Effect of mechanically induced micro deformations on extensibility and strength of individual softwood pulp fibers and sheets

Abstract

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.

Probing Effect of Papirindustriens Forskningsinstitut (PFI) Refining on Aggregation Structure of Cellulose: Crystal Packing and Hydrogen-Bonding Network

“…The zero-span tensile index was usually used in characterizing the tensile strength of fibers. The results of the zero-span tensile index showed that PFI refining did not reduce fiber strength, which is consistent with the report of Kouko et al [24]. The above results showed that PFI refining improved the extent of fibrillation (especially the internal fibrillation), the swelling of fibers, and the tensile strength of sheets without a decrease of the tensile strength of fibers.…”

Differences and similarities between kraft and oxygen delignification of softwood fibers: effects on chemical and physical properties

“…An acid treatment was used to quantify the weak spots in fibers from kraft cooked and oxygen delignified pulps. The acid will preferentially attack the weak spots in the fibers and the chemical attack will lead to cleavage at the dislocated areas (Ander et al 2005(Ander et al , 2008Courchene et al 2002;Kouko et al 2019).…”

A novel rotation generator of hydrodynamic cavitation for the fibrillation of long conifer fibers in paper production

“…Its overall objective is to achieve desired paper-making properties such as increased drainage rate of pulp, higher tensile index, burst index and density of paper, and decreased air permeability of paper [3][4][5][6]. Primarily, refining causes breakage of hydrogen bonds among the microfibrils, which subsequently increases the surface of microfibrils and the ability of fibers to establish links between them and thus the fibrillation of fibers [7,8].…”