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Genese des Microstructures et Consequences sur les Proprietes Mecaniques dans les Polymeres Semi-Cristallins Renforces par des Charges Lamellaires

Abstract : This work is devoted to the development of new materials based on polymer semi-cristalline matrix (PA, PE) for packaging application. Among the possibilities to improve the barrier and the mechanical properties of semi-cristalline the use of nanometer size lamellar shape particles, such as montmorillonite, is certainly the most interesting one. The main advantages of montmorillonite are its low cost, a great potential specific area (700m2/g), a high aspect ratio (100) and good swelling properties. When dispersed homogeneously in a polymer matrix, even at a very low weight ratio, the nanolayers can greatly enhance the thermal stability, mechanical and barrier properties, as reported in the literature. Though significant progress has been made in developing nanocomposites with different polymer matrices, a general understanding has yet to emerge and particularly on the structure-properties relationships.

This manuscript is constructed according to two observations in order to understand the structure-properties relationships of semi-cristalline polymer-clay nanocomposites:

- On the one hand, today most techniques used in a standard procedure (X-Ray Diffraction, Transmission Electron Microscopy) do not allow a correct interpretation of polymer-clay nanocomposite structure and dispersion. In this work, we propose an Image Analysis Procedure (I.A.P.) based on TEM and Optical Microscopy observations to characterize the clay dispersion in polymer clay nanocomposites. Thanks to it, we have shown it was possible to evaluate morphological and dispersion parameters that can be directly related to the nanocomposite processing, the clay weight ratio and to the nature of the compatibilizer. Moreover, complementary experiments by Small Angle X-Ray Scattering, environnemetal Microscopy (ESEM) and rheological measurements, have shown that the morphological interpretation with the IAP was representative of the material in its whole.

- On the other hand, the analysis of the properties of semi-cristalline nanocomposites most often does not take into account the real state of dispersion of the nanocomposite, the crystalline texture, the clay particle orientation and also the matrix- filler possible interactions. The last part of this work is devoted to the relative importance of these parameters on the mechanical properties. Among others, we have noticed in PE-clay nanocomposites that the most exfoliated systems were not the ones that had the best reinforcement. Ever since, we have tried to characterize more deeply the origin of the coupling between the polymer crystallites and the clay particles. Two procedures were proposed. At last, a qualitative approach by Finite Element Modelling helps to confirm the key role of the interactions in the reinforcement of semi-cristalline nanocomposites.
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https://tel.archives-ouvertes.fr/tel-00173869
Contributor : Alexandre Vermogen <>
Submitted on : Thursday, September 20, 2007 - 5:15:11 PM
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  • HAL Id : tel-00173869, version 1

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Alexandre Vermogen. Genese des Microstructures et Consequences sur les Proprietes Mecaniques dans les Polymeres Semi-Cristallins Renforces par des Charges Lamellaires. Matériaux. INSA de Lyon, 2006. Français. ⟨tel-00173869⟩

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