Softwood kraft pulp fines: application and impact on specific refining energy and strength properties

Daniel Mandlez, Lukas Zangl-Jagiello, Rene Eckhart*, Wolfgang Bauer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Along with the emergence of micro and nanofibrillated celluloses and their application in papermaking, the influence of the so called fines fraction of pulps on both process and product properties has received increasing research interest in recent years. Several researchers have experimented with primary and/or secondary pulp fines to assess their effects on paper properties with not always consistent results. Our work focuses on the targeted application of the primary fines fraction of an unbleached softwood kraft pulp. The primary fines are separated from the pulp to be subsequently added to achieve blends of 5%,9% and 12% primary fines content. These blends were then refined in a PFI mill to evaluate the effect of the primary fines on refining as well as on paper properties of hand sheets prepared from these pulps. It is shown that the addition of primary fines enhances tensile strength in the unrefined and slightly refined state, while the maximum tensile strength of the highly refined reference pulp is not increased. A slightly increased dewatering resistance (Schopper Riegler) at comparable air permeability (Gurley) for a given tensile strength was also observed. The linear relationship between tensile index and apparent sheet density seems to be affected in the unrefined and slightly refined state where the breaking length of the fines enriched samples is higher for a given apparent density.
Original languageEnglish
Pages (from-to)10359-10367
Number of pages9
Issue number17
Early online date9 Oct 2020
Publication statusPublished - Nov 2020


  • Fines
  • Pulp
  • Softwood
  • Refining
  • Beating
  • PFI

ASJC Scopus subject areas

  • Polymers and Plastics


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