Differences and similarities between kraft and oxygen delignification of softwood fibers: effects on chemical and physical properties
2021 (English)In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 28, no 5, p. 3149-3167Article in journal (Refereed) Published
Abstract [en]
The fiber properties after oxygen delignification and kraft pulping were studied by looking into the chemical characteristics and morphology. The effect of the two processes on the fibers was evaluated and compared over a wider kappa number range (from 62 down to15). Wide-angle X-ray scattering, nuclear magnetic resonance and fiber saturation point were used to characterize the fiber network structure. Fiber morphology and fiber dislocations were evaluated by an optical image analysis. The total and surface fiber charges were studied by conductometric and polyelectrolyte titrations. The fiber wall supramolecular structure, such as crystallinity, size of fibril aggregates, pore size and pore volume, were similar for the two processes. The selectivity, in terms of carbohydrate yield, was equal for kraft cooking and oxygen delignification, but the selectivity in terms of viscosity loss per amount of delignification is poorer for oxygen delignification. Clearly more fiber deformations (2–6% units in curl index) in the fibers after oxygen delignification were seen. Introduction of curl depended on the physical state of the fibers, i.e. liberated or in wood matrix. In the pulping stage, the fiber continue to be supported by neighboring fibers, as the delignified chips maintain their form. However, in the subsequent oxygen stage the fibers enter in the form of pulp (liberated fibers), which makes them more susceptible to changes in fiber form. Graphic abstract: [Figure not available: see fulltext.] © 2021, The Author(s).
Place, publisher, year, edition, pages
Springer Science and Business Media B.V. , 2021. Vol. 28, no 5, p. 3149-3167
Keywords [en]
Curl, Deformations, Fiber charge, Fiber vulnerability, Selectivity, Water retention value, Crystallinity, Delignification, Fibers, Geometrical optics, Kraft pulp, Morphology, Oxygen, Polyelectrolytes, Pore size, X ray scattering, Chemical and physical properties, Chemical characteristic, Fiber deformation, Fiber saturation points, Optical image analysis, Oxygen delignifications, Polyelectrolyte titration, Supramolecular structure, Wood
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:ri:diva-52901DOI: 10.1007/s10570-021-03713-0Scopus ID: 2-s2.0-85101488810OAI: oai:DiVA.org:ri-52901DiVA, id: diva2:1546844
Note
Funding details: Wallenberg Wood Science Center, WWSC; Funding text 1: The authors in this paper would like to thanks Jasna Srndovic for the NMR and WAXS measurements. The authors gratefully acknowledge the financial support received from STFI's Intressentförening and Önnesjöstiftelsen. The Wallenberg Wood Science Center (WWSC) funded by Knut and Alice Wallenberg (KAW) Foundation and the Wood and Pulping Chemistry Research Network (WPCRN) at KTH are gratefully acknowledged for financial support for Dr. Sevastyanova.
2021-04-232021-04-232022-05-10Bibliographically approved