Defence of doctoral thesis: Pernilla Karlsson – Swelling of Cellulose Fibrillar Matrices and Gels

Abstract

One of the major challenges of today´s society is to find a sustainable way to create a living based on the resources on earth. It is a challenge that includes a transition from fossil-based materials to renewable/biodegradable raw materials and also the creation of an environmentally friendly circular material flow. In the search for renewable and biodegradable raw materials, the forest has gained renewed interest. In Sweden, 70 % of the area is covered with forest and, together with a long history of a sustainable forestry, this means that there are environmental and economic gains if this resource is utilized in a correct way and research and development into new wood-based materials has advanced significantly during the last decades. The wood component that has gained the most attention is cellulose and due to the ability of cellulose to act as a light-weight reinforcing component in composites and also due to the variability by which cellulose can be modified in order to obtain a wide range of useful properties. One advantage of cellulose-based materials is that they can be processed in water since the cellulose is hydrophilic and is softened by exposure to water. At the same time, this is one of the major drawbacks of cellulose-based materials since their properties deteriorate when exposed to water, whether as moist air or as condensed liquid. To optimize the use of cellulose fibers/fibrils/gels, knowledge of the effect on the inherent properties of cellulose in contact with water needs to be extended. This project has therefore focused on a fundamental understanding of the reasons behind the water uptake/swelling in a cellulose-rich fiber assembly immersed in water.