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MATERIALS 45
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assess the dimensional stability of the panels after accelerated type for bending tests: 12 in the parallel direction and 12 in
aging. It should be noted that the Residual TS parameter used the perpendicular direction. From each 12 specimen group, 6
here differs from the thickness swelling after water immersion specimens were subjected to accelerated aging, and 6 were
used to determine the water absorption characteristics of panels tested in the non aged condition.
as defined in ASTM D1037 12. The MOR/MOE specimen dimensions were determined
In this study, Residual TS refers to the irreversible increase in based on panel thickness according to ASTM D1037 12: 282.8

specimen thickness resulting from the aging treatment, measured mm × 76.2 mm for PB1 (9.7 mm thickness), 340.4 mm × 76.2
after reconditioning to equilibrium moisture content (EMC). mm for PB2 (12.1 mm thickness), and 431.6 mm × 76.2 mm
The thickness of the bending MOR and MOE test specimens for the MDF (15.9 mm thickness).
was measured both before and after the aging cycles using a The corresponding test spans were 232.8 mm, 290.4 mm,
digital micrometre with an accuracy of ±0.001 mm. and 381.6 mm, and were maintained constant for both non
For each specimen, thickness measurements were taken aged and aged specimens to enable a direct comparison.
at three specific locations in the middle of the specimen width Static bending tests were performed with loading rates
at one quarter, one half, and three quarters of the specimen of 4.7 mm/min, 5.8 mm/min, and 7.6 mm/min for PB1, PB2,
length. The mean value of these three measurements was and MDF, respectively. MOR and MOE were calculated using

calculated to represent the average thickness of each specimen. standard equations.
The initial thickness (T₀) was measured after conditioning The moisture content of the MOR/MOE specimens was
the specimens at 20°C and 65% RH until EMC was reached determined according to ASTM D1037 12. After completing the
prior to aging tests. bending tests, all tested MOR/MOE specimens were weighed
The final thickness (T₁) was measured after completion of immediately, then oven dried at 103 ± 2°C for 48 h to obtain
the accelerated aging cycles and subsequent reconditioning at oven dry mass.
the same temperature and RH conditions. Residual TS was Moisture content was calculated as the ratio of water mass

then calculated as: Residual TS (%) = [(T₁ – T₀) / T₀] × 100. to oven dry mass. The moisture content of all specimens
from each panel was averaged to determine the EMC for
Mechanical Properties that panel type.
Mechanical properties of the particleboards and MDF panels The IB strength was evaluated using 12 specimens (50
were evaluated according to ASTM D1037 12, and values mm × 50 mm) per panel type. Six specimens from each
were compared with ANSI A135.6 2012 for siding and ANSI panel type were tested in the non aged condition, and the
A208.2 2022 for the MDF, when applicable. remaining six specimens were subjected to accelerated aging
To assess panel durability after accelerated aging, static
bending tests were conducted. The bending MOR and MOE

were determined for both non aged specimens (control) and iStockphoto
specimens subjected to accelerated aging.
To assess anisotropy related to the panel production
direction, specimens were cut both parallel and perpendicular
to the mat formation direction, as required by the ANSI A135.6
2012 standard.
A total of 24 specimens were prepared for each panel