Skip to main content
SLU publication database (SLUpub)

Research article2012Peer reviewed

Optical properties of thermomechanical pulp (TMP) obtained from sulfite-pretreated Norway spruce with focus on two-photon spectral imaging (TPSI)

Hafrén, Jonas; Nelsson, Erik; Gerritsen, Hans C.; Bader, Arjen N.


Chips of Norway spruce have been impregnated with Na2SO3 and refined at two specific energy consumptions levels at full mill scale. The optical properties of thermomechanical pulps (TMPs) obtained were analyzed in terms of brightness, light scattering, opacity, and autofluorescence by spectral imaging. Even at low sulfite dosage (0.24% sulfite by dry weight) light absorption was reduced, and the brightness was elevated, and a clear dose-response effect was observed. Two-photon spectral imaging (TPSI) showed that sulfonation, impregnation, and refining affect the fluorescence properties differently. Compared to native wood, both processed wood chips and pulp fibers revealed blue-shifted fluorescence maxima, a characteristic of shortened conjugated systems. Two sub-populations of fibers with different optical properties were observed, and the fluorescence of one fiber population was red shifted.


microscopy; optical properties; pulp; refining, spectral imaging; sulfonation; two-photon excitation; wood

Published in

2012, Volume: 66, number: 7, pages: 817-824

      SLU Authors

    • Hafrén, Jonas

      • Department of Forest Products, Swedish University of Agricultural Sciences

    UKÄ Subject classification

    Paper, Pulp and Fiber Technology

    Publication identifier


    Permanent link to this page (URI)