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SUPERVISOR DECLARATION
" I declare that I have read this thesis and in my opinion this report is sufficient in terms
of scope and qua I ity for the award of the degree of Bachelor of Mechanical Engineering
(Structure & Materials)"
Signature
Supervisor
Date
: ...... ~ .............. . : DR. MOHD ZULKEFLI BIN SELA MAT
: 28 JUNE 2013
DR. MOHD ZULKEFLI BIN SELAMAT Pensyarah Kanan
Fakulti Kejuruteraan Mekanikal Universiti Teknikal Malaysia Melakl
© Universiti Teknikal Malaysia Melaka
THE EFFECT OF STAINLESS STEEL ON THE PROPERTIES OF GRAPHITE
POL YPROPYLENE COMPOSITE FOR BIPOLAR PLATE
FAIRUZ F AZILLAH BINTI SHUIIlMI
This report is submitted to Faculty of Mechanical Engineering as a
requirements to get award of
Degree of Mechanical Engineering ( Structure & Material)
Faculty of Mechanical Engineering
Universiti Teknikal Malaysia Melaka
JUNE2013
© Universiti Teknikal Malaysia Melaka
DECLARATION
"I hereby declare that the work in this report is my own except for swnmaries
and quotations which have been duly acknowledgment."
Signature
Author
Date
: ......... ~ .. : .... . ....... . ..... .
: F AIRUZ F AZILLAH BINTI SHUHIMI
: 28 JUNE 2013
© Universiti Teknikal Malaysia Melaka
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ACKNOWLEDGEMENT
Assalamualaikum w.b.t
Very grateful to Allah S.W.T because of Allah' s endowment, I can execute this
Final Year Project 1 report at the right time. I would like to take this opportunity to
express my deepest heartfelt and thank to all those who have guided and supported me
during my Final Year Project either directly or indirectly.
First of all I would like to thank GOD for this opportunity, and to my parents and
siblings for their love and support. I would like to thank Dr. Mohd Zulkefli bin Selamat
as supervisor, Mr Mohd Syakir bin Ahmad as him assistant researcher and all lecturers
with respect to their direction, guidance, assistance and unselfish support. Special thanks
to my nice appreciation to panels during presentation, Dr. Mohd Fadzli bin Abdollah,
Dr.Olawale Friday, Mr. Omar bin Bapokutty for their valuable advice and nice support
on behalf of me to satisfy this project. Also thanks to all the technicians and staffs from
Department of Mechanical Engineering for their instruction, continuous support and
supervision.
Finally, I would also like to thank those individuals who have contribute to the
success of my training and whose name are not mentioned. They may be my family
members, other FKM staff, friends, and individuals I meet during project progress.
Thank you for all the support and contribution for the success of my Final Year Project
at Universiti Teknikal Malaysia Melaka.
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ABSTRACT
Over the past decade, rapid progress has been made in the understanding and
development of Conductive Polymer Composites (CPC) as conducting materials. This
project is aimed to study the effects of stainless steel (St) loading on the electrical and
mechanical properties of Graphite (G)/ Stainless steel (St)/ polypropylene (PP)
composite of bipolar plates for polymer electrolyte membrane fuel cells (PEMFC). St is
selected as second filler because it offers good electrical conductivity, high bulk thermal
conductivities, good corrosion resistance and constant particle shape. The analysis of the
G/St/PP composites ratio and the properties of G, St and PP together with the impact of
Graphite (G) as a main filler and Stainless Steel (St) as second filler whereas
polypropylene (PP) as a binder has been carry out. The impact of fillers on the
composite properties was evaluated as well as the ratio of the weight percentage (wt%)
of the composite with 80% for multi-filler material and 20% binder material. The St wt
% is vary from 5 wt % up to 30 wt % of total wt % of multi-filler materials. After
formation of composite through compression molding, the effects of St in G/St/PP
composite have been determined through various tests such as electrical conductivity,
flexure strength, density and hardness before can be used as composition of G/St/PP
composite for bipolar plate. The result showed the analysis for Flexural Strength, Bulk
Density and Shore Hardness meet the required characteristics of bipolar plate as in the
Department of Energy (DOE). But for electrical conductivity, the results showed a very
slight increase which is less than 1 OOS/cm.
