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Theses

Perméation des gaz dans les polymères semi-cristallins par modélisation moléculaire

Abstract : The gas permeability through the polymers is a property that is exploited in many industrial fields. The objective of this thesis is to better understand the problem of sealing of flexible pipes with polymers. Thus, the permeability of H2S, CO2 and CH4 in polyethylene (PE) was studied during this work. Permeability is a property resulting from the dissolution of gases in the polymer and then diffusion of these products through the material. Solubility, which characterizes the ability of a gas to be absorbed in the polymer, is a property of equilibrium, which can be studied by Monte Carlo techniques. Diffusion coefficient, which characterizes the ability of a gas to move more or less rapidly into the polymer network, will in turn studied by molecular dynamics.Below the melting temperature, polyethylene is in semi-crystalline state. This state is composed of regions containing randomly oriented chains (amorphous regions) and regions containing chains oriented regularly on a network (crystalline regions). The complex morphology of semi-crystalline polymers has nanometric heterogeneities, which is not easily accessible by molecular simulation. In order to study the solubility and diffusion coefficient of gases in semi-crystalline polyethylene, we model only the amorphous phase in this work. However, the effect of crystalline regions on the amorphous phase will be taken into account in the simulation by an ad-hoc constraint.
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Submitted on : Tuesday, March 29, 2011 - 9:34:07 AM
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Peyman Memari Namin. Perméation des gaz dans les polymères semi-cristallins par modélisation moléculaire. Autre. Université Paris Sud - Paris XI, 2011. Français. ⟨NNT : 2011PA112016⟩. ⟨tel-00580716⟩

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