Wood Science and Technology

, Volume 52, Issue 4, pp 889–907 | Cite as

Analyzing reversible changes in hygroscopicity of thermally modified eucalypt wood from open and closed reactor systems

  • M. Wentzel
  • M. Altgen
  • H. Militz


Eucalyptus nitens was thermally modified in either an open or a closed reactor system at different temperatures and water vapor pressures. Reversible changes in equilibrium moisture content (EMC) and volumetric swelling (Smax) were analyzed during cycles that included repeated conditioning at 20 °C/65% RH, water-soaking and vacuum-drying at room temperature. These cycles partially diminished the reduction in EMC and Smax measured directly after the modification process. The recovery of drying-related annealing effects of amorphous polymers was considered the main effect during water-soaking cycles of wood from the open reactor system, while the removal of the cell wall bulking effect was the main effect in the wood modified in the closed system in nearly saturated water vapor. Water-soaking cycles also changed the dynamic vapor sorption behavior to a considerable extent, leading to a lower reduction in EMC by thermal modification over the entire RH range measured. Exposure of the samples to 95% RH during the dynamic vapor sorption measurements was incapable of removing reversible effects to the same extent as repeated water soaking.


  1. Alén R, Kotilainen R, Zaman A (2002) Thermochemical behavior of Norway spruce (Picea abies) at 180–225 °C. Wood Sci Technol 36:163–171. CrossRefGoogle Scholar
  2. Altgen M, Militz H (2016) Influence of process conditions on hygroscopicity and mechanical properties of European beech thermally modified in a high-pressure reactor system. Holzforschung 70:971–979. CrossRefGoogle Scholar
  3. Altgen M, Hofmann T, Militz H (2016a) Wood moisture content during the thermal modification process affects the improvement in hygroscopicity of Scots pine sapwood. Wood Sci Technol 50:1181–1195. CrossRefGoogle Scholar
  4. Altgen M, Willems W, Militz H (2016b) Wood degradation affected by process conditions during thermal modification of European beech in a high-pressure reactor system. Eur J Wood Prod 74:653–662. CrossRefGoogle Scholar
  5. Andersson S, Serimaa R, Vaananen T, Paakkari T, Jamsa S, Viitaniemi P (2005) X-ray scattering studies of thermally modified Scots pine (Pinus sylvestris L.). Holzforschung 59:422–427. CrossRefGoogle Scholar
  6. Bendtsen BA (1966) Sorption and swelling characteristics of salt-treated wood. U.S. Forest Service Research Paper FPL 60, Forest Products Laboratory, MadisonGoogle Scholar
  7. Biziks V, Andersons B, Sansonetti E, Andersone I, Militz H, Grinins J (2015) One-stage thermo-hydro treatment (THT) of hardwoods: an analysis of form stability after five soaking–drying cycles. Holzforschung 69:563–571. CrossRefGoogle Scholar
  8. Boonstra MJ, van Acker J, Kegel E, Stevens M (2007) Optimisation of a two-stage heat treatment process: durability aspects. Wood Sci Technol 41:31–57. CrossRefGoogle Scholar
  9. Borrega M, Kärenlampi P (2008) Effect of relative humidity on thermal degradation of Norway spruce (Picea abies) wood. J Wood Sci 54:323–328. CrossRefGoogle Scholar
  10. Borrega M, Kärenlampi P (2010) Hygroscopicity of heat-treated Norway spruce (Picea abies) wood. Eur J Wood Prod 68:233–235. CrossRefGoogle Scholar
  11. Burmester A (1975) Zur Dimensionsstabilisierung von Holz (The dimensional stabilization of wood). Holz Roh Werkst 33:333–335 (in German) CrossRefGoogle Scholar
  12. Čermák P, Rautkari L, Horáček P, Saake B, Rademacher P, Sablík P (2015) Analysis of dimensional stability of thermally modified wood affected by re-wetting cycles. BioResources 10:3242–3253Google Scholar
  13. Čermák P, Vahtikari K, Rautkari L, Laine K, Horáček P, Baar J (2016) The effect of wetting cycles on moisture behaviour of thermally modified Scots pine (Pinus sylvestris L.) wood. J Mater Sci 51:1504–1511. CrossRefGoogle Scholar
