tensile, thermal and electrical ... - chem.mtu.edu thesis - tensile and conductivity... · 3.2.5...

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TENSILE, THERMAL AND ELECTRICAL CONDUCTIVITY PROPERTIES OF

EPOXY COMPOSITES CONTAINING CARBON BLACK AND GRAPHENE

NANOPLATELETS

By

Aaron S. Krieg

A THESIS

Submitted in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE

In Chemical Engineering

MICHIGAN TECHNOLOGICAL UNIVERSITY

2018

© 2018 Aaron S. Krieg

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This thesis has been approved in partial fulfillment of the requirements for the Degree of

MASTER OF SCIENCE in Chemical Engineering.

Department of Chemical Engineering

Thesis Advisor: Dr. Julia A. King

Committee Member: Dr. Gregory Odegard

Committee Member: Dr. Ibrahim Miskioglu

Department Chair: Dr. Pradeep Agrawal

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Table of Contents

List of figures ..................................................................................................................... iv

List of tables ...................................................................................................................... vii

Preface..................................................................................................................................x

Acknowledgements ............................................................................................................ xi

Abstract ............................................................................................................................. xii

1 Introduction .................................................................................................................1

1.1 References ........................................................................................................2

2 Materials .....................................................................................................................5

2.1 Materials ...........................................................................................................5

2.2 Matrix Material .................................................................................................5

2.3 Filler Materials .................................................................................................8

2.3.1 Asbury Carbons TC307 Graphene Nanoplatelets ...............................8

2.3.2 Akzo Nobel EC-600 JD Carbon Black ...............................................9

2.4 Formulation Naming Convention ...................................................................10

2.5 References ......................................................................................................11

3 Fabrication and Experimental Methods ....................................................................12

3.1 Fabrication Methods .......................................................................................12

3.1.1 Neat Epoxy Test Specimen Fabrication ............................................15

3.1.2 TC307 GNP/Epoxy Test Specimen Fabrication ...............................16

3.1.3 Ketjenblack EC-600 JD CB/Epoxy Test Specimen Fabrication .......17

3.1.4 TC307 GNP/Ketjenblack EC-600 JD CB/Epoxy Test Specimen

Fabrication ........................................................................................18

3.2 Experimental Test Methods ............................................................................18

3.2.1 Field Emission Scanning Electron Microscopy (FESEM) Test

Method ..............................................................................................18

3.2.2 Through-Plane Electrical Resistivity Test Method ...........................26

3.2.3 In-Plane Electrical Resistivity Test Method .....................................27

3.2.4 Thermal Conductivity: Guarded Heat Flow Meter Test Method ......29

3.2.5 Mechanical Tensile Property Test Method .......................................31

3.3 References ......................................................................................................33

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4 Results .......................................................................................................................35

4.1 Microscopy Results ........................................................................................35

4.1.1 Asbury Carbon’s TC307 GNP in Epoxy Microscopy Results .........35

4.1.2 Akzo Nobel’s Ketjenblack EC-600 JD CB in Epoxy Microscopy

Results ..............................................................................................38

4.2 Electrical Resistivity Results ..........................................................................40

4.2.1 Asbury Carbon’s TC307 GNP in Epoxy Electrical Resistivity

Results ..............................................................................................40

4.2.2 Akzo Nobel’s Ketjenblack EC-600 JD CB in Epoxy Electrical

Resistivity Results ............................................................................42

4.2.3 TC307 GNP and Ketjenblack EC-600 JD CB in Epoxy Electrical

Resistivity Results ............................................................................44

4.2.4 Determining Synergistic Effects of Multiple Fillers on Electrical

Resistivity .........................................................................................46

4.3 Thermal Conductivity Results ........................................................................48

4.3.1 Asbury Carbon’s TC307 GNP in Epoxy Thermal Conductivity

Results ..............................................................................................48

4.3.2 Akzo Nobel’s EC-600 JD CB in Epoxy Thermal Conductivity

Results ..............................................................................................49

4.3.3 TC307 GNP and EC-600 JD CB in Epoxy Thermal Conductivity

Results ..............................................................................................50

4.4 Tensile Results ...............................................................................................51

4.4.1 Asbury Carbon’s TC307 GNP in Epoxy Tensile Results .................51

4.4.2 Akzo Nobel’s EC-600 JD CB in Epoxy Tensile Results ..................53

4.4.3 TC307 GNP and EC-600 JD CB in Epoxy Tensile Results .............56

4.4.4 Tensile Modulus Modeling ...............................................................59

4.5 References ......................................................................................................62

5 Conclusions and Future Work ..................................................................................65

5.1 Electrical Resistivity Properties for Neat Epoxy, GNP/Epoxy, CB/Epoxy,

and GNP/CB/Epoxy Composites ...................................................................66

5.2 Thermal Conductivity Properties for Neat Epoxy, GNP/Epoxy, CB/Epoxy,

and GNP/CB/Epoxy Composites ...................................................................68

5.3 Tensile Properties for Neat Epoxy, GNP/Epoxy, CB/Epoxy, and

GNP/CB/Epoxy Composites ..........................................................................68

5.4 Recommendations for Future Work ...............................................................70

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A Appendix A: Electrical Resistivity Results...............................................................72

B Appendix B: Thermal Conductivity Results at 55°C ................................................79

C Appendix C: Tensile Results ....................................................................................83

D Copyright documentation..........................................................................................93

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List of figures

Figure 2-1: Formation of EPON™ Resin 862 from Epichlorohydrin and Bisphenol F…..6

Figure 2-2: EPIKURE™ Curing Agent W Structure……………………………………..6

Figure 2-3: Crosslinking of EPON™ Resin 862 with EPIKURE™ Curing Agent W……7

Figure 2-4: Structure of Graphene Nanoplatelets…………………………………………8

Figure 2-5: Structure of Carbon Black Aggregate………………………………………...9

Figure 3-1: FlackTek SpeedMixer DAC 150.1 FVZ…………………………………….12

Figure 3-2: Steel Rectangular Bar Molds, Steel Disk-Molds……………………………13

Figure 3-3: Fisher Isotemp® Vacuum Oven Model 282A with a Welch 1402

DuoSeal®……………………………………………………………………15

Figure 3-4: Hitachi S-4700 Field Emission Scanning Electron Microscope (FESEM)…19

Figure 3-5: Delta Shopmaster 16” Variable Speed Scroll Saw with Quickset II Blade…20

Figure 3-6: Cressington 208HR High Resolution Sputter Coater with a Cressington…..20

Figure 3-7: Logitech Vacuum Impregnator……………………………………………...21

Figure 3-8: Struers LaboForce-3 Metallographic Specimen Grinder/Polisher…………..23

Figure 3-9: Buehler EcoMet 4 Rotary Polisher………………………………………….24

Figure 3-10: Buehler VibroMet I Vibratory Polisher……………………………………25

Figure 3-11: March Jupiter II Reactive Ion Etcher………………………………………26

Figure 3-12: Keithley 6517A Electrometer/High Resistance Meter……………………..27

Figure 3-13: Diagram of Through Plane Electrical Resistivity Test…………………….27

Figure 3-14: Keithley 2400 Source Meter……………………………………………….28

Figure 3-15: Netzsch Model TCA 300 Thermal Conductivity Analyzer………………..30

Figure 3-16: Circle Grinder……………………………………………………………...30

Figure 3-17: Diagram of Through-Plane Thermal Conductivity Test Method………….31

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Figure 3-18: Ceast Router………………………………………………………………..32

Figure 3-19: Tinus Olsen Hydraulic Mechanical Testing Machine With Epsilon

Axial Extensometer………………………………………………….…...…33

Figure 4-1: Field Emission Microscope Micrograph of 5 wt% TC307 GNP in Epoxy at

x10,000 Magnification……………………………………………….………35

Figure 4-2: Field Emission Microscope Micrograph of 5 wt% TC307 GNP in Epoxy at

x30,000 Magnification……………………………………………….……....36

Figure 4-3: Field Emission Microscope Micrograph of 10 wt% TC307 GNP in

Epoxy at x10,000 Magnification.....................................................................37

Figure 4-4: Field Emission Microscope Micrograph of 10 wt% TC307 GNP in

Epoxy at x30,000 Magnification.....................................................................37

Figure 4-5: Field Emission Microscope Micrograph of 1 wt% EC-600 JD in Epoxy at

x50,000 Magnification…………………………………………………...…..38


x100,000 Magnification………...……………………………………….…..39


x200,000 Magnification……………………………………………………..39

Figure 4-8: Log (electrical resistivity) results for TC307 GNP/Epoxy Composites….....42

Figure 4-9: Log (Electrical Resistivity) Results for Ketjenblack EC-600 JD

CB/Epoxy…………………………………………………………………….44

Figure 4-10: Log (Electrical Resistivity) Results for Ketjenblack EC-600 JD/TC307

Epoxy Composites……………………………………………………...….46

Figure 4-11: Ultimate Tensile Strength Results for TC307 GNP in Epoxy

Composites…………………………………………………………………52

Figure 4-12: Strain at Ultimate Strength Results for TC307 GNP in Epoxy

Composites………………………………………………………………....53

Figure 4-13: Tensile Modulus Results for TC307 GNP in Epoxy Composites………….53

Figure 4-14: Ultimate Tensile Strength Results for Ketjenblack EC-600 JD CB in Epoxy

Composites…………………………………………………………………55

Figure 4-15: Strain at Ultimate Tensile Strength Results for Ketjenblack EC-600 JD CB

in Epoxy Composites……………………………………………………....55

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Figure 4-16: Tensile Modulus Results for Ketjenblack EC-600 JD CB in Epoxy………56

Figure 4-17: Ultimate Tensile Strength Results for Ketjenblack EC-600 JD CB and

TC307 GNP in Epoxy Composites……………………………….………..57

Figure 4-18: Strain at Ultimate Tensile Strength Results for Ketjenblack

EC-600 JD CB and TC307 GNP in Epoxy Composites………...………….58

Figure 4-19: Tensile Modulus Results for Ketjenblack EC-600 JD CB and TC307

GNP in Epoxy Composites………………….…………………………..…58

Figure 4-20: Tensile Modulus of GNP/Epoxy Composites with Einstein, Guth-

Smallwood, and 3D Halpin-Tsai Models ………………………………….62

Figure C-1: Tensile Results for Neat Epoxy……………...……………………………...83

Figure C-2: Tensile Results for 5 wt% TC307 GNP in Epoxy Composites…………......84

Figure C-3: Tensile Results for 10 wt% TC307 GNP in Epoxy Composites……………85



Figure C-6: Tensile Results for 0.33 wt% Ketjenblack EC-600 JD CB in Epoxy

Composites……………………………………...…………………………...88

Figure C-7: Tensile Results for 0.67 wt% Ketjenblack EC-600 JD in Epoxy

Composites…………………………………………………………………...89

Figure C-8: Tensile Results for 1 wt% Ketjenblack EC-600 JD in Epoxy

Composites………………………………………………………………....90

Figure C-9: Tensile Results for 0.33 wt% Ketjenblack EC-600 JD CB and 5 wt% TC307

GNP in Epoxy Composites………………………………………………….91

Figure C-10: Tensile Results for 0.33 wt% Ketjenblack EC-600 JD CB and 10 wt%

TC307 GNP in Epoxy Composites…………………………………………92

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List of tables

Table 3-1: Filler Loading Levels in Epoxy…………………………………...………….14

Table 3-2: Grinding and Polishing Steps……………………………………….………..22

Table 4-1: Electrical Resistivity Results for TC307 GNP in Epoxy Composites………..41

Table 4-2: Electrical Resistivity Results for Ketjenblack EC-600 JD CB in Epoxy…….43

Table 4-3: Electrical Resistivity Results for Ketjenblack EC-600 JD CB/TC307

GNP………………………………………………………………………..…45

Table 4-4: Weight Percent Filler in Factorial Design Formulations……………………..47

Table 4-5: Factorial Design Analysis for the Logarithm of the Electrical Resistivity…..48

Table 4-6: Thermal Conductivity Results for TC307 GNP in Epoxy Composites………49

Table 4-7: Thermal Conductivity Results for Ketjenblack EC-600 JD CB in Epoxy…...50

Table 4-8: Thermal Conductivity Results for Ketjenblack EC-600 JD CB and TC307

GNP in Epoxy……………………………………………………………...…51

Table 4-9: Tensile Results for TC307 GNP in Epoxy Composites……………………...52

Table 4-10: Tensile Results for Ketjenblack EC-600 JD in Epoxy Composites………...54

Table 4-11: Tensile Results for TC307 GNP and Ketjenblack EC-600 JD in Epoxy…...57

Table 5-1: A Summary of the Conclusions Made About the Composite Types Tested…65

Table 5-2: Potential Applications for Composite Formulations Tested for ER………….67

Table A-1: ASTM D257 Through-Plane Electrical Resistivity Results for Neat

Epoxy………………………………………………………………………...72

Table A-2: ASTM D257 Through-Plane Electrical Resistivity Replicate Results for

Neat Epoxy…………………………………………………………………..72

Table A-3: ASTM D257 Through-Plane Electrical Resistivity Results for 5 wt%

TC307 GNP in Epoxy Composites…………………………………………..73

Table A-4: ASTM D257 Through-Plane Electrical Resistivity Replicate Results for 5

wt% TC307 GNP in Epoxy Composites …………………………..………..73

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Table A-5: ASTM D257 Through-Plane Electrical Resistivity Results for 10 wt% TC307

GNP in Epoxy Composites………………………………………..……........74

Table A-6: ASTM D4496 Two Point In-Plane Electrical Resistivity Results for

15 wt% TC307 GNP in Epoxy Composites.....................................................74

Table A-7: ASTM D4496 Two Point In-Plane Electrical Resistivity Results for

20 wt% TC307 GNP in Epoxy Composites.....................................................75

Table A-8: ASTM D257 Through-Plane Electrical Resistivity Results for 0.33%

Ketjenblack EC-600 JD CB in Epoxy Composites ………………...………..75


0.33% Ketjenblack EC-600 JD CB in Epoxy Composites……..……………76

Table A-10: ASTM D4496 Two Point In-Plane Electrical Resistivity Results for 0.67%

Ketjenblack EC-600 JD CB in Epoxy Composites…………………………76

Table A-11: ASTM D4496 Two Point In-Plane Electrical Resistivity Results for 1 wt%

Ketjenblack EC-600 JD CB in Epoxy Composites…………………………77

Table A-12: ASTM D4496 Two Point In-Plane Electrical Resistivity Results for 0.33

wt% Ketjenblack EC-600 JD CB and 5 wt% TC307 GNP in Epoxy

Composites………………………………………………………….………77

Table A-13: ASTM D4496 Two Point In-Plane Electrical Resistivity Replicate Results

for 0.33 wt% Ketjenblack EC-600 JD CB and 5 wt% TC307 GNP in Epoxy

Composites………………………………………………………………….78


wt% Ketjenblack EC-600 JD CB and 10 wt% TC307 GNP in Epoxy

Composites……………………………………………………………….....78

Table B-1: Thermal Conductivity of Neat Epoxy………………………………………..79

Table B-2: Thermal Conductivity of 5 wt% TC307 GNP in Epoxy Composites………..79

Table B-3: Thermal Conductivity of 10 wt% TC307 GNP in Epoxy Composites………80



Table B-6: Thermal Conductivity of 0.33 wt% Ketjenblack EC-600 JD CB in Epoxy

Composites…………………………………………………………………...81

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Composites…………………………………………………………………...81

Table B-8: Thermal Conductivity of 1 wt% Ketjenblack EC-600 JD CB in Epoxy

Composites…………………………………………………………………...81

Table B-9: Thermal Conductivity of 0.33 wt% Ketjenblack EC-600 JD CB and 5 wt%

TC307 GNP in Epoxy Composites…………………………………………..82



Table C-1: Tensile Results for Neat Epoxy……………………………………………...83

Table C-2: Tensile Results for 5 wt% TC307 GNP in Epoxy Composites……………...84

Table C-3: Tensile Results for 10 wt% TC307 GNP in Epoxy Composites…………….85



Table C-6: Tensile Results for 0.33 wt% Ketjenblack EC-600 JD CB in Epoxy

Composites…………………………………………………………………...88

Table C-7: Tensile Results for 0.67 wt% Ketjenblack EC-600 JD in Epoxy

Composites……………………………………………………………….…..89

Table C-8: Tensile Results for 1 wt% Ketjenblack EC-600 JD in Epoxy

Composites……………………………………………………………….…..90

Table C-9: Tensile Results for 0.33 wt% Ketjenblack EC-600 JD CB and 5 wt% TC307

GNP in Epoxy Composites…………………………………………………..91

Table C-10: Tensile Results for 0.33 wt% Ketjenblack EC-600 JD CB and 10 wt%


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Preface

The work contained in this thesis was conducted in the department of Chemical

Engineering at Michigan Technological University from May 2017 to December 2017.

