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Thermodynamics and Kinetics of Engineered Carbon Nanotubes Composite Polymers

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

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  1. 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

  2. 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.

  3. 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

  4. 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.

  5. 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

  6. 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?

  7. 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

  8. 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

  9. 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. +

  10. 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.

  11. kinetics • Particle migration • Self diffusion • Shear induced Time scale of motion for diffusing particles Assume particle aggregate size Temp Viscosity of polymer

  12. 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.

  13. 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

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

  15. 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

  16. 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

  17. Rheology

  18. Rheology • Appearance of shoulder with increasing amount of PVDF • CNT cancels the effect of the addition of PVDF 2 1

  19. Thermal analysis PET, PET+CNT PVDF, PVDF+CNT

  20. Thermal analysis 95/5 90/10 85/15

  21. Dynamic Mechanical Analysis

  22. Dynamic Mechanical Analysis

  23. PET85PV15+CNT Electron microscopy PET85PV15

  24. 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

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

  26. Questions?

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