Hydration of microcrystalline cellulose and milled cellulose studied by sorption calorimetry.

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Hydration of microcrystalline cellulose and milled cellulose studied by sorption calorimetry.

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Publication Article, peer reviewed scientific
Title Hydration of microcrystalline cellulose and milled cellulose studied by sorption calorimetry.
Author(s) Kocherbitov, Vitaly ; Ulvenlund, Stefan ; Kober, Maria ; Jarring, Kjell ; Arnebrant, Thomas
Date 2008
English abstract
The hydration of two different polymorphs of microcrystalline cellulose (cellulose I and II), as well as the hydration of amorphous cellulose was studied using water sorption calorimetry, gravimetric water vapor sorption, nitrogen sorption, and X-ray powder diffraction. Amorphous cellulose was prepared by means of ball-milling of microcrystalline cellulose (MCC). Whereas X-ray data showed the untreated MCC to consist of cellulose I, the amorphous cellulose was found to recrystallize into cellulose II after contact with water or water vapor at relative humidities (RHs) above 90%. Sorption isotherms show an increase of water sorption in the sequence cellulose I < cellulose II < amorphous cellulose. The enthalpy of water sorption becomes more exothermic in the same sequence. The specific area of cellulose is dramatically higher when calculated from the water adsorption than when calculated from nitrogen adsorption. A proposed mechanism of water sorption by MCC implies the adsorption of water molecules at solid-solid interfaces, i.e., between neighboring microfibrils, which explains the observed difference between water and nitrogen. The Brunauer-Emmett- Teller (BET) model is therefore not appropriate for the description of the hydration of cellulose. Rather, the Langmuir model represents a more accurate description of water sorption by MCC at low RH. At higher RH, the water adsorption competes with capillary condensation. The thickness of microfibrils, as calculated using the fitting of the sorption isotherm of MCC with the Langmuir equation, is about 4 nm. This value compares favorably with literature data.
DOI http://dx.doi.org/10.1021/jp711554c (link to publisher's fulltext)
Publisher American Chemical Society
Host/Issue Phys. Chem. B.;12
Volume 112
Pages 3728-3734
Language eng (iso)
Subject(s) Hydration
Research Subject Categories::NATURAL SCIENCES::Chemistry::Physical chemistry::Surface and colloid chemistry
Research Subject Categories::NATURAL SCIENCES::Chemistry::Physical chemistry::Biophysical chemistry
Research Subject Categories::PHARMACY::Pharmaceutical chemistry
Handle http://hdl.handle.net/2043/6409 (link to this page)

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