The work done in this thesis has been published in the following article in the Journal of

Composite Materials:

Krieg, A. S., King, J. A., Jaszczak, D. C., Miskoglu, I., Mills, O. P., & Odegard, G. M.

"Tensile and conductivity properties of epoxy composites containing carbon black and

graphene nanoplatelets." Journal of Composite Materials (Copyright © 2018):

0021998318771460. Reprinted by permission of SAGE Publications.

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Acknowledgements

I would like to thank my advisor Dr. Julie King for being a good mentor that genuinely

cares about her students. I would also like to give a special thanks to my committee

members, Dr. Gregory Odegard and Dr. Ibrahim Miskioglu, for their guidance and

helpful insights throughout the project.

Additionally, I would like to gratefully thank the NSF I/UCRC on Novel High

Voltage/Temperature Materials and Structures (Grant IIP-1362040) and the Lorna and

James Mack Endowed Chair for funding this project. I also thank the Asbury Carbons

and Akzo Nobel for providing the carbon fillers used in this study. I would also like to

thank Casey Elkins from Flak Tek for assistance in designing the mixing methods used

for this project.

I would also like to thank employees at the Michigan Tech who contributed to this study:

Owen Mills for his fantastic work doing imaging on the field emission scanning electron

microscope and Gerald Anzolone for preparing the specimens for imaging. I must also

thank Jerry Norkol and Steve Winsiewski for their artful resourcefulness in addressing

the technical issues that would arise.

I would also like to thank the following undergraduate students for their assistance on this

project: Nate Baldwin, Sarah Boyd, Anna Hohnstadt, Lexi Fitzpatrick, Emilia Kuemin,

Evan Murphy, Leif Odegard, Rebecca Phipps, Austin Weick, Carson Williams, Charlie

Biyong, and Nick Olson.

Finally, I’d like to thank my family who have always told me that almost anything can be

accomplished if you work hard enough. My father Scott Krieg and mother Rhonda Krieg

for their continued support. I’d like to thank my brother Christopher Krieg for facilitating

my interest in science and for his informed guidance. I’d also like to thank my wife

Karleigh Krieg and son Trez Krieg who inspire me every day to be somebody and to

never give up.

xii

Abstract

Adding carbon fillers to a polymer produces composites with unique conductivity

and tensile properties. Varying amounts of carbon black (CB: < 1 wt%), graphene

nanoplatelets (GNP: < 20 wt%), and combination (0.33 wt% CB with < 10 wt% GNP) of

fillers were compounded in epoxy. The thermal and electrical conductivities and tensile

properties were evaluated. These composites can be used for electrically insulating, static

dissipative, or semi-conductive applications depending on the electrical resistivities (ER).

The 0.33wt% CB/5wt% GNP composite caused the ER to significantly decrease,

which is likely due to the highly branched CB forming conductive networks with GNP.

Concerning single filler composites, adding ≤ 1 wt% CB did not significantly change the

composite tensile properties; however, adding GNP did change tensile properties. One

possible application for the 10 wt% GNP composite is in Polymer Core Composite

Conductors for transmission lines, which require improved thermal conductivity and

mechanical properties.

1

1 Introduction

Composites with varying concentrations of conductive fillers in an insulating

polymer can be used for a variety of applications. After a composite’s electrical

percolation threshold (the point at which the conductivity has significantly increased with

the addition of a small amount of conductive filler) has been reached, it can be used for

static dissipative [electrical resistivity (ER) ranging from ~1010 to 105 ohm-cm] and

semi-conductive (ER ranging from 104 to 10 ohm-cm) applications. If the composites

electrical percolation threshold has not been reached, then the composites can be used for

electrical insulating applications such as Polymer Core Composite Conductors (PCCCs).

PCCCs are used by utility companies to transmit more power over existing electrical

transmission rights-of-ways than traditional transmission lines. The composite core in

PCCCs are used for their high specific strength and stiffness. PCCCs consist of an inner

core comprised of a carbon fiber (CF)/epoxy and a thinner outer shell that consists of

glass fiber (GF)/epoxy. The insulating glass composite material of the outer shell

prevents the electrically conductive carbon composite inner core from transmitting a

current. Since the composite core is considerably lighter than the conventional steel cores

used to reinforce transmission lines, more aluminum strands can be added to increase the

electrical capacity of the lines by a factor of 2[1-3].

Graphene nanoplatelets (GNPs) are short graphitic stacks consisting of individual

layers of graphene that often increase the elastic modulus (stiffness), electrical

conductivity (1/ER), and thermal conductivity of a composite and are available at a

2

relatively low cost (approximately $5-$50/lb) compared to the higher costs of carbon

nanotubes[4-9]. Increasing the composite thermal conductivity can allow these materials

to be used in heat sink applications. Various models have been used to predict the tensile

modulus of GNP in epoxy composites at different filler loading levels. These models

consider the constituent properties, concentrations of each constituent, and the filler

aspect ratio and orientation[7][10-16]. Carbon black (CB) is a cost effective filler (~ $5-

15/lb) that has often been used to increase the electrical conductivity (1/ER) of a

composite[17-19]. An investigation was carried out to determine if the addition of a small

amount of CB to GNP composites with varying filler concentrations of GNP increased

the electrical conductivity more than the additive effect of each filler by itself. The

composite formulations fabricated and tested in this study have not been previously

reported in the open literature.

1.1 References

[1] “Engineering Transmission Lines with High Capacity Low Sag ACCC® Conductors

Manual”. CTC Global. 2026 McGaw Avenue Irvine, CA 92614. (2011).

[2] Hoffman J, Middleton J, and Kumosa, M. “Effect of a surface coating on flexural

performance of thermally aged hybrid glass/carbon epoxy composite rods”. Compos. Sci.

Technol., (2015);106:141-148.

[3] Middleton J, Burks B, Wells T, Setters AM, and Jasiuk I, and Kumosa M. “The effect

of ozone on polymer degradation in Polymer Core Composite Conductors”. Polym.

Degrad. Stabl., (2013);98: 436-445.

[4] XG Sciences Inc. xGnP® Brand Graphene Nanoplatelets Product Information. 3101

Grand Oak Drive, Lansing, MI, (2010).

[5] Kalaitzidou K, Fukushima H, and Drzal, LT. “Mechanical properties and

morphological characterization of exfoliated graphite-polypropylene nanocomposites.

Composites Part A: Applied Science and Manufacturing”, (2007); 38: 1675- 1682.

3

[6] Fukushima H, Drzal LT, Rook BP, and Rich MJ. “Thermal conductivity of exfoliated

graphite nanocomposites”. Journal of Thermal Analysis and Calorimetry, (2006); 85:

235 238.

[7] Kalaitzidou K, Fukushima H, Miyagawa H, and Drzal L T. “Flexural and tensile

moduli of polypropylene nanocomposites and comparison of experimental data to

Halpin-Tsai and Tandon-Weng models”. Polymer Engineering and Science, (2007); 47:

1796-1803.

[8] Kalaitzidou K, Fukushima H, and Drzal LT. “A new compounding method for

exfoliated graphite-polypropylene nanocomposites with enhanced flexural properties and

lower percolation threshold”. Composites Science and Technology, (2007); 67:2045-

2051.

[9] Asbury Carbons, Thermocarb Graphite TC-Series Product Information, 405 Old Main

Street, Asbury, NJ 08802, (2013).

[10] Halpin, J.C., and Kardos, J. L. “The Halpin-Tsai equations: A review”. Polymer

Engineering and Science, (1976); 16: 344-352.

[11] Agarwal B.D. and Broutman L. J. “Analysis and Performance of Fiber

Composites”. Wiley, New York, NY, (1980).

[12] Mallick P. K. “Composites Engineering Handbook”, Marcel Dekker, Inc., New

York, NY, (1997).

[13] Halpin J. C. “Stiffness and Expansion Estimates for Oriented Short Fiber

Composites”. Journal of Composite Materials (1969); 3: 732-734.

[14] Karrad, S, Lopez Cuesta JM., and Crespy A. “Influence of a fine talc on the

properties of composites with high density polyethylene and polyethylene/polystyrene

blends”. Journal of Materials Science (1998); 33: 453- 461.

[15] Jain S, Reddy MM, Mohanty AK, Misra M, and Chosh AK. “A new biodegradable

flexible composite sheet from poly(lactic acid)/poly(ε-caprolactone ) blends and

microtalc”. Macromol. Mater Engr. (2010); 295: 750-762.

[16] Guth E. “Theory of Reinforcement”. Journal of Applied Physics (1945); 16: 20- 25.

[17] Donnet J-B, Bansal R C, and Wang M-J. “Carbon Black”, 2nd edition, New York,

NY: Marcel Dekker, Inc, (1993).

[18] Huang J –C. “Carbon black filled conducting polymers and polymer blends”. Adv.

Polym. Technol. (2002); 21, 299-313.

4

[19] Akzo Nobel Electrically Conductive Ketjenblack Product Literature, 300. S.

Riverside Plaza, Chicago, IL, (1999).

5

2 Materials

2.1 Materials

For this project there were two carbon fillers used in an epoxy matrix that were

studied. The carbon fillers assessed in the study were Asbury Carbons TC307 graphene

nanoplatelets and Akzo Nobel Ketjenblack EC-600 JD carbon black. The thermoset

polymer system used as the matrix was Hexions EPON™ Resin 862 with EPIKURE™

Curing Agent W.

2.2 Matrix Material

The epoxy matrix used in this study is a phenolic glycidyl ether resin, Hexion’s

EPON™ 862 (diglycidyl ether of bisphenol F, DGEBPF) that is cured with an amine

hardening agent, EPIKURE Curing Agent W (diethyltoluenediamine, DETDA). EPON™

Resin 862 is a low viscosity liquid epoxy resin manufactured from the condensation

reaction between epichlorohydrin and the phenol group on bisphenol F. The reaction that

produces EPON Resin 862 is shown in Figure 2-1. The viscosity of EPON™ Resin 862

at 25°C is ~35 P. EPIKURE™ Curing Agent W is an aromatic diamine with a viscosity

of ~200 cP [1]. The molecular structure of EPIKURE™ Curing Agent W is shown in

Figure 2-2.

6

Epichlorohydrin Bisphenol F EPON™ Resin 862

Figure 2-1: Formation of EPON™ Resin 862 from Epichlorohydrin and Bisphenol F -

drawn from reaction given in vendor literature

EPIKURE™ Curing Agent W

Figure 2-2: EPIKURE™ Curing Agent W Structure

EPON™ Resin 862/EPIKURE™ W is a thermoset epoxy system with a curing

cycle of 121°C for 2 hours followed by 177°C for 2 hours. The formation of the cured

thermoset system results from the epoxide groups on the EPON™ Resin 862 reacting

with the amine groups on the EPIKURE™ Curing Agent W. As the reaction progresses,

the system becomes a branched crosslinked structure as shown in Figure 2-3. The cured

EPON™ Resin 862/EPIKURE™ W system has a density of 1.20 g/cm³ [1].

7

EPON™ Resin 862 EPIKURE™ W EPON™ Resin 862 + EPIKURE™ W

EPON™ Resin 862 EPON™ Resin 862 + EPIKURE™ W

Figure 2-3: Crosslinking of EPON™ Resin 862 with EPIKURE™ Curing Agent W

8

2.3 Filler Materials

2.3.1 Asbury Carbons TC307 Graphene Nanoplatelets

Graphene nanoplatelets consist of small stacks of graphene sheets. Each graphene

sheet is a single layer of graphite with the structure seen in Figure 2-4. GNP’s are

available in a variety of particle sizes and surface modifications.

Figure 2-4: Structure of Graphene Nanoplatelets

The graphene nanoplatelets used in this study are Asbury Carbons TC307 grade,

which is a high purity synthetic graphite that is manufactured using a proprietary

technique. TC307 GNP are composed of platelets with a mean particle diameter of <1 μm

and a thickness of ~10-15 nm. The graphene nanoplatelets are comprised of

approximately 8 layers, a specific gravity of 2 and have a mean BET surface area of 350

m²/g. The graphene is electrically conductive and has a resistivity of 0.26 ohms-cm [2].

9

2.3.2 Akzo Nobel EC-600 JD Carbon Black

The carbon black used in this study is Akzo Nobel’s Ketjenblack EC-600 JD

which is an electrically conductive carbon black that consists mainly of elemental carbon

in the form of spherically shaped particles that have been fused together to form

aggregates. Ketjenblack EC-600 JD is a carbon black with a highly branched structure

that enables the formation of electrical networks across the polymer matrix with

relatively low concentrations of carbon black. Due to the unique morphology of

Ketjenblack EC-600 JD carbon black, only 1/6 of the amount is required to achieve the

same conductivity of conventional electroconductive carbon blacks [3].

