Influence of processing parameters on regeneration kinetics and morphology of porous cellulose from cellulose–NaOH–water solutions
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The kinetics of cellulose regeneration in acetic acid bath from cellulose–8% NaOH–water solutions and gels is studied as a function of gelation conditions, acid concentration and bath temperature. The diffusion coefficient of NaOH from cellulose solution or gel into regenerating bath was calculated. It does not depend either on gelation mode or on acid concentration. On the contrary, cellulose regeneration from non-gelled solutions is slower than from a gel. The increase in bath temperature induces diffusion coefficient increase obeying Arrhenius law. Scanning electron microscopy images of regenerated swollen-in-water freeze-dried cellulose and of the same samples dried in supercritical CO2 show highly porous morphology.
KeywordsCellulose Gelation Regeneration Diffusion Cellulose–NaOH solution Morphology Supercritical drying Freeze-drying
This work was supported by ANR (France), project N ANR-06-MAPR-0004. Authors are grateful to S. Fabry-Berthon, A. Rigacci and P. Ilbizian (CEP, Mines ParisTech, Sophia-Antipolis, France) for supercritical drying, to S. Rousselle (University of Nice-Sophia-Antipolis, France) for the help in diffusion coefficient measurements and to P. Navard (CEMEF, Mines ParisTech, Sophia-Antipolis, France) for fruitful discussions.
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