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ABSTRAK
Lebih sedekad yang lalu, kemajuan pesat telah dibuat dalam memahami dan
pembangunan konduktif Polimer Komposit (CPC) yang mengendalikan bahan-bahan.
Projek ini bertujuan untuk mengkaji kesan daripada keluli tahan karat (St) pada sifat
sifat elektrik dan mekanikal Grafit (G) I keluli tahan karat (St) I polipropilena (PP)
komposit plat dwikutub bagi polimer elektrolit sel bahan api membran. St dipilih sebagai
pengisi kedua kerana ia menawarkan kekonduksian elektrik yang baik, konduktiviti haba
yang tinggi, ketahanan kakisan yang baik dan bentuk zarah yang berterusan. Analisis
nisbah komposit G I St I PP dan sifat-sifat G, St PP dan bersama-sama dengan kesan
Grafit (G) sebagai pengisi utama dan keluli tahan karat (St) sebagai pengisi kedua
manakala polipropilena (PP) sebagai pengikat telah menjalankan. Kesan pengisi pada
sifat-sifat komposit telah dinilai serta nisbah peratusan berat (% berat) dengan 80%
untuk bahan pelbagai pengisi dan 20% bahan pengikat. Berat St°/o yang berbeza-beza
dari 5% sehingga 30% daripada jumlah berat bahan pelbagai pengisi. Selepas
pembentukan komposit melalui pengacuan mampatan, kesan St dalam G I St I PP
komposit telah ditentukan melalui pelbagai ujian seperti kekonduksian elektrik,
kekuatan lenturan, kepadatan dan kekerasan sebelum boleh digunakan sebagai
komposisi G I St I PP gubahan plat dwikutub. Hasilnya menunjukkan analisis untuk
kekuatan lenturan, ketumpatan dan kekerasan memenuhi ciri-ciri yang diperlukan plat
dwikutub oleh Jabatan Tenaga. Tetapi bagi kekonduksian elektrik, keputusan
menunjukkan peningkatan yang sangat sedikit iaitu kurang daripada 1 OOS/cm.
© Universiti Teknikal Malaysia Melaka
CHAPTER
CHAPTER I
CONTENT
TITLE
TITLE PAGE
DECLARATION
ACKNOWLEDGEMENT
ABSTRACT
ABSTRAK
CONTENT
LIST OF FIGURE
LIST OF TABLE
LIST OF APPENDIX
LIST OF SYMBOLS
LIST OF ABBREVIATION
INTRODUCTION
1.1 BACKGROUND
1.1.1 Proton exchange membrane
fuel cell
1. I .1.1 Polymer Electrolyte
Membrane Fuel Cell
PAGES
11
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vi-ix
X-Xl
XU
xiii
xiv
xv
1
3
Operation 4
1.1.2 Component of PEMFC 5
1.1 .2.1 Membrane Electrolyte
Assembly (MEA) 7
© Universiti Teknikal Malaysia Melaka
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CHAPTER2
1.2
1.3
1.4
1.1.2.2 Catalysts
OBJECTIVE
SCOPE OF STUDY
PROBLEM STATEMENT
LITERATURE REVIEW
2.1 CONDUCTIVE POLYMER
COMPOSITES
2.1.1 Conductively Filled Polymers
2.1.2 Polymers Filled with Conductive
Solids
2.2 BIPOLAR PLATE MATERIALS
2.2.1 Filler
2.2.1. l Graphite
2.2.1.2Stainless Steel
2.2.2 Binder
2.2.2.1 Polypropylene
2.3 FABRICATION OF BIPOLAR PLATE
2.3.1 Injection Molding
2.3.1.1 Equipment
2.3.1.2 Power Requirements
2.3.2 Compression Molding
2.3.2.1 Basic Process of
Compression Molqing
2.3.2.2 Advantages
2.3.2.3 Disadvantage
2.4 TESTING METHOD
2.4.1 Electrical Properties
2.4.2 Mechanical Properties
© Universiti Teknikal Malaysia Melaka
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9
9
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11
12
