Utilization of cellulosic building blocks in material design: Dissertation

In this thesis, three cellulosic building blocks: pulp fibres, cellulose nanofibrils (CNF) and polymeric cellulose were utilized in the development of 1D-, 2D- and 3D-applications. For their efficient utilization in material and application design, systematic analysis of the materials and their interactions was conducted using complementary analytical tools. Cellulose pulp fibres were used as building blocks for 1D fibre yarn production, CNF was used for 2D films and polymeric cellulose for 3D modification and functionalization of cellulosic textiles. Pulp fibres were converted into yarns without dissolution and regeneration using a deep eutectic solvent (DES) acting as a rheology modifier and dispersing agent, and therefore, enabling the spinning of yarn. The intrinsic properties of cellulose I crystalline structure were retained in the final product. In order to understand the effect of DES on cellulose fibres, as well as, to improve the macroscale properties of the final product, the changes in pulp fibre composition and morphology due to DES were examined. As a result, electrostatically bound residuals of DES were revealed, which had an effect on charge of the fibres, and therefore, also affecting the properties of the fibre yarn. In 2D CNF films the effect of a major hemicellulose in hardwood, xylan, on the stability and properties of CNF films was examined and the effect of xylan on surface interactions was linked to macroscale film properties. Removal of xylan had affected the microscale stability and water uptake properties, however, the film properties in larger scale, such as barrier properties, remained intact. 3D modifications of textiles were conducted using 3D-printing and two cellulose derivatives, cellulose acetate and acetoxypropyl cellulose. Macroscale properties, such as the adhesion, of the materials were analysed. The obtained results were linked to the strength of material interactions during adsorption. As an outcome, promising material combinations for textile applications were determined and several application prototypes for textile modification and functionalization were demonstrated.
Overall, the work demonstrates the significance of understanding the macroscale material properties and the surface interactions of the chosen cellulosic building blocks with other substances in the development of new cellulosic materials and applications.