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

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

doi:10.4067/s0718-221x2018005011001

Reza Hajihassani, Saeed Kazemi Najafi + Show 2 more

Open Access

https://doi.org/10.4067/s0718-221x2018005011001

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Abstract

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.

Highlights

Wood as a natural composite biopolymer has some unique advantages for industrial applications; such as easy access, appropriate ecological assessment, high strength/weight ratio, flexibility, easy processing, lightness, reusability, renewability, environmental compatibility, etc
The reduction rate of the density was much less in the combined hydro-thermo-mechanical treatment (CHTMT) wood than that of the hygrothermal treatment (HTT) wood
The density was increased by compression set (Figure 2)

Summary

Introduction

Wood as a natural composite biopolymer has some unique advantages for industrial applications; such as easy access, appropriate ecological assessment, high strength/weight ratio, flexibility, easy processing, lightness, reusability, renewability, environmental compatibility, etc. There are some technological limiting factors for application of the wood for structural purposes; such as moisture absorption, dimensional instability, biodegradation, photodegradation as well as weathering. This natural material may need to be transformed in order to achieve the desired functionality (Navi and Sandberg 2011).

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