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Evaluation des paramètres physiques et physico-chimiques qui influencent l'accessibilité de la cellulose

Abstract : Cellulose, a bio-polymer belonging to polysaccharides family, has been for years the research topic of many studies having the purpose to better control its modification and processing. Since it is not melting below its degradation temperature, cellulose needs to go through a step of dissolution in order to be processed. However, the processes used today are not fully optimized resulting in a loss of material or final product quality. This limitation is partly due to its complex structure which makes cellulose chains difficult to be accessed to reactants. The scientific scope of our work was to analyse and try to understand some of the parameters that can have an influence on cellulose accessibility: wet state, application of an elongational mechanical stress, irradiation. We showed that the porous structure of cellulose is an important parameter to consider in its accessibility. Thus, in presence of a poor solvent such as water-NaOH cellulose, fibres show better accessibility in the never dried state compared with fibres in the dried state, due to a more open structure of fibres. The porosity was also shown to be an important factor controlling the hornification mechanism, as shown when studying model cellulose surfaces. We were able to show that the existence of a microporosity linked to the viscose process was the main inhibiting parameter preventing two opposite walls of a collapsing pore during drying to be irreversibly glued. Micropores generate a high rugosity that is preventing the formation of a tight array of hydrogen bonds. Finally, we showed that another factor to consider in the chemical modification of cellulose is the need for chain to be mobile enough to reach a high range of steric conformations.
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Submitted on : Monday, August 1, 2011 - 11:44:11 AM
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  • HAL Id : pastel-00612881, version 1

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Monica Spinu. Evaluation des paramètres physiques et physico-chimiques qui influencent l'accessibilité de la cellulose. Matériaux. École Nationale Supérieure des Mines de Paris, 2010. Français. ⟨NNT : 2010ENMP0070⟩. ⟨pastel-00612881⟩

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