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Élaboration et caractérisation d’une matrice polypropylène chimiquement modifiée et chargée GNP/graphène fonctionnalisés

Abstract : In the last decade, the environmental awareness of the need to reduce human impact on the environment affects the research sector. Reducing the fuel consumption and the human gas emissions became a priority, the humanity needs to switch to more eco-efficient patterns of consumption. In the transport field, numerous new lines of research are possible, like lighter structure. Composite materials, like multi-layered steel/polymer, appeared to be the perfect candidates to reach that objective. The polymer part of such material needs to present good shock absorption and thermo-electrical properties, and good compatibility with a metallic surface. The objective of this thesis is the elaboration and characterization of a polymer material with such properties that can be produced at industrial scale. To obtain good compatibility with the metal surfaces, the isotactic polypropylene-grafted-Maleic anhydride was selected as the initial material. This matrix presents good chemical property, its major drawback is its brittleness. A crosslinking reaction based on the reaction between MAH and amine groups was used to modify the mechanical properties of the matrix. The PP-g-MAH were crosslinked by twin-screw reactive extrusion with different configurations. The reaction affects the microstructure and the mechanical behavior of the materials, with a switch from brittle to ductile. The switch is explained by the variation of micro-mechanism of deformation implied by the crosslinked network. The solution used to modify the thermo-electrical properties of the material is the dispersion of different carbon nano-fillers such as graphite. To raise the dispersion quality of the fillers, and the compatibility between the carbon filler and the polymer matrix, a new method of functionalization of the graphite, by plasma discharge was developed. This new method implied a diminution of the filler thickness and an oxidation of the graphene surface, without any significative degradation of the fillers quality. Two types of nanocomposites were produced, one with an unmodified graphite filler and another one with a graphite modified by plasma treatment. Even with high filler concentration no electrical percolation was obtained, a high fillers exfoliation process need to be obtained. The functionalization of the graphite implied a carbon dispersion improvement, thus a better compatibility between the filler and the matrix.
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Submitted on : Thursday, October 8, 2020 - 5:43:11 PM
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Adrien Létoffé. Élaboration et caractérisation d’une matrice polypropylène chimiquement modifiée et chargée GNP/graphène fonctionnalisés. Matériaux. Université de Lorraine, 2020. Français. ⟨NNT : 2020LORR0076⟩. ⟨tel-02961858⟩

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