Abstract

Primary refined softwood was subjected to highconsistency (HC) or low-consistency (LC) secondary refining, and the nature of the development of the internal and external fiber microstructure and ultrastructure has been compared. The primary refining of mixed softwood as a raw material was performed in pilot scale by the advanced thermomechanical pulp process. The study was aiming at the comparative characterization of LC and HC pulps at the fiber level when produced with similar and well-characterized handsheet properties. The formerly described Simons ’ staining method was applied. A significant degree of fiber wall delamination/internal fibrillation (D/IF) was observed during both LC and HC refining. Both the energy input and the refining consistency had a significant impact on elevating the degree of fiber wall D/IF. The statistical evaluation of internal fiber development indicated that the fiber populations in LC- and HC-refined pulps had a similar degree of fiber wall D/IF despite having a large difference in refining energy input (420 kW h odt in LC than in HC refining. The characteristic of the external fiber development from HC and LC refining was very different. Secondary LC refining promoted fiber surfaces with ribbons of thin hairlike threads arising from the inner secondary S2 layer that occasionally developed along the whole fiber length. Broad sheet- and lamellaetype external fibrillation from the S2 was typical for HC refining, and these characteristics were rarely observed in the LC pulps. The mechanisms for LC and HC fiber development are proposed. The cell wall characteristics (internal and external) of the pulp fibers appear to govern most of the physical and optical properties in handsheets.Primary refined softwood was subjected to highconsistency-1 ), confirming that D/IF was promoted more energyefficiently Keywords: (D/IF), fiber characterization, fiber development, surface ultrastructure of fibers, HC refining, LC refining, SEM, Simons’ stainingATMP, delamination/internal fibrillation

Keywords

ATMP; delamination/internal fibrillation (D/IF); fiber characterization; fiber development; surface ultrastructure of fibers; HC refining; LC refining; SEM; Simons' staining

Published in

Holzforschung
2013, Volume: 67, number: 7, pages: 735-745
Publisher: WALTER DE GRUYTER GMBH

SLU Authors

• Fernando, Dinesh

  • Department of Forest Products, Swedish University of Agricultural Sciences
    

• Daniel, Geoffrey

  • Department of Forest Products, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Wood Science


Publication identifier

DOI: https://doi.org/10.1515/hf-2012-0135

Permanent link to this page (URI)

https://res.slu.se/id/publ/56141