Micromorphology and topochemistry of extractives in Scots pine and Norway spruce thermomechanical pulps: a cytochemical approach |
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Authors: | Dinesh Fernando Jonas Hafrén Jan Gustafsson Geoffrey Daniel |
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Institution: | (1) Wood Ultrastructure Research Centre (WURC), Department of Wood Science, Swedish University of Agricultural Sciences, PO Box 7008, SE-750 07 Uppsala, Sweden;(2) Falun Research Centre, Stora Enso Research, S-791 80 Falun, Sweden |
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Abstract: | Due to the increasing demand for Norway spruce as prime raw material for high-yield pulping, recent interest has focused on
Scots pine as an alternative. However, the intrinsic properties of Scots pine, particularly the high amounts of extractives
and the fiber properties, have been considered a disadvantage for thermomechanical pulping. A study was therefore conducted
on the variations in the spatial distribution and redistribution of lipophilic extractives in spruce and pine wood and thermomechanical
pulp (TMP) using cytochemical staining methods and chemical analysis. Chemical analyses showed chips from pine thinnings and
sawmill slabs to contain three to five and two to three times, respectively, more extractives than found in spruce; in particular,
the amount of triglycerides differed significantly. Results from staining techniques on the abundance and distribution of
extractives (i.e., fats) between pine and spruce correlated with amounts detected by Fourier transform infrared spectroscopy
and gel permeation chromatography. Cytochemical observations revealed information pertaining to species-specific distribution
and redistribution of extractives among TMP fines and fibers and indicated the presence of a molecular film of extractives.
Results indicate that the high concentrations of extractives in pine ray parenchyma are released during TMP processing and
are redistributed onto the surfaces of the pulps, negatively affecting energy usage during primary refining. |
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Keywords: | Cytochemical staining Extractives Norway spruce Scots pine Thermomechanical pulp fibers |
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