratitude is

due to all the lecturers and technician who have given me their opinion and advice.

Without their encouragement and faith, this project might have remained just another

dream.

Lastly, thanks go to Universiti Teknologi Malaysia for financial support through

the PTP-UTM fellowship and also in providing me such good environment and facilities

for this project.

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ABSTRACT

Sulfonated polysulfone membranes with varying degree of sulfonation have been

successfully synthesized by electrophilic substitution via sulfonation process in this study.

Sulfonated dense membranes were fabricated using locally available pneumatically-

controlled casting machine. Characterizations of different degree of sulfonated

polysulfone membranes were conducted through swelling effects, ion exchange capacity

(IEC), Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimeter (DSC),

X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and proton conductivity

measurement. It was observed that an increase in the degree of sulfonation increases the

water uptake of the membranes and sulfonic acid group in the polymer membrane. From

FTIR, it was clearly confirmed the occurrence of sulfonation in the polymer structure as

the evidence of the SO3 stretching band was noticed at frequency of 1027 cm-1. It was

found from TGA that the sulfonic acid group started to decompose at 250ºC and

decomposition of the polymer main chain decreases by increasing the degree of

sulfonation. The Tg value detected in this study was increased accordingly with the

degree of sulfonation though some hindrance was found to decrease the Tg value during

the experiments. Proton conductivity measurement of sulfonated polysulfone membrane

was found to increase with operating temperature and degree of sulfonation. It was found

that at higher temperature (80ºC), SPSU10 membrane exhibits proton conductivity value

at par with that of Nafion 117 membrane. It was also observed from XRD analysis that

dimethylformamide solvent was prone to form hydrogen bonding with sulfonic groups

hence allows formation of a more regular structure which leads to an incipient crystalline

character of the material structure. SEM micrographs showed clearly the altered

microstructure of polysulfone polymer before and after the sulfonation process.

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ABSTRAK

Membran sulfonan polisulfona dengan pelbagai darjah pengsulfonan telah berjaya

diperolehi dalam ujikaji ini melalui tindakbalas penukargantian elektrofilik iaitu proses

pengsulfonan. Membran pengsulfonan padat disediakan menggunakan mesin penuangan

bersistem kawalan pneumatik. Pencirian darjah membran pengsulfonan polisulfona telah

dijalankan melalui kesan pembengkakan, kapasiti penukaran ion (IEC), analisis

gravimetrik terma (TGA), Pemeteran Kalori Pengimbasan Kebezaan (DSC), X-ray

Diffraction (XRD), Kemikroskopan Elektron Imbasan (SEM) dan keberaliran.

Diperhatikan bahawa dengan meningkatnya darjah pengsulfonan, tahap pembengkakan

dan kumpulan asid sulfonik dalam membran polimer diperolehi meningkat. Daripada

analisis Spektroskopi Infra-Merah Penukaran Fourier (FTIR), jelas terbukti bahawa

tindakbalas pengsulfonan telah berlaku pada struktur polimer dengan adanya regangan

ikatan SO3 pada frekuensi 1027 cm-1. Daripada analisis terma, didapati bahawa kumpulan

asid sulfonik mula menyusut pada suhu 250ºC dan suhu penyusutan rantaian polimer

utama menurun dengan peningkatan darjah pengsulfonan. Nilai suhu peralihan kaca (Tg)

yang diperolehi dalam ujikaji ini meningkat berkadar terus dengan darjah pengsulfonan

walaupun terdapat beberapa faktor yang mempengaruhi penurunan nilai suhu peralihan

kaca semasa eksperimen dijalankan. Didapati bahawa nilai keberaliran proton bagi

membran pengsulfonan polisulfona meningkat dengan peningkatan suhu operasi dan

darjah pengsulfonan. Pada kenaikan suhu 80ºC didapati bahawa membran SPSU10

menunjukkan nilai keberaliran proton pada tahap yang setanding dengan membran

Nafion 117. Melalui analisis Belauan Sinar-X (XRD), didapati bahawa larutan

dimetilformamida (DMF) berupaya bertindakbalas dengan kumpulan sulfonik dan

menghasilkan ikatan hidrogen dimana pembentukan ikatan ini menghasilkan struktur

yang lebih tersusun yang menjurus kepada sifat kristal pada struktur bahan. Gambar

mikrograf SEM menunjukkan perubahan struktur mikro bagi sulfonan polisulfona

sebelum dan selepas proses pengsulfonan.

