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- Jardeby, K, et al.
(författare)
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Characterisation of the undissolved residuals in CMC-solutions
- 2004
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Ingår i: Cellulose. - 0969-0239 .- 1572-882X. ; 11:2, s. 195-202
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Tidskriftsartikel (refereegranskat)abstract
- The undissolved fibre and gel residuals that had not completely reacted to form fully dissolved carboxy-methyl cellulose (CMC) in the production of CMC were studied to clarify the reactivity of wood components in the pulp. The undissolved residuals, the pulp and the CMC were therefore analysed on the fibre level, the cell-wall level and the chemical composition level. The results may be interpreted as indicating that the presence of undissolved residuals in the CMS was not due to any chemical difference. The undissolved residuals were shown to consist mainly of swollen cell wall parts and some whole wood cells, mainly thick-walled compression wood and summerwood cells. They react more slowly in the mercerisation and etherification, probably because of a greater diffusion resistance due to their larger dimensions or to a more dense structure. These cells are assumed to be less accessible for chemical penetration, but they may also contain supramolecular structures that slow down the CMC reaction.
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- Wickholm, K., et al.
(författare)
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Quantification of cellulose forms in complex cellulose materials : A chemometric model
- 2001
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Ingår i: Cellulose. - Stockholm : Kluwer Academic Publishers. - 0969-0239 .- 1572-882X. ; 8:2, s. 139-148
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present a chemometric model for quantifying the cellulose forms with different states of order found within cellulose I fibrils. The relative amounts of the different cellulose forms, that is crystalline cellulose I, para-crystalline cellulose and cellulose at accessible and inaccessible cellulose surfaces, were determined by non-linear least squares fitting of the C4-region in CP/MAS C-13-NMR (Cross-Polarisation Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance) spectra. By correlating these results from the C4-region with the full spectral data we obtained a model which is able to provide an assessment of the relative amounts of the different cellulose forms directly from NMR-spectra of complex lignocellulosic samples. Furthermore, this model enabled new assignments to be made in the C1-region for signals from cellulose at accessible fibril surfaces.
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