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Wood Research and Technology


Cellulose – Hemicelluloses – Lignin – Wood Extractives

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The effect of ionic liquid and superbase pre-treatment on the spring-back, set-recovery and Brinell hardness of surface-densified Scots pine

Benedikt Neyses
  • Corresponding author
  • Wood Science and Engineering, Luleå University of Technology, Forskargatan 1, SE-93187 Skellefteå, Sweden
  • Email
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Olov Karlsson
  • Wood Science and Engineering, Luleå University of Technology, Forskargatan 1, SE-93187 Skellefteå, Sweden
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Dick Sandberg
  • Wood Science and Engineering, Luleå University of Technology, Forskargatan 1, SE-93187 Skellefteå, Sweden
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
Published Online: 2019-10-07 | DOI: https://doi.org/10.1515/hf-2019-0158


Compressing the surface of sawn timber results in a substantial increase in hardness, and this opens up new market opportunities of using low-density timber species as the raw material for high-value wood products. Unfortunately, widespread commercialisation is hindered by the lack of an industrially viable surface densification process, the major obstacle being the set-recovery (SR) of the densified wood cells upon exposure to moisture. Our hypothesis is that partial dissolution of the crystalline cellulose during densification will largely prevent the SR of densified wood. We therefore evaluated the effect of ionic liquid (IL) or organic superbase pre-treatment on the elastic spring-back (SB), SR and Brinell hardness (HB) of surface-densified wood. Specimens of Scots pine were treated with solutions of ILs or superbases, and then densified in a hot press at temperatures between 200°C and 270°C. The SR was reduced from 90% for the control group to only about 10% for the treated materials. The treated and densified specimens exhibited a higher HB than their untreated and densified counterparts. The method presented in this study is a precursor to the development of a continuous densification process adapted for an open system. Further studies are needed to understand the underlying mechanisms of the pre-treatment.

Keywords: chemical treatment; surface modification; wood compression; wood modification


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About the article

Received: 2019-05-28

Accepted: 2019-08-23

Published Online: 2019-10-07

Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

Research funding: Financial support from the Swedish Innovation Agency (Vinnova) through the Innovation Potential for the Bio-Based Society (IPOS) DP2 project (2017-02697) is gratefully acknowledged.

Employment or leadership: None declared.

Honorarium: None declared.

Citation Information: Holzforschung, 20190158, ISSN (Online) 1437-434X, ISSN (Print) 0018-3830, DOI: https://doi.org/10.1515/hf-2019-0158.

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