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On the relationship between wood fibre wall swelling, charged groups, and delamination during refining
Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. (FSCN)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. (FSCN)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. (FSCN)
2013 (English)In: Journal of Science & Technology for Forest Products and Processes, ISSN 1927-6311, E-ISSN 1927-632X, Vol. 3, no 4, 30-34 p.Article in journal (Refereed) Published
Abstract [en]

The influence of sulphonic and carboxylic acid groups in combination with the effect of counter-ion form on the swelling capacity of mechanical pulp fibres was studied by means of water retention value (WRV) measured in the temperature range from 25oC to 95oC. Mechanical pulp fibres (TMP) were treated with hydrogen peroxide, sodium sulphite, or both under conditions resembling those used in chemi-thermomechanical and bleaching processes commonly used in the industry. In conventional chemi-thermo-mechanical processes, sulphite treatment is used before refining, whereas peroxide treatment can be used both before and after refining. However, in this study, sulphite was also used after peroxide treatment. When sodium sulphite-treated pulps are subjected to a subsequent hydrogen peroxide step, all pulps show a decrease in sulphonic acid groups, which can be attributed to dissolution of highly charged lignin. Pulps treated with a high hydrogen peroxide charge (4%) show a loss in carboxylic acid groups during subsequent treatment with sodium sulphite. This loss is probably due to dissolution of highly charged fibre material such as demethylated pectins. Both the increased degree of sulphonation and carboxylation of lignin reduce the softening temperature reducing the degree of cross-linking in the lignin matrix. This softening probably improves the compressibility of the fibre pads in the sample holders of the WRV centrifuge, which would counteract the otherwise expected increase in WRV due to increased swelling potential. This phenomenon makes it difficult to see clear trends in WRV as a function of increasing degrees of sulphonation and carboxylation. When changing the counter-ion form from proton or calcium form to sodium form, there is, however, always a clear increase in WRV in the range from 20% to 30%.

Place, publisher, year, edition, pages
2013. Vol. 3, no 4, 30-34 p.
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:miun:diva-24054Scopus ID: 2-s2.0-84905389461OAI: oai:DiVA.org:miun-24054DiVA: diva2:778120
Note

Export Date: 7 January 2015

Available from: 2015-01-09 Created: 2015-01-07 Last updated: 2015-01-09Bibliographically approved

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