Influence of the quality of microcrystalline cellulose on the outcome of TEMPO-mediated oxidation
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In an attempt to prepare cellulose nanocrystals (CNCs) by TEMPO-mediated oxidation of microcrystalline cellulose (MCC), a new species of MCC called AaltoCell was placed under scrutiny. Unlike Avicel, AaltoCell is a never-dried species, still containing ca. 10% xylan in its structure. According to thermoporosimetry, the pore size distributions of AaltoCell and Avicel did not differ from each other but after TEMPO-oxidation, AaltoCell exhibited a far lower degree of porosity, hypothetically ascribed to its hemicellulose content. Surprisingly, the charge density imposed by TEMPO-oxidation did not vary between AaltoCell and Avicel despite the different microfibril widths observed, respectively. After TEMPO-oxidation and centrifugation the fine fraction share, indicating the CNC yield, was not more than 11% for AaltoCell, compared to 20% from Avicel.
KeywordsCellulose nanocrystals Cellulose oxidation Porosity Microcrystalline cellulose Thermoporosimetry
We acknowledge Academy of Finland (259500) for financial support, and would kindly acknowledge Moriam Most and Leena Nolvi for helping with the thermoporosity measurements and calculations, and Jenna Järvenpää and Professor Olli Dahl, the inventor of AaltoCell-process for providing the AaltoCell, with the DP determinations and hemicellulose analysis.
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