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TABLE OF CONTENTS

CHAPTER TOPIC PAGE

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES xi

LIST OF FIGURES xiii

LIST OF APPENDICES xvi

CHAPTER 1 INTRODUCTION 1

1.1 Research Background 1

1.2 Problem Statement 5

1.3 Research Objectives 7

1.4 Scope of the Research 7

CHAPTER 2 LITERATURE REVIEW 8

2.1 Membrane Separation Process 8

2.2 Ion Exchange Membrane Separation 11

2.3 Fuel Cell Technology Review 13

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2.3.1 History of Fuel Cells 14

2.3.2 Type of Fuel Cells 17

2.3.2.1 Phosphoric Acid Fuel Cell 18

2.3.2.2 Molten Carbonate Fuel Cell 19

2.3.2.3 Solid Oxide Fuel Cell 20

2.3.2.4 Alkaline Fuel Cell 21

2.3.2.5 Proton Exchange Membrane Fuel Cell 22

2.3.3 Potential Application in Fuel Cells 25

2.3.4 Advantages of Fuel Cells 26

2.4 Proton Exchange Membrane Fuel Cell (PEMFC)

System 27

2.4.1 Basic reaction and structure 27

2.4.2 Membrane Electrode Assembly (MEA) 29

2.4.2.1 Electrolyte 30

2.4.2.2 Electrode 31

2.4.2.3 Gas Diffusion Layer 32

2.4.2.4 Bipolar Plates 32

2.5 Electrochemical Impedance Spectroscopy (EIS) 33

2.6 State of the Art Polymer Electrolyte Membrane

Properties 35

2.6.1 Transport Phenomena in Nafion Membrane 40

2.6.2 Water Uptake in Nafion Membrane 44

2.7 Membrane Classification in Fuel Cell 45

2.8 Sulfonation Process 46

2.8.1 Fourier Transform Infrared (FTIR)

Frequency for Sulfonated Membranes 53

2.8.2 Effects of Sulfonation on Membrane Properties 55

2.8.2.1 Membrane thermal stability 55

2.8.2.2 Ionic Conductivity 58

2.8.2.3 Water Uptake/ Swelling 61

2.8.3 Sulfonated Polysulfone 62

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2.8.4 Blend and Composite Sulfonated Polymer 64

CHAPTER 3 RESEARCH METHODOLOGY 67

3.1 Material Selection 67

3.1.1 Polysulfone 67

3.1.2 Trimethylsilyl chlorosulfonate 69

3.1.3 Sodium methoxide/ Sodium methylate 69

3.1.4 Chloroform 70

3.1.5 Dimethylformamide 71

3.1.6 Methanol 72

3.2 Experimental Stages 72

3.2.1 Sulfonation Process 73

3.2.2 Preparation of polymeric solution 76

3.2.3 Membrane Fabrication 76

3.2.4 Membrane Characterization 77

3.2.4.1 CHNOS Elemental Analysis 77

3.2.4.2 Ion Exchange Capacity (IEC) 78

3.2.4.3 Water Uptake Mesurement 78

3.2.4.4 Fourier Transform Infrared (FTIR) 79

3.2.4.5 Thermal Gravimetric Analysis (TGA) 79

3.2.4.6 Differential Scanning Calorimetry 79

3.2.4.7 X-ray Diffraction 80

3.2.4.8 Scanning Electron Microscopy 80

3.2.4.9 Proton Conductivity Measurement 80

CHAPTER 4 RESULT AND DISCUSSION 81

4.1 Sulfonation Process Condition 81

4.2 CHNOS Elemental Analysis 82

4.3 Confirmation of Sulfonation Process by FTIR Spectra 85

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4.4 Effects of Sulfonation on Membrane Properties 89