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19
23
23
25
25
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26
27
27
28
28
29
29
30
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CHAPTER3 METHODOLOGY
3.1 CHARACTERIZATION OF
RAW MA TERI.AL 33
3.2 PRE-MIXING 35
3.3 MELT COMPOUNDING 36
3.4 CRUSH AND PULVERIZE 37
3.5 COMPRESSION MOLDING 38
3.6 TESTING
3.6.1 Electrical Properties 41
3.6.2 Mechanical Properties
3.6.2.1 Flexural Testing 42
3.6.2.2 Bulk Density Testing 43
3.6.2.3 Shore Hardness Testing 43
CHAPTER4 RESULT AND ANALYSIS
4.1 ELECTRICAL CONDUCTIVITY
TEST RESULT 44
4.1.1 Determination of Electrical
Conductivity 45
4.2 FLEXURAL TEST 47
4.3 BULK DENSITY 48
4.4 SHORE HARDNESS 49
CHAPTERS DISCUSSION
5.1 DISCUSSION OF RESULT
5.1.1 Electrical Conductivity Testing 51
5.1.2 Flexural Testing 52
5.1.3 Bulk Density Testing 52
5.1.4 Shore Hardness Testing 53
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5.2 DISCUSSION OF PROBLEM
ENCOUNTERED
5.2.1 Materials flows out of the mold
5.2.2 Material attached to the mold
5.2.3 Mold plate loose
5.2.4 Surface of sample not uniform
and broken
5.3 SOLUTIONS
CHAPTER6 CONCLUSION AND RECOMMENDATION
6.1 CONCLUSION
6.2 RECOMMENDATION
REFERENCES
BIBLIOGRAPHY
APPENDIX
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LIST OF FIGURE
BIL TITLE PAGE
Figure I.I Fuel cell 2
Figure I.2 Polymer Electrolyte Membrane Fuel Cell (PEMFC) 3
Figure I.3 Operation of PEMFC 4
Figure I.4 The illustration of components of PEMFC 5
Figure I.5 Bipolar Plates 6
Figure 2.I Dependence of composite conductivity on the volume I2
fraction of conductive fillers
Figure 2.2 Schematic representation of conductive particles dispersed 13
in a polymer matrix at different particle volume fractions
Figure 2.3 Classification of materials for BPs used in PEM fuel cells I4
Figure 2.4 Graphite Specimen I6
Figure 2.5 Graphite Unit Cell I7
Figure 2.6 Stainless steel AISI 3I6 (Fe/CrI8/NilO/Mo3) 20
Figure 2.7 Polypropylene 23
Figure 2.8 Chemical structures for polypropylene 23
Figure 2.9 Injection Molding Machine 25
Figure 2.IO Jandel Four Point Probe 29
Figure 2.I I Zwick Shore hardness tester and flexural testing machine 30
Figure 2.I2 Density Meter Tester 30
Figure 3.I Flow Chart Methodology 32
Figure 3.2 Powder of material (a) G, (b) St and (c) PP 33
© Universiti Teknikal Malaysia Melaka
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Figure 3.3 Measured the weight of graphite and stainless 34
steel due the percentage
Figure 3.4 Ball Mill machine 35
Figure 3.5 Steel Ball 35
Figure 3.6 Measure the weight of St/G and PP 36
Figure 3.7 Internal Mixer Machine 36
Figure 3.8 Outcomes from Internal Mixer Machine (St/GIPP) 37
Figure 3.9 Crusher machine 37
Figure 3.10 Outcomes of crusher process 37
Figure 3.11 Centrifugal Mill machine 38
Figure 3.12 Outcomes of pulverize process 38
Figure 3.13 Four-Point Probe Tester 41
Figure 3.14 Cutter machine 42
Figure 3.15 Standard sizes for Flexural 42
Figure 3.16 Three Point Flexural Test 42
Figure 3.17 Setting the sample to the supporting span 42
Figure 3.18 Electronic Densimeter 43
Figure 3.19 Standard size for density test 43
