Fibrillation and characterization of lignin-containing neutral sulphite (NS) pulps rich in hemicelluloses and anionic charge

Saara Hanhikoski*, Iina Solala, Panu Lahtinen, Klaus Niemelä, Tapani Vuorinen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

Abstract

The potential of neutral sulphite pulpsfrom softwood with different yields (c. 58–84%) andhigh residual lignin contents (c. 10–25 wt%) wasinvestigated as a raw material for lignin-containingcellulose nanofibrils (LCNFs) by following theirfibrillation during grinding. It was found that thelower yield (58–65%) pulps needed two grindingcycles to produce fibrillated fibers with water retentionvalues (WRV) as high as 400 g/g (at the energyconsumption level of 1400 kWh/t). In contrast, thehigh yield (77–84%) pulps fibrillated more slowly,requiring five grinding cycles to reach comparableWRV values. Apparently, higher crosslinking degreesof lignin in the high yield pulps are hampering thefibrillation, although the high hemicellulose contents(21–24 wt%) and the high charge densities (200–350lmol/g, originating from carboxylic and sulphonicacid groups) of the pulps were expected to enhance thefibrillation. Nevertheless, regardless of the differentfibrillation behaviour, most of the pulps formed c.10–15% of nanosized material below 30 nm andsignificant amounts of fibrils with size under 100 nmbased on the centrifugation method and FE-SEMimages. As the pulps were of moderate to high yieldand fibrillated easily without any chemical or enzy-matic pretreatments, they show promise for cost-efficient production of LCNFs. The nanopapers pre-pared from the fibrillated pulps showed tensilestrengths (73–125 MPa) comparable with the nanopa-pers from high yield mechanical pulps, whereas thewater contact angles (41°–58°) were closer the thoseof chemical pulps.
Original languageEnglish
Number of pages12
JournalCellulose
Early online date29 May 2020
DOIs
Publication statusE-pub ahead of print - 29 May 2020
MoE publication typeA1 Journal article-refereed

Keywords

  • Galactoglucomannan
  • Lignin-containing cellulose nanofibrils (LCNFs)
  • Nanopaper
  • Softwood
  • Neutral sulphite pulp
  • Sulphonic acid group

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