Abstract
Juniper (Juniperus communis) is a slowly growing softwood species that has unusually high elasticity. To demonstrate the utilization of the material properties of juniper, conventional kraft pulping was used to prepare juniper pulp, whose handsheet and fiber properties were subsequently analyzed. A large number of uncooked fiber bundles remained after pulping, the screened yield was low, and kappa number high. Also the viscosity value of juniper pulp was lower than that of common industrial softwood pulps, due to the harsh pulping conditions required. Juniper fibres had thicker cell walls, smaller diameters, and shorter lengths than those of the more conventional softwood species, while the microfibril angle, which was measured by X-ray diffraction, was significantly higher (22-37°). Moreover, the strength properties of juniper pulp handsheets were lower than those of common softwood pulps. The intriguing elastic properties of juniper wood, however, were apparent in the handsheet properties. Tensile stiffness was determined to be merely half of the value typical for softwood pulps, whereas the breaking stretch was more than twice higher. Although a large-scale industrial use of juniper is not possible, one can speculate that it may be feasible to mimic its properties via transgenic modification to faster growing species.
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Kraft Pulping of Juniperus communis Results in Paper with Unusually High Elasticity
Tuomas Hänninen,a Eero Kontturi,a,* Kirsi Leppänen,b Ritva Serimaa,b and Tapani Vuorinen a
Juniper (Juniperus communis) is a slowly growing softwood species that has unusually high elasticity. To demonstrate the utilization of the material properties of juniper, conventional kraft pulping was used to prepare juniper pulp, whose handsheet and fiber properties were subsequently analyzed. A large number of uncooked fiber bundles remained after pulping, the screened yield was low, and kappa number high. Also the viscosity value of juniper pulp was lower than that of common industrial softwood pulps, due to the harsh pulping conditions required. Juniper fibres had thicker cell walls, smaller diameters, and shorter lengths than those of the more conventional softwood species, while the microfibril angle, which was measured by X-ray diffraction, was significantly higher (22-37°). Moreover, the strength properties of juniper pulp handsheets were lower than those of common softwood pulps. The intriguing elastic properties of juniper wood, however, were apparent in the handsheet properties. Tensile stiffness was determined to be merely half of the value typical for softwood pulps, whereas the breaking stretch was more than twice higher. Although a large-scale industrial use of juniper is not possible, one can speculate that it may be feasible to mimic its properties via transgenic modification to faster growing species.
DOI: 10.15376/biores.6.4.3824-3835
Keywords: Juniperus communis; Kraft pulping; Microfibril angle; Paper properties
Contact information: a: Department of Forest Products Technology, School of Chemical Technology, Aalto University, P.O. Box 16300, 00076 Aalto, Finland; b: Department of Physics, Division of materials physics, University of Helsinki, P.O.B. 64, FI-00014 University of Helsinki, Finland;
* Corresponding author: eero.kontturi@aalto.fi