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MATERIALS 47
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reduction in MOR, with retention rates ranging from 66 percent
to 74 percent (Table 3). Both PB1 (66–74% retention) and Andrey Sayfutdinov
PB2 (67% retention) retained more than 50 percent of original
MOR in both directions, confirming their suitability for exterior
applications.
The MDF achieved 67–69 percent MOR retention, exceeding

the 50 percent advanced bond integrity requirement specified
in ANSI A208.2 2022 for interior MDF.
The comparison between parallel and perpendicular MOR
values revealed that only PB2 showed significant differences in
both non aged and aged conditions, with MOR approximately
25 percent higher in the parallel direction (Table 3).
This suggests preferential particle alignment during mat
formation. PB1 and MDF showed no significant directional (64%), while MDF showed consistent retention across both
differences in MOR. directions (53–54%).

The comparison of parallel and perpendicular MOE values
Table 3. Bending MOR values for PB1, PB2 and MDF
under non aged and aged conditions, with retention rates. revealed a significant difference in PB2 under non aged
Panel Direction Non Aged Aged MOR MOR conditions, with 35 percent higher MOE in the parallel direction.
Type MOR (MPa) (MPa) Retention (%) After aging, PB1 developed a significant anisotropy (18%
PB1 Parallel 18.1 (11.4) 13.4 (14.8) 74
Perpendicular 17.9 (14.2) 11.9 (5.9) 66 higher parallel MOE), indicating that particles may have some
PB2 Parallel 19.7 (14.4) 13.2 (13.8) 67 orientation within the mat. MDF remained isotropic throughout,
Perpendicular 15.7 (11.2) 10.5 (6.8) 67
MDF Parallel 26.3 (6.8) 18.2 (6.2) 69 confirming random fibre distribution.
Perpendicular 26.5 (3.9) 17.9 (4.6) 67
Table 4. Bending MOE values for PB1, PB2 and MDF
*Values in parentheses are coefficients of variation (%). All differences under non aged and aged conditions, with retention rates.
between non aged and aged were significant at α = 0.05.*
Panel Direction Non Aged Aged MOE MOE
Type MOE (MPa) (MPa) Retention (%)
Non aged MOE values ranged from 2225 MPa (PB2
PB1 Parallel 2835 (12.8) 1653 (11.7) 58
perpendicular) to 3060 MPa (MDF parallel). The ANSI A135.6 Perpendicular 2510 (7.1) 1405 (3.0) 56
2012 standard does not specify MOE requirements, but the PB2 Parallel 2996 (13.9) 1690 (19.4) 56
Perpendicular 2225 (9.2) 1424 (7.3) 64
MDF exceeded the minimum requirement of 2160 MPa for
MDF Parallel 3060 (4.9) 1622 (5.0) 53
Grade 130 by 42 percent. Perpendicular 3040 (1.8) 1630 (2.8) 54
After accelerated aging, MOE retention rates were 53–64 *All differences between non aged and aged were significant
at α = 0.05.*
percent (Table 4), which were notably lower than MOR retention
rates (66–74%).
This behaviour is typical for wood based composites subjected Internal bond Strength
to moisture cycling: moisture induced damage mechanisms Non aged IB values were 1.47 MPa (PB1), 1.18 MPa (PB2),
such as springback and debonding reduce bending stiffness and 1.28 MPa (MDF). After accelerated aging, particleboards
to a greater extent than bending strength. demonstrated high IB retention rates of 71 percent (PB1) and
PB2 demonstrated the highest perpendicular MOE retention 75 percent (PB2).