Ketjenblack EC-600 JD carbon black has a density of 1.8 g/cm³ and an electrical

resistivity of 0.01-0.1 ohm-cm. The carbon black pellets range between 100 μm and 2

mm in size and consist of primary aggregates that range from 30-100 nm in size. The

Ketjenblack EC-600 JD has a Brunauer-Emmett-Teller (BET) surface area of 1,250 m²/g.

The aggregates have a pore volume between 480-510 cm³/100g [3]. The morphology of

carbon black aggregates can be seen in Figure 2-5.

Figure 2-5: Structure of Carbon Black Aggregate [3]

10

2.4 Formulation Naming Convention

A naming convention was generated to organize the samples in a relatively simple

and unique way that allows the specimens to be individually identified and distinguished

from one another. Each sample was numbered and labeled according to the constituents

of the composite and the date of its fabrication. The naming system is as follows:

U 862 – a b – cd - date - e

Where:

U = project description

862 = EPON™ Resin 862

a = weight percent of filler, if there are no fillers in the composite then this entry is

omitted

b = filler type (T= Asbury Carbons TC307 GNP, A=Akzo Nobel Ketjenblack EC-600

JD), if there are no fillers in the matrix then this entry is omitted

c = weight percent of second filler, if there are no fillers in the matrix or it is a single

filler composite then this entry is omitted

d = second filler type (T = Asbury Carbons TC307 GNP, A=Akzo Nobel Ketjenblack

EC-600 JD), if there are no fillers in the matrix or it is a single filler composite then this

entry is omitted

e = specimen number

11

2.5 References

[1] Hexion EPON™ Resin 862/EPIKURE™ Curing Agent W Product Literature, 180

Broad St, Columbus, OH 43215. (2017).

[2] Asbury Carbons Synthetic Graphite Product Literature, 405 Old Main St., Asbury, NJ

08802. (2015).

[3] Akzo Nobel Electrically Conductive Ketjenblack Product Literature, 300 S. Riverside

Plaza, Chicago, IL, 60606. (1999).

12

3 Fabrication and Experimental Methods

3.1 Fabrication Methods

A FlackTek SpeedMixer DAC 150.1 FVZ, shown in Figure 3-1, was used to

disperse the carbon fillers randomly across the matrix. The FlackTek SpeedMixer is a

bladeless high-shear mixer that uses centrifugal forces to achieve a uniform dispersion.

The DAC 150.1 FVZ model has a weight capacity of 100 g per cup and holds a single

cup at a time.

Figure 3-1: SpeedMixer

Figure 3-1: FlackTek SpeedMixer DAC 150.1 FVZ

Mixing methods for GNP and CB composite materials were determined by trial

and error through coordinated efforts with FlackTek Inc. technicians. The concentration

of filler in the master batch was chosen to achieve a viscosity similar to that of peanut

butter at 23 °C. The mixing method for each type of composite was determined once

13

material consistency had been achieved. In the case of each type of composite, fillers

were loaded in incremental concentrations until it was too viscous to pour into steel

rectangular- and disk-molds shown in Figure 3-2. The steel rectangular disk molds

produce 20 bars (165 mm long by 19 mm wide by 3.3 mm thick) and the steel disk molds

produce 5 disks (64 mm diameter and 3.2 mm thick). Table 3-1 shows the concentrations

(shown in wt% and the corresponding vol%) for the composite formulations tested in this

study.

Figure 3-2: (left) Steel Rectangular Disk Molds, (right) Steel Disk-Molds

14

Table 3-1: Filler Loading Levels in Epoxy

Formulation Filler Content

wt% (vol%)

Neat 0.0 (0.0)

GNP

5.0 (3.1)

10.0 (6.3)

15.0 (9.6)

20.0 (13.0)

CB

0.33 (0.22)

0.67 (0.44)

1.0 (0.67)

GNP/CB

CB: 0.33 (0.20) GNP: 5.0 (3.1)

CB: 0.33 (0.20) GNP: 10.0 (6.3)

The epoxy/amine system used in this study was degassed and cured in a Fisher

Isotemp® Vacuum Oven Model 282A with a Welch 1402 DuoSeal® Vacuum Pump,

shown in Figure 3-3. The cure cycle was obtained from the polymer systems product

literature. The finalized mixing procedures and cure cycles are described in the following

subsections. For this entire project, each batch yielded a total of 450 g of material

obtained by 5 mixing cups which each contained 90 g of the material. Also, a ratio of 100

g of epoxy was added to 26.4 g of hardener to prepare the polymer matrices used

throughout this project [1] A 450 g batch of material makes 20 rectangular bars (165 mm

long by 19 mm wide by 3.3 mm thick) and 5 disks (64 mm diameter and 3.2 mm thick).

15

Figure 3-3: Fisher Isotemp® Vacuum Oven Model 282A with a Welch 1402 DuoSeal®

Vacuum Pump

3.1.1 Neat Epoxy Test Specimen Fabrication

To manufacture the neat epoxy samples, 100 g of EPON™ 862 was added to 26.4

g of EPIKURE Curing Agent W. The mixture was mixed by hand for 3 min at 23°C. The

mixture was then degassed inside an oven at 90°C and 29 inches Hg vacuum for 30 min

and poured into a rectangular shaped mold (165 mm long by 19 mm wide by 3.3 mm

thick). The curing cycle for this aerospace epoxy resin was 121°C for 2 h followed by 2 h

at 177°C. Samples were allowed to cool to ambient temperature before being removed

from the mold [2].

16

3.1.2 TC307 GNP/Epoxy Test Specimen Fabrication

To manufacture the GNP/epoxy composites, master batches of 30 wt% GNP were

compounded by adding the appropriate amount of TC307 GNP on top of EPON™ 862

epoxy resin in a mixing cup. The epoxy resin and GNP were mixed for a total of 2.5 min

at 3,000 rpm in a FlackTek SpeedMixer DAC 150.1 FVZ.

The mixed masterbatch was diluted to achieve the desired amount of filler in each

formulation. Neat epoxy resin, masterbatch, and hardener were poured into mixing cups

and mixed at 2,250 rpm for 3 min in the SpeedMixer. The material was degassed in the

mixing cups at 90 °C and 29 inches Hg vacuum for 35 min. Rectangular- and disc-

shaped steel molds were coated with Mann Ease Release 300, then assembled and

preheated in an oven at 90 °C. The degassed mixture was then poured into the steel molds

and degassed again for another 35 minutes.

The fully degassed material was cured in an oven by heating the mold to 121 °C

and holding it at that temperature for 2 hours followed by raising the temperature of the

oven to 177 °C and sustaining that temperature for an additional 2 hours. The oven was

then turned off and the cured epoxy was allowed to cool to ambient temperature in the

oven at an average cooling rate of 1 °C/min. Twenty rectangular bars (3.2 mm thick by

165 mm long by 19 mm wide) and 5 disks (64 mm diameter and 3.2 mm thick) were

fabricated per each batch using this method.

17

3.1.3 Ketjenblack EC-600 JD CB/Epoxy Test Specimen Fabrication

To manufacture the CB/epoxy composites, master batches of 5 wt% CB were

compounded by adding the appropriate amount of EC-600 JD CB on top of EPON™ 862

epoxy resin in a mixing cup. The epoxy resin and CB were mixed for 1.5 min at 2,500

rpm in a FlackTek SpeedMixer DAC 150.1 FVZ. Four zirconium mixing cylinders were

placed into the cup and the cups were mixed 3 times for 1.5 minutes at 2,500 rpm in the

SpeedMixer while allowing to cool back to ambient temperature after each time the cups

were mixed.

The mixed masterbatch was diluted to achieve the desired amount of filler in each

formulation. Neat epoxy resin, masterbatch, and hardener were poured into mixing cups

and mixed twice at 3,500 rpm for 1.5 min in the SpeedMixer. The walls on the inside of

the cups were scraped and mixed by hand in between mixes. Rectangular- and disc-

shaped steel molds were coated with Mann Ease Release 300, then assembled and

preheated in an oven at 90°C. The mixture was then poured into the steel mold and

degassed for 35 minutes. The same curing cycle was used as described for the

GNP/epoxy composites. Twenty rectangular bars (3.2 mm thick by 165 mm long by 19

mm wide) and 5 disks (64 mm diameter and 3.2 mm thick) were fabricated using this

method.

18

3.1.4 TC307 GNP/Ketjenblack EC-600 JD CB/Epoxy Test Specimen Fabrication

To manufacture the GNP/CB/epoxy composites, masterbatches of GNP and CB

were fabricated using the same procedure described for the GNP/epoxy and CB/epoxy

composites. The appropriate amount of GNP and CB masterbatches were combined and

diluted to achieve the desired amount of fillers in each formulation. Neat epoxy resin,

masterbatch, and hardener were poured into mixing cups and mixed twice at 3,500 rpm

for 1.5 min in the SpeedMixer. The walls on the inside of the cups were scraped and

mixed by hand in between mixes. Rectangular- and disc- shaped steel molds were coated

with Mann Ease Release 300, then assembled and preheated in an oven at 90°C. The

mixture was then poured into the steel mold and degassed for 35 minutes. The same

curing cycle was used as described for the GNP/epoxy composites. Twenty rectangular

bars (3.2 mm thick by 165 mm long by 19 mm wide) and 5disks (64 mm diameter and

3.2 mm thick) were fabricated using this method.

3.2 Experimental Test Methods

3.2.1 Field Emission Scanning Electron Microscopy (FESEM) Test Method

A Hitachi S-4700 field emission scanning electron microscope (FESEM), shown

in Figure 3-4, was used to image GNP/epoxy and CB/epoxy composite samples. FESEM

is useful for high resolution imaging. The upper secondary electron detector was used to

collect high resolution images of the samples surface topology.

19

Figure 3-4: Hitachi S-4700 field emission scanning electron microscope (FESEM)

The GNP in epoxy samples were prepared for FESEM by cutting small cubes

from the tested tensile specimen using a Delta Shopmaster 16” Variable Speed Scroll

Saw with Quickset II Blade Changing Feature Model SS350, as shown in Figure 3-5. The

samples were cut with dimensions of approximately 3 mm long so that the tensile fracture

surface would be viewed. The samples were blown with a pressurized air nozzle to

remove residual particles from the saw and then were placed tensile fracture surface up

on an aluminum sample mount before being sputtered with a 2nm thick

platinum/palladium coating using a Cressington 208HR High Resolution Sputter Coater,

shown in Figure 3-6. The film thickness was measured with a Cressington MTM-20

Thickness Controller, also shown in Figure 3-6. The accelerating voltage was set to 2.0

kV at a working distance of 13.6 mm.

20

Figure 3-5: Delta Shopmaster 16” Variable Speed Scroll Saw with Quickset II Blade

Changing Feature Model SS350

Figure 3-6: Cressington 208HR High Resolution Sputter Coater with a Cressington

MTM-20 Thickness Controller

21

CB in epoxy samples were mounted and polished to perform microscopic

analysis. To view the CB in epoxy, the following sample preparation method was used.

First, the 1 wt% CB/epoxy composite samples were mounted in an epoxy puck. The

tensile fracture surface was placed in the bottom of 1.25” metallographic mount molds

and placed into a Logitech vacuum impregnator, shown in Figure 3-7. While the

specimen chamber was evacuated, Epotek 301 epoxy was prepared and mixed. Epotek

301 epoxy is a two-component room temperature curing epoxy available from Epoxy

Technology, Inc. with a relatively low viscosity of 100-200 cPs at 23 °C. Part A of the

Epotek 301 epoxy consists of diglycidyl ether of bisphenol A (DGEBPA) and a

proprietary reactive diluent. Part B of the system is trimethyl-1,6-hexanediamine [3]. The

epoxy was then vacuum degassed and introduced to the specimen chamber while still

under vacuum. Upon filling the mold with liquid epoxy, the specimen chamber was

returned to ambient pressure and the filled mold was removed and placed in a desiccator

to cure for 24 hours at 25 °C.

Figure 3-7: Logitech Vacuum Impregnator

22

Table 3-2 shows the grinding and polishing steps. After removing the epoxy-

impregnated specimen, the sample was ground using a Struers LaboForce-3

metallographic specimen grinder/polisher, shown in Figure 3-8. The grinder was fitted

with pressure sensitive adhesive PSA-backed #400 grit fixed SiC grinding disks and was

ground at 250 rpm with a force of 5 N until the surface of the mount was flat. Grinding

continued at 250 rpm with #800 and #1500 grit PSA-backed fixed SiC media for 2

minutes each and the sample surface was exposed.

Table 3-2: Grinding and Polishing Steps

Surface Lubricant Abrasive Time Force RPM Direction

SiC - 400 grit Water SiC - 400 grit Till plane 5 N 250 Contra

SiC - 800 grit Water SiC - 800 grit 2 min 5 N 250 Contra

SiC - 1500 grit Water SiC - 1500 grit 2 min 5 N 250 Contra

Hudcloth Red Soln. METADI Supreme

9 μm 15 sec - 250 Contra

Hudcloth Green Soln. METADI Supreme


Hudcloth White Soln.

Alumina Suspension


Hudcloth Water Diamond Paste

0.25 μm 1 hour - - -

Hudcloth White Soln. Master Prep

0.05 μm 1 hour - - -

23

Figure 3-8: Struers LaboForce-3 metallographic specimen grinder/polisher

A Buehler EcoMet 4 Rotary Polisher, shown in Figure 3-9, was fitted with an

abrasive Hudcloth nap cloth and used to remove scratches made from grinding. The flat

surface of the puck was polished by hand using multi-crystalline diamond, starting with

METADI Supreme 9 µm media, METADI Supreme 3 µm media, and then 1 µm alumina

suspension media all while rotating at 250 rpm and for 15 seconds with each media.

24

Figure 3-9: Buehler EcoMet 4 Rotary Polisher

Intermediate and final polishing were completed on a Buehler VibroMet I

Vibratory Polisher, shown in Figure 3-10, fitted with a Hudcloth nap cloth. 0.25 µm

diamond paste and 0.05 µm colloidal silica polishing suspension were used for

intermediate and final polishing, respectively for an hour each. The specimens were

cleaned between each grinding and polishing step by sonicating for five minutes in

distilled water. Water was used for the lubricant throughout the grinding and polishing

steps.

25

Figure 3-10: Buehler VibroMet I Vibratory Polisher

The polished composite surface was dry etched in a March Jupiter II parallel plate

reactive ion etcher, shown in Figure 3-11. The composite was etched with oxygen plasma

at 100 standard cm³/min of 𝑂2 for 5 min. The etching was done at low pressure, 249

mTorr, and at 300 W. The sample was sputter coated with a layer of Pt/Pd with a

thickness of approximately 5 nm using a Cressington 208HR high resolution sputter

coater. Coating thickness was measured with a Cressington MTM-20 film thickness

controller. Images were acquired with the Hitachi S4700 field emission scanning

electron microscope (FESEM). The microscope was operated at 10 kV of accelerating

voltage with a 10 μA emission current. The working distance was 6.3 mm using the

upper secondary electron detector.