4.4.1 Water uptake and Ion Exchange Capacity (IEC) 89

4.4.2 Thermal stability 91

4.4.3 Proton/ Ionic conductivity 96

4.4.4 Membrane microsructure 101

CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS 104

5.1 Conclusions 107

5.2 Recommendations 109

REFERENCES 112

Appendices A- P 127-135

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LIST OF TABLES

TABLE NO. TITLE PAGE

1.1 U.S. sales of fuel cell by type, 2000-2005 ($ Millions) 3

2.1 Membrane separations and materials 9

2.2 Different fuel cell technologies, main characteristics,

intended applications and main developers 24

2.3 Properties of Nafion membrane 37

2.4 Membrane ionic conductivities and conductances 38

2.5 Ionomer membrane in membrane fuel cell 45

2.6 Some of significant sulfonated polymer being studied

by various researchers 48

2.7 The standard frequency for sulfonic group. 53

2.8 A typical frequency value of sulfonic group obtained by

various researchers. 54

2.9 Ion exchange capacity (IEC) value obtained by researchers in

fuel cell R&D. 60

2.10 Proton conductivity value of other sulfonated membranes

obtained by researchers in fuel cell R&D. 60-61

3.1 Properties of polysulfone 68

3.2 Properties of trimethylsilyl chlorosulfonate (TMSCS) 69

3.3 Properties of sodium methylate/ methoxide 70

3.4 Properties of chloroform 70

3.5 Properties of dimethylformamide (DMF) 71

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4.1 Sulfonation process condition 82

4.2 Elemental analysis for sulfonated polysulfone membrane 83

4.3 Infrared assignments of polysulfone and its sulfonated derivative 87

4.4 Influence of the degree of sulfonation on the water uptake 90

4.5 Water uptake of sulfonated polysulfone membrane and ion

exchange capacity (IEC) values 90

4.6 Glass transition (Tg) value of sulfonated polysulfone

membrane at different heating rate. 94

4.7 Area resistivity (Rarea) of SPSU and Nafion 117 membranes 97

4.8 Ionic conductivity of SPSU and Nafion 117 membranes 97

4.9 The activation energy value of SPSU and Nafion 117 membranes 101

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LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.1 U.S. sales of fuel cell by type, 2000-2005 3

2.1 Classification of ion exchange membrane 11

2.2 The cationic membrane with fixed carboxylic acid groups

is permeable to cations such as sodium ions but is impermeable

to anions such as chloride. 12

2.3 Proton Exchange membrane Fuel Cell 14

2.4 Grove’s ‘gas battery’ (1839) produced a voltage of about 1 volt 15

2.5 The potential field of application in fuel cell technology. 25

2.6 PEMFC basic principle 27

2.7 Membrane Electrode Single Cell Stack Assembly 29

2.8 The Nyquist plot 34

2.9 Structure of Nafion membrane 36

2.10 Dais membrane polymeric structure 39

2.11 Schematic of fuel cell illustrating modes of water transport

through and uptake into fuel cell 41

2.12 Cluster network model 41

2.13 Modification of cluster network model 43

2.14 Ion transfer inside Nafion polymer backbone 44

2.15 Basic principle of aromatic electrophilic substitution 47

2.16 The structure of PSU with up to two sulfonic acid groups

per monomer unit 63

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3.1 Chemical structure of polysulfone 67

