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MATERIALS 59
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The EMC values for untreated wood were 13.5 and 14.7
percent, respectively. The EMC reduction was only 1.5–3.3 Caroline Grondin
percent. The EMC (98% of RH) of black poplar (Populus nigra
L.) was reduced from 27 percent for untreated wood to 26,

23, and 16 percent for wood TM in nitrogen at 160, 190 and
220 deg C, respectively.
The EMC of beech wood (Fagus sylvatica) after TM in
nitrogen at 175 deg C for two hours and 185 deg C for
three hours at 10 bar pressure was five to seven percent
(65% of RH) and 13–23 percent (100% of RH), respectively,
whereas the untreated wood’s EMC was 10 percent and 30
percent, respectively. TM beech wood had the lowest EMC
when heated to 185 deg C compared to other specimens.

After TM at 190 deg C for 2.5 hours in a nitrogen
environment at a constant 10 bar pressure, the EMC of beech The ASE values for both wood species tended to decrease
wood was 13 percent (90% RH), while that of untreated wood within five soaking–drying cycles. Because of the leaching of
was 26 percent. thermal degradation products from TM wood, the CWTWC
Swelling in the tangential, radial, and axial directions of TM increased and the wood structure became more susceptible
beech was 4.3, 2.1, and 0.15 percent, respectively, whereas to water.
in untreated beech it was 12, 6, and 0.3 percent, respectively. According to the ASE data, birch wood TM in nitrogen

This is consistent with our findings that EMC and swelling of with an initial pressure of four bar appeared to be more
TM wood in nitrogen under pressure can be reduced more suitable for achieving improved dimensional stability than
than twice compared to untreated wood. three, five, or six bar.
For pine wood, the difference between four and six bar
Conclusions initial nitrogen pressure at 170 deg C was minimal. As a
The results clearly revealed that TM in nitrogen in closed, consequence, the optimal option for TM at 160 and 180 deg
pressurised process can improve the dimensional stability of C was determined to be five bar initial pressure.
birch and pine wood, as well as reduce moisture and water When compared to untreated wood, TM birch wood’s
absorption. Birch wood was less resistant to TM because its EMC was 51–64 percent lower and its VS was 48–67 percent

ML (5.9%–12%) was higher than that of pine wood (2.6%–9%). lower, but TM pine wood’s EMC was 29–56 percent and its
Our findings reveal that TM in a closed system under VS was 29–61 percent lower.
pressure in nitrogen induces similar ML at 170–180 deg C EMC and VS were greatly reduced at all RHs (65, 75, and
to TM in an open system in a nitrogen flow at Tmax above 98%). When compared to the data available in the literature,
200 deg C. the EMC values for birch and pine wood were significantly
TM caused a shrinkage in the tangential, radial, and total lower, suggesting the efficiency of the TM process.
volume of birch and pine wood. Birch wood after TM had Increases in TM process parameters (Tmax, time at Tmax, and

ASE values ranging from 22 to 69 percent, while pine wood’s initial pressure) resulted in decreased EMC for pine wood. FDM
ASE was 27 to 58 percent. ENQUIRY NO. 3401