  14. Demirbaş A (2000) Mechanisms of liquefaction and pyrolysis reactions of biomass. Energy Convers Manag 41:633–646. CrossRefGoogle Scholar
  15. Endo K, Obataya E, Zeniya N, Matsuo M (2016) Effects of heating humidity on the physical properties of hydrothermally treated spruce wood. Wood Sci Technol 50:1161–1179. CrossRefGoogle Scholar
  16. Esteves B, Pereira H (2009) Wood modification by heat treatment: a review. BioResources 4:370–404Google Scholar
  17. Esteves B, Domingos I, Pereira H (2007) Improvement of technological quality of eucalypt wood by heat treatment in air at 170–200 °C. For Prod J 57:47–52Google Scholar
  18. Esteves B, Graca J, Pereira H (2008) Extractive composition and summative chemical analysis of thermally treated eucalypt wood. Holzforschung 62:344–351. CrossRefGoogle Scholar
  19. Giebeler E (1983) Dimensional stabilization of wood by moisture–heat–pressure-treatment. Holz Roh Werkst 41:87–94. CrossRefGoogle Scholar
  20. Glass SV, Boardmann CR, Zelinka SI (2017) Short hold times in dynamic vapor sorption measurements mischaracterize the equilibrium moisture content of wood. Wood Sci Technol 51:243–260. CrossRefGoogle Scholar
  21. Hakkou M, Pétrissans M, Gérardin P, Zoulalian A (2006) Investigations of the reasons for fungal durability of heat-treated beech wood. Polym Degrad Stab 91:393–397. CrossRefGoogle Scholar
  22. Hill CAS (2006) Wood modification: chemical, thermal and other processes. Wiley, West SussexCrossRefGoogle Scholar
  23. Hill CAS, Jones D (1996) The dimensional stabilisation of Corsican pine sapwood by reaction with carboxylic acid anhydrides. The effect of chain length. Holzforschung 50:457–462. CrossRefGoogle Scholar
  24. Hill CAS, Ramsay J, Keating B, Laine K, Rautkari L, Hughes M, Constant B (2012) The water vapour sorption properties of thermally modified and densified wood. J Mater Sci 47:3191–3197. CrossRefGoogle Scholar
  25. Himmel S, Mai C (2015) Effects of acetylation and formalization on the dynamic water vapor sorption behavior of wood. Holzforschung 69:633–643. CrossRefGoogle Scholar
  26. Lesar B, Gorišek Z, Humar M (2009) Sorption properties of wood impregnated with boron compounds, sodium chloride and glucose. Dry Technol 27:94–102. CrossRefGoogle Scholar
  27. Majka J, Czajkowski Ł, Olek W (2016) Effects of cyclic changes in relative humidity on the sorption hysteresis of thermally modified spruce wood. BioResources 11:5265–5275CrossRefGoogle Scholar
  28. Mayes D, Oksanen O (2002) ThermoWood handbook. Finnish Thermowood Association, HelsinkiGoogle Scholar
  29. Metsä-Kortelainen S, Antikainen T, Viitaniemi P (2006) The water absorption of sapwood and heartwood of Scots pine and Norway spruce heat-treated at 170 °C, 190 °C, 210 °C and 230 °C. Holz Roh Werkst 64:192–197. CrossRefGoogle Scholar
  30. Militz H, Altgen M (2014) Processes and properties of thermally modified wood manufactured in Europe. In: Schultz TP, Goodell B, Nicholas DD (eds) Deterioration and protection of sustainable biomaterials. ACS symposium series, vol 1158. Oxford University Press, Oxford, pp 269–285CrossRefGoogle Scholar
  31. Obataya E, Higashihara T (2017) Reversible and irreversible dimensional changes of heat-treated wood during alternate wetting and drying. Wood Sci Technol 51:739–749. CrossRefGoogle Scholar
  32. Pönni R, Galvis L, Vuorinen T (2014) Changes in accessibility of cellulose during kraft pulping of wood in deuterium oxide. Carbohydr Polym 101:792–797. CrossRefPubMedGoogle Scholar
  33. Popescu CM, Hill CAS (2013) The water vapour adsorption–desorption behaviour of naturally aged Tilia cordata Mill. wood. Polym Degrad Stab 98:1804–1813. CrossRefGoogle Scholar
  34. Repellin V, Guyonnet R (2005) Evaluation of heat-treated wood swelling by differential scanning calorimetry in relation to chemical composition. Holzforschung 59:28–34. CrossRefGoogle Scholar
  35. Rowell R, Ellis WD (1978) Determination of dimensional stabilization of wood using the water-soak method. Wood Fiber Sci 10:104–111Google Scholar