26

Figure 3-11: March Jupiter II Reactive Ion Etcher

3.2.2 Through-Plane Electrical Resistivity Test Method

Through-plane volumetric electrical conductivity tests were conducted at 23 °C

on as-molded disk samples with an electrical resistivity greater than 107 ohm-cm in

accordance with ASTM D257 [4]. The electrical resistivity was measured by applying a

constant voltage (typically 100 V) to the test specimen using a Keithley 6517A

Electrometer/High Resistance Meter and an 8009 Resistivity Test Fixture, as shown in

Figure 3-12. Figure 3-13 shows a picture illustrating this apparatus. Keithley 6524 High

Resistance Measurement Software was used to automate the conductivity measurement.

A minimum of five specimens were tested for each formulation. The test specimens were

from the molded disk that was 6.4 cm in diameter and 3.2 mm thick. The samples were

conditioned at 23 °C and 50% relative humidity for two days prior to testing.

27

Figure 3-12: (left) Keithley 6517A Electrometer/High Resistance Meter, (right)

Keithley 8009 Resistivity Test Fixture

Figure 3-13: Diagram of Through Plane Electrical Resistivity Test

3.2.3 In-Plane Electrical Resistivity Test Method

In-plane volumetric electrical conductivity tests were conducted at 23 °C on

rectangular samples with an electrical resistivity of less than 107 ohm-cm in accordance

28

with ASTM D4496 [5]. The test samples were prepared by scratching a 3.2 mm thick, 19

mm wide and 60 mm long rectangular sample with a razor blade, placing the sample in

liquid nitrogen, and manually breaking the cryogenic sample at the desired locations,

which produced a fracture surface at each end of the in-plane sample. The 3.2 mm thick

by 19 mm fracture surfaces were coated with silver paint and dried for one hour. The

electrical resistivity was measured by using two probes to conduct the tests on the

samples by placing one probe on each silver painted fracture surface and applying a

constant voltage to the sample using a Keithley 2400 Source Meter, shown in Figure 3-

14. The current flowing across the sample was measured on the source meter. At least 5

samples were tested for each formulation. The electrical resistivity was calculated using

Equation 3-1. The samples were conditioned at 23 °C and 50% relative humidity for two

days prior to testing.

Figure 3-14: Keithley 2400 Source Meter

29

𝐸𝑅 = (∆𝑉)(𝑤)(𝑡)

(𝑖)(𝐿) [3-1]

where:

ER = Electrical Resistivity, ohm-cm

∆V = Voltage drop, volts

w = sample width, cm

t = sample thickness, cm

i = current, amps

L = length over which ∆V is measured

3.2.4 Thermal Conductivity: Guarded Heat Flow Meter Test Method

The through-plane thermal conductivity of disk samples was measured at 55 °C

using a Netzsch Model TCA 300 Thermal Conductivity Analyzer, shown in Figure 3-15.

The test samples were prepared by grinding 3.2 mm thick disks to a 5 cm diameter using

the circle grinder, shown in Figure 3-16.

30

Figure 3-15: Netzsch Model TCA 300 Thermal Conductivity Analyzer

Figure 3-16: Circle Grinder

31

The samples were tested in accordance with the ASTM F433 guarded heat flow

method [6]. The thermal conductivity was measured at 55 °C because this temperature

was as close to ambient temperature as could be measured while still maintaining a

temperature gradient in the apparatus. Figure 3-17 shows a diagram of the test method

used to measure through-plane thermal conductivity [7]. For each formulation, at least

four samples were tested. The samples were conditioned at 23 °C and 50% relative

humidity for two days prior to testing.

Figure 3-17: Diagram of Through-Plane Thermal Conductivity Test Method [7]

3.2.5 Mechanical Tensile Property Test Method

Specimens were tested for tensile properties at 23 °C according to ASTM D638

and ASTM Type I sample geometry: 65 mm long by 3.2 mm thick [8]. A Ceast router,

shown in Figure 3-18, was used to grind the specimens into dog-bone shaped samples

with a width of 12.6 mm. For each formulation, at least 5 samples were tested at a

32

crosshead rate of 1 mm/min using a Tinus Olsen hydraulic mechanical testing machine,

shown in Figure 3-19. Stress values are recorded by the testing machine and an axial

extensometer from Epsilon Technology Corporation that was used to collect the strain

values. Tensile modulus was determined from the initial slope of the stress-strain curve.

For each formulation, at least 5 samples of each composite were tested. The samples were

conditioned at 23 °C and 50% relative humidity for two days prior to testing.

Figure 3-18: Ceast Router

33

Figure 3-19: Tinus Olsen Hydraulic Mechanical Testing Machine With Epsilon Axial

Extensometer

3.3 References

[1] Hexion EPON™ Resin 862/EPIKURE™ Curing Agent W Product Literature. 180

Broad St, Columbus, OH 43215. (2017).

[2] Klimek-McDonald DR, King JA, Miskioglu I, Pineda EJ, and Odegard GM.

“Determination and modeling of mechanical properties for graphene nanoplatelet/epoxy

composites”. Polymer Composites (2016): 10.1002/pc.24137.

[3] Epoxy Technology, Inc. EPO-TEK® 301 Product Literature, 14 Fortune Drive,

Billerica, MA 01821. (2016).

[4] Standard Test Methods for DC Resistance or Conductance of Insulating Materials,

ASTM Standard D257-91, American Society for Testing and Materials, Philadelphia, PA

(1998).

[5] Standard Test Methods for DC Resistance or Conductance of Moderately Conductive

Materials, ASTM Standard D4496-04, American Society for Testing and Materials,

Philadelphia, PA. (2008).

[6] Standard Test Methods for Evaluating Thermal Conductivity of Gasket Materials,

ASTM Standard F433, American Society for Testing and Materials, Philadelphia, PA

(2008).

34

[7] Operation & Maintenance Manual, Holometrix Model TCA-300, 25 Wiggins Ave,

Bedford, MA 01730. (1997).

[8] Standard Test Methods for Tensile Properties of Plastics, ASTM Standard D638,

American Society for Testing and Materials, Philadelphia, PA (2008).

35

4 Results

4.1 Microscopy Results

4.1.1 Asbury Carbon’s TC307 GNP in Epoxy Microscopy Results

A Hitachi S-4700 field emission scanning electron microscope (FESEM) was

used to image GNP/epoxy composite samples. The specimens viewed were 5 wt% and 10

wt% TC307 GNP in epoxy. The microscope was operated at 2 kV of accelerating voltage

and at magnifications of x10,000, and x30,000. Figure 4-1 shows a FESEM image of a

tensile fracture surface for 5 wt% TC307 GNP in epoxy at a magnification of x10,000.

The figure shows TC307 GNP scattered throughout the matrix and demonstrates a three-

dimensional random orientation of TC307 in the epoxy composite. Figure 4-2 is a

FESEM image of the same fracture surface using a magnification of x30,000. The figures

show the platelets to be <1 μm in diameter.

Figure 4-1: Field emission microscope micrograph of 5 wt% TC307 GNP in epoxy at

x10,000 magnification

36



Figure 4-3 shows a FESEM image of a tensile fracture surface for 10 wt% TC307 GNP in

epoxy at a magnification of x10,000. The figure also demonstrates a uniform three-

dimensional random orientation of TC307 in the epoxy composite. Figure 4-4 is a

FESEM image of the same fracture surface using a magnification of x30,000 and shows

more platelets with diameters of <1 μm.

37





38

4.1.2 Akzo Nobel’s Ketjenblack EC-600 JD CB in Epoxy Microscopy Results

A Hitachi S-4700 field emission scanning electron microscope (FESEM) was used to

image CB/epoxy composite samples. The microscope was operated at 10kV of

accelerating voltage and at magnifications of x50,000, x100,000, and x200,000. Figure 4-

5, Figure 4-6, and Figure 4-7 show FESEM images of tensile fracture surfaces for 1 wt%

Ketjenblack EC-600 JD CB in epoxy at magnifications of x50,000, x100,000 and

x200,000, respectively. The images show a network formation of primary aggregates

with sizes between 30-100 nm.

Figure 4-5: Field emission microscope micrograph of 1 wt% EC-600 JD in epoxy at


39





40

4.2 Electrical Resistivity Results

4.2.1 Asbury Carbon’s TC307 GNP in Epoxy Electrical Resistivity Results

Table 4-1 shows the ER results for neat epoxy as well as 5, 10, 15 and 20 wt %

GNP in epoxy composites produced and tested in this project. Figure 4-8 shows the ER

results by plotting the log (electrical resistivity in Ω-cm) as a function of the filler volume

fraction. All of the ER data obtained from test specimens were displayed in the graph.

Filler concentrations of 5 and10 wt% TC307 resulted in an electrical resistivity similar to

the values obtained from neat epoxy specimens.

A percolation threshold of ~7 vol% (12 wt%) TC307 GNP was observed in the

data. The percolation threshold is the point where the electrical resistivity of the

composite significantly decreases over a narrow filler concentration differential. The

complete electrical conductivity results can be found in Appendix A. Adding up to 20

wt% TC307 GNP resulted in a decrease in ER from 2.88 × 1016 Ω-cm for the neat epoxy

to 6.05 × 105 Ω-cm. Both 5 and 10 wt% TC307 GNP in epoxy composites can be used

in electrically insulating applications. The 15 and 20 wt% TC307 GNP in epoxy

composites can be used in static dissipative applications (electrical resistivities of ~1010

to 105 Ω-cm).

Wang et al. has reported a percolation threshold of ~2 wt% GNP produced by

Ningbo Institute of Materials Technology and Engineering in a matrix of Dow 6105

cycloaliphatic epoxy cured with a methyl-hexahydrophthalic anhydride monomer [1]. A

41

percolation threshold of ~5 wt% XG Science’s M25 GNP with an average particle

diameter of 25 μm and thickness of 6 nm was observed by Prolongo et al. in an Araldite

LY556 DGEBPA epoxy matrix cured with an XB3473 amine hardener [2].

Chandrasekaran et al. observed a percolation threshold of ~0.25% GNP from Punto

Quantico with a thickness of 13 nm and a diameter of 35 μm in an Araldite LY556

DGEBPA epoxy resin cured with an Aradure 917 anhydride hardener in a solvent based

fabrication method, different from the fabrication process used in this study [3].

Table 4-1: Electrical Resistivity Results for TC307 GNP in Epoxy Composites

Formulation

Filler Content

wt% (vol%)

Electrical Resistivity (ohm-cm)

Standard Deviation (ohm-cm) Count

Neat Epoxy 0 (0) 2.88E+16 3.20E+15 6

Neat Epoxy Replicate 0 (0) 1.85E+16 2.91E+14 6

5 wt% TC307 5.0 (3.1) 1.40E+16 9.36E+14 5

5 wt% TC307 Replicate 5.0 (3.1) 1.42E+16 1.76E+15 5

10 wt% TC307 10.0 (6.2) 9.41E+15 7.46E+14 5

15 wt% TC307 15.0 (9.6) 7.42E+06 3.72E+06 7

20 wt% TC307 20.0 (13.0) 6.05E+05 1.34E+05 5

42

Figure 4-8: Log (electrical resistivity) results for TC307 GNP/epoxy composites

4.2.2 Akzo Nobel’s Ketjenblack EC-600 JD CB in Epoxy Electrical Resistivity Results

Table 4-2 shows the ER results for neat epoxy as well as 0.33, 0.67, and 1.00 wt%

CB in epoxy composites produced and tested in this project. Figure 4-9 shows the ER

results by plotting the log (electrical resistivity in Ω-cm) as a function of the filler volume

fraction. All of the ER data obtained from test specimens were displayed in the graph. A

filler concentration of 0.33 wt% Ketjenblack EC-600 JD CB resulted in an electrical

resistivity similar to the values obtained from neat epoxy specimens.

A percolation threshold of ~0.3 vol% Ketjenblack EC-600 JD was observed in the

data. The CB electrical percolation threshold is very low due to the highly branched and

high surface area structure of Ketjenblack EC-600 JD CB. The complete electrical

conductivity results can be found in Appendix A. The 0.33 wt% Ketjenblack EC-600 JD

0

2

4

6

8

10

12

14

16

18

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Lo

g E

lect

rica

l R

esis

tivit

y,

(ohm

-cm

)

GNP Volume Fraction

43

CB in epoxy composites can be used for electrically insulating applications. The 0.67 and

1.00 wt% EC-600 JD CB in epoxy composites can be used for semi-conductive

applications (electrical resistivities of ~101 to 104 Ω-cm).

Lu et al. reported a percolation threshold of 4 wt% CB from Nanyang Carbon

Limited Company with primary aggregate sizes of 100-400 nm in a DGEBPA epoxy

solidified with a low molecular weight polyamide of 650 type using in situ

polymerization [4]. A percolation threshold of ~5 wt% furnace black CB with primary

particle sizes of 3 μm was observed by Abdel-Aal et al. in a Epikot 828 epoxy resin with

an 8 wt% glycerol plasticizer and cured with a Kayo 128 aromatic hardener [5]. Etika et

al. observed a percolation threshold of ~0.5 wt% of Columbian Chemicals Conductex

7055 Ultra CB with a primary particle size of 42 nm in a Dow Chemical D.E.R. 354

epoxy cured with a Dixie Chemicals ECA 100 curing agent [6].

Table 4-2: Electrical Resistivity Results for Ketjenblack EC-600 JD CB in Epoxy

Composites

Formulation

Filler Content

wt% (vol%)



Neat Epoxy 0 (0) 2.88E+16 3.05E+15 6

Neat Epoxy Replicate 0 (0) 1.85E+16 2.91E+14 6

0.33 wt% EC-600 JD 0.33 (0.22) 2.50E+14 1.30E+14 5

0.33 wt% EC-600 JD Replicates 0.33 (0.22) 2.93E+14 1.32E+14 5

0.67 wt% EC-600 JD 0.67 (0.44) 6.44E+03 1.61E+03 6

1.00 wt% EC-600 JD 1.0 (0.67) 7.56E+02 5.44E+01 6

44

Figure 4-9: Log (Electrical Resistivity) Results for Ketjenblack EC-600 JD CB/Epoxy

Composites

4.2.3 TC307 GNP and Ketjenblack EC-600 JD CB in Epoxy Electrical Resistivity Results

Table 4-3 shows the ER results for neat epoxy as well as 0.33 wt% CB/5 wt%

GNP and 0.33 wt% CB/10 wt% GNP in epoxy composites produced and tested in this

project. Figure 4-10 shows the ER results by plotting the log (electrical resistivity in Ω-

cm) as a function of the total filler volume fraction (CB and GNP). All of the ER data

obtained from test specimens were displayed in the graph. Both formulations, 0.33 wt%

CB/5 wt% GNP and 0.33 wt% CB/10 wt% GNP, resulted in electrically conductive

composites.

