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Thermodynamics and Kinetics of Engineered Carbon Nanotubes Composite Polymers. Lior Zonder. THE 5 th INTERNATIONAL CONFERENCE Nanotechnology Applications for the Plastics & Rubber Industries Monday February 1 st , 2010. Motivation. Carbon nanotubes (CNT) Mechanical properties

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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


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.


Motivation

  • Conductive plastics

    • Not new concept

    • Formation of 3D network throughout the bulk

10%

1%

  • Carbon nanotubes

  • Low percolation threshold

  • Due to aspect ratio

  • Carbon black

  • High loadings

  • Loss of mechanical properties


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.


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


Background

  • Why CNT distribute unevenly in polymer blend?

    • thermodynamics: particles interact more favorably with one of the polymers thus decreasing the system’s free energy

    • kinetics: viscosity ratio as a distributing factor

  • What are the circumstances that cause one factor to dominate over the other?


Thermodynamics

  • Expressed in terms of interfacial interactions

  • Particle will tend to locate to minimize interfacial tension

  • Quantified by the wetting parameter

1

2

particles are present only in polymer 1

Particles are present in polymer 2

particles are concentrated at the interface between the polymers


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


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 2007;48:6029–40.

+


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.


kinetics

  • Particle migration

    • Self diffusion

    • Shear induced

Time scale of motion for diffusing particles

Assume particle aggregate size

Temp

Viscosity of polymer


  • Shear significantly accelerates particle migration

    • Only when thermodynamic drive exists

+

<

<

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


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


Experimental

Material selection

  • PET- high performance engineering thermoplastic

  • Forms a non miscible, partially compatible blend with PVDF

  • The polymers have different polarities


Methodology

  • Melt blending of PET with 5,10,15%w PVDF with and without 0.5%w CNT in a batch mixer

  • PET neat, PVDF neat and PET+cnt, PVDF+cnt as control

  • All components added together

  • Tests

    • Parallel plate rheometer

    • Differential scanning calorimeter

    • Dynamic mechanical analysis

    • Scanning electron microscopy


Rheology

  • Polymer melt oscillated between parallel plate

  • Rheological and viscoelastic behavior of melts

PVDF, PVDF+CNT

3

PET+CNT,

PET/PVDF Blends+CNT

2

PET, PET/PVDF Blends

1


Rheology


Rheology

  • Appearance of shoulder with increasing amount of PVDF

  • CNT cancels the effect of the addition of PVDF

2

1


Thermal analysis

PET,

PET+CNT

PVDF,

PVDF+CNT


Thermal analysis

95/5

90/10

85/15


Dynamic Mechanical Analysis


Dynamic Mechanical Analysis


PET85PV15+CNT

Electron microscopy

PET85PV15


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


Future work

  • Investigation of kinetic effects by

    • Sequential blending

    • Processing conditions

    • Altering viscosities by MW control

  • Relating rheological behavior to microstructure

  • Electrical properties characterization


Questions?


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