Polymers

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Molecular Simulation of the Rheology of Nanocomposite Polymer Materials, RMIT University / Swinburne University / VPAC, Melbourne, Australia. (VPAC E-Research Program Grants Scheme 2005)

Extending the preliminary results from our earlier work (described below), this study combines higher molecular weight model polymer molecules (18,000g/mol), with larger filler particles, to develop more realistic and experimentally comparable simulations. These are used to elucidate the effects of changing the filler size/shape on the rheological behaviour of the nano-composite.

Micro- and Nano-Structured Polymeric Composites, Rheology and Materials Processing Centre, Melbourne, Australia. (RMIT University Research Investment Fund 2004)

“The shear-rate dependence of viscosity is studied for model polymer melts containing various concentrations of spherical filler particles by molecular-dynamics simulations, and the results are compared with the experimental results for calcium-carbonate-filled polypropylene. …Some important qualitative similarities in shear behaviour are observed. …Shear viscosities, zero-shear viscosities, and the rate of shear thinning are all seen to increase with filler content in both the experimental and simulated systems. …Our results indicate that there exists a value of the ratio of [filler size to polymer size] such that the zero-shear-rate viscosity of the composite becomes approximately independent of the filler particle volume fraction.” [Kairn et al Journal of Chemical Physics 123 (19) 194905 (2005)]

Non-Equilibrium Molecular Dynamics Studies of Complex Fluids, RMIT University / Swinburne University / VPAC, Melbourne, Australia. (VPAC Expertise Grants Scheme 2001-2002)

“Relationships between viscometric behaviour and concentration are observed and evaluated through a series of nonequilibrium molecular dynamics simulations of the behaviour of 20-site poymers in solution with explicit solvent across the full concentration range. [The model 20-site bead-rod molecules correspond approximately to 1800 g/mol   polyethylene.] The zero-shear viscosities, first normal stress coefficients and steady-state shear compliance of the solutions are examined alongside conformational properties including the excluded volume effect. The variation of viscosity with concentration in these solutions is described by the Huggins equation up to relatively high concentrations. …The dilute and melt behaviours of this system are accurately described by the theories of Zimm and Rouse, respectively.” [Kairn et al ,International Journal of Thermophysics 25 1075-1084 (2004)]

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