Influence of combined hygro-thermo-mechanical treatment on technical characteristics of poplar wood


  • Reza Hajihassani
  • Behbood Mohebby
  • Saeed Kazemi Najafi
  • Parviz Navi


Compression set, hygrothermal treatment, mechanical properties, physical properties, Populus deltoides, wood densification


Combined hygro-thermo-mechanical technique was adopted and used for densification of poplar wood instead of sole treatment. This technique is combination of two techniques of hygrothermal treatment and densification of wood. For treatment, poplar wood blocks were initially treated hygrothermally at temperatures of 130, 150 and 170°C for holding time of 20, 40 minutes. Afterwards, the densification process was carried out under a hot press (temperature 160°C for 20 minutes). For densification compression set was adjusted for 40 and 60 percent based on the initial thickness (radial direction) of the blocks. The densified and non-densified wood blocks were tested for physical and mechanical properties as density, water absorption, thickness swelling, springback, bending strength, modulus of elasticity as well as shear strength parallel to grain. Results revealed that wood properties were enhanced due to the combined hygro-thermo-mechanical -treatment. According to the results, wood density was increased due to the combined hygro-thermo-mechanical -treatment significantly. The treatment improved the dimensional stability of the densified samples. It was also found that the combined hygro-thermo-mechanical -treatment could significantly improve mechanical properties and also reduce the springback in the densified poplar wood.


Download data is not yet available.


Alvira, P.; Tomas-Pejo, E.; Ballesteros, M.; Negro, M.J. 2010. Pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis. A Review. Bioresour Technol 101: 4851–4861.

Anshari, B.; Guan, Z.W.; Kitamori, A.; Jung, K.; Hassel, I.; Komatsu, K. 2011. Mechanical and moisture-dependent swelling properties of compressed japanese cedar. Construction and Building Materials 25: 1718–1725.

Assor, C.; Placet, V.; Chabbert, B.; Habrant, A.; Lapierre, C.; Pollet, B.; Perre, P. 2009. Concomitant changes in viscoelasticity properties and amorphous polymers during the hydrothermal treatment of hardwood and softwood. J Agric Food Chem 57: 6830–6837.

ASTM D 143-09. 2014. American Society for Testing of Materials. Standard methods of testing small clear specimens of timber.

Biswas, A.K.; Yang, W.; Blasiak, W. 2011. Steam pretreatment of salix to upgrade biomass fuel for wood pellet production. Fuel Process Technol 92: 1711– 1717.

Blomberg, J. 2005. Elastic strain at semi-isostatic compression of scots pine (Pinus sylvestris). J Wood Sci 51: 401–404.

Boonstra, M.J.; Tjeerdsma, B. 2006. Chemical analysis of heat treated softwoods. Holz Roh Werkst 64: 204-211.

Boonstra, M.J.; Blomberg, J. 2007. Semi-isostatic densification of heat-treated radiate pine. Wood Sci Technol 41: 607–617.

Boonstra, M.J.; Vanacker, J.; Kegel, E.; Stevens, M. 2007. Optimization of a two-stage heat treatment process: durability aspects. Wood Sci Technol 41: 31–57.

Dwainto, W.; Inoue, M.; Norimoto, M. 1997. Fixation of deformation of wood by heat treatment. Makuzai Gakkaishi 43(4): 303-309.

Dwianto, W.; Morooka, T.; Norimoto, M.; Kitajima, T. 1999. Stress selaxation of sugi (Cryptomeria japonica D. Don) wood in radial compression under high temperature steam. Holzforschung 53: 541–546.

Esteves, B.; Marques, A.V.; Domingos, I.; Pereira, H. 2007. Influence of steam on the properties of pine (Pinus pinaster) and eucalypt (Eucalyptus globulus) wood. Wood Sci Technol 41: 193–207.

Fukuta, S.; Takasu, Y.; Sasaki, Y.; Hirashima, Y. 2007. Compressive deformation process of Japanese cedar(Cryptomeria japonica). Wood Fiber Sci 39: 548–555.

Garrote, G.; Domínguez, H.; Parajó, J.C. 1999. Hydrothermal processing of lignocellulosic materials. Holz Roh Werkst 57: 191–202.

Gong, M.; Lamason, C.; LI, L. 2010. Interactive effect of surface densification and post-heat-treatment on aspen wood. Journal of Materials Processing Technol 210: 293–296.

