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Theses

Influence du vieillissement sur l'effet mémoire des polymères / Modélisation du mécanisme de mémoire de forme

Abstract : The aim of this thesis is to characterize the Shape Memory Effect (SME) of the (40% PCL/60% SBS) blend and to study the influence of the molecular weight and the physicochemical properties on this SME. Firstly, experimental characterization is performed in order to evaluate the physicochemical, morphological and mechanical properties of the used materials. The (PCL/SBS) blend exhibits a Total SME (TSME) as it recovers 100% of its original shape after one shape memory cycle. The energy stored in the structure acts as the driving force that can be responsible for this SME. Therefore, an original method using a witness is used to establish the stress-strain evolution during recovery. Secondly, to change the molecular weight of PCL in the blend, enzymatic hydrolytic degradation using an Amano Lipase from Pseudomonas fluorescens is carried out. The influence of hydrolysis on the pure PCL properties is evaluated. Then, sampling is carried out and (PCL/SBS) blends with different PCL molecular weights are obtained. Subsequently, these blends are submitted to experimental and shape memory tests to study the relationship between the molecular weight and the SME. The results show that the decrease in the molecular weight causes morphological and structural changes: the increase in stiffness and the embrittlement of the mixture, the decrease in compatibility, the increase in heterogeneity and the loss of thermo-dynamical balance of phases. These changes in the molecular weight and in the properties of blends influence its recovery capacity. The blend with the TSME is transformed to a polymer with partial SME. Finally, a bi-parabolic model is used to predict the viscoelastic behavior of the (40% PCL / 60% SBS) blend before and after its enzymatic hydrolytic aging.
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  • HAL Id : tel-03117959, version 1

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Abir Ben Abdalah. Influence du vieillissement sur l'effet mémoire des polymères / Modélisation du mécanisme de mémoire de forme. Matériaux. HESAM Université; Université de Sousse (Tunisie), 2020. Français. ⟨NNT : 2020HESAE046⟩. ⟨tel-03117959⟩

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