Authors
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Martin A. Hubbe
Department of Forest Biomaterials, North Carolina State University, Campus Box 8005, Raleigh, NC 27696-8005, USA
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Björn Sjöstrand
Pro2BE, The research environment for Processes and Products for a circular Biobased Economy, Department of Engineering and Chemical Sciences, Karlstad University, SE-65188, Karlstad, Sweden
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Magnus Lestelius
Pro2BE, The research environment for Processes and Products for a circular Biobased Economy, Department of Engineering and Chemical Sciences, Karlstad University, SE-65188, Karlstad, Sweden
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Helena Håkansson
Pro2BE, The research environment for Processes and Products for a circular Biobased Economy, Department of Engineering and Chemical Sciences, Karlstad University, SE-65188, Karlstad, Sweden
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Agne Swerin
Pro2BE, The research environment for Processes and Products for a circular Biobased Economy, Department of Engineering and Chemical Sciences, Karlstad University, SE-65188, Karlstad, Sweden
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Gunnar Henriksson
Pro2BE, The research environment for Processes and Products for a circular Biobased Economy, Department of Engineering and Chemical Sciences, Karlstad University, SE-65188, Karlstad, Sweden; KTH Royal Institute of Technology, School of Engineering Sciences in Chemistry, Biotechnology and Health, Department of Fiber and Polymer Technology, Division of Wood Chemistry and Pulp Technology., SE-10044 Stockholm, Sweden
Keywords:
Osmotic pressure, Donnan equilibrium, Dissociation, Hydrophilicity, Crystallinity, Water retention value
Abstract
Factors affecting the swelling of cellulosic fibers are considered in this review. Emphasis is placed on aqueous systems and papermaking fibers, but the review also considers cellulose solvent systems, nanocellulose research, and the behavior of cellulosic hydrogels. The topic of swelling of cellulosic fibers ranges from effects of humid air, continuing through water immersion, and extends to hydrogels and the dissolution of cellulose, as well as some of its derivatives. The degree of swelling of cellulose fibers can be understood as involving a balance between forces of expansion (especially osmotic pressure) vs. various restraining forces, some of which involve the detailed structure of layers within the fibril structure of the fibers. The review also considers hornification and its effects related to swelling. The expansive forces are highly dependent on ionizable groups, pH, and the ionic strength of solution. The restraining forces depend on the nature of lignin, cellulose, and their detailed structural arrangements.
