Impact of residual extractives on the thermal stability of softwood Kraft pulp

Paul Jusner, Stefano Barbini, Sonja Schiehser, Markus Bacher, Elisabeth Schwaiger, Antje Potthast, Thomas Rosenau*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

4 Citations (Scopus)
37 Downloads (Pure)


Wood extractives are known to cause problems during the production of pulp and paper and to impact their mechanical properties. In the present work, we systematically explored whether minute residual amounts of extractives that reprecipitate on the fiber surface in the final stages of the pulping process would lower the thermal resilience of softwood Kraft pulp. Pulp samples subjected to different extraction methods were characterized by means of thermogravimetric analysis. The compound classes constituting the respective extracts were identified and quantified via gas chromatography-mass spectrometry/flame ionization detector (GC-MS/FID) and the influence of the individual compound classes on the thermal stability of the samples was investigated separately. Soxhlet extraction with an ethanol/toluene solvent system clearly led to increased thermal stability. Besides fatty acids and resin acids also sterols and sterol esters that do not carry carboxylic acid functionalities contributed to the deterioration of the thermal pulp properties. Lateral order indices derived from Fourier transformed infrared spectra and crystallinity indices derived from solid-state 13C nuclear magnetic resonance spectra indicate that upon thermal degradation, the presence of even minute amounts of extractives leads to an increased degree of supramolecular disorder. Moreover, the characterization of the samples’ carbohydrate composition by means of acidic hydrolysis showed a tendency towards facilitated pyrolysis of the hemicelluloses if extractives were present in the pulp.

Original languageEnglish
Pages (from-to)8797-8810
Number of pages14
Issue number16
Publication statusPublished - Nov 2022
MoE publication typeA1 Journal article-refereed


  • Carbohydrate composition
  • Extractives
  • Softwood Kraft pulp
  • Supramolecular order
  • Thermal stability
  • Thermogravimetric analysis (TGA)


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