Journal of Wood Science

, Volume 63, Issue 6, pp 591–605 | Cite as

Effect of thermo-hydro-mechanical densification on microstructure and properties of poplar wood (Populus tomentosa)

Original article


This study aimed at developing a thermo-hydro-mechanical (THM) processing to compress poplar wood and investigating the effects of high temperature, moisture, and pressure during the THM processing on the changes in microstructure, porosity, mechanical properties, and dimensional stability of compressed poplar wood. The variations in these properties were correlated and their mathematical relations were determined. Poplar woods with high moisture content were compressed using different pressures at a temperature of 160 °C for different periods. The compression level was characterized by the volume compression ratio (CR), which is defined as the ratio of the compression volume and the original volume of sample before and after THM processing. The obtained results indicated that the high pressure of THM process caused the collapsing of wood cell lumens and the developing of a certain amount of fractures in the cell wall. The damage level of wood cells increased with increasing pressure and time. Moreover, the pressure narrowed the cell lumens, which decreased significantly the pore volume in wood substrate. The pore size distribution shifted from the level of macropores to those of mesopores and micropores after THM process. The THM process created superior mechanical property, especially for those with higher CR. Besides, it was revealed that the process decreased dramatically the set recovery of treated woods and improved their dimensional stability. A significant improvement was achieved in terms of the mechanical and physical properties of compressed poplar wood via the structural reformation during the THM process.


Thermo-hydro-mechanical process Microstructure Porosity Bending property Dimensional stability 



The authors appreciate the financial support from the National Nonprofit Institute Research Grant of CAFINT (CAFYBB2017ZX003).


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Copyright information

© The Japan Wood Research Society 2017

Authors and Affiliations

  1. 1.Key Laboratory of Wood Science and Technology of State Forestry AdministrationResearch Institute of Wood Industry, Chinese Academy of ForestryBeijingPeople’s Republic of China
  2. 2.China National Bamboo Research Center, Key Laboratory of High Efficient Processing of Bamboo of Zhejiang ProvinceHangzhouPeople’s Republic of China
  3. 3.CanmetEnergy, Ottawa, Natural Recourse CanadaOttawaCanada

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