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Graphene-reinforced elastomers for demanding environments
Robert J Young, Ian A. Kinloch, Dimitrios G. Papageorgiou, J. Robert Innes and Suhao Li
School of Materials and National Graphene InstituteThe University of Manchester
Oxford Road, Manchester M13 9PL, UK
Different forms of carbon
Diamond Graphite
High resolution TEM
2 nm
World’s first 2D solidSingle layer of carbon atomsYoung’s Modulus = 1.05 TPa
Exfoliated in Manchester from graphite using Scotch tape
Graphene
(Sarah Haigh, 2012)
(Novoselov, Geim et al, Science 2004)
Graphene-based nanocarbons
C60 Nanotubes Graphite
Graphene
A. K. Geim, K. S. Novoselov, Nature Materials, 6, (2007) 183-190
MorphologicalThinnest imaginable material – one atom thickHighest surface area – 2630 m2/g
Transparent to light (97.7 %)
MechanicalStiffness = 1 TPaStrength = 130 GPa
Electrical and thermalRecord thermal conductivity (6000 W/m/K)Highest current density at room temp (million times of that in copper)Highest intrinsic mobility (100 times more than Si)Lightest charge carrier (Dirac fermions)Longest mean free path at room temp (microns)
ChemicalRelatively easily functionalised & processable
BarrierImpervious to even Helium but can have controlled porosity
Graphene superlatives
UK National Graphene Institute (NGI)Collaborative Graphene Research Facility, University of Manchester
• £70M investment for the commercialisation of graphene (UK government and EU Regional Development Fund)
Graphene Engineering Innovation Centre – under construction
• £60M investment from Masdar and HEFCE
The National Graphene Institute
2011
2013
UK government support – George Osborne
Visit of President Xi of China2015
F
A key benefit, especially in the near term, is multi-functionality, e.g. in OLED packing it is transparent, an oxygen barrier, flexible, and conductive.
I billion €
over 10 years
Graphene in reality
MonolayerBilayer
>10 layerGraphite
Nanoplatelets
Graphene oxideKnown since 1850’s, 25 to 30 % O- Can be reduced
• Inelastic scattering of light• Laser spot size down to 1 µm• Spectra obtained for many non-metallic materials• Particularly useful for nanomaterials• Large stress-induced band shifts (stress sensing!)
specimen
laserbeam
scatteredlight
The technique of choice for the
characterisation of graphene
Raman spectroscopy
Mechanically-exfoliated graphene
1500 2000 2500 30000
10000
20000
30000
40000
50000
>5 Layers
3 Layers
1 Layer
Inte
nsity
(a.
u.)
Raman Wavenumber (cm-1)
Mechanically-Cleaved Graphene
2 Layers
2DG
Optical micrographRaman spectra
• Raman spectrum can be obtained from a single layer of carbon atoms
• Raman spectroscopy allows the number of layers to be “counted”
Deformation of a graphene monolayer
Optical micrographRaman 2D
band downshifts with strain
(Advanced Materials, 22 (2010) 2694-2697). 2450 2500 2550 2600 2650 2700 2750
Raman Wavenumber (cm-1)
0%
Inte
nsity
(A
.U.)
0.2%
0.4%
(b)
Inte
nsity
(A
.U.)
Monolayer
Deformation of a graphene monolayer
High 2D band shift rate implies a high Young’s modulus
for graphene ∼ I TPa
0.0 0.1 0.2 0.3 0.4
2620
2625
2630
2635
2640
2645
2650
2D P
ositi
on (
cm-1)
Strain (%)
Uncoated First Loading
Graphene/polymer interface intact
Shift rate of graphene 2D= -60 cm-1/% strain
Single graphene layer on the surface of a PMMA beam
(Advanced Materials, 22 (2010) 2694-2697).
Mapping of axial strain across a single graphene fl ake
Strain in graphene
where)/ln(
2 m
tTE
Gn
g
=
The length factor, ηl, can be determined from the critical length
Critical length ∼ 3 µm
Shear lag
theory
(ACS Nano, 5 (2011) 3079-3084).
Stress direction
−=)cosh(
2cosh
1m ns
l
xns
eeg
Graphene composites
PMMA-graphene composites - preparation
• Gram scale production of graphene using
electrochemical exfoliation (UoM IP).