3.2 Chemical structure of trimethysilyl chlorosulfonate 69

3.3 Chemical structure of dimethylformamide 71

3.4 The experimental workflow of research study 72

3.5 Sulfonation process sequence 74

3.6 Sulfonation reaction process for sulfonated polysulfone (SPSU) 75

3.7 Sulfonation and polymeric solution apparatus 76

3.8 Pneumatically–controlled casting machine 77

4.1 FTIR spectrum of PSU and SPSU membranes 86

4.2 FTIR spectrum of O-H stretching for SPSU membrane 88

4.3 SO3H concentration of SPSU sample as a function of

sulfonation degree and water content 91

4.4 TGA spectrum for polysulfone and sulfonated polysulfone

samples 92

4.5 DSC spectrum of PSU and SPSU membranes at

heating rate 5ºC/min 95

4.6 DSC spectrum of PSU and SPSU membranes at

heating rate 10ºC/min 95

4.7 Proton conductivity of sulfonated PSU membranes as a function

of degree of sulfonation at different operating temperatures 98

4.8 Area resistance of sulfonated PSU membranes as a function

of degree of sulfonation. 98

4.9 Conductivity of SPSU membrane and Nafion 117 membrane as

a function of operating temperature (25 C – 80 C). 100

4.10 The Arrhenius plot of proton conductivity as a function of

temperature for SPSU membranes and Nafion 117 membrane 100

4.11 X-ray diffraction spectrums of polysulfone and sulfonated

polysulfone membrane 102

4.12 Scanning electron microscopy pictures of surface topology of

the membranes (a) PSU, (b) SPSU5, (c) SPSU6, (d) SPSU9,

(e) SPSU10 and (f) Nafion 117 104

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4.13 Scanning electron microscopy pictures of cross section of PSU

and SPSU membranes at different magnification level (a) 600

and (b) 1200 105

4.14 Scanning electron microscopy pictures of cross section of SPSU

and Nafion 117 membranes at different magnification level

(a) 600 and (b) 1200 106

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LIST OF APPENDICES

APPENDIX TITLE PAGE

A PSU at heating rate 5ºC /min 127

B SPSU5 at heating rate 5ºC /min 127

C SPSU6 at heating rate 5ºC /min 128

D SPSU9 at heating rate 5ºC /min 128

E SPSU10 at heating rate 5ºC /min 129

F PSU at heating rate 10ºC /min 129

G SPSU5 at heating rate 10ºC /min 130

H SPSU6 at heating rate 10ºC /min 130

I SPSU9 at heating rate 10ºC /min 131

J SPSU10 at heating rate 10ºC /min 131

K The Nyquist plot for SPSU5 membrane at various

operating temperature (25 C – 80 C) 132

L The Nyquist plot for SPSU6 membrane at various

operating temperature (25 C – 80 C) 132

M The Nyquist plot for SPSU9 membrane at various

operating temperature (25 C – 80 C) 133

N The Nyquist plot for SPSU10 membrane at various

operating temperature (25 C – 80 C) 133

O The Nyquist plot for Nafion 117 membrane at various

operating temperature (25 C – 80 C) 134

P Calculation of the activation energy (Ea) 135

CHAPTER 1

INTRODUCTION

1.1 Research Background

Energy consumption has increased drastically in the last century due to the

increase of human population and activities. World’s dependent on hydrocarbon

fuel to create power has proven to be the major source for energy production.

Nevertheless, high contribution of dangerous toxic and effluent release during the

process cause hazardous threat to the environment and human life. This

phenomenon has seriously driven research into a new modern technology

producing clean energy without harnessing the environment as far as clean fuel is

concerned. Fuel cell is the most efficient technology for present and future

upcoming life as it shows excellent performance in term of its zero emission

contaminate byproduct, high efficiency, flexibility, processability and durability.

Fuel cells are the latest promising energy producers for the future

century. Countries like United States, United Kingdom, Japan and Canada are

currently in the race for the reality makeover of fuel cell technology in multiple

fields especially in transportation, stationary power and micro electronic devices.

In addition, fuel cell research activities in Asian region especially in Japan, China

and Taiwan (Lee et al., 2002) are now accelerating, as they are in progress to

demonstrate the fuel cell bus and scooters for future application in the region.

2

Malaysia as one of the rapid emergence countries has also embarked into

fuel cell technology since 1998 under Intensify Research in Priority Area (IRPA)

grant, which focusing on the Proton Exchange Membrane Fuel Cell for

transportation application. This project was the pioneered project in Malaysia, and

the second phase of the project is now underway to further develop the upcoming

technology in the region. From this effort, Malaysia has emerged to be one of the

possible contributors to this viable technology and probably will be ready to joint

others as an active participant in this future technology.

