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Wood Science and Technology

, Volume 50, Issue 5, pp 883–894 | Cite as

Wood densification and thermal modification: hardness, set-recovery and micromorphology

  • Kristiina Laine
  • Kristoffer Segerholm
  • Magnus Wålinder
  • Lauri Rautkari
  • Mark Hughes
Original

Abstract

The density of wood can be increased by compressing the porous structure under suitable moisture and temperature conditions. One aim of such densification is to improve surface hardness, and therefore, densified wood might be particularly suitable for flooring products. After compression, however, the deformed wood material is sensitive to moisture, and in this case, recovered up to 60 % of the deformation in water-soaking. This phenomenon, termed set-recovery, was reduced by thermally modifying the wood after densification. This study presents the influence of compression ratio (CR = 40, 50, 60 %) and thermal modification time (TM = 2, 4, 6 h) on the hardness and set-recovery of densified wood. Previously, set-recovery has mainly been studied separately from other properties of densified wood, while in this work, set-recovery was also studied in relation to hardness. The results show that set-recovery was almost eliminated with TM 6 h in the case of CR 40 and 50 %. Hardness significantly increased due to densification and even doubled compared to non-densified samples with a CR of 50 %. Set-recovery reduced the hardness of densified (non-TM) wood back to the original level. TM maintained the hardness of densified wood at an increased level after set-recovery. However, some reduction in hardness was recorded even if set-recovery was almost eliminated.

Keywords

Compression Ratio Densified Wood Wood Compression Thermal Modification Brinell Hardness 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgments

The authors would like to thank Joachim Seltman (SP, Sweden) and Niko Tuominen (Aalto University) for technical support. The study was supported by the EcoBuild Centre, Stiftelsen Nils och Dorthi Troëdssons forsknings fond and the Finnish Cultural Foundation.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • Kristiina Laine
    • 1
  • Kristoffer Segerholm
    • 1
    • 2
  • Magnus Wålinder
    • 1
  • Lauri Rautkari
    • 3
  • Mark Hughes
    • 3
  1. 1.Department of Civil and Architectural EngineeringKTH Royal Institute of TechnologyStockholmSweden
  2. 2.SP Technical Research Institute of SwedenStockholmSweden
  3. 3.Department of Forest Products TechnologyAalto UniversityEspooFinland

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