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MATERIALS 57
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comparison to the radial direction (1.5%–2.5%), TM pine wood heating and cooling, etc.).
also showed a larger reduction in the tangential direction As a result, many cycling tests were carried out in which
(2.9%–4.5%). wood was subjected to several soaking and drying cycles.
Following TM, the pine wood showed the greatest Birch wood after TM had ASE values ranging from 22

tangential and radial direction changes at 170 deg C with an to 69 percent. ASE decreased after the second and third
initial pressure of four bar and at 180 deg C. All TM at 160 soaking–drying cycles, but did not change significantly after
deg C resulted in the lowest dimensional changes. After TM, the fourth and fifth cycles.
the volumetric changes in pine wood were 4.4–6.9 percent. After the first cycle, ASE was 40–69 percent, while after
After 1.5–3.5 hours of TM at 185 deg C in a nitrogen the fifth cycle, it was down to 22–63 percent. This decrease
flow at 10 bar pressure, the ML of beech wood was 11–17 is caused by the leaching of thermal destruction products
percent and eight percent for pine wood. from TM wood, which makes its structure more accessible
After TM in an oven at 220 deg C for 20 hours under a to water. The sample ML after each cycle also supports this
nitrogen environment, the ML of short- and long-rotation teak statement (data not shown).

(Tectona grandis L.f) was 13.4 and 9.2 percent, respectively. The soaking water was light brown after each cycle,
Mimosa scabrella and Pinus oocarpa wood samples were suggesting the absence of degradation products. The primary
TM in a nitrogen atmosphere at 180, 200, and 220 deg C ML can be attributed to the degradation of hemicellulose and
for one hour. After TM, the ML for Mimosa scarabella wood extractives, which are very vulnerable to thermal destruction.
was 4.3, 7.0, and 8.9 percent, and for Pinus oocarpa it was Birch wood had the lowest ASE values (22–23% after
4.5, 4.9, and 6.3 percent, respectively. the fifth cycle) after TM. Increasing the initial pressure from
After being exposed to nitrogen for two ,four, six and eight 3 to 4 bar at 160 deg C raised ASE from 24 to 33 percent.

hours, black poplar (Populus nigra L.) TM yielded 0.9 percent Simultaneously, changing the initial pressure from four to
ML at 160 deg C, 0.8–1.1 percent at 170 deg C, 0.8–3.0 five bar significantly reduced the ASE values after the fifth
percent at 180 deg C, 0.8–3.5 percent at 190 deg C, 4.0–7.1 cycle from 42 to 26 percent.
percent at 200 deg C, and 6.8–14.0 percent at 220 deg C. At the maximum TM time of 120 min, an increase in initial
Temperature had a higher impact on ML than treatment time. pressure from four to six bar reduced ASE values after the
Our findings reveal that TM in a closed system under fifth cycle from 45 to 41 percent. At 170 deg C, raising the
pressure in a nitrogen flow induces a similar ML at lower Tmax
(170–180 deg C) as TM in an open system in a nitrogen flow
Khara Woods
at Tmax above 200 deg C.

Anti-Swelling Efficiency & Cell Wall Water Capacity
ASE is one of the most important indicators of modified
wood materials. It demonstrates the material’s resistance to
dimensional change under simulated, cyclic conditions of
complete soaking and drying.
Almost all TM wood is used to make cladding and decking.

Dimensional stability is critical in such applications due to the
influence of cyclic weather conditions (moistening and drying,