Concern with the environment and earth limited resources has led to

introduction of commercial application of fuel cells, mainly in the field of ground

transport and distributed power generation. General Motors, Daimler Chrysler,

Ford, Ballard, Honda, Toyota and other big companies in the world are seriously

concentrating on polymer electrolyte membrane fuel cell (PEMFC) into car and

buses and several prototype has been demonstrated to verify the performance and

to upgrade the current performance of fuel cell system. Meanwhile for high

capacity power generation, Solid Oxide Fuel Cell (SOFC) has made their marked

success in the fuel cell field as they have been verified to achieve high performance

and efficiency in high capacity grid power supply and distributed generation

(Casanova and Veyo, 2001).

According to a study performed by Business Communications Co., Inc.

(US) (www.bccresearch.com), the fuel cell market is estimated at about $218

million in 2000. With commercialization of most of the fuel cell technologies

rapidly falling in place, this market is expected to have a steep increase to an

estimated $2.4 billion by 2005, an AAGR (average annual growth rate) of more

than 61.7%. With the technology’s extensive use in the vehicle market, proton

exchange membrane fuel cell sales have become the dominant version in the

market, bringing 2000 sales of $104 million up to $1.6 billion by 2005. Research

on the fuel cells R&D and intellectual property (IP) studies have found that

PEMFC was the highest amount for patent disclosure in fuel cell field and

membrane was the most area being studied in PEMFC. This suggests that

3

fundamental research is still playing a critical role in fuel cell development, even

while much of the industrial emphasis is on commercialization and manufacturing

processes (Barrett, 2002).

Table 1.1: U.S. sales of fuel cell by type, 2000-2005 ($ Millions)

2000 2005 AAGR % 2000-2005

Proton exchange membrane 104.0 1640.0 73.6

Solid Oxide 54.0 260.0 36.9

Molten carbonate 25.0 450.0 78.3

Phosphoric acid 20.4 35.6 11.8

Alkaline 15.0 30.0 14.9

Total 218.4 2415.6 61.7

Figure 1.1: U.S. sales of fuel cell by type, 2000-2005

4

Fuel cells are distinguished primarily by the type of electrolyte and the

operating temperature used. There are five types of fuel cell, which include:

Alkaline Fuel Cell (AFC), Proton Exchange Membrane Fuel Cell (PEMFC),

Phosphoric Acid Fuel Cell (PAFC), Molten Carbonate Fuel Cell (MCFC) and Solid

Oxide Fuel Cell (SOFC). However, Proton Exchange Membrane Fuel Cell

(PEMFC) has received numerous attentions from world automotive producers due

to its high power density and high flexibility in operation.

Membranes used in fuel cell applications are basically a proton exchange

membrane type that is capable of transporting the proton within the membrane

structure. The proton exchange membrane is a solid, organic polymer usually poly

(perflourosulfonic acid) which was used as an electrolyte in Proton Exchange

Membrane Fuel Cell (PEMFC) (which also can be known as Polymer Electrolyte

Membrane Fuel Cell). The existence of PEMFC has been long acknowledged back

in 1960s but it did not perform reliably in space fuel cell projects due to the high

cost of the membranes and expensive auxiliary system for heat and water removal.

A surprising technology turn over occurred in 1990’s when PEMFC appeared as

the most attractive object for development especially in fleet and vehicles

application. This is driven by significant high power densities obtained as a result

of new development of membrane types in recent years (Kordesch and Simadar,

1996; Carretta et al., 2001).

Although the US General Electric Company (GE) initiated the development

of PEMFC in 1950s, it was the introduction of Nafion by DuPont that ensured

continuing interest in these systems. Initially Nafion was manufactured for

membrane cells used in the production of chlorine (chlor-alkali cells). By 1990,

Ballard had overcome many of the engineering problems associated with PEMFC

systems and this had stimulated many groups in the United States and Japan to

improve the properties of the original Nafion material (Steele and Heinzel, 2001).

The material generally used up to now, a sulfonated fluoropolymer first

developed by US space scientists in the early 1970s, is effective but expensive.