After adding only a small amount of Ketjenblack EC-600 JD (0.33 wt%) to the 5

and 10 wt% TC307 in epoxy formulations, a dramatic decrease in electrical resistivity

0

2

4

6

8

10

12

14

16

18

0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008

Lo

g E

lect

rica

l R

esis

tivit

y,

(ohm

-cm

)

CB Volume Fraction

45

was observed. Adding 0.33 wt% CB to the 5 wt% GNP composites decreased the

electrical resistivity from 1.4 x 1016 Ω-cm to 1.5 x 104 Ω-cm. Adding 0.33 wt% CB to

the 10 wt% GNP composites further decreased the electrical resistivity from 9.4 x 1015

Ω-cm to 6.4 x 103 Ω-cm. The complete electrical conductivity results can be found in

Appendix A. Both hybrid composite formulations can be used for semi-conductive

applications (electrical resistivities of ~101 to 104 Ω-cm). An ER of 107 Ω-cm was

reported by Fan et al. for a composite containing 0.9 wt% GNP with 270 μm diameter

from Qingdao Graphite Company and 0.1 wt% Ketjenblack EC-600 JD CB in an E44

BPA epoxy resin supplied by Wuxi Resin Factory cured with a dicyandiamide curing

agent supplied by Tianjin Chemical Reagent No. 6 Factory [6].

Table 4-3: Electrical Resistivity Results for Ketjenblack EC-600 JD CB/TC307 GNP in

Epoxy Composites

Formulation

Filler Content

wt% (vol%)



Neat Epoxy 0 (0)

2.88E+16 3.05E+15 6

Neat Epoxy Replicate 0(0)

1.85E+16 2.91E+14 6

0.33 wt% EC-600 JD and 5 wt% TC307

CB: 0.33 (0.22) GNP: 5.0 (3.1) 1.56E+04 1.87E+03 6

0.33 wt% EC-600 JD and 5 wt% TC307 Replicate

CB: 0.33 (0.22) GNP: 5.0 (3.1) 1.44E+04 2.40E+03 6

0.33 wt% EC-600 JD and 10 wt% TC307

CB: 0.33 (0.22) GNP: 10.0 (6.2) 6.40E+03 1.88E+03 5

46

Figure 4-10: Log (Electrical Resistivity) Results for Ketjenblack EC-600 JD/TC307

epoxy composites

4.2.4 Determining Synergistic Effects of Multiple Fillers on Electrical Resistivity

The combinations of EC-600 JD CB and TC307 in epoxy produced significantly

lower ER values than either CB or GNP did by themselves. Factorial designs are the most

efficient way to determine the effect of each filler and to investigate potential interactions

between fillers. By using factorials, the effect of each factor on the electrical resistivity of

the composite can be quantified by a calculated “effect”. The effects of each factor can be

compared to determine which of the filler and combination of fillers produced a larger

change in the electrical resistivity values of the composite material [7]. A two-factor two-

level factorial design with a replicate was administered with low and high loadings of CB

and GNP to determine the individual and synergistic effects of both fillers. A complete

set of replicate formulations were produced for each formulation in order to verify

0

2

4

6

8

10

12

14

16

18

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07

Lo

g E

lect

rica

l R

esis

tivit

y,

(ohm

-cm

)

Total Filler Volume Fraction (CB+GNP)

47

experimental results in the statistical analysis. The formulations that make up the factorial

experiment are shown in Table 4-4.

Table 4-4: Weight Percent Filler in Factorial Design Formulations

Terms Ketjenblack EC-600 JD wt% TC307 wt%

(1) 0 0

A 0.33 0

B 0 5

AB 0.33 5

The factorial assessment was conducted on a Minitab version 17 Statistical

Software package. For all statistical calculations, the 95% confidence level was used. For

this analysis, the effects and P values for the log(ER) results were calculated. By taking

the logarithm of ER values, data can be easily compared in terms of orders of magnitude.

Small p values indicate that a factor, a filler, may have a significant effect on the log(ER)

result of the composite. The effects and P values are given in Table 4-5 for each filler

combination. The negative effect terms observed in the table demonstrate that composites

containing only single fillers cause a statistically significant decrease in electrical

resistivity.

Composites containing only carbon black have a larger effect term than the

composites that contained only graphene nanoplatelets. It is also noted that the

combinations of different fillers had a statistically significant effect on the log(ER) of the

composite. The negative effect of the interaction term means that adding 0.33 wt% CB

and 5 wt% GNP to epoxy caused the composite ER to be lower than what would be

48

expected from the additive effect of each single filler. The results suggest that the highly

branched CB and the GNP are likely forming electrically conductive networks. Fan et al.

also demonstrated that adding a small amount of CB decreased the ER of GNP/epoxy

composites [8].

Table 4-5: Factorial Design Analysis for the Logarithm of the Electrical Resistivity

(ohm-cm)

Terms Effect P

Constant - 0

5.0 wt% GNP -5.235 0

0.33 wt% CB -6.952 0

5.0 wt% GNP/0.33 wt% CB -5.022 0

4.3 Thermal Conductivity Results

4.3.1 Asbury Carbon’s TC307 GNP in Epoxy Thermal Conductivity Results

Table 4-6 shows the mean (with standard deviation) through-plane thermal

conductivity results of the studied composites as a function of filler volume and weight

fraction for the TC307 GNP composites. Compounding TC307 GNP in the epoxy matrix

doubled the thermal conductivity from ~0.2 W/m-K for the neat epoxy to ~0.4 W/m-K

for 20 wt% TC307 GNP epoxy composites. The resulting increase in thermal

conductivity could be useful in thermal dissipative applications. Adding more than 20

wt% TC307 GNP resulted in a material that was too viscous to fabricate samples from. It

has been reported by Wang et al. that adding 5 wt% XG Sciences GnP-C750 (GNP with

<1 μm average particle diameter, ~5 to 10 nm thickness, surface area ~750 𝑚2/g) to

EPON 828 epoxy resin with an m-phenylene diamine curing agent resulted in a slight

49

increase in thermal conductivity from ~0.22 to 0.24 W/m-K [9]. This is a result that is

consistent with the data reported in this study.

Table 4-6: Thermal Conductivity Results for TC307 GNP in Epoxy Composites


wt% (vol%)

Thermal Conductivity

(W/m-K) Count

Neat 0 (0) 0.206 ± 0.006 5

5% GNP 5.0 (3.1) 0.266 ± 0.002 5

10% GNP 10.0 (6.2) 0.304 ± 0.002 5

15% GNP 15.0 (9.6) 0.364 ± 0.008 4

20% GNP 20.0 (13.0) 0.394 ± 0.009 4

4.3.2 Akzo Nobel’s EC-600 JD CB in Epoxy Thermal Conductivity Results



fraction for the Ketjenblack EC-600 JD CB composites. Compounding up to 1 wt%

Ketjenblack EC-600 JD CB in the epoxy matrix had no appreciable effect on the thermal

conductivity of the composite. The CB/epoxy composites had a thermal conductivity of

~0.2 W/m-K. Adding more than 1.0 wt% Ketjenblack EC-600 JD CB resulted in a

material that was too viscous to fabricate samples from due to the highly branched and

high surface area of the CB. An increase in composite thermal conductivity from ~0.2

W/m-K to ~0.4 W/m-K was observed by Abdel-Aal when adding 10 wt% of a lower

surface area CB to epoxy [5].

50

Table 4-7: Thermal Conductivity Results for Ketjenblack EC-600 JD CB in Epoxy

Composites


wt% (vol%)


(W/m-K) Count

Neat 0 (0) 0.206 ± 0.006 5

1/3% CB 0.33 (0.22) 0.212 ± 0.002 5

2/3% CB 0.67 (0.44) 0.216 ± 0.001 5

1% CB 1.0 (0.67) 0.210 ± 0.005 5

4.3.3 TC307 GNP and EC-600 JD CB in Epoxy Thermal Conductivity Results



fraction for the TC307 GNP/Ketjenblack EC-600 JD CB composites. Compounding

TC307 GNP and Ketjenblack EC-600 JD CB in the epoxy matrix increased the thermal

conductivity from ~0.2 W/m-K for the neat epoxy to ~0.3 W/m-K for 0.33 wt%

Ketjenblack EC-600 JD CB and 10 wt% TC307 GNP in epoxy composites. The thermal

conductivity results of the 0.33 wt% CB and 5 wt% GNP in epoxy as well as the 0.33

wt% CB and 10 wt% GNP in epoxy were similar to that of the 5 wt% GNP in epoxy and

10 wt% GNP in epoxy composites, respectively.

51

Table 4-8: Thermal Conductivity Results for Ketjenblack EC-600 JD CB and TC307

GNP in Epoxy Composites


wt% (vol%)


(W/m-K) Count

Neat 0 0.206 ± 0.006 5

0.33 wt% CB 5 wt% GNP

CB: 0.33 (0.22) GNP: 5.0 (3.1) 0.265 ± 0.002 5


CB: 0.33 (0.22) GNP: 10.0 (6.2) 0.304 ± 0.008 5

4.4 Tensile Results

4.4.1 Asbury Carbon’s TC307 GNP in Epoxy Tensile Results

Table 4-9 shows the mean (with standard deviation) ultimate tensile strength,

strain at ultimate tensile strength, and tensile modulus for the TC307 GNP in epoxy

composites measured according to ASTM D638. Adding GNP to the epoxy caused the

ultimate tensile strength to decrease from 77.6 MPa for the neat composites to 49.9 MPa

for the 20 wt% (13.0 vol%) TC307 GNP, shown in Figure 4-11. The strength remained

similar to that of the neat epoxy up to 10 wt% (6.3 vol%) GNP and then a steady decrease

in strength was observed for up to 20 wt% (13.0 vol%) GNP. The strain at ultimate

tensile strength decreased from 7.98% for the neat epoxy to 1.54% for the 20 wt% (13.0

vol%) TC307 GNP in epoxy composites, shown in Figure 4-12. The strain at ultimate

tensile strength decreased quickly with initial loading of TC307 GNP and decreased more

steadily with higher loadings. The tensile modulus steadily increased from 2.72 GPa for

the neat epoxy to 3.69 GPa for the composites containing 20 wt% (13.0 vol%) TC307

GNP in epoxy, shown in Figure 4-13. An increase in tensile modulus from ~2.7 GPa for

52

neat epoxy to 3.2 GPa for 5 wt% GnP-C750 in epoxy composites have been reported by

Wang et al. It was also observed that the tensile strength remained similar to that of the

neat resin [9]. Wang’s result was similar to what was observed in this study.

Table 4-9: Tensile Results for TC307 GNP in Epoxy Composites

Formulation Filler

Content wt% (vol%)

Tensile Modulus

(GPa)

Ultimate Tensile

Strength (Mpa)

Strain at Ultimate Tensile Strength

(%) Count

Neat 0 (0) 2.72 ± 0.04 77.6 ± 0.9 7.98 ± 0.35 6

5 wt% GNP 5.0 (3.1) 2.97 ± 0.07 72.9 ± 1.5 3.85 ± 0.12 7

10 wt% GNP 10.0 (6.2) 3.20 ± 0.11 70.0 ± 2.4 3.27 ± 0.27 5

15 wt% GNP 15.0 (9.6) 3.37 ± 0.04 61.8 ± 3.9 2.36 ± 0.23 5

20 wt% GNP 20.0 (13.0) 3.69 ± 0.08 49.9 ± 2.0 1.54 ± 0.08 5

Figure 4-11: Ultimate Tensile Strength Results for TC307 GNP in Epoxy

Composites

0

10

20

30

40

50

60

70

80

90

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Ult

imat

e T

ensi

le S

tren

gth

(M

Pa)

GNP Volume Fraction

53

Figure 4-12: Strain at Ultimate Strength Results for TC307 GNP in Epoxy Composites

Figure 4-13: Tensile Modulus Results for TC307 GNP in Epoxy Composites

4.4.2 Akzo Nobel’s EC-600 JD CB in Epoxy Tensile Results


strain at ultimate tensile strength, and tensile modulus for the Ketjenblack EC-600 JD CB

0

1

2

3

4

5

6

7

8

9

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Str

ain a

t U

ltim

ate

Str

ength

(%

)

GNP Volume Fraction

2.5

2.7

2.9

3.1

3.3

3.5

3.7

3.9

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Ten

sile

Mo

dulu

s (G

Pa)

GNP Volume Fraction

54

in epoxy composites measured according to ASTM D638. Adding CB to the epoxy

resulted in a slight decrease in ultimate tensile strength from 77.6 MPa for neat epoxy to

80.4 MPa for 1.0 wt% Ketjenblack EC-600 JD CB composites, as shown in Figure 4-14.

A slight decrease in the strain at ultimate tensile strength was observed with the strain

from 8.0% for neat epoxy to 7.3% for 1.0 wt% Ketjenblack EC-600 JD CB composites,

as shown in Figure 4-15. Adding the CB resulted in no change in tensile modulus from

the neat epoxy. All CB composite formulations tested demonstrated an elastic modulus of

2.7 GPa, as shown in Figure 4-16. Abdel-Khalil et al. observed a decrease in tensile

strength from ~48 MPa for neat epoxy to ~38 MPa for 5 wt% carbon black made using

coconut shells in a diglycidyl ether of bisphenol A cured with an isophorone hardener.

They also reported a decrease in strain from ~4.4% for neat epoxy to 2.2% for 5 wt%

carbon black. In their study, the elastic modulus did not change with the addition of up to

5 wt% carbon black in epoxy [5].

Table 4-10: Tensile Results for Ketjenblack EC-600 JD in Epoxy Composites

Formulation Filler

Content wt% (vol%)

Tensile Modulus

(GPa)

Ultimate Tensile

Strength (Mpa)

Strain at Ultimate Tensile Strength

(%) Count

Neat 0 (0) 2.72 ± 0.04 77.6 ± 0.9 7.98 ± 0.35 6

0.33 wt% CB 0.33 (0.22) 2.72 ± 0.04 81.8 ± 0.4 7.28 ± 0.21 6

0.67 wt% CB 0.67 (0.44) 2.74 ± 0.04 81.5 ± 0.6 7.25 ± 0.38 5

1.0 wt% CB 1.0 (0.67) 2.74 ± 0.04 80.4 ± 0.4 7.34 ± 0.35 6

55

Figure 4-14: Ultimate Tensile Strength Results for Ketjenblack EC-600 JD CB in

Epoxy Composites

Figure 4-15: Strain at Ultimate Tensile Strength Results for Ketjenblack EC-600 JD

CB in Epoxy Composites

0

10

20

30

40

50

60

70

80

90

0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008

Ult

imat

e T

ensi

le S

tren

gth

(M

Pa)

CB Volume Fraction

0

1

2

3

4

5

6

7

8

9

0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008

Str

ain a

t U

ltim

ate

Str

ength

(%

)

CB Volume Fraction

56

Figure 4-16: Tensile Modulus Results for Ketjenblack EC-600 JD CB in Epoxy

Composites

4.4.3 TC307 GNP and EC-600 JD CB in Epoxy Tensile Results


strain at ultimate tensile strength, and tensile modulus for the TC307 GNP and

Ketjenblack EC-600 JD CB in epoxy composites measured according to ASTM D638.

