The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Aalto

Role of External Fibrillation in Pulp and Paper Properties

Taegeun Kang

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Forest Products Technology for public examination and debate in Auditorium Puu II at Helsinki University of Technology (Espoo, Finland) on the 28th of September, 2007, at 12 noon.

Overview in PDF format (ISBN 978-951-22-8917-2)   [1131 KB]
Dissertation is also available in print (ISBN 978-951-22-8916-5)

Abstract

The purpose of this thesis was to clarify the role of external fibrillation in pulp and paper properties. If the degree of external fibrillation could be controlled and the role of external fibrillation were known, this would provide better possibilities for utilizing the full potential of fibrous material.

External fibrillation caused by refining is inevitable, but its role has not been clearly explained, because conventional refiners produce a variety of simultaneous effects, such as internal fibrillation, external fibrillation, straightening or curling of fibers and fines formation. Therefore, a special type of refiner was required for evaluating the specific role of external fibrillation. An ultra-fine friction grinder consisting of two grinding stones was found to overcome the limitation related to conventional refiners.

Using the grinder, it was possible to promote external fibrillation while keeping the internal fibrillation and curl constant. An increase in external fibrils attached to fibers was found to increase the retention of filler during sheet forming in a high-vacuum dewatering device. Promoting the degree of external fibrillation contributed to strengthening the bonding layer between fibers, resulting in improved tensile strength and internal bond strength. Recycling reduced fiber swelling and paper strength, but for externally fibrillated fibers this loss was restored by refining more than for internally fibrillated fibers, even beyond the swelling and strength of the nonrecycled fibers. Increasing external fibrillation alone was found to play an important role in fiber and paper properties, so it can be used as means to control those properties more effectively.

This thesis consists of an overview and of the following 6 publications:

  1. Kang, T. and Paulapuro, H., New Mechanical Treatment for Chemical Pulp. Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering. 220 (2006) 3, p. 161-166. © 2006 Professional Engineering Publishing. By permission.
  2. Kang, T. and Paulapuro, H., Effect of External Fibrillation on Paper Strength. Pulp & Paper Canada. 107 (2006) 7/8, p. 51-54. © 2006 Pulp and Paper Technical Association of Canada (PAPTAC). By permission.
  3. Kang, T. and Paulapuro, H., Characterization of Chemical Pulp Fines. Tappi Journal. 5 (2006) 2, p. 25-28. © 2006 by authors.
  4. Kang, T., Somboon, P. and Paulapuro, H., Fibrillation of Mechanical Pulp Fibers. Paperi ja Puu – Paper and Timber. 88 (2006) 7, p. 409-411. © 2006 Paperi ja Puu Oy. By permission.
  5. Kang, T. and Paulapuro, H., Effect of External Fibrillation on the Retention of Filler. Japan Tappi Journal. 60 (2006) 8, p. 88-92. © 2006 Japan Technical Association of the Pulp and Paper Industry (JAPAN TAPPI). By permission.
  6. Kang, T. and Paulapuro, H., Recycle Potential of Externally Fibrillated Chemical Pulp. Progress in Paper Recycling. 15 (2006) 2, p. 11-17. © 2006 Progress in Paper Recycling. By permission.

Keywords: external fibrillation, ultra-fine friction grinder, refining, strength, recycling, retention

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© 2007 Helsinki University of Technology

Last update 2011-05-26