5

Sulfonate groups, introduced by complexing the perfluorinated polymer with

sulfonic acid, turned out to be good ionic conductors, particularly when associated

with water molecules. Dupont has long dominated the market with its NafionTM

brand, though Asahi Chemicals and others have introduced similar thermoplastic

copolymers subsequently. These materials conduct well, resist attack by acids,

bases and oxidants and have good mechanical properties, which are retained over

time. On the downside, they are sensitive to contaminants and methanol, upset by

over or under-hydration, lose performance in prolonged operation above about

80˚C, and cost hundreds of dollars per square meter.

Research groups have sought to improve the existing material or find

alternative polymer that possess similar performance as standard Nafion. For low

cost, however, a more radical approach is needed and the search has been on for

alternative polymer backbones, including ‘disposable’ hydracarbon. One possibility

to introduce the sulfonate group into the polymer structure is by sulfonation. This is

due to its simple processing and reaction, which depends mainly on the properties

of the sulfonating agent and polymer base unit.

In order to achieve higher performance and efficient system, PEMFC needs

to have a good and stable membrane operating at desired temperature and pressure.

Thus, it is essential to identify the economical and effective ways to produce and

manufacture the ideal membrane with desirable properties.

1.2 Problem Statement

As mentioned above, the development of fuel cells was driven by the space

industry in the 1960s. At that time the PEM materials were crosslinked,

sulphonated polystyrenes. Sulphonated fluorocarbon membranes such as Nafion

TM, which was introduced by DuPont in the early 1970s, then superseded

sulfonate polystyrenes as the preferred membrane materials for PEMFC. Since

6

then, Nafion remains the industry standard until today, but this material has the

downside of being very costly to produce and require heat, high pressure and a high

level of hydration to perform effectively (Johnstone, 2001).

The development of low cost membranes materials for fuel cells has gained

wide attention and turned to be the most challenging in the field of membrane

community in the last few years. Many hydrocarbon polymers such as

polysulfones, polyethersulfones, polyetherketones, polyether etherketones,

polyimides, polybenzimidazole, polyoxadiazole, polyphosphazenes have been

claimed to be possible substitutes for perflourinated ionomers provided that a

charge group (sulfonic) is introduced into the structural unit (Kopitzke, 1999;

Lufrano et al., 2000; 2001; Hogarth and Glipa, 2001). Among the aforementioned

polymers, the polysulfone is considered to be the most interesting polymer due to

its low cost, commercial availability and ease of processing. Though this study on

sulfonated polysulfone might not be the first in the world but however it can be

considered as a landmark for the research in fuel cell membrane in the Asian region

by using sulfonation process.

Based on the latest purchase pricing of the Nafion membrane material

(which is PTFE polymer) and polysulfone polymer (Amoco Udel P1700), it was

found that 1 kg of PTFE flouro polymer worth RM 690 meanwhile polysulfone

polymer price is RM 198 for 1 kg of polymer. It was clearly seen that the price of

PTFE polymer is five times higher than the of polysulfone polymer. If the

production and manufacturing cost of modifying PTFE membrane were to be

included in the comparison with modifying polysulfone polymer, it is expected that

this gap of difference would be much more higher. Therefore, in order to minimize

the overall cost of PEMFC system; search on the cost-effective polymer is very

crucial in PEMFC research and development. Thus the main drivers of research

into fuel cell membrane materials is the development of cost-effective material that

can operate at low pressure and high temperature conditions and possess the

performance at par with Nafion (Wnek et al., 1999; Marsh, 2001).

7

1.3 Research Objectives

As described in the research background and problem statement section,

therefore the objectives of this research are:

(a) to develop and characterize the sulfonated polysulfone membrane for

polymer electrolyte membrane fuel cell (PEMFC) application.

(b) to study and compare the performance of SPSU membrane with that state of

the art Nafion membrane.

1.4 Scope of the Research

In order to accomplish the set objectives, the following scope of works has

been drawn.

(a) Performing the sulfonation reaction at ambient temperature.

(b) Development of a sulfonated polymer solution making and fabrication of

sulfonated dense membranes.

(c) Physical and chemical characterization of the produced sulfonated

membranes.

(d) Studies of effects of sulfonation process on polysulfone polymer by

swelling (water uptake), thermal stability, proton conductivity measurement

and membrane microstructure.