Étude de mélanges de cellulose dans des solutions aqueuses de soude

Abstract : Dissolution and processing of cellulose are two topics of intensive research and prospective industrial applications as well.Among known cellulose solvents, aqueous soda solution is the less polluting one.The scientific aspect of the work concerns the studies of the structure, dissolution and structuring of cellulose in 9%soda/water solutions.First, the phase diagram of aqueous soda solutions was built.The systems consists of soda hydrates and water, both able to crystallise, and amorphous water that does not crystallise even at -60°C.The structure of cellulose/soda/water was proposed depending on the cellulose type (microcrystalline and cellulose pulp).In both cases, from two to three hydroxyl groups of the cellulose glucopyranose unit are bound to soda hydrates.The flow and gelation of cellulose/soda/water was studied.They demonstrate suspension properties.The gelation takes place at any temperature being faster with temperature increase.The industrial aspect of the work concerns the study of the new process of sponges preparation from cellulose/soda mixtures by employing a complicated temperature/time cycle.The objective was to understand the physico-chemical phenomena during mixture freezing at -18°C which is essential for the sponges preparation with good mechanical properties.The structure changes during different stages of the cycle were revealed, with gelation at 0°C and phase separation at -18°C.The latter leads to crystallisation which is responsible for the properties of the final product and which is the key of the process.
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  • HAL Id : tel-00274837, version 1

Citation

Cédric Roy. Étude de mélanges de cellulose dans des solutions aqueuses de soude. Mécanique [physics.med-ph]. École Nationale Supérieure des Mines de Paris, 2002. Français. ⟨NNT : 2002ENMP1043⟩. ⟨tel-00274837⟩

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