Properties of highly hydrated softwood kraft fibers

Abstract

Chemical modification of pulp can improve pulp quality. Mercerization as a method to modify natural fiber has a history of two hundred years, and the mechanism of mercerization is a simple transformation from cellulose I to cellulose II. Mercerized pulp has been profoundly investigated. The target of this thesis was to understand whether mercer-ization and PFI-refining can improve the properties of softwood kraft pulp. First, softwood kraft pulp was treated with NaOH(15wt%) to produce highly hydrated softwood kraft fibers. Then, PFI-refining was introduced to improve the pulp property. Afterward, the modified pulp was made into handsheets. The original pulp and modified pulp were analyzed by different devices to demonstrate fiber properties and their chemical components. DSC tests and WRV were performed to explore the swelling property and thermoporometry. Various sheet strength tests are applied to study bonding potential and strength properties. Our results verified that mercerization (15wt% NaOH) can turn cellulose I into cellulose II, improve the swelling of the pulp, and increase the volume of micropores while decreasing the strength properties. Moreover, PFI-refining does not influence thermoporometry but can boost the tensile strength of the sheet made from both kraft pulp and mercerized pulp.