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Industrial hardwoods such as Eucalyptus species, Betula pendula, and Acacia mangium required different chemical charges during kraft pulping and presented distinct profiles of polysaccharides removal. The corresponding kraft pulps showed different chlorine dioxide consumption during bleaching. Woods and corresponding kraft pulps were characterized by chemical methods, 1H and 13C NMR spectroscopy, X-ray diffraction analysis, and gel permeation chromatography. The ease of lignin degradation and dissolution was essentially determined by differences in the proportion of syringyl and guaiacyl units and in the degree of condensation. The bleaching response was shown to be related also to the content of β-O-4 structures in the residual lignin. The relative stability of xylans during the pulping was suggested to be associated with differences in structure and molecular weight. The higher retention of Eucalyptus xylans was attributed essentially to their peculiar structure, including O-2-substituted uronic acid groups linked to other cell wall polysaccharides.

Wood Biopolymers

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