Hydrothermal Treatment of Eucalyptus Grandis Wood

Abstract

Among the technological alternatives to improve the quality and use of eucalyptus wood is heat treatment, as the wood has some features that may limit its use, such as dimensional instability, high anisotropy, and heterogeneous coloring. This study is aimed at evaluating the effect of time of hydrothermal treatment on physical, chemical, and mechanical properties of solid wood of Eucalyptus grandis. We used three trees of E. grandis, selecting only the heartwood, and prepared test specimens with dimensions of 30cmx8cmx3cm (length, width, and thickness). The hydrothermal treatment was performed in a Parr reactor using three reaction times (5, 15, and 25min) at 140°C. Partial removal of extractives occurred, especially in the outer layer of wood. There was an increase of up to 58% of its permeability because of the partial clearing of the vessel elements. There was no degradation of the main constituents of the wood, so loss of mechanical strength was observed. The hydrothermal treatment promoted the partial removal of the hydroxyl groups and/or a structural rearrangement of the hemicelluloses and cellulose, causing a reduction of the hygroscopicity of E. grandis.

Hydrothermal Modification of Wood: A Review

“…collapsed during post-treatment kiln drying, which indicated that the treatment significantly altered the cell-wall structure. Further, de Freitas et al [ 43 ] reported that hydrothermal modification promoted the partial cleaning of the elements (vessels). Shi et al [ 53 ] hydrothermally treated poplar wood ( Populus sp.)…”

“…The reduction in the bending strength of oak was remarkable even at low temperatures. De Freitas et al [43] investigated the effects of hydrothermal modification on Eucalyptus grandis wood and revealed that hydrothermal modification at 140 • C for 25 min promoted changes in some properties, such as a reduction in hygroscopicity and the homogenization of superficial color, without the loss of mechanical resistance. In addition, Rasdianah et al [44] reported that the superheated-steam treatment of two tropical hardwood types-namely, light red meranti (Shorea spp.)…”

Effect of Age on Heartwood / Sapwood Relationship, Extractive Contente, and Permeability of Teak Wood

“…The wood permeability was measured from a cylindrical sample of 0.85 cm radius and 4 cm length ( Figure 1C), which were collected in parallel from the diametrical strip of each disc at 0%, 45%, and 75% of the selected area ( Figure 1B). The wood permeability at atmospheric pressure was calculated based on Darcy's Law, following the method described in Freitas et al (2019). The experimental apparatus consisted of 4 air flowmeters, connected in series to a vacuum pump (Figure 2) with the following flow ranges: 0.04 to 0.50 LPM; 0.50 to 2.50 LPM; 2.5 to 5.0 LPM; and 5.0 to 25.0 LPM.…”

“…The pressure applied was -3 inHg and the airflow was measured with the flowmeter at the lowest measurement range. Air flow and pressure gradient were used to calculate the wood permeability using the following equation (Freitas et al, 2019…”