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