Figure 3.20 Digital Shore Hardness 43
Figure 4.1 Graph of conductivity versus St wt% 45
Figure 4.2 Graph of flexural strength versus St wt% 47
Figure 4.3 Graph of Density versus St wt.% 48
Figure 4.4 Graph of shore hardness versus St wt% 49
Figure 5.1 Materials flow out of the mold 54
Figure 5.2 Material attached to the mold 54
Figure 5.3 Mold plate loose 55
Figure 5.4 Surface of sample broken 55
Figure 5.5 Mold plate sprayed with lubricant oil 56
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LIST OFT ABLE
BIL TITLE PAGE
Table 2.1 Principal property of filler 16
Table 2.2 Composition ranges for 316L stainless steel 22
Table 2.3 Mechanical properties of 316L stainless steel 22
Table 2.4 Typical physical properties for 316L grade
stainless steels 22
Table 2.5 Properties of polypropylene 24
Table 2.6 The power requirement of injection molding by 26
different material
Table 3.1 Raw material properties of G/St/PP 33
Table 3.2 Composition based on weight percentages 34
Table 4.1 Average result for Conductivity of St/GIPP 45
Table 4.2 Data from top and bottom of composite 20% St 45
Table 4.3 Average result for Flexural Strength of St/GIPP 47
Table 4.4 Bulk Density of St/GIPP 48
Table 4.5 Shore hardness St/GIPP 48
Table 5.1 U.S Department of Energy (US DOE) 51
© Universiti Teknikal Malaysia Melaka
BIL
A
B
c D
E
F
LIST OF APPENDIX
TITLE
FLOW CHART OF STUDY
GANTT CHART FINAL YEAR PROJECT 1 & 2
ASTM C611 ELECTRICAL RESISTIVITY
ASTM D790-03 FLEXURAL TEST
ASTM C559-90 BULK DENSITY
ASTM C886-98 HARDNESS
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LIST OF SYMBOL
PEMFC = Proton Exchange Membrane Fuel Cell I Polymer Electrolyte
Membrane Fuel Cell
PEM = Polymer Electrolyte Membrane
BPs = Bipolar Plate
DC = Direct Current
H20 =Hydrogen
02 =Oxygen
MEA = Membrane Electrolyte Assembly
G =Graphite
St = Stainless Steel
pp = Polypropylene
PPS = Polyphenylene sulfide
PVDF = Polyvinylidene fluoride
CPCs = Conductive Polymer Composites
IP Cs = Inherently Conducting Polymers
SP Es = Solid Polymer Electrolytes
Cr = Chromium
Ni =Nickel
Mo = Molybdenum
LDPE = Low-Density Polyethylene
HDPE = High-Density Polyethylene
MFR = Melt Flow Rate
MFI = Melt Flow Index
DOE =US-Department of Energy
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Wt.%
Siem
MP a
Cm
µA
g/cm3
LIST OF ABBREVIATION
= Weight Percentage
= Siemens/centimeter
= Mega Pascal
= centimeter
= micron Ampere
= gram/centimeter3
W ·m- = Watt per metre
µA cm/\ (-2) =Micro ampere(s) per square centimeter
µm
nm
ncm
E
mK
oc
= micrometer
=nanometer
= ohm-centimeter
=Young's Modulus
= milli Kelvin
= Degree Celsius
© Universiti Teknikal Malaysia Melaka
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1
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND
One of the maJor factors limiting fuel cell commercialization is the
development of bipolar plates, which are one of PEMFC's key components. Several
types of materials are currently used in bipolar plates, including non-porous graphite
plates, metallic plates with or without coating and a number of composite plates .
