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.
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Modification of Cellulosic Fibers by Carboxymethyl Cellulose – Effects on Fiber and Sheet Properties

Minna Blomstedt

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 AS1 at Helsinki University of Technology (Espoo, Finland) on the 30th of November, 2007, at 12 noon.

Overview in PDF format (ISBN 978-951-22-9060-4)   [1544 KB]
Dissertation is also available in print (ISBN 978-951-22-9059-8)

Abstract

The main purpose of this study was to determine whether fiber and sheet properties can be improved by modifying the surface of ECF-bleached softwood and hardwood pulps with carboxymethyl cellulose (CMC). The main objectives of the study were to evaluate;

Fiber properties were investigated by fiber analysis, measurement of water retention values (WRV) and confocal laser scanning microscopy (CLSM). Sheet properties were studied by testing the sheets and by imaging the CMC-modified sheets with environmental scanning electron microscopy (ESEM). The role of fines was studied by fractionating hardwood pulps before and after CMC modification. All CMC treatments were made for both beaten and unbeaten pulps, in order to examine the significance of beating.

In general, the sorption degree of CMC on pulp increased with more extensive beating whereas it decreased with a higher degree of substitution of CMC. After CMC modification the water retention value (WRV) increased for both hardwood pulps and especially for softwood pulps, which accounted for a significant improvement in the internal and tensile strength properties of the handsheets. A unique feature in these experiments was that tensile properties improved remarkably for the CMC-modified hardwood handsheets when dried under restraint, which is considered closer to the drying process in real papermaking conditions. The addition of CMC and surfactant increased the internal and tensile strength properties further. Specific microfibril bonds on the surface of the handsheets revealed by electron microscopy could partly explain the improved strength properties of the CMC-modified softwood sheets. As the sorption conditions used in this study were similar to those in a commercial papermaking system, the surface modification method may be useful in practice, for example, after the refining stage. Preliminary results show that also the vessel picking tendency of eucalyptus pulp could be significantly reduced through CMC modification.

This thesis consists of an overview and of the following 5 publications:

  1. Blomstedt, M., Mitikka-Eklund, M. and Vuorinen, T. (2007) Simplified modification of bleached softwood pulp with carboxymethyl cellulose. Appita Journal 60 (4): 309-314. © 2007 Appita. By permission.
  2. Blomstedt, M. and Vuorinen, T. (2007) Modification of softwood kraft pulp with carboxymethyl cellulose and cationic surfactants. Journal of Wood Science 53 (3): 223-228. © 2007 by authors and © 2007 Springer Japan. By permission.
  3. Blomstedt, M. and Vuorinen, T. (2006) Fractionation of CMC-modified hardwood pulp. Appita Journal 59 (1): 44-49. © 2006 Appita. By permission.
  4. Blomstedt, M., Kontturi, E. and Vuorinen, T. (2007) Optimising CMC sorption in order to improve tensile stiffness of hardwood pulp sheets. Nordic Pulp and Paper Research Journal 22 (3): 336-342. © 2007 by authors.
  5. Blomstedt, M., Kontturi, E. and Vuorinen, T. (2007) Surface modification of eucalyptus pulp by carboxymethylcellulose: effects on fiber properties and sheet strength. O Papel (6): 51-63. © 2007 by authors.

Keywords: chemical pulp, surface modification, CMC, ESEM, fractionation, sheet and fiber properties

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© 2007 Helsinki University of Technology

Last update 2011-05-26