, Volume 19, Issue 3, pp 879–889 | Cite as

Morphological changes in never-dried kraft fibers under mechanical shearing

  • Kaarina Kekäläinen
  • Mirja Illikainen
  • Jouko Niinimäki


The modification of bleached never-dried cellulose fibers was studied under controlled compression and shearing conditions. Fibers were further treated in a high-intensity mixing device in low-consistency to determine if the fiber structure was weakened in the in-pad attrition. The difference between the development of the softwood and hardwood fibers was examined. The fiber properties were analyzed using a fiber morphology analyzer, fractional fiber analysis and an electron microscope. The results indicate that the shearing under the controlled compression at high consistency modified the softwood and hardwood fibers already at low-energy consumptions. The fiber length and width decreased, and the formation of curls and kinks was pronounced. However, the intensive mixing after in-pad attrition revealed that the fiber structure was not weakened under compression and shear forces; conversely, the fiber cell wall was more resistant for the intensive mixing. When comparing the results for hardwood and softwood fibers, the softwood fibers were more modified during in-pad attrition, whereas the fiber wall strengthening was more significant in the hardwood fibers.


Cellulose structure Fiber morphology Bleached kraft pulp Compressibility Internal friction In-pad attrition 



The authors thank Mr. Jani Österlund for his help during the practical work and the Graduate School in Chemical Engineering (GSCE) for the financial support.


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Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  • Kaarina Kekäläinen
    • 1
  • Mirja Illikainen
    • 1
  • Jouko Niinimäki
    • 1
  1. 1.Fibre and Particle Engineering Laboratory, Department of Process and Environmental EngineeringUniversity of OuluOuluFinland

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