Hakkou, M.; Pétrissans, M.; Zoulalian, A.; Gérardin, P. 2005. Investigation of wood wetability changes during heat treatment on the basis of chemical analysis. Polymer Degradation and Stability 89: 1-5.

Hillis, W.E. 1984. High temperature and chemical effects on wood stability. Part 1: General Considerations. Wood Sci Technol 18: 281–293.

Hsu, W.E.; Schwald, W.; Schwald, J.; Shields, J.A. 1988. Chemical and physical changes required for producing dimensionally stable wood-based composites. Wood Sci Technol 22: 281–289.

Inoue, M.; Norimoto, M.; Tanahashi, M.; Rowell, M.R. 1993. Steam or heat fixation of compressed wood. Wood Fiber Sci 25 (3): 224–235.

Ito, Y.; Tanahashi, M.; Shigematsu, M.; Shinoda, Y.; Ohta, C. 1998. Compressive-molding of wood by high-pressure steam-treatment. Part 1: Development of compressively molded squares from thinning. Holzforschung 52: 211–216.

Kutnar, A.; Kamke, F.A.; Petri, M.; Sernek, M. 2008. The influence of viscoelastic thermal compression on the chemistry and surface energetics of wood. Colloids and Surfaces A: Physicochem Eng Aspects 329: 82–86.

Lam, P.S. 2011. Steam explosion of biomass to produce durable pellet. Ph.D. Dissertation, The University of British Columbia, Vancouver, Canada.

Lam, P.S.; Sokhansanj, S.; Bi, X.; Lim, C.J.; Melin, S. 2011. Energy input and quality of pellets made from steam exploded douglas fir (Pseudotsuga menziesii). Energy Fuel 25: 1521–1528.

Liu, S. 2008. A kinetic model on autocatalytic reactions in woody biomass hydrolysis. J Biobased Mater Bio 2: 135–147.

Metsa-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 (3): 192–197.

Mirzaei, G.; Mohebby, B.; Tasooji, M. 2012. The effect of hydrothermal treatment on bond shear strength of beech wood. European Journal of Wood and Wood Products 70: 705-709.

Mohebby, B.; Sanaei, I. 2005. Influences of the hydro-thermal treatment on physical properties of beech wood (Fagus orientalis). The international research group on wood protection (IRG). 36th Annual Meeting, Bangalore, India 24 – 28 April, IRG Document No. IRG/WP 05-40303.

Mohebby, B.; Sharifinia-Dizboni, H.; Kazemi-Najafi, S. 2009. Combined hydro-thermo-mechanical modification (CHTM) as an innovation in mechanical wood modification. In: Proceeding of 4th European Conference on Wood Modification (ECWM4). Stockholm, Sweden, 353-360.

Navi, P.; Girardet, F. 2000. Effects of thermo-hydro-mechanical treatment on the structure and properties of wood. Holzforschung 54: 287–293.

Navi, P.; Heger, F. 2004. Combined densification and thermo-hydro-mechanical processing of wood. MRS Bull 29: 332–336.

Navi, P.; Sandberg, D. 2011. Thermo-hydro-mechanical processing of wood. Engineering Sciences 360 p.

Popescu, C.M.; Popescu, M.C. 2013. A near infrared spectroscopic study of the structural modifications of lime (Tilia cordata Mill.) wood during hydro-thermal treatment. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115: 227–233.

Ramos, L.P. 2003. The chemistry involved in the steam pretreatment of lignocellulosic materials. Quim Nova 26: 863–871.

Stamm, A.J. 1964. Wood and cellulose science. New York: Ronald Press p. 549.

Tjeerdsma, B.F.; Militz, H. 2005. Chemical changes in hydrothermal treated wood. FTIR analysis of combined hydro thermal and dry heat-treated wood. Holz Roh Werkst 63 (2): 102-111.

Welzbacher, C.R.; Wehsener, J.; Rapp, A.O.; Haller, P. 2008. Thermo-mechanical densification combined with thermal modification of Norway spruce (Picea abies Karst) in industrial scale-dimensional stability and durability aspects. Holz Roh Werkst 66: 39–49.




How to Cite

Hajihassani, R., Mohebby, B., Kazemi Najafi, S., & Navi, P. (2018). Influence of combined hygro-thermo-mechanical treatment on technical characteristics of poplar wood. Maderas-Cienc Tecnol, 20(1), 117–128. Retrieved from