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A Prediction of Nanocomposite Permeability from Monte Carlo Simulations and the Implications of the Constrained Polymer Region. Sumit Gogia Patrick Kim Vincent Yu. Introduction. Nanoparticles Generally between 1-100 nm in length High surface area to volume ratio Nanocomposites

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A Prediction of Nanocomposite Permeability from Monte Carlo Simulations and the Implications of the Constrained Polymer Region

SumitGogia

Patrick Kim

Vincent Yu


Introduction
Introduction Simulations and the Implications of the Constrained Polymer Region

  • Nanoparticles

    • Generally between 1-100 nm in length

    • High surface area to volume ratio

  • Nanocomposites

    • Polymers with dispersed nanoparticles

    • Polymer-clay nanocomposites

      • Increased tensile strength

      • Increased elastic modulus

      • Decreased gas permeability


Applications
Applications Simulations and the Implications of the Constrained Polymer Region

  • Food packaging

    • Prolong shelf life

  • Tennis balls

    • Prevent depressurization

  • Protective equipment

    • Reduce thickness


Tortuous path model
Tortuous path model Simulations and the Implications of the Constrained Polymer Region

  • Impermeable clay plates create tortuous paths for permeating molecules

  • Nanocomposite is less permeable as a result (Nielsen, 1967)


Tortuous path model1
Tortuous path model Simulations and the Implications of the Constrained Polymer Region

  • Two main factors determine the magnitude of the tortuous path

    • Aspect ratio (α)

    • Volume fraction (ϕ)


Constrained polymer model
Constrained polymer model Simulations and the Implications of the Constrained Polymer Region

  • Polymer-clay interactions

    • May cause phase changes in the pristine polymer

    • Significant effect observed in amorphous polymers (Adame and Beall, 2009)


Computer simulation
Computer simulation Simulations and the Implications of the Constrained Polymer Region

  • Allows complete control over variables

  • Easily reproducible and verifiable

  • Quicker than gas permeation measurements


Quantifying tortuosity
Quantifying Simulations and the Implications of the Constrained Polymer Regiontortuosity

  • Tortuosity

    • is the diffusion coefficient of pristine polymer

    • is the diffusion coefficient of resulting nanocomposite

    • is the distance that a molecule has to travel to diffuse through the nanocomposite

    • is the distance that a molecule has to travel to diffuse through the pristine polymer


Monte carlo simulation
Monte Carlo simulation Simulations and the Implications of the Constrained Polymer Region


Monte carlo simulation1
Monte Carlo simulation Simulations and the Implications of the Constrained Polymer Region


Simulation parameters
Simulation parameters Simulations and the Implications of the Constrained Polymer Region

  • Run on a supercomputing grid over a period of one month

  • Data obtained for and

  • Other parameters (t is time)


Data Simulations and the Implications of the Constrained Polymer Region


Results and discussion
Results and discussion Simulations and the Implications of the Constrained Polymer Region

  • We suggest considering τ as a function of χ, where

    • μ is a geometric factor depending on clay shape

    • s is the cross-sectionalarea of a clay plate

    • is the number of clay plates per volume


Data Simulations and the Implications of the Constrained Polymer Region


Results and discussion1
Results and discussion Simulations and the Implications of the Constrained Polymer Region

  • χ is composed of two main components:

    • Cross-sectional area of clay plates per volume of polymer

    • Average distance travelled by a molecule to get around a clay plate


Conclusion
Conclusion Simulations and the Implications of the Constrained Polymer Region

  • Established τ as a function of χ

  • χ is more accurate than αϕ

  • Monte Carlo simulations

    • Improved efficiency

    • Feasible


Further research
Further research Simulations and the Implications of the Constrained Polymer Region

  • Account for more variables in simulations

    • Clay plate size

    • Orientation

    • Incomplete exfoliation

  • Calculate effect of constrained polymer region


Acknowledgements
Acknowledgements Simulations and the Implications of the Constrained Polymer Region

  • Gary Beall, Texas State University

  • Max Warshauer, Texas State University

  • Siemens Foundation

  • University of Texas at Austin

  • Our families

Further information

Website: code.google.com/p/rwalksim


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