Densification of wood veneers by compression combined with heat and steam

Effects of High-Pressure Treatment on Poplar Wood: Density Profile, Mechanical Properties, Strength Potential Index, and Microstructure

“…It is noteworthy that the lowest ad/ao of all strength was found in 200 MPa treated specimens, which reflected that 200 MPa of treatment further pressed the wood samples and caused more compression defects on wood cells than other HP treatments. (b=1), and BH (b=2.14) for HP-isostatic densification compared with other densification methods a TM compression (Hu 2005) b THM compression (Fang et al 2012) c VTC compression (Rutnar et al 2008) The strength potential index was also used as an indicator to compare the HP densification with other thermal densification methods (e.g., TM, THM, and VTC) in the destructive level of wood cells. The ad/ao for traditional compression methods was calculated based on the data published in previous studies (Hu 2005;Rutnar et al 2008;Fang et al 2012).…”

“…The first solution is impregnation method that involves filling wood cell cavities with fluid substances (Devi et al 2003;Sun et al 2016). The other way is to densify wood through compression by reducing its void volumes without adding any chemicals (Navi and Heger 2004;Welzbacher et al 2008;Fang et al 2012;Laine et al 2016). Since the impregnation method can cause damage to ecological characteristics of natural wood, making the material into one containing potentially harmful residues that can be harmful to both the environment and human health, compression technologies are more widely used in wood densification for furniture use.…”

“…This technique resulted in an improvement of the quality of densified wood products. During the past few decades, thermo-hydro-mechanical (THM) compression, thermo-mechanical (TH) compression, viscoelastic thermal compression (VTC), and sandwich compression have been developed (Navi and Heger 2004;Welzbacher et al 2008;Kutnar et al 2009;Fang et al 2012;Gao et al 2016;Laine et al 2016). Navi and Girardet (2000) reported that the mechanical properties of spruce, pine, and beech wood were significantly enhanced by THM treatment, particularly in the shear strength, with the increase rate of more than tenfold.…”

The Influence of Process Parameters on the Density Profile and Hardness of Surface-densified Birch Wood (Betula pendula Roth)

“…Applying such a solution is unjustified if the main goal of densification is to obtain materials with a high wood surface hardness, for example flooring materials or wall strips. It should be noted that the main problem involved in thermo-mechanical treatment of wood is a tendency for dimensions to change after the modification, most frequently referred to as "set-recovery" (Fang et al 2012;Popescu et al 2014;Laine et al 2016). Kutnar et al (2009) stated that wood with the highest degree of compression shows the highest potential for compression strain recovery.…”

Study of Chemical Modification by Impregnation of Fresh Poplar Log and by Hot-Press Drying Process

“…Also, many more attempts have been made to develop a suitable process for the densification of wood including compression treatment combined with steam and heat. Usually, density enhancement is achieved through a dynamic process that combines temperature ranging from 130 to 220 °C, saturated steam, and mechanical compression perpendicular to the grain (Boonstra and Blomberg 2007;Dogu et al 2010;Fang et al 2012aFang et al , 2012bHigashihara et al 2000;Inoue et al 2008;Kutnar et al 2009;Kutnar and Kamke 2012;Wu et al 2010). Water-soluble, low molecular weight resin systems have been studied extensively and are supposed to have non-bonding cell wall swelling during impregnation processes (Inoue et al 1991a(Inoue et al , 1991bOhmae et al 2002).…”