Carbon Nanotube Based Composites - Processing, Properties, Modelling and Application

220 Pages·2012·6.771 MB·220\220

by  Pantano, Antonio

Carbon Nanotube Based
Composites:
Processing, Properties,
Modelling and Application
Antonio Pantano
A Smithers Group Company
Shawbury, Shrewsbury, Shropshire, SY4 4NR, United Kingdom
Telephone: [phone] Fax: [phone]
http://www.polymer-books.com
First Published in 2012 by
Smithers Rapra Technology Ltd
Shawbury, Shrewsbury, Shropshire, SY4 4NR, UK
©2012, Smithers Rapra Technology Ltd
All rights reserved. Except as permitted under current legislation no part
of this publication may be photocopied, reproduced or distributed in any
form or by any means or stored in a database or retrieval system, without
the prior permission from the copyright holder.
A catalogue record for this book is available from the British Library.
Every effort has been made to contact copyright holders of any material reproduced
within the text and the authors and publishers apologise if
any have been overlooked.
ISBN: 978-1-84735-585-0 (Hardback)
978-1-84735-586-7 (Softback)
978-1-84735-587-4 (ebook)
Typeset by Argil Services
P
reface
In the last decade carbon nanotubes (CNT) have attracted the interest of the
international scientific community because of their exceptional mechanical properties,
high thermal conductivity and peculiar electronic properties (ballistic transport). The
sp2 carbon-carbon bond in the basal plane of graphene is the stiffest and strongest in
nature. CNT possess an ideal arrangement of these bonds in their cylindrical and nearly
defect-free structures, and hence approach the maximum theoretical tensile stiffness
and strength. Experiments and atomistic simulations have confirmed that CNT really
have an extremely high modulus, Young’s modulus > 1 TPa, and a strength around
100 GPa that is significantly higher than the few GPa of the carbon fibres. CNT also
have a 20-30% elastic limit of the strain before failure and a very low density of about
1.75 g/cm3. Thermal conductivity as high as 6000 W/m K have been recorded for
CNT, an excellent value if compared to the conductivity of copper that is 385 W/m K.
Electrical conduction in defect-free CNT is believed to be ballistic in nature, implying
the absence of inelastic scattering and involving little energy dissipation. Since the
Joule heating is very small due to the absence of scattering, carbon nanotubes can
deal with current density of 1011 A m-2; this value is about 1000 greater than copper.
One way to take advantage of the marvellous properties of the CNT is to incorporate
them in a matrix to build composite materials. The best candidates for this are
undoubtedly polymers, which thanks to their strength, toughness, low weight and
easy processing have been used in a broad variety of industrial applications. Such
extraordinary mechanical properties, together with high ratios (100-10000) of
geometric aspect, stiffness-to-weight and strength-to-weight, all point to CNT as
being ideal reinforcing agents in advanced composites. It is not only the stiffness
and strength of the polymer that can be improved by adding CNT: thermal and
electrical conductivities, optical properties, toughness, fatigue resistance and damping
characteristics of formed composites can also be enhanced.
There are a few examples of applications of CNT-enriched polymer composites:
aerospace structures, sporting goods, automotive components, medical devices, optical
barriers, photovoltaic devices, conducting plastics, materials with high electrostatic
dissipation, electromagnetic interference shielding, efficient electrostatic painting of
plastics, composite mirrors, plastics with high thermal dissipation, biomaterial devices,
iii
Carbon Nanotube Based Composites: Processing, Properties, Modelling and Application
strain sensors, damage sensing, gas sensors, optoelectronics, transparent electronics
and electromechanical actuation.
This interesting potential has attracted the attention of both industry and academia,
which have committed to this research field an impressive amount of work, as
shown by the very high number of publications. However, before we can see a more
extensive use of CNT-enhanced polymer composites there are a few difficult challenges
that need to be addressed: in particular it is important to develop inexpensive mass
production techniques for CNT; to be able to accurately control their geometrical
features (like diameter, length and chirality); to achieve the ability to disperse the
CNT homogeneously throughout the matrix; and to efficiently transfer mechanical
load from the matrix to the CNT.
The objective of this book is to bring together all available information on the
CNT-based composites. Details of the more important processing techniques for
manufacturing CNT–polymer composites are discussed in Chapter 1, including
preprocessing treatments as purification, graphitisation and functionalisation. Chapter
2 explores the state of the art concerning mechanical, thermal, electrical and optical
properties of CNT composites made of the most frequently used polymer matrixes.
There is quick access to a vast amount of the available data on the mechanical and
electrical properties of CNT composites. In Chapter 3 there is a review of the numerical
models, which have been developed in attempts to improve the understanding of the
effects of CNT in a polymer matrix. Chapter 4 provides numerous examples of the
possible applications of this category of composites.