Figure 4-17 shows that adding TC307 GNP to the 0.33 wt% CB composite decreased the

ultimate strength of the composite from 81.8 MPa for the 0.33 wt% CB composite to 61.6

MPa for the 10 wt% GNP and 0.33 wt% CB composite. A decrease in strain at the

ultimate strength was observed in Figure 4-18 from 7.28% for the 0.33 wt% CB

composite to 2.45% for the 10 wt% GNP and 0.33 wt% CB composite. Figure 4-19

shows that the addition of TC307 GNP to the 0.33 wt% CB in epoxy composite increased

the tensile modulus from 2.72 GPa for the 0.33 wt% CB composite to 3.27 GPa for the 10

0

0.5

1

1.5

2

2.5

3

0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008

Ten

sile

Mo

dulu

s (G

Pa)

CB Volume Fraction

57

wt% GNP and 0.33 wt% GNP composites.

Table 4-11: Tensile Results for TC307 GNP and Ketjenblack EC-600 JD in Epoxy

Composites


wt% (vol%)

Tensile Modulus

(GPa)

Ultimate Tensile

Strength (Mpa)

Strain at Ultimate Tensile

Strength (%) Count

Neat 0 (0) 2.72 ± 0.04 77.6 ± 0.9 7.98 ± 0.35 6


CB: 0.33 (0.22) GNP: 5.0 (3.1)

3.20 ± 0.08 68.3 ± 2.9 3.09 ± 0.27 5


CB: 0.33 (0.22) GNP: 10.0 (6.2)

3.27 ± 0.10 61.6 ± 2.5 2.45 ± 0.20 6

Figure 4-17: Ultimate Tensile Strength Results for Ketjenblack EC-600 JD CB and

TC307 GNP in Epoxy Composites

0

10

20

30

40

50

60

70

80

90

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07

Ult

imat

e T

ensi

le S

tren

gth

(M

Pa)

Total Volume Fraction (CB+GNP)

58

Figure 4-18: Strain at Ultimate Tensile Strength Results for Ketjenblack EC-600 JD

CB and TC307 GNP in Epoxy Composites

Figure 4-17: Tensile Modulus Results for Ketjenblack EC-600 JD CB and TC307 GNP

in Epoxy Composites

0

1

2

3

4

5

6

7

8

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07

Str

ain a

t U

ltim

ate

Str

ength

(%

)


0

0.5

1

1.5

2

2.5

3

3.5

4

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07

Ten

sile

Mo

dulu

s (G

Pa)


59

The ultimate strength decreased when 0.33 wt% Ketjenblack EC-600 JD CB was

added to 5 wt% and 10 wt% TC307 in epoxy composites from 72.9 and 70.0 GPa for the

5 wt% and 10 wt% GNP composites to 68.3 and 61.6 GPa for the 5 wt% and 10 wt%

GNP composites with 0.33 wt% CB. The tensile modulus increased when adding 0.33

wt% Ketjenblack EC-600 JD CB to 5 wt% and 10 wt% TC307 in epoxy composites from

2.97 and 3.2 GPa for the 5 wt% and 10 wt% GNP composites to 3.20 and 3.27 for the 5

wt% and 10 wt% GNP composites with 0.33 wt% CB. The strain at ultimate strength

decreased when 0.33 wt% Ketjenblack EC-600 JD CB was added to 5 wt% and 10 wt%

TC307 in epoxy composites from 3.85% and 3.27% for the 5 wt% and 10 wt% GNP

composites to 3.09% to and 2.45% for the 5 wt% and 10 wt% GNP composites with 0.33

wt% CB.

4.4.4 Tensile Modulus Modeling

The experimental tensile modulus results of this study were compared to several different

models: Einstein’s, Guth and Smallwood’s, and Halpin-Tsai’s model. Einstein’s

equation, shown in Equation 4-1, predicts the elastic modulus of composite materials

using the volume fraction of the filler (𝑉𝑓) and the elastic modulus of the matrix (𝐸𝑚)

[10-12]. Einstein’s equation was originally developed for calculating incremental changes

in viscosity of suspensions with the inclusion of hard spheres. Later, an analogy had been

discovered between hydrodynamics of suspensions with rigid spheres and the

elastostatics of solids with the inclusion of rigid particles, allowing us to use this formula

as an approximation for the elastic modulus of an isotropic composite with small filler

loading levels.

60

𝐸𝐶 = 𝐸𝑚(1 + 2.5𝑉𝑓) [4-1]

Guth and Smallwood generalizes Einstein’s model for larger filler concentrations by

adding another term to the polynomial series expansion in order to account for

interparticle interactions as shown in Equation 4-2 [11][13][14].

𝐸𝐶 = 𝐸𝑚(1 + 2.5𝑉𝑓 + 14.1𝑉𝑓2) [4-2]

Halpin and Tsai developed a model that uses the fillers aspect ratio (L/t), shape factor (ξ),

volume fraction (𝑉𝑓) and elastic modulus (𝐸𝑓) as well as the elastic modulus of the matrix

(𝐸𝑚) to predict the modulus of the composite material (𝐸𝑐). The Halpin-Tsai model

predicts the tensile modulus of a composite with unidirectional and discontinuous fillers

by calculating theoretical longitudinal and transversal moduli of the composite using

Equation 4-3 and Equation 4-4. The parameters of 𝜂𝐿 and 𝜂𝑇 are calculated using

Equation 4-5 and Equation 4-6.

𝐸𝐿

𝐸𝑀=

1+ξ𝜂𝐿𝑉𝑓

1−𝜂𝐿𝑉𝑓 [4-3]

𝐸𝑇

𝐸𝑀=

1+2𝜂𝑇𝑉𝑓

1−𝜂𝑇𝑉𝑓 [4-4]

𝜂𝐿 =

𝐸𝑓

𝐸𝑀−1

𝐸𝑓

𝐸𝑀+ξ

[4-5]

𝜂𝑇 =

𝐸𝑓

𝐸𝑀−1

𝐸𝑓

𝐸𝑀+2

[4-6]

61

The composite tensile modulus for two-dimensional and three-dimensional (3D)

random orientation of fillers was calculated using Equation 4-7 and Equation 4-8. In this

study, the composites produced consist of 3D randomly oriented fillers [14-17].

𝐸𝐶 =3

8𝐸𝐿 +

5

8𝐸𝑇 [4-7]

𝐸𝐶 =1

5𝐸𝐿 +

4

5𝐸𝑇 [4-8]

Where 𝐸𝐶 is the composite tensile modulus. The tensile modulus of the matrix, 𝐸𝑀,

was experimentally determined to be 2.72 GPa and was used in these models. GNP

consists of multiple sheets stacked on one another. Though the tensile modulus of

graphene sheets are around 1000 GPa in the plane of the sheet, the van der Waal’s

dispersion bonding forces between sheets fail much sooner than the graphitic carbon-

carbon bonding within the sheets. The failure between sheets leads to further exfoliation

of the particle and so the modulus of exfoliation is used as the tensile modulus of the

filler for modeling purposes. Hence, the tensile modulus of the filler used in this model,

𝐸𝐹, is equal to 36.5 GPa [18]. For platelets, the filler shape factor, ξ, is equal to 0.667

(L/t) [19]. The filler aspect ratio, L/t, is 60 (mean platelet length = 750 nm and thickness

= 12.5 nm), which leads to a shape factor of 40.

Figure 4-18 shows the experimental tensile modulus data (mean with ±1 standard

deviation) for GNP/epoxy composites along with the predictions made by the Einstein,

Guth and Smallwood, and Halpin-Tsai 3D models. Microscopy performed on the

GNP/epoxy composites indicate that there is a 3D random orientation of GNP in the

62

epoxy matrix. Over the entire filler volume fraction range studied in this project, the

Einstein model gave the best prediction of composite tensile modulus.

Figure 4-20: Tensile Modulus of GNP/Epoxy Composites with Einstein, Guth-

Smallwood, and 3D Halpin-Tsai Models

4.5 References

[1] Wang Y, Yu J, Dai W, Song Y, Wang D, Zheng L, and Jiang N. “Enhanced thermal

and electrical properties of epoxy composites reinforced with graphene nanoplatelets”.

Polymer Composites (2016); 36: 556-565.

[2] Prolongo SG, Moriche R, Jimenez-Suarez A, Sanchez, M, and Urena A. “Advantages

and disadvantages of the addition of graphene nanoplatelets to epoxy resins”. European

Polymer Journal (2014); 61: 206-214.

[3] Chandrasekaran, S, Seidel, C, and Schulte K. “Preparation and characterization of

graphite nano-platelet (GNP)/epoxy nano-composite: mechanical, electrical, and thermal

properties”. European Polymer Journal (2013); 49: 3878-3888.

[4] Lu X, La P, Guo X, and Wei Y. “Study on microstructure and mechanical properties

of epoxy resin/carbon black composites prepared by in situ polymerization”. Applied

Mechanics and Materials (2012); 109: 156-160.

2.5

2.7

2.9

3.1

3.3

3.5

3.7

3.9

4.1

4.3

4.5

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Ten

sile

Mo

dulu

s (G

Pa)

GNP Volume Fraction

TC307 Tensile Modulus

TC307 Einstein Model

TC307 Guth/Smallwood Model

TC307 3D Halpin-Tsai Model

63

[5] Abdel-Aal N, El-Tantawy F, Al-Hajry A, and Boudoudina M. “Epoxy

resin/plasticized carbon black composites. Part 1. Electrical and thermal properties and

their applications”. Polymer Composites (2008); 29: 511-517.

[6] Etika KC, Liu L, Hess, LA and Grunlan JC. “The influence of synergistic stabilization

of carbon black and clay on the electrical and mechanical properties of epoxy

composites”. Carbon (2009); 47: 3128-3136.

[7] Montgomery, DC. “Design and analysis of experiments”, 5th edition, New York, NY:

Wiley, Inc., 2001.

[8] Fan Z, Zheng C, Wei T, Zhang Y, and Luo G. “Effect of carbon black on electrical

property of graphite nanoplatelets/epoxy resin composites”. Polymer Engineering and

Science (2009); 49: 2041-2045.

[9] Wang F, Drzal LT, Quin Y, and Huang Z. “Mechanical properties and thermal

conductivity of graphene nanoplatelet/epoxy composite”. Material Science. 2015; 50:

1082-1093

[10] Einstein A. “Investigation on the Theory of the Brownian Movement”. Annals of

Physics. 1906: pp. 289-306.

[11] Karrad, S, Lopez Cuesta JM., and Crespy A. “Influence of a fine talc on the

properties of composites with high density polyethylene and polyethylene/polystyrene

blends. Materials Science. 1998; 33:453-461.

[12] Jain S, Reddy MM, Mohanty AK, Misra M, and Chosh AK. “A new biodegradable

flexible composite sheet from poly(lactic acid)/poly(ε-caprolactone) blends and micro-

talc”. Macromolecular Materials Engineering. 2010; 295: 750-762.

[13] Guth E. “Theory of Filler Reinforcement”. Journal of Applied Physics. 1945.

[14] Halpin J. C. “Stiffness and expansion estimates for oriented short fiber composites”.

Composite Materials 1969; 3: 732-734.

[15] Halpin, J.C., and Kardos, J. L. “The Halpin-Tsai equations: a review”. Polymer

Engineering and Science 1976; 16: 344-352.

[16] Agarwal B.D. and Broutman L. J. “Analysis and performance of fiber composites”.

Wiley, New York, NY, 1980.

[17] Mallick P.K. “Composites engineering handbook”. Marcel Dekker, Inc., New York,

NY, 1997.

[18] Marsh, H., Rodriguez-Reinoso, F. “Sciences of carbon materials”. Universidad de

Alicante, San Vicente del Raspeig Alicante, Spain, 2001.

64

[19] Van Es M. “Polymer-clay nanocomposite: The importance of particle dimensions”.

Ph.D. dissertation, Delft University of Technology. Delft, Netherlands, 2001.

65

5 Conclusions and Future Work

Conclusions were made about the composite types according to the results of tensile,

thermal and electrical conductivity tests. The conclusions were organized into a table as

shown in Table 5-1. The following sections describe the conclusions in more detail.

Table 5-1: A summary of the conclusions made about the composite types tested

Property

Carbon Black

Composites

(up to 1 wt%)

GNP Composites

(up to 20 wt%)

CB/GNP Composites

(0.33 wt% CB and up

to 10 wt% GNP)

ER

- Composites made

electrically

Conductive

- Percolation

threshold

at ~0.3 vol%

-Composites made

electrically

conductive

- Percolation

threshold

at ~12 wt%

(~7 vol%)

-Composites made

electrically

conductive

- Synergistic effect of

CB and GNP on ER

of composite

Tensile -Tensile properties

unchanged

- Mild decreases

in strength

- Large decreases

in strain

- Mild increases

in modulus

- Einstein's model best

- Mild decrease

in strength

- Large decrease

in strain

- Mild increases

in modulus

TC

-Thermal

conductivity

unchanged

-Thermal conductivity

doubled at 20 wt%

GNP composites

-GNP dominates

thermal conductivity

66

5.1 Electrical Resistivity Properties for Neat Epoxy, GNP/Epoxy, CB/Epoxy, and GNP/CB/Epoxy Composites

Electrical resistivity (ER) tests were conducted for neat epoxy, GNP/epoxy,

CB/epoxy, and GNP/CB/epoxy composites. The data was used to determine the

percolation threshold of the carbon single filler epoxy composites (GNP/epoxy and

CB/epoxy) and to determine if there were synergistic effects between CB and GNP filler

concentrations by conducting a factorial design on the composite ER. The ER of the neat

epoxy is 2.88 × 1016 Ω-cm. Adding up to 20 wt% GNP to the neat epoxy decreased the

ER to 6.05 × 105 Ω-cm. The percolation threshold for the GNP/epoxy composites was

observed to be at ~7 vol% (12 wt%) GNP. Adding up to 1 wt% CB to the neat epoxy

decreased the ER to 756 Ω-cm. The percolation threshold for the CB/epoxy composites

was determined to be 0.3 vol% Ketjenblack EC-600 JD CB. Adding 1/3 wt% CB to up to

10 wt% GNP decreased the ER from 9.41 × 1015 Ω-cm for the 10 wt% GNP in epoxy

formulation to 6,400 Ω-cm for the 0.33 wt% CB/10 wt% GNP/epoxy composite.

