The vertical density profile (VDP) of thermo-hydro-mechanically (THM) densified wood is a result of the combined effect of process parameters and properties of unmodified wood. The effect of thermosetting resins on VDP of THM densified wood has not been extensively studied. The aim of this study was to determine the combined effect of methylated melamine–formaldehyde (MF) resin impregnation along with thermal compression at 150 °C on the VDP of poplar wood acquired by X-ray densitometry. Four different stress levels were applied: 0, 10, 20 and 30 kg/cm². Control specimens (without MF) were also impregnated and densified under the same conditions. The results showed that the use of MF increased the density compared to control specimens for the respective CR level. The increase in CR resulted in a linear decrease in WPG values as a result of the MF loss during pressing. Due to the bulking effect of cell walls, thermal compression resulted in higher CR for control than for MF-treated specimens. In the case of uncompressed specimens, MF-treated specimens showed slight density peaks near the surfaces probably due to migration of MF solution from the core to the heated surfaces of the specimens. MF-impregnated specimens generally showed a more uniform density profile since the differences between maximum density and minimum density were smaller than the control ones. Peak width did not seem to be affected by CR for MF-treated specimens. Maximum density was not formed in the outer surface of the specimens but was measured in deeper regions as CR increased. This trend was clearer for control specimens than for MF-impregnated ones.

中文翻译：

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三聚氰胺甲醛浸渍和热压参数对致密杨木密度分布的影响

热-水-机械（THM）致密化木材的垂直密度分布（VDP）是工艺参数和未改性木材性能综合作用的结果。尚未广泛研究热固性树脂对THM致密木材的VDP的影响。这项研究的目的是确定甲基化三聚氰胺-甲醛（MF）树脂浸渍以及在150°C下热压缩对X射线光密度法获得的杨木VDP的综合影响。施加了四个不同的应力水平：0、10、20和30 kg / cm ²。在相同条件下，对照样品（无MF）也被浸渍和致密化。结果表明，与相应的CR水平的对照样品相比，使用MF可以提高密度。由于压制过程中MF的损失，CR的增加导致WPG值线性下降。由于细胞壁的膨胀效应，热压缩导致对照的CR比MF处理的样本更高。在未压缩样品的情况下，经过MF处理的样品在表面附近显示出轻微的密度峰，这可能是由于MF溶液从样品芯到样品加热表面的迁移所致。由于最大密度和最小密度之间的差异小于对照，因此MF浸渍的样品通常显示出更均匀的密度分布。对于MF处理的样品，峰宽似乎不受CR影响。最大密度未在样品的外表面形成，但随着CR的增加，在更深的区域进行了测量。对照样品的这种趋势比MF浸渍的样品更明显。