• Melt processing of composites using standard
compounding and injection moulding.
Graphite
Graphene composites
0 2 4 6 8 102.2
2.4
2.6
2.8
3.0
3.2
You
ng m
odul
us (
GP
a)
Loading (wt.%)
0 1 2 3 4 5 6Loading (vol.%)
<5 µm flake20 µm flake
Injection moulded PMMA-graphene composites
Larger flakes give better reinforcement
Mechanical testing of PMMA graphene nanocomposites
(Valles, Abdelkader, Young, Kinloch, Faraday Discussions 2014, 173, 379-390)
Review – Graphene/elastomer nanocomposites
Open access - DOI:10.1016/j.carbon.2015.08.055
Dimitrios G. Papageorgiou,
Potts JR, Shankar O, Murali S, Du L, Ruoff RS. Latex and two-roll mill processing of thermally-exfoliated graphite oxide/natural rubber nanocomposites. Composites Science and Technology. 2013;74(0):166-72.
Latex Premixing Two-roll Mill
Graphite-oxide/natural-rubber nanocomposites
Stress-strain curves show significant reinforcement
Latex premixing seems to lead to better properties than conventional processing
Graphene-elastomer strain sensors
Boland CS, Khan U, Backes C, O’Neill A, McCauley J, Duane S, et al. Sensitive, High-Strain, High-Rate Bodily Motion Sensors Based on Graphene–Rubber Composites. ACS Nano. 2014;8(9):8819-30.
Rubber bands swelled and infiltrated with graphene nanoplatelets• Electrically conductive• Resistance changes with strain – body motion sensor
Graphene/natural-rubber nanocompositesNatural rubber compounded with different phr of graphene nanoplatelets
Scanning electron micrographs of the component materials
Particle diametersM5 – 5 µm
M15 – 15 µmM25 – 25 µm
(all ∼7 nm thick)
Graphene/natural-rubber nanocompositesNatural rubber compounded with different phr of graphene nanoplatelets
Scanning electron micrographs of the compounds
0 2 4 6 8 10 120
2
4
6
8
10
12
14
16
18
Increasinggraphene
content
NR20
NR15NR10 NR5
NR
Str
ess
(MP
a)
Strain (mm/mm)
Graphene/natural-rubber nanocomposites
Significant reinforcement is found- increase in stiffness
Suhao Li (2016)Unpublished data
Natural rubber with different phr of M15 graphene nanoplatelets
Stress-strain curves
Graphene/natural-rubber nanocomposites
Significant solvent uptake, swelling and mass increase is found• Final mass, M
∞, decreases with graphene loading
Suhao Li (2016)Unpublished data
Natural rubber with different phr of graphene nanoplatelets in toluene
0
1
2
3
4
5
6
0 2 4 6
Mt/M0 versus t1/2
t1/2/hr1/2
0
0.2
0.4
0.6
0.8
1
1.2
0 2 4 6
M15 5phr
M15 10phr
M15 15phr
M15 20phr
NR
Mt/M∞versus t1/2
t1/2/hr1/2
Mt/M0 Mt/M∞
M∞
Gravimetric Determination of the Diffusion Characteristics of Polymers using Small SpecimensA.J. Cervenka, R.J. Young, K. Kueseng, Journal of Polymer Science: Part B: Polymer Physics, 42, 2122–2128 (2004)
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
NR 5 phr 10 phr 15 phr 20 phr
M5
M15
M25
Graphene/natural-rubber nanocomposites
Significant increases in thermal conductivity is found• Depends upon particle size
Suhao Li (2016)Unpublished data
Natural rubber with different phr of graphene nanoplatelets
The
rmal
con
duct
ivity
(W
/mK
)
Graphene/nitrile-rubber nanocomposites
Significant reinforcement is found- increase in stiffness and strength
0 1 2 3 4 5 6 70
1
2
3
4
5
6
7
8
9
NBR20
NBR15
NBR10
NBR5
Str
ess
(MP
a)
Strain (mm/mm)
NBR
Increasinggraphene
content
Suhao Li and J Robert Innes (2016)Unpublished data
Nitrile rubber with different phr of graphene nanoplatelets
Stress-strain curves