The 0.33 wt% Ketjenblack EC-600 JD CB/epoxy composite and the 5 and 10 wt%

TC307 GNP/epoxy composites could be used for electrically insulating applications,

including Polymer Core Composite Conductors to be used in power transmission lines.

The 0.67 and 1.0 wt% CB in epoxy composites and both of the combination composites

(0.33 wt% CB with 5 wt% GNP and 0.33 wt% CB with 10 wt% GNP) could be used for

semi-conductive applications. The 15 wt% GNP and 20 wt% GNP in epoxy composites

could be used for static dissipative applications. These results are organized in Table 5-1.

67

Table 5-2: Potential applications for composite formulations tested for ER

Application Formulation ER (Ω-cm)

Electrically Insulating Applications

( > 1011Ω-cm)

-PCCC transmission lines

0.33 wt% CB/epoxy 2.50 x 10^14

5 wt% GNP/epoxy 1.40 x 10^16

10 wt% GNP/epoxy 9.41 x 10^15

Static Dissipative Applications

(~105 to 1010Ω-cm)

-Sensitive electronics

15 wt% GNP/epoxy 7.42 x 10^6

20 wt% GNP/epoxy 6.05 x 10^5

Semi-conductive Applications

(~10 to 104 Ω-cm)

-Aerospace

0.67 wt% CB/epoxy 6,440

1.0 wt% CB/epoxy 756

0.33 wt% CB/5 wt%

GNP/epoxy 15,600

0.33 wt% CB/10 wt%

GNP/epoxy 6,400

The factorial design on the GNP and CB concluded that at the 95% confidence

level, the combination of adding 5 wt% GNP and 0.33 wt% CB to an epoxy composite

caused the ER to decrease by a statistically significant amount. The ER decreased more

than what would be expected from the additive effect of each independent filler in epoxy

by itself. The results suggest that the highly branched CB and the GNP are likely forming

electrically conductive networks. Per the authors’ knowledge, electrical conductivity

properties for these loading levels of Asbury Carbons TC307 GNP and Ketjenblack EC-

600 JD in this epoxy system (EPON 862 with EPIKURE Curing Agent W) have not been

previously reported in the open literature.

68

5.2 Thermal Conductivity Properties for Neat Epoxy, GNP/Epoxy, CB/Epoxy, and GNP/CB/Epoxy Composites

Adding 20 wt% GNP to epoxy caused the composite thermal conductivity to

double from ~0.2𝑊

𝑚∙𝐾 to ~0.4

𝑊

𝑚∙𝐾. Adding up to 1 wt% CB in epoxy did not appreciably

change the thermal conductivity of the neat epoxy which remained at about ~0.2𝑊

𝑚∙𝐾.

The thermal conductivity of the CB/GNP/epoxy composites were similar to the thermal

conductivities of the similar loading of GNP/epoxy composites. Higher thermal

conductivities could help dissipate heat in high temperature and voltage applications such

as in PCCC technology. Per the authors’ knowledge, thermal conductivity properties for

these loading levels of Asbury Carbons TC307 GNP and Ketjenblack EC-600 JD in this

epoxy system (EPON 862 with EPIKURE Curing Agent W) have not been previously

reported in the open literature.

5.3 Tensile Properties for Neat Epoxy, GNP/Epoxy, CB/Epoxy, and GNP/CB/Epoxy Composites

For the GNP/epoxy composites (5, 10, 15 and 20 wt% GNP), the ultimate tensile

strength did not change much from the neat epoxy for the 5 and 10 wt% TC307 GNP in

epoxy composites (~70 MPa) and decreased to 49.9 MPa at 20 wt% TC307 GNP in

epoxy composites. The strain at the ultimate tensile strength decreased immediately for

epoxy composites after compounding with GNP from 8.0% for neat epoxy to 1.5% for 20

wt% TC307 GNP. The GNP/epoxy composites showed steady increases in elastic

modulus from 2.72 GPa for neat epoxy to 3.69 GPa for the 20 wt% TC307 GNP in epoxy

69

composites. The tensile results for the 5 and 10 wt% GNP in epoxy are encouraging

because they can be used in Polymer Core Composite Conductors in power transmission

lines, where the increased elastic modulus and thermal conductivity (useful to dissipate

heat) are needed along with good strength (~70 MPa) and acceptable strain (≥ 3.3%).

The Einstein model for the elastic modulus was the model that predicted the tensile

modulus best.

For the CB/epoxy composites (0.33, 0.67, and 1.0 wt% CB), the strength, strain,

and modulus remained relatively constant at ~80 MPa, ~7.3%, and 2.7 MPa, respectively.

This result is exciting because the ER of the 0.67 and 1.0 wt% CB/epoxy was

significantly reduced without degradation of the tensile properties. Per the authors’

knowledge, tensile properties for these loading levels of Asbury Carbons TC307 GNP

and Ketjenblack EC-600 JD in this epoxy system (EPON 862 with EPIKURE Curing

Agent W) have not been previously reported in the open literature.

The combination filler composites experienced decreases in ultimate strength and

strain and increases in elastic modulus when adding 0.33 wt% CB to 5 and 10 wt%

GNP/epoxy composites. Adding 0.33 wt% CB to the TC307 GNP composites decreased

the ultimate strength of the composite from 70 MPa for the 10 wt% GNP composites to

61.6 MPa for the 10 wt% GNP and 0.33 wt% CB composite. A decrease in strain at the

ultimate strength was observed from 3.3% for the 10 wt% GNP composites to 2.45% for

the 10 wt% GNP and 0.33 wt% CB composite. The addition of 0.33 wt% CB to TC307

GNP in epoxy composites increased the tensile modulus from 3.2 GPa for the 10 wt%

GNP composite to 3.3 GPa for the 10 wt% GNP and 0.33 wt% GNP composites. The

70

author could not find published papers in the open literature that reported the tensile

properties of similar loading levels of combinations of TC307 GNP and EC-600 JD CB

in epoxy.

5.4 Recommendations for Future Work

This project demonstrated that adding GNP to an epoxy matrix will increase the

elastic modulus of the composite. There are many types of GNP with a variety of sizes

that can be compounded into an epoxy matrix to be characterized. This project also

demonstrated that adding CB to an epoxy will increase the electrical conductivity of the

composite. Other conductive carbon blacks are available that can be compounded into a

epoxy matrix to be characterized. It could also be beneficial to experiment with higher

filler volume fractions as well as different combinations of the TC307 GNP and

Ketjenblack EC-600 JD CB in order to characterize the tensile properties as well as the

thermal and electrical conductivities.

Other tests can be done to further characterize the composite materials fabricated in

this study. The conductive composite materials to be used in high voltage applications

and with an ER between 101 − 104 Ω-cm can be tested for the glass transition

temperature and the insulating composite materials can be tested for the dielectric

constant. An aging study could be done on the conductive composite materials as well to

determine how the properties change after the material has undergone simulated aging

71

processes similar to that which would be experienced by high voltage transmission lines

in real world conditions.

72

A Appendix A: Electrical Resistivity Results

Table A-1: ASTM D257 Through-Plane Electrical Resistivity Results for Neat Epoxy

Sample Number

Applied Voltage

(V) Volume Electrical Resistivity (Ω-cm)

A862-4-17-12-1 100 2.8174E+16

A862-4-17-12-2 100 3.1263E+16

A862-4-17-12-3 100 2.8694E+16

A862-4-17-12-4 100 3.3570E+16

A862-4-17-12-5 100 2.5305E+16

A862-4-17-12-6 100 2.5670E+16

Average 2.8779E+16

Standard Deviation 3.2010E+15

Count 6


Neat Epoxy

Sample Number

Applied Voltage


U862-W-6-22-17-1 100 1.8415E+16

U862-W-6-22-17-2 100 1.8105E+16

U862-W-6-22-17-3 100 1.8485E+16

U862-W-6-22-17-4 100 1.8457E+16

U862-W-6-22-17-5 100 1.9001E+16

U862-W-6-22-17-6 100 1.8404E+16

Average 1.8478E+16


Count 6

73

Table A-3: ASTM D257 Through-Plane Electrical Resistivity Results for 5 wt% TC307


Sample Number

Applied Voltage


U862-W-5T-6-23-17-1 100 1.2495E+16

U862-W-5T-6-23-17-2 100 1.4459E+16

U862-W-5T-6-23-17-3 100 1.3771E+16

U862-W-5T-6-23-17-4 100 1.4868E+16

U862-W-5T-6-23-17-5 100 1.4472E+16

Average 1.4013E+16


Count 5

Table A-4: ASTM D257 Through-Plane Electrical Resistivity Replicate Results for 5

wt% TC307 GNP in Epoxy Composites

Sample Number

Applied Voltage


U862-W-5T-11-2-17-1 100 1.4008E+16

U862-W-5T-11-2-17-2 100 1.2254E+16

U862-W-5T-11-2-17-3 100 1.4985E+16

U862-W-5T-11-2-17-4 100 1.6758E+16

U862-W-5T-11-2-17-5 100 1.3006E+16

Average 1.4202E+16


Count 5

74

Table A-5: ASTM D257 Through-Plane Electrical Resistivity Results for 10 wt%


Sample Number

Applied Voltage


U862-W-10T-6-26-17-1 100 8.4584E+15

U862-W-10T-6-26-17-2 100 1.0553E+16

U862-W-10T-6-26-17-3 100 9.3155E+15

U862-W-10T-6-26-17-4 100 9.3646E+15

U862-W-10T-6-26-17-5 100 9.3627E+15

Average 9.4108E+15


Count 5



Sample Number

Applied Voltage


U862-W-15T-6-29-17-16 10 1.7635E+06

U862-W-15T-6-29-17-19 10 7.1472E+06

U862-W-15T-6-29-17-20 10 6.3793E+06

U862-W-15T-6-29-17-22 10 1.0233E+07

U862-W-15T-6-29-17-23 10 8.8090E+06

U862-W-15T-6-29-17-24 10 1.3061E+07

U862-W-15T-6-29-17-25 10 4.5661E+06

Average 7.4228E+06


Count 7

75



Sample Number

Applied Voltage


U862-W-20T-7-12-17-7 10 5.8562E+05

U862-W-20T-7-12-17-8 10 5.0352E+05

U862-W-20T-7-12-17-9 10 6.2961E+05

U862-W-20T-7-12-17-10 10 4.8639E+05

U862-W-20T-7-12-17-2 10 8.2087E+05

Average 6.0520E+05


Count 5

Table A-8: ASTM D257 Through-Plane Electrical Resistivity Results for 0.33%

Ketjenblack EC-600 JD CB in Epoxy Composites

Sample Number

Applied Voltage


U862-W-0.33A-8-15-17-1 10 2.8039E+14

U862-W-0.33A-8-15-17-2 10 3.5058E+14

U862-W-0.33A-8-15-17-3 10 3.9075E+14

U862-W-0.33A-8-15-17-4 10 1.1813E+14

U862-W-0.33A-8-15-17-5 10 1.1196E+14

Average 2.5036E+14


Count 5

76


0.33% Ketjenblack EC-600 JD CB in Epoxy Composites

Sample Number

Applied Voltage


U862-W-0.33A-11-1-17-1 10 1.4651E+14

U862-W-0.33A-11-1-17-2 10 2.4172E+14

U862-W-0.33A-11-1-17-3 10 4.2299E+14

U862-W-0.33A-11-1-17-4 10 2.1244E+14

U862-W-0.33A-11-1-17-5 10 4.4208E+14

Average 2.9315E+14


Count 5

Table A-10: ASTM D4496 Two Point In-Plane Electrical Resistivity Results for 0.67%


Sample Number

Applied Voltage


U862-W-0.67A-8-14-17-6 0.5 4.4278E+03

U862-W-0.67A-8-14-17-6a 0.5 6.9152E+03

U862-W-0.67A-8-14-17-7 0.5 9.1601E+03

U862-W-0.67A-8-14-17-7a 0.5 5.5546E+03

U862-W-0.67A-8-14-17-17 0.5 5.8028E+03

U862-W-0.67A-8-14-17-17a 0.5 6.7857E+03

Average 6.4411E+03


Count 6

77



Sample Number

Applied Voltage


U862-W-1A-8-3-17-1a 0.1 7.3775E+02

U862-W-1A-8-3-17-1 0.1 8.2728E+02

U862-W-1A-8-3-17-8 0.1 7.5528E+02

U862-W-1A-8-3-17-8a 0.1 8.0832E+02

U862-W-1A-8-3-17-21 0.1 7.2331E+02

U862-W-1A-8-3-17-21a 0.1 6.8150E+02

Average 7.5557E+02


Count 6


wt% Ketjenblack EC-600 JD CB and 5 wt% TC307 GNP in Epoxy Composites

Sample Number

Applied Voltage


U862-W-0.33A-5T-8-28-17-17 2.5 1.5477E+04

U862-W-0.33A-5T-8-28-17-17a 2.5 1.4590E+04

U862-W-0.33A-5T-8-28-17-23 2.5 1.6970E+04

U862-W-0.33A-5T-8-28-17-16 2.5 1.3889E+04

U862-W-0.33A-5T-8-28-17-16a 2.5 1.3934E+04

U862-W-0.33A-5T-8-28-17-18 2.5 1.8582E+04

Average 1.5574E+04


Count 6

78

Table A-13: ASTM D4496 Two Point In-Plane Electrical Resistivity Replicate Results

for 0.33 wt% Ketjenblack EC-600 JD CB and 5 wt% TC307 GNP in Epoxy Composites

Sample Number

Applied Voltage


U862-W-0.33A-5T-8-28-17-18a 2.5 1.5646E+04

U862-W-0.33A-5T-8-28-17-20a 2.5 1.3100E+04

U862-W-0.33A-5T-8-28-17-21 2.5 1.4829E+04

U862-W-0.33A-5T-8-22-17-18 2.5 1.8349E+04

U862-W-0.33A-5T-8-22-17-21a 2.5 1.3369E+04

U862-W-0.33A-5T-8-22-17-19 2.5 1.1459E+04

Average 1.4459E+04


Count 6


wt% Ketjenblack EC-600 JD CB and 10 wt% TC307 GNP in Epoxy Composites

Sample Number

Applied Voltage


U862-W-0.33A-10T-8-24-17-20 5 4.7260E+03

U862-W-0.33A-10T-8-24-17-21 5 7.9261E+03

U862-W-0.33A-10T-8-24-17-22 5 4.7698E+03

U862-W-0.33A-10T-8-24-17-23 5 5.7482E+03

U862-W-0.33A-10T-8-30-17-18a 5 8.8384E+03

Average 6.4017E+03


Count 5

79

B Appendix B: Thermal Conductivity Results at 55°C

Table B-1: Thermal Conductivity of Neat Epoxy

Test Date Sample Number Through Plane Thermal Conductivity (W/m•K)

