Page 60 - FDMAsia MayJun2024

58 MATERIALS MAY/JUN 2024 FDM ASIA | www.fdmasia.com

initial pressure from three to four bar enhanced ASE from treatments ranged from 13 to 20 percent after the first cycle
38 to 47 percent. to 21–29 percent after the fifth cycle.
However, initial pressure increase from four to six bar reduced The maximum CWTWC was observed after TM, having the
the ASE values from 47 to 23 percent after the fifth cycle. lowest ASE (22% after the fifth cycle). Our findings revealed

TM birch wood’s cell wall total water capacity (CWTWC) was a clear link between ASE and CWTWC alterations after TM.
reduced to 10–29 percent compared to untreated birch wood
(32–35%). The CWTWC for all specimens increased slightly Equilibrium Moisture Content & Dimensional Changes
during five soaking–drying cycles. This can be explained by EMC is an indicator of a material’s theoretical ability to
the leaching of natural extractives from untreated wood and absorb moisture from the air. Prolonged EMC exceeding 20
thermal destruction products from the TM wood. percent is regarded as the threshold above which a favourable
The majority of the extractives were soaked out within environment for the development of microorganisms (rot fungus,
the first, second, and third cycles, resulting in minor CWTWC blue stain, mould) in wood products has been produced. All
variations after the fourth cycle. After TM at 160–180 deg C in wood modification techniques, in general, attempt to limit

saturated steam in a closed system under pressure, a similar water and moisture absorption.
trend was found with aspen (Populus tremula), birch (Betula When compared to untreated wood, TM birch wood’s
pendula), and grey alder (Alnus incana) wood. EMC was 51–64 percent lower and VS was 48–67 percent
Birch wood had the lowest CWTWC (10–14%) after TM, lower, with substantial reductions in all RHs.
which had the highest ASE (63%). The CWTWC for the other The EMC of untreated birch wood at 65, 75, and 98
percent RH was 9.6, 12.9, and 17.4 percent, respectively.

Lucia Hatalova At 65, 75, and 98 percent RH, the EMC of TM birch wood
dropped to 3.7–4.7 percent, 4.6-5.6 percent, and 6.6–7.9
percent, respectively.
TM wood absorbs much less moisture in high-humidity
conditions (RH of 98%). As a result, TM wood has a substantially
lower theoretical probability of infection and microbial growth
than untreated wood.
The VS of untreated birch wood at 65, 75, and 98 percent
RH was 4.8, 6.5, and 9.6 percent, respectively. TM birch wood’s
VS at 65, 75, and 98 percent RH was reduced to 1.6–2.5

percent, 2.1–3.1 percent, and 3.3–4.6 percent, respectively.
The lowest EMC and VS values at all RH levels were
obtained after TM. Differences in EMC and VS between the
other TM regimes were not statistically significant, because
the error limits overlapped.
After TM in a nitrogen atmosphere at 180, 200, and 220
deg C for one hour, the EMC (65% RH) of Mimosa scabrella

and Pinus oocarpa wood was 12.0, 11.6, and 11.3 percent
and 12.7, 12.9, and 11.4 percent, respectively.