The bipolar plate is one of the most important components in a PEM fuel cell.
A polymer composite bipolar plate possessing high strength and high stiffness has been
developed by making use of carbon fiber network in a specific form as the filler
component. The bipolar plates are in weight and volume the major part of PEM fuel cell
stack, and also a significant effect to the stack cost.
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Figure 1.1: Fuel cell
So far, many different materials for bipolar plates have been investigated and an
alternative solution consists in polymer composite that combine the process ability and
mechanical properties of the polymeric phase and the conductivity of the carbon fillers.
Both thermo-set resins and thermoplastics were considered and combined to many
different carbon fillers. [ 1]
The interests and limitations of these formulations are presented in terms of
process ability and most relevant properties. A composite material is made by combining
two or more materials to give a unique combination of improved properties, such that
each component retains its physical identity.
In order to improve their commercial liability, many scientific and
technological efforts are being performed on fuel cell systems. On the technical point of
view, bipolar plates should fulfill functional challenges besides ensuring the mechanical
strength of the stack. As a result an optimal material for bipolar plate application should
present an unusual balance of properties, essentially high electrical conductivity and
good mechanical strength.
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1.1.1 Proton exchange membrane fuel cell
Proton exchange membrane fuel cell (PEMFC), also known as polymer
electrolyte membrane (PEM) fuel cells are a type of fuel cell being developed for
transport applications as well as for stationary fuel cell applications and portable fuel
cell applications. Their distinguishing features include lower temperature/pressure
ranges (50 to I 00 °C) and a special polymer electrolyte membrane.
PEMFC are electrochemical devices that convert the chemical energy of
reactants (a fuel and an oxidant) directly to electrical energy in the form of low voltage
direct current (DC) electricity and heat. They have been receiving significant attention
due to their high power density, energy efficiency, and environmentally friendly
characteristics. [2]
Power
llcat
End-plate gos and cooling manifold
Bipolar now-rlate interconnect
--- Membrane l:leclrol)~C sscmbl} tMEA)
Figure 1.2: Polymer Electrolyte Membrane Fuel Cell (PEMFC) [7]
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1.1.1 .1 Polymer Electrolyte Membrane Fuel Cell Operation
I. Pure hydrogen constantly flows from a simple cylinder containing
compressed hydrogen into the fuel cell and onto the anode it is then split
into hydrogen ions and electrons.
2. The electrons cannot pass through the electrolyte therefore ; they pass
through the external circuit creating an electric charge.
3. The electrolyte is sandwiched between the anode and cathode, which 1s
permeable to protons but does not conduct electrons. Hydrogen ions
(protons) permeate across the electrolyte to the cathode. Electrons flow
through an external circuit and provide power.
4. Oxygen is fed into the fuel cell onto the cathode (positive electrode). The
cathode combines electrons, protons and oxygen to form the by product
which is water. The water then leaves the cell . This is a continuous process
so as hydrogen and oxygen is supplied. [3]
.-.-- Ol (Oxygen) from Air
HHt(8S"C) Watu or Air Cool•d
Flow Fi•ld Plate
~----- Gas Diffusion Elec:tro<H (Cathode)
------ Cit.al~!
Figure 1.3: Operation of PEMFC [4]
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1.1.2 Component of PEMFC
The components of PEMFC are bipolar plates, electrolyte membrane with
anode and cathode(MEA) and catalyst.