This book reviews the status of worldwide research in both single-walled and multi-
walled CNT-based composites. It serves as a practical guide to CNT-based composites
and is a useful reference to students and researchers from both academia and industry.
iv
C
ontents
1 Processing of Carbon Nanotube-Polymer Composites ................................1
1.1 Preprocessing ..................................................................................1
1.1.1 Purification and Graphitisation ..........................................1
1.1.1.1 Purification .......................................................1
1.1.1.2 Graphitisation ...................................................5
1.1.2 Covalent Functionalisation ................................................8
1.1.2.1 ‘Grafting To’ Method ......................................10
1.1.2.2 ‘Grafting From’ Method .................................12
1.1.3 Non-Covalent Functionalisation ......................................15
1.2 Solution Processing .......................................................................19
1.3 Melt-Mixing ................................................................................26
1.4 In Situ Polymerisation ...................................................................33
1.5 Carbon Nanotube Fibres and Films ..............................................37
1.5.1 Carbon Nanotube Fibres and Composite Fibres ..............37
1.5.2 Carbon Nanotube Films ..................................................41
1.6 Bulk Mixing ..................................................................................43
2 Properties of Carbon Nanotube-Polymer Composites ..............................49
2.1 Mechanical Properties ...................................................................49
2.1.1 Polyethylene–Carbon Nanotube Composites ...................52
2.1.2 Polymethyl Methacrylate–Carbon Nanotube Composites 54
2.1.3 Polypropylene–Carbon Nanotube Composites .................55
2.1.4 Polyvinyl Alcohol–Carbon Nanotube Composites ...........58
2.1.5 Polystyrene–Carbon Nanotube Composites .....................59
vii
Carbon Nanotube Based Composites: Processing, Properties, Modelling and Application
2.1.6 Polyvinyl Chloride–Carbon Nanotube Composites ..........61
2.1.7 Polystyrene-co-Butyl Acrylate–Carbon Nanotube
Composites ......................................................................62
2.1.8 Epoxy–Carbon Nanotube Composites .............................63
2.1.9 Nylon–Carbon Nanotube Composites .............................67
2.1.10 Polyimide–Carbon Nanotube Composites .......................70
2.1.11 Polystyrene-b-Butadiene-co-Butylene-b-Styrene–Carbon
Nanotube Composites .....................................................72
2.1.12 Methyl-ethyl Methacrylate–Carbon Nanotube
Composites ......................................................................72
2.1.13 Polyethyleneimine–Carbon Nanotube Composites ...........78
2.2 Thermal properties .......................................................................80
2.2.1 Polyethylene–Carbon Nanotube Composites ...................82
2.2.2 Polymethyl Methacrylate–Carbon Nanotube Composites 85
2.2.3 Polypropylene–Carbon Nanotube Composites .................88
2.2.4 Polyvinyl Alcohol-Carbon Nanotube Composites ............92
2.2.5 Polystyrene–Carbon Nanotube Composites .....................92
2.2.6 Polyvinyl Chloride–Carbon Nanotube Composites ..........92
2.2.7 Polystyrene-co-Butyl Acrylate–Carbon Nanotube
Composites ......................................................................92
2.2.8 Epoxy–Carbon Nanotube Composites .............................93
2.2.9 Nylon–Carbon Nanotube Composites .............................96
2.2.10 Polyimide–Carbon Nanotube Composites .......................97
2.2.11 Methyl-ethyl Methacrylate–Carbon Nanotube
Composites ......................................................................97
2.3 Electrical Properties ......................................................................97
2.3.1 Polyethylene–Carbon Nanotube Composites .................100
2.3.2 Polymethyl Methacrylate–Carbon Nanotube
Composites ....................................................................102
2.3.3 Polypropylene–Carbon Nanotube Composites ...............102
2.3.4 Polyvinyl Alcohol–Carbon Nanotube Composites .........103
viii
Contents
2.3.5 Polystyrene–Carbon Nanotube Composites ...................103
2.3.6 Polyvinyl Chloride–Carbon Nanotube Composites ........103
2.3.7 Polystyrene-co-Butyl Acrylate–Carbon Nanotube
Composites ....................................................................106
2.3.8 Epoxy-Carbon Nanotube Composites ...........................106
2.3.9 Nylon-Carbon Nanotube Composites ............................109
2.3.10 Polyimide-Carbon Nanotube Composites ......................110
2.3.11 Other CNT-based Composites .......................................114
2.4 Optical Properties .......................................................................115
2.4.1 Photoluminescence .........................................................115
2.4.2 Light Emission and Photonic Properties .........................116
2.4.3 Optical Non-Linearity and Optical Limiters ..................116
3 Numerical Modelling of Carbon Nanotube - Polymer Composites ........123
3.1 Introduction ................................................................................123
3.2 Modelling Procedures .................................................................125
3.2.1 Micromechanical Approach ...........................................125
3.2.2 Numerical–Analytical Approach ....................................127
