Pulp compositions and their influence on the production of dialcohol cellulose

Sammanfattning: The characteristics of products made from pulp can be modified through different methods. If the pulp is refined either laboratory or industrially, the fibres in the pulp become more flexible and therefore creates stronger bonds to each other, which results in a final product with a higher strength. The refining process also causes the formation of small fibre pieces that are called fines, which also contribute to the increased strength. The major component in pulp is cellulose, which can be chemically modified to materials with changed properties. Periodate oxidation of cellulose results in dialdehyde cellulose that can be further reduced with sodium borohydride to obtain dialcohol cellulose, which is a material with a higher ductility compared to regular cellulose. In this thesis, different pulp compositions and their influence on the production of dialcohol cellulose (DALC) were investigated. The aim of the study was to find out how the ductility of paper sheets made from DALC were affected by the presence of fines in the pulp. Nine different pulp compositions were prepared for the modification: unrefined pulp, unrefined pulp with added fines, industrially refined pulp, dewatered industrially refined pulp, and pulp refined 1000, 3000, 5000, 10 000 and 15 000 revolutions with a PFI Mill. Paper sheets were made with a Rapid Köthen sheet former and the mechanical properties of the sheets were tested with a Zwick Roell tensile tester. The surface of the sheets were analyzed using a scanning electron microscope (SEM). The results obtained from the tensile tests showed that DALC made from unrefined pulp and DALC made from pulp highly refined with a PFI Mill, resulted in sheets with a high strain-at-break. For each increased degree of refining with the PFI Mill, the resulting DALC sheets showed an improved elongation and tensile strength. When DALC was produced from industrially refined pulp and from unrefined pulp with added fines, the resulting sheets had a lower strain-at-break. These findings indicate that the presence of fines in the pulp do have a negative effect on the ductility of the resulting DALC sheets.