  36. Runkel ROH (1954) Studien über die Sorption der Holzfaser. Erste Mitteilung: die Sorption der Holzfaser in morphologisch-chemischer Betrachtung (Studies on the sorption of wood fibers. Part 1: sorption of wood fibers from an morphological–chemical viewpoint). Holz Roh Werkst 12:226–232. (in German) CrossRefGoogle Scholar
  37. Runkel ROH, Lüthgens M (1956) Studien über die Sorption der Holzfaser. Zweite Mitteilung: Untersuchungen über die Heterogenität der Wassersorption der chemischen und morphologischen Komponenten verholzter Zellwände (Studies on the sorption of wood fibers. Part 2: examinations of the heterogeneity of water sorption of chemical and morphological components of lignified cell walls). Holz Roh Werkst 14:424. (in German) CrossRefGoogle Scholar
  38. Salmén L (2015) Wood morphology and properties from molecular perspectives. Ann For Sci 72:679–684. CrossRefGoogle Scholar
  39. Salmén L, Burgert I (2009) Cell wall features with regard to mechanical performance. A review. Special issue of COST Action E35 2004–2008: wood machining—micromechanics and fracture. Holzforschung 63:121–129. CrossRefGoogle Scholar
  40. Seborg RM, Tarkow H, Stamm AJ (1953) Effect of heat upon the dimensional stabilisation of wood. J For Prod Res Soc 3:59–67Google Scholar
  41. Stamm AJ (1956) Dimensional stabilization of wood with carbowaxes. For Prod J 6:201–204Google Scholar
  42. Stamm AJ, Hansen LA (1937) Minimizing wood shrinkage and swelling effect of heating in various gases. Ind Eng Chem Res 29:831–833. CrossRefGoogle Scholar
  43. TAPPI (1997) Solvent extractives of wood and pulp. Test method T 204 cm-07. Technical Association of the Pulp and Paper Industry, AtlantaGoogle Scholar
  44. Thybring EE, Thygesen LG, Burgert I (2017) Hydroxyl accessibility in wood cell walls as affected by drying and re-wetting procedures. Cellulose 24:2375–2384. CrossRefGoogle Scholar
  45. Tiemann HD (1917) Effect of different methods of drying on the strength and the hygroscopicity of wood. In: Tiemann HD (ed) The kiln drying of lumber—a practical and theoretical treatise, 3rd edn. J. P. Lippincott Co., Philadelphia, pp 256–264Google Scholar
  46. Tjeerdsma BF, Boonstra M, Pizzi A, Tekely P, Militz H (1998) Characterisation of thermally modified wood: molecular reasons for wood performance improvement. Holz Roh Werkst 56:149–153. CrossRefGoogle Scholar
  47. Vahtikari K, Rautkari L, Noponen T, Lillqvist K, Hughes M (2017) The influence of extractives on the sorption characteristics of Scots pine (Pinus sylvestris L.). J Mater Sci 52:10840–10852. CrossRefGoogle Scholar
  48. Weiland JJ, Guyonnet R (2003) Study of chemical modifications and fungi degradation of thermally modified wood using DRIFT spectroscopy. Holz Roh Werkst 61:216–220. CrossRefGoogle Scholar
  49. Welzbacher CR, Rapp AO (2007) Durability of thermally modified timber from industrial-scale processes in different use classes: results from laboratory and field tests. Wood Mater Sci Eng 2:4–14. CrossRefGoogle Scholar
  50. Willems W (2009) A novel economic large-scale production technology for high quality thermally modified wood. In: Proceedings of the 4th European conference on wood modification, Stockholm, SwedenGoogle Scholar
  51. Willems W, Altgen M, Militz H (2015a) Comparison of EMC and durability of heat treated wood from high versus low water vapour pressure reactor systems. Int Wood Prod J 6:21–26CrossRefGoogle Scholar
  52. Willems W, Lykidis C, Altgen M, Clauder L (2015b) Quality control methods for thermally modified wood. Holzforschung 69:875–884. CrossRefGoogle Scholar
  53. Zaman A, Alen R, Kotilainen R (2000) Thermal behavior of scots pine (Pinus sylvestris) and silver birch (Betula pendula) at 200–230 °C. Wood Fiber Sci 32:138–143Google Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Wood Biology and Wood Products, Faculty of Forestry and Forest EcologyUniversity of GoettingenGöttingenGermany
  2. 2.Department of Bioproducts and BiosystemsAalto UniversityAaltoFinland

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