3.2.2.1 The Mori–Tanaka Method ............................128
3.2.2.2 Calculation of the Correlation Matrix Adil ....132
1
3.2.2.3 Calculation of the Stiffness Matrix of the
Equivalent Inclusion C .................................133
1
3.2.2.4 Finite Element Model Design -
Representative Volume Element Geometry ....133
3.2.2.5 Finite Element Model Design - Matrix
Constitutive Model .......................................134
3.2.2.6 Finite Element Model Design -
Carbon Nanotube .........................................135
3.2.2.7 Finite Element Model Design -
Contact Model ..............................................135
3.2.2.8 Deformation Mode .......................................136
ix
Carbon Nanotube Based Composites: Processing, Properties, Modelling and Application
3.2.2.9 Calculation of the Equivalent Young’s
Modulus of the MWCNT .............................136
3.2.2.10 Calculation of the Eshelby Tensor .................136
3.3 Numerical Results .......................................................................138
3.3.1 Results of the Micromechanical Approach .....................138
3.2.1 Results of the Numerical–Analytical Approach .............145
4 Applications of Carbon Nanotube–Polymer Composites ........................149
4.1 Strain Sensors .............................................................................149
4.2 Damage Sensors ..........................................................................152
4.3 Gas Sensors .................................................................................153
4.4 Electromechanical Actuators .......................................................154
4.5 Conducting Plastics .....................................................................156
4.6 Photovoltaic Devices ...................................................................157
4.7 Optoelectronics ...........................................................................157
4.8 Electrostatic Dissipation .............................................................157
4.9 Electromagnetic Interference Shielding ........................................160
4.10 Optical Barriers ..........................................................................160
4.11 Cost-Effective Transparent Electronics ........................................160
4.12 Composite Mirrors .....................................................................162
4.13 Plastics with High Thermal Dissipation ......................................163
4.14 Biomaterial Devices ...................................................................164
5 Conclusions and Future Prospects ..........................................................167
Abbreviations ....................................................................................................169
Index ..............................................................................................................175
x
1
Processing of Carbon Nanotube-Polymer
Composites
1.1 Preprocessing
Before being incorporated into a matrix to build composite materials, carbon
nanotubes (CNT) are usually pretreated with a purification technique, and often
functionalised for improving bonding between the polymer matrix and the nanotube.
1.1.1 Purification and Graphitisation
The key techniques for manufacturing carbon nanotubes are: arc discharge, laser
ablation and chemical vapour deposition. None of them are able to produce pure
nanotubes; at the end of the production process they are mixed with other entities,
such as carbon nanoparticles, amorphous carbon, residual catalyst and other unwanted
species. Moreover, carbon nanotubes produced by these three methods contain
numerous defects that can affect their exceptional properties. That’s why raw CNT
materials are usually purified and sometimes go through a graphitisation procedure.
1.1.1.1 Purification
Purification of carbon nanotubes refers to the separation from impurities: residual
metals from metal catalysts, amorphous carbon, graphitic particles, carbon shells,
fullerenes and multi-shell carbon nanocapsules [1-10], see Figure 1.1.
The most used methods are: gas-phase oxidation, intercalation methods, liquid-phase
oxidation and physical separation.
Intercalation techniques use nanoparticles and other graphitic contaminants, and
since they have a rather open structure they can be more readily intercalated with a
variety of materials that can close nanotubes. For example, an intercalation technique
uses copper chloride, which is reduced to metallic copper - in this way, using copper
as an oxidation catalyst it is possible to oxidise the nanoparticles away. The final
1
Carbon Nanotube Based Composites: Processing, Properties, Modelling and Application
material may be contaminated with residues of intercalates and this is a limitation
of the method.
Surfactant is often used to induce physical separations and then the solution is
treated by sonication, filtration, centrifugation or chromatographic methods. Physical
methods usually leave some amorphous carbon particle and multi-shell nanocapsules,
thus it is not a very efficient method. Therefore, it is not easy to eliminate all the
metal encapsulated at the tips of the CNT. Sonication applied for a long time often
damages the carbon nanotubes, which are broken into shorter tubes.
Figure 1.1 Transmission electron microscopy images of: a) as-grown single-walled
carbon nanotubes (SWCNT), (b) and (c) after purification treatments. Reproduced
with permission from M. Zhang, M. Yudasaka, A. Koshio and S. Iijima, Chemical
Physics Letters, 2001, 349, 1-2, 25. ©2001, Elsevier [1].
2