Thermodynamics and Kinetics of Engineered Carbon Nanotubes Composite Polymers

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Thermodynamics and Kinetics of Engineered Carbon
Nanotubes Composite Polymers
Lior Zonder

• THE 5th INTERNATIONAL CONFERENCE
• Nanotechnology Applications
• for the Plastics Rubber Industries
•  
• Monday February 1st, 2010

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Motivation

• Carbon nanotubes (CNT)
• Mechanical properties
• Electrical properties
• Enhancement of electrical properties of high
  performance polymer compounds
• Electrostatic dissipation
• Electrostatic painting
• EMI shielding
• Transparent electrical conductors
• Lightweight conductive materials
• PEM fuel cells

Marx, G.K.L., et al., Applied Physics Letters,
2003. 83(14) p. 2928.
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Motivation

• Conductive plastics
• Not new concept
• Formation of 3D network throughout the bulk

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• Carbon nanotubes
• Low percolation threshold
• Due to aspect ratio

• Carbon black
• High loadings
• Loss of mechanical properties

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Motivation

• Further reduction in filler content achieved by
  matrix morphology control
• Specific location of filler in multi-phase system
• Percolation network forms in one phase or at the
  interphase
• Double percolation concept

10-7
10-12-10-10
Wu, D., et al.,. Biomacromolecules, 2009. 10(2)
p. 417-424.
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Objective

• Understand the forces involved in determining CNT
  location in a two phase polymer blend
• Thermodynamic
• Kinetic
• Establishing the relationship between mixing
  procedure, material morphology and properties
• Develop a model relating kinetic and
  thermodynamic factors to final morphology

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Background

• Why CNT distribute unevenly in polymer blend?
• thermodynamics particles interact more favorably
  with one of the polymers thus decreasing the
  systems free energy
• kinetics viscosity ratio as a distributing
  factor
• What are the circumstances that cause one factor
  to dominate over the other?

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Thermodynamics

• Expressed in terms of interfacial interactions
• Particle will tend to locate to minimize
  interfacial tension
• Quantified by the wetting parameter

particles are present only in polymer 1
Particles are present in polymer 2
particles are concentrated at the interface
between the polymers
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Thermodynamics

• Issues
• Interfacial energies between each polymer and
  filler are calculated using theoretical models
• Temperature dependence of the surface energy
• Melt mixing
• Viscous polymer restrict rearrangement due to
  thermodynamic drive
• Thermodynamic equilibrium is not obtained

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Kinetics

• Melt mixing is a dynamic process
• Final blend morphology and CNT dispersion state
  influenced by
• Mixing procedure
• Sequence of addition of components
• Melting point difference

Elias L, Fenouillot F, Majeste J-C, Cassagnau P.
Polymer 200748602940.

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Kinetics- cont

• Viscosity
• Viscosity ratio as a distributing factor

Hydrophilic silica- prediction particles in EVA
PP/EVA All components added together
Hydrophobic silica- prediction particles at the
interface
Elias, L., et al., J. Polym. Sci B 46(18) p.
1976-1983.
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kinetics

• Particle migration
• Self diffusion
• Shear induced

Time scale of motion for diffusing particles
Assume particle aggregate size
Temp
Viscosity of polymer
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• Shear significantly accelerates particle
  migration
• Only when thermodynamic drive exists

lt
lt
Hong, J.S., et al.,. J. Appl. Polym. Sci., 2008.
108(1) p. 565-575.
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Summary

• At equilibrium particles locate to minimize free
  energy
• Morphology and dispersion can be kinetically
  controlled
• Slow down or accelerate migration of particles
• Only if thermodynamic drive exists
• When no thermodynamic drive exists, kinetics
  (viscosity ratio) is a dominate factor

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Experimental

• Material selection
• PET- high performance engineering thermoplastic
• Forms a non miscible, partially compatible blend
  with PVDF
• The polymers have different polarities

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Methodology

• Melt blending of PET with 5,10,15w PVDF with and
  without 0.5w CNT in a batch mixer
• PET neat, PVDF neat and PETcnt, PVDFcnt as
  control
• All components added together
• Tests
• Parallel plate rheometer
• Differential scanning calorimeter
• Dynamic mechanical analysis
• Scanning electron microscopy

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Rheology

• Polymer melt oscillated between parallel plate
• Rheological and viscoelastic behavior of melts

PVDF, PVDFCNT
PETCNT, PET/PVDF BlendsCNT
PET, PET/PVDF Blends
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Rheology
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Rheology
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1

• Appearance of shoulder with increasing amount of
  PVDF
• CNT cancels the effect of the addition of PVDF

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Thermal analysis
PET, PETCNT
PVDF, PVDFCNT
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Thermal analysis
95/5
90/10
85/15
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Dynamic Mechanical Analysis
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Dynamic Mechanical Analysis
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Electron microscopy
PET85PV15

• PET85PV15CNT

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Preliminary conclusion

• CNT located mostly in PET phase
• Selective location of nanoparticles can be
  studied by tools such as rheometry and DSC
• The presented work is a preliminary stage for a
  wider study

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Future work

• Investigation of kinetic effects by
• Sequential blending
• Processing conditions
• Altering viscosities by MW control
• Relating rheological behavior to microstructure
• Electrical properties characterization

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• Questions?