7/28/2017 862W4-17-12-1 0.1980

7/28/2017 862W4-17-12-3 0.2091

7/28/2017 862W4-17-12-4 0.2096

8/2/2017 862W4-17-12-5 0.2113

8/2/2017 862W4-17-12-6 0.2000

Average 0.2056

Standard Deviation 0.0061

Number of Samples 5

Table B-2: Thermal Conductivity of 5 wt% TC307 GNP in Epoxy Composites


7/24/2017 862W-5T-6-23-17-1 0.2691

7/24/2017 862W-5T-6-23-17-2 0.2652

7/24/2017 862W-5T-6-23-17-3 0.2649

7/24/2017 862W-5T-6-23-17-4 0.2655

7/24/2017 862W-5T-6-23-17-5 0.2649

Average 0.2659


Number of Samples 5

80



7/24/2017 862W-10T-6-23-17-1 0.3011

7/24/2017 862W-10T-6-23-17-2 0.3033

7/24/2017 862W-10T-6-23-17-3 0.3033

7/24/2017 862W-10T-6-23-17-4 0.3055

7/24/2017 862W-10T-6-23-17-5 0.3048

Average 0.3036


Number of Samples 5



8/14/2017 862W-15T-2 0.3598

8/14/2017 862W-15T-3 0.3630

8/14/2017 862W-15T-4 0.3751

8/14/2017 862W-15T-5 0.3583

Average 0.3641


Number of Samples 4



8/16/2017 862W-20T-1 0.3900

8/16/2017 862W-20T-2 0.3998

8/16/2017 862W-20T-3 0.4020

8/16/2017 862W-20T-4 0.3830

Average 0.3937


Number of Samples 4

81


Composites


9/6/2017 862W-0.33A-1 0.2117

9/6/2017 862W-0.33A-2 0.2115

9/6/2017 862W-0.33A-3 0.2107

9/6/2017 862W-0.33A-4 0.2097

9/6/2017 862W-0.33A-5 0.2137

Average 0.2115


Number of Samples 5


Composites


9/11/2017 862W-0.67A-1 0.2151

9/11/2017 862W-0.67A-2 0.2167

9/11/2017 862W-0.67A-3 0.2148

9/11/2017 862W-0.67A-4 0.2157

9/11/2017 862W-0.67A-5 0.2167

Average 0.2158


Number of Samples 5

Table B-8: Thermal Conductivity of 1 wt% Ketjenblack EC-600 JD CB in Epoxy

Composites


9/11/2017 862W-1A-1 0.2063

9/11/2017 862W-1A-2 0.2103

9/11/2017 862W-1A-3 0.2139

9/11/2017 862W-1A-4 0.2154

9/11/2017 862W-1A-5 0.2043

Average 0.2100


Number of Samples 5

82




9/13/2017 862W-0.33A5T-1 0.2666

9/13/2017 862W-0.33A5T-2 0.2646

9/13/2017 862W-0.33A5T-3 0.2671

9/13/2017 862W-0.33A5T-4 0.2632

9/13/2017 862W-0.33A5T-5 0.2614

Average 0.2646


Number of Samples 5




9/18/2017 862W-0.33A10T-1 0.3091

9/18/2017 862W-0.33A10T-2 0.3068

9/18/2017 862W-0.33A10T-3 0.2982

9/18/2017 862W-0.33A10T-4 0.3115

9/18/2017 862W-0.33A10T-5 0.2925

Average 0.3036


Number of Samples 5

83

C Appendix C: Tensile Results

Figure C-1: Tensile Results for Neat Epoxy

Table C-1: Tensile Results for Neat Epoxy

Sample No.

Ultimate Tensile Stress (Mpa)

Strain at Ultimate Tensile Stress

(%)

Tensile Fracture Stress (MPa)

Strain at Tensile Fracture Stress

(%)

Tensile Modulus

(GPa)

A862-12-6-11 3 76.998 8.013 76.986 8.189 2.717

A862-4-17-12 3 77.854 8.18 75.559 12.209 2.757

A862-4-17-12 4 78.9 7.898 77.279 10.858 2.782

A862-4-17-12 7 76.976 8.272 74.873 11.852 2.71

A862-4-17-12 10 76.591 8.201 74.569 11.701 2.691

A862-4-17-12 12 78.065 7.335 78.065 7.335 2.678

Average 77.56 7.98 76.22 10.36 2.72

Standard Deviation 0.86 0.35 1.42 2.08 0.04

Count 6 6 6 6 6

0

10

20

30

40

50

60

70

80

90

0 0.05 0.1 0.15

Str

ess (

MP

a)

Strain (mm/mm)

Neat Epoxy

A862-12-6-11(3)

A862-4-17-13(3)

A862-4-17-12(4)

A862-4-17-12(7)

A862-4-17-12(10)

A862-4-17-12(12)

84

Figure C-2: Tensile Results for 5 wt% TC307 GNP in Epoxy Composites

Table C-2: Tensile Results for 5 wt% TC307 GNP in Epoxy Composites

Specimen

Ultimate Tensile Stress (MPa)


(%)

Tensile Fracture Stress (Mpa)


(%)

Tensile Modulus

(GPa)

U862-W-5T-6-23-17-1 72.561 3.799 72.561 3.799 2.917

U862-W-5T-6-23-17-2 75.816 3.991 75.816 3.991 3.061

U862-W-5T-6-23-17-3 73.597 3.829 73.597 3.829 3.044

U862-W-5T-6-23-17-5 71.561 3.68 71.561 3.68 2.911

U862-W-5T-6-23-17-6 73.127 3.789 73.127 3.789 3.036

U862-W-5T-6-23-17-9 72.191 3.835 72.191 3.835 2.91

U862-W-5T-6-23-17-11 71.672 4.03 71.672 4.03 2.927

Average 72.93 3.85 72.93 3.85 2.97

Std Dev 1.47 0.12 1.47 0.12 0.07

Count 7 7 7 7 7

0

10

20

30

40

50

60

70

80

0 0.01 0.02 0.03 0.04 0.05

Str

ess (

MP

a)

Strain (mm/mm)

U862-W-5T-6-23-17

1

2

3

5

6

9

11

85



Specimen



(%)



(%)

Tensile Modulus

(GPa)

U862-W-10T-6-28-17-1 73.633 3.621 73.633 3.621 3.073

U862-W-10T-6-28-17-9 69.704 3.239 69.704 3.239 3.179

U862-W-10T-6-28-17-11 68.154 2.98 68.154 2.98 3.362

U862-W-10T-6-28-17-12 71.074 3.47 71.074 3.47 3.24

U862-W-10T-6-28-17-13 67.601 3.06 67.601 3.06 3.125

Average 70.03 3.27 70.03 3.27 3.2

Std Dev 2.43 0.27 2.43 0.27 0.11

Count 5 5 5 5 5

0

10

20

30

40

50

60

70

80

0 0.01 0.02 0.03 0.04

Str

ess (

MP

a)

Strain (mm/mm)

U862-W-10T-6-28-17

1

9

11

12

13

86



Specimen



(%)



(%)

Tensile Modulus

(GPa)

U862-W-15T-6-29-17-2 59.123 2.2 59.123 2.2 3.352

U862-W-15T-6-29-17-10 65.675 2.52 65.675 2.52 3.429

U862-W-15T-6-29-17-11 56.559 2.049 56.559 2.049 3.377

U862-W-15T-6-29-17-13 64.639 2.57 64.639 2.57 3.379

U862-W-15T-6-29-17-14 63.227 2.48 63.227 2.48 3.331

Average 61.84 2.36 61.84 2.36 3.37

Std Dev 3.86 0.23 3.86 0.23 0.06

Count 5 5 5 5 5

0

10

20

30

40

50

60

70

0 0.005 0.01 0.015 0.02 0.025 0.03

Str

ess (

MP

a)

Strain (mm/mm)

U862-W-15T-6-29-17

2

10

11

13

14

87



Specimen



(%)



(%)

Tensile Modulus

(GPa)

U862-W-20T-7-12-17-5 52.887 1.66 52.887 1.66 3.706

U862-W-20T-7-12-17-6 49.785 1.51 49.785 1.51 3.775

U862-W-20T-7-12-17-7 48.39 1.53 48.39 1.53 3.57

U862-W-20T-7-12-17-9 50.276 1.56 50.276 1.56 3.667

U862-W-20T-7-12-17-10 47.911 1.44 47.911 1.44 3.728

Average 49.85 1.54 49.85 1.54 3.69

Std Dev 1.96 0.08 1.96 0.08 0.08

Count 5 5 5 5 5

0

10

20

30

40

50

60

0 0.005 0.01 0.015 0.02

Str

ess (

MP

a)

Strain (mm/mm)

U862-W-20T-7-12-17

5

6

7

9

10

88

Figure C-6: Tensile Results for 0.33 wt% EC-600 JD in Epoxy Composites

Table C-6: Tensile Results for 0.33 wt% Ketjenblack EC-600 JD CB in Epoxy

Composites

Specimen



Stress (%)


Strain at Tensile Fracture

Stress (%)

Tensile Modulus

(GPa)

U862-W-0.33A-8-21-17-12 81.360 7.431 81.360 7.431 2.738

U862-W-0.33A-8-21-17-14 82.100 7.340 81.599 8.471 2.753

U862-W-0.33A-8-21-17-15 81.940 6.920 81.900 7.411 2.760

U862-W-0.33A-8-21-17-16 81.610 7.361 81.320 8.519 2.724

U862-W-0.33A-8-21-17-20 81.470 7.150 80.630 8.450 2.669

U862-W-0.33A-8-21-17-22 82.240 7.489 82.200 7.960 2.691

Average 81.79 7.28 81.50 8.04 2.72

Std Dev 0.36 0.21 0.54 0.52 0.04

Count 6 6 6 6 6

0

10

20

30

40

50

60

70

80

90

0 0.02 0.04 0.06 0.08 0.1

Str

ess (

MP

a)

Strain (mm/mm)

U862-W-0.33A-8-21-17

12

14

15

16

20

22

89

Figure C-7: Tensile Results for 0.67 wt% Ketjenblack EC-600 JD in Epoxy Composites

Table C-7: Tensile Results for 0.67 wt% Ketjenblack EC-600 JD in Epoxy Composites

Specimen



Stress (%)



Stress (%)

Tensile Modulus

(GPa)

U862-W-0.67A-8-14-17-1 82.190 7.600 81.911 8.140 2.696

U862-W-0.67A-8-14-17-11 80.890 7.281 80.890 7.281 2.735

U862-W-0.67A-8-14-17-16 81.390 7.570 81.000 8.390 2.719

U862-W-0.67A-8-14-17-18 81.930 6.661 81.930 6.661 2.789

U862-W-0.67A-8-14-17-20 80.940 7.151 80.829 7.640 2.766

Average 81.47 7.25 81.31 7.62 2.74

Std Dev 0.58 0.38 0.56 0.69 0.04

Count 5 5 5 5 5

0

10

20

30

40

50

60

70

80

90

0 0.02 0.04 0.06 0.08 0.1

Str

ess (

MP

a)

Strain (mm/mm)

U862-W-0.67A-8-14-17

1

11

16

18

20

90

Figure C-8: Tensile Results for 1 wt% Ketjenblack EC-600 JD in Epoxy Composites

Table C-8: Tensile Results for 1 wt% Ketjenblack EC-600 JD in Epoxy Composites

Specimen



Stress (%)



Stress (%)

Tensile Modulus

(GPa)

U862-W-1A-8-3-17-2 80.131 7.310 80.131 7.310 2.712

U862-W-1A-8-3-17-5 80.660 7.311 80.660 7.311 2.714

U862-W-1A-8-3-17-7 80.510 7.331 80.510 7.331 2.749

U862-W-1A-8-3-17-13 79.870 7.719 79.870 7.719 2.699

U862-W-1A-8-3-17-14 80.312 6.731 80.312 6.731 2.798

U862-W-1A-8-3-17-15 80.820 7.660 80.820 7.660 2.742

Average 80.38 7.34 80.38 7.34 2.74

Std Dev 0.35 0.35 0.35 0.35 0.04

Count 6 6 6 6 6

0

10

20

30

40

50

60

70

80

90

0 0.02 0.04 0.06 0.08 0.1

Str

ess (

MP

a)

Strain (mm/mm)

U862-W-1A-8-3-17

2

5

7

13

14

15

91



Table C-9: Tensile Results for 0.33 wt% Ketjenblack EC-600 JD CB and 5 wt% TC307


Specimen



(%)



(%)

Tensile Modulus

(GPa)

U862-W-0.33A-5T-8-28-17-2 66.115 2.879 66.115 2.879 3.3

U862-W-0.33A-5T-8-28-17-3 65.309 2.8 65.309 2.8 3.151

U862-W-0.33A-5T-8-28-17-4 71.905 3.44 71.905 3.44 3.252

U862-W-0.33A-5T-8-28-17-6 70.791 3.3 70.791 3.3 3.112

U862-W-0.33A-5T-8-28-17-7 67.292 3.039 67.292 3.039 3.176

Average 68.28 3.09 68.28 3.09 3.2

Std Dev 2.91 0.27 2.91 0.27 0.08

Count 5 5 5 5 5

0

10

20

30

40

50

60

70

80

0 0.01 0.02 0.03 0.04

Str

ess (

MP

a)

Strain (mm/mm)

U862-W-0.33A-5T-8-28-17

2

3

4

6

7

92



Table C-10: Tensile Results for 0.33 wt% Ketjenblack EC-600 JD CB and 10 wt%


Specimen



(%)



(%)

Tensile Modulus

(GPa)

U862-W-0.33A-10T-8-30-17-2 60.324 2.36 60.324 2.36 3.282

U862-W-0.33A-10T-8-30-17-4 65.608 2.799 65.608 2.799 3.166

U862-W-0.33A-10T-8-30-17-6 63.236 2.57 63.236 2.57 3.172

U862-W-0.33A-10T-8-30-17-7 59.097 2.26 59.097 2.26 3.312

U862-W-0.33A-10T-8-30-17-13 59.679 2.301 59.679 2.301 3.276

U862-W-0.33A-10T-8-30-17-15 61.67 2.382 61.67 2.382 3.424

Average 61.6 2.45 61.6 2.45 3.27

Std Dev 2.46 0.2 2.46 0.2 0.1

Count 6 6 6 6 6

0

10

20

30

40

50

60

70

0 0.005 0.01 0.015 0.02 0.025 0.03

Str

ess (

MP

a)

Strain (mm/mm)

U862-W-0.33A-10T-8-30-17

2

4

6

7

13

15

93

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