As the press time increased, except for IB, the mean properties
of MDF were not significantly different (P < 0.05) (Table 6). MDF
made from 4-min press time showed lower IB than those made
from press time of 6 min. Similar results were also stated by karegarfard
et al. (2003) and Habibi et al. (2003). IB values ranged from
0.434 to 0.487 N/mm2. More complete polymerization of Urea
formaldehyde occurs with longer press time (Maloney, 1989). In addition, with the increase of press time, heat transfers to core layers
resulting in solid bonds (Maloney, 1989). The mean values of
properties for the 12 treatments are presented graphically in (Figs.
2–5) to allow a quick comparison of the effects of variables on the
MDF properties. Mechanical strength values of MDF prepared from
canola straw were close to the minimum requirements for MDF
specified in the ANSI A208.2 standard. It is obvious that MDFs
made from canola straw have much weaker water resistance than
the maximum requirements specified in MDFs standards (ANSI
A208.2, BS 1142). This may be related to the fact that no wax
and depithing were used during the board production. It seems
that the addition of wax would improve the dimensional stability
of the boards (Maloney, 1989).
As the press time increased, except for IB, the mean propertiesof MDF were not significantly different (P < 0.05) (Table 6). MDFmade from 4-min press time showed lower IB than those madefrom press time of 6 min. Similar results were also stated by karegarfardet al. (2003) and Habibi et al. (2003). IB values ranged from0.434 to 0.487 N/mm2. More complete polymerization of Ureaformaldehyde occurs with longer press time (Maloney, 1989). In addition, with the increase of press time, heat transfers to core layersresulting in solid bonds (Maloney, 1989). The mean values ofproperties for the 12 treatments are presented graphically in (Figs.2–5) to allow a quick comparison of the effects of variables on theMDF properties. Mechanical strength values of MDF prepared fromcanola straw were close to the minimum requirements for MDFspecified in the ANSI A208.2 standard. It is obvious that MDFsmade from canola straw have much weaker water resistance thanthe maximum requirements specified in MDFs standards (ANSIA208.2, BS 1142). This may be related to the fact that no waxand depithing were used during the board production. It seemsthat the addition of wax would improve the dimensional stabilityof the boards (Maloney, 1989).
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