Bipolar Plate
Cita,yst MEA . catalyst
Bipolir Plit'
Figure 1.4: The illustration of components of PEMFC
1.1.2.1 Bipolar Plate
Bipolar plates are responsible for collecting and transporting electrons from the
anode and cathode, as well as, connecting individual fuel cells in series to form a fuel
cell stack of the required voltage. They are also responsible, for providing thermal
conduction to help regulate fuel cell temperature and removing heat from the electrodes,
delivering fuel gas and air to the membrane electrode assembly (MEA), and carrying
exhaust gas and product water away from the MEA.
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Figure 1.5: Bipolar Plate [5]
In polymer electrolyte membrane fuel cell (PEMFC) design, bipolar plate should require
as follows [6]:The requirement also the target of DOE requirement for bipolar pate.
a. Good electrical conductivity (> 100 S cm/\(-1) bulk conductivity)
b. High Shore Hardness (>40)
c. Good bulk density (- 1.85 g cm/\(-3))
d . Good flexural strength (>25 MPa)
e. High tensile strength (>41 MPa)
f. Low permeability for hydrogen (<2x [ 10 ] /\(-6) cm/\3)
g. High thermal conductivity(> I 0 W cm/\(-1 ))
h. High chemical and corrosion resistance (< I µA cm/\(-2))
1. Low surface contact resistance
J. Mechanical stability toward compression forces
k. Low-cost material being process-able with mass production techniques
I. Low weight and volume
m. Recyclable materials.
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1.1.2.2 Membrane Electrolyte Assembly (MEA)
A key component of a PEM fuel cell is the Membrane Electrolyte Assembly or
MEA. The MEA consists of two electrodes, the anode and the cathode. These are porous
carbon electrodes, which are each coated on one side with a low amount of platinum
catalyst and separated by a proton exchange membrane (PEM). The PEM is the
electrolyte in this assembly. It is a thin sheet that is only pe1meable for protons and
water. It must allow hydrogen protons to pass through but prohibit the passage of
electrons and gases. [8]
1. Anode - The anode, the negative side of the fuel cell , has several jobs . It
conducts the electrons that are freed from the hydrogen molecules so they can
be used in an external circuit. Channels etched into the anode disperse the
hydrogen gas equally over the surface of the catalyst.
2. Cathode - The cathode, the positive side of the fuel cell , also contains channels
that dist1ibute the oxygen to the surface of the catalyst. It conducts the electrons
back from the external circuit to the catalyst, where they can recombine with
the hydrogen ions and oxygen to forn1 water.
3. Polymer electro lyte membrane - The polymer electrolyte membrane (PEM)-a
specially treated material that looks something like ordinary kitchen plastic
wrap- conducts only positively charged ions and blocks the electrons. The
PEM is the key to the fuel cell technology; it must pe1mit on ly the necessary
ions to pass between the anode and cathode. Other substances passing through
the electrolyte would dismpt the chemical reaction.[9]
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1.1.2.3 Catalysts
The PEMFC catalysts are the reaction sites where the electrochemical reactions
occur. They are usually very thinly coated onto carbon paper or cloth.The catalyst is a
porous platinum coating on the anode which speeds up the reaction.
The platinum coating prevents the formation of hydrogen peroxide which 1s
highly corrosive to the fuel cell.
In a fuel cell, hydrogen gas flows to the anode. There, with the help of the
catalyst, the molecules are broken down into protons (hydrogen ions) and electrons. The
positively charged protons go through the porous membrane and migrate toward the
cathode. [l OJ
1.2 OBJECTIVE
The main objectives of this analysis are to analyze regarding composites and
therefore the electrical conductivity of G, St and PP together with the impact of Graphite
as a main filler and Stainless Steel as second filler. This analysis evaluated as well as the
ratio of the weight percentage of the composite.
Those objectives evaluated are to assist and complete this study:
1. To study the effect of Stainless steel on the properties of GI PP composite.
2. To determine the critical loading of St in GIPP composite for bipolar plate.
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