Effect of superheated steam pressure on the physical and mechanical properties of sandwich-densified wood

Two-step hot isostatic pressing densification achieved non-porous fully-densified wood with enhanced physical and mechanical properties

“…According to a previous report, bers under isostatic compression acquire an irregular shape 26 . Furthermore, the cell walls of DNW and DDW were not damaged and maintained their original integrity, indicating that most of the cell walls of the inner layers were softened by chemical and thermal pretreatment during the densi cation process 40 . In that sense, the HIP process preserves one of the most important aspects of VTC densi cation since it modi es the wood in the absence of microfractures.…”

“…exposure to chemical agents during the deligni cation process and thermal exposure during the densi cation process, and the reasons why this color change occurs have been extensively explained elsewhere 10,40,[48][49][50] . During chemical exposure, some functional groups are altered (removal of chromophores from lignin, breaking of chemical bonds, and removal of extractives) while during thermal exposure some water-soluble compounds are altered.…”

“…By comparison, wood treated with our two-step densi cation process resists water immersion, which enables the developed material to improve its strength even in geographical locations with high rainfall. This is because the process promotes the hygroscopic dimensional stability of the material after the reduction of the number of hydrophilic groups by the degradation of hemicellulose 40 . After the removal of hemicellulose and lignin during deligni cation, the ability of wood to adsorb water molecules is reduced 52 , and this is further enhanced by coating the closed pores.…”