PAPER making! FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL O U S SO Volume 6, Number 1, 2020
Effect of mechanically induced micro deformations on extensibility and strength of individual softwood pulp fibers and sheets Jarmo Kouko, Marina Jajcinovic, Wolfgang Fischer, Annika Ketola, Ulrich Hirn, Elias Retulainen. Tensile tests of individual bleached kraft pulp fibers and paper sheets of industrial origin were conducted in order to investigate the effect of refining and small-scale fiber deformations on the extensibility of fibers and paper. The shape of the tensile curves of most of the fibers was concave upward (i.e., increasing slope) and consisted of two or three phases suggesting that the fibrillar structure and disordered regions in the fiber wall were straightened out during straining. Only a few of the individual BSKP fiber tensile curves were apparently linear. Elongation of the individual kraft fibers varied from 8 to 32% and the average elongation was not increased by high consistency refining. Tensile test results of laboratory sheets made of the same BSKP pulp suggested that the fiber bonding not only governs paper strength, but also is highly relevant for the elongation of fiber networks. The key conclusion related to this investigation and freely dried sheets was that the increased network elongation and strength after refining is mainly due to increased inter-fiber bonding and a higher shrinkage tendency of the fiber network and not due to the increased elongation or strength of individual fibers. Contact information: J. Kouko A. Ketola E. Retulainen VTT Technical Research Centre of Finland Ltd, Koivurannantie 1, 40400 Jyva¨skyla¨, Finland M. Jajcinovic W. Fischer U. Hirn Institut fu¨r Papier-, Zellstoff- und Fasertechnik, Graz University of Technology, Inffeldgasse 23, 8010 Graz, Austria. Also CD Laboratory for Fiber Swelling and Paper Performance, Inffeldgasse 23, 8010 Graz, Austria Cellulose (2019) 26:1995 – 2012 https://doi.org/10.1007/s10570-018-2163-y This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http:// creativecommons.org/licenses/by/4.0/)
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Article 1 – Effect of Fibre Deformations on Strength
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