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CHANGES IN HYGROSCOPIC PROPERTIES OF POPLAR AND BLACK PINE INDUCED BY THERMAL TREATMENT

机译：热处理引起的杨树和黑松果组织特性的变化

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摘要

The aim of the present research is to comprehend the response of poplar (Populus sp.) and pine (Pinus nigra L.) wood to thermal modification at the temperature of 180°C and 200°C, for 3 different treatment durations of 3, 5 and 7 hours, in the presence of air, by examining their physical and hygroscopic properties and comparing these species properties one another. Specifically, in this research, the mass loss of the samples due to the treatment, the density, the equilibrium moisture content (EMC) and the hygroscopic properties (radial, tangential and longitudinal swelling and absorption percentages) were examined. As the treatment intensity increased, the mass loss of pine and poplar boards due to treatment also increased, which corresponds to the loss of moisture, and the chemical constituents of wood due to their degradation (evaporation of volatile extracts, loss of products through thermal degradation etc.). The thermal treatment has led to a reduction in the recovery rate of the pine and poplar plates of their original weight due to reduced moisture recovery, which is more pronounced as the treatment temperature and duration increase. The EMC of all heat-treated pine and poplar samples was reduced compared to the corresponding control value, even in the case of the less intensive treatment (180°C-3h) and as the intensity increased, EMC decreased further (20.73%-38.43% for pine and 18.76%-49.20% for poplar). Thermal treatments reduced the density of pine (0.76-20.24%) and poplar (1.04-24.42%), and as the treatment intensity increased, larger reduction was recorded. The hygroscopic properties of heat-treated pine were improved in every case due to thermal treatments. The most intensive treatment tended to slightly increase the adsorption and radial-tangential swelling rates, without approaching the control levels. Referring to poplar, all treatments, even the less intensive ones, improved the hygroscopic nature of wood, reducing the adsorption and tangential-radial swelling rates compared to the control sample. Therefore, confirming the results of literature, the thermal treatment was found to improve the hygroscopic behavior of pine and poplar and to further reduce tangential swelling levels in relation to radial direction, contributing to the limitation of wood anisotropy.
机译：本研究的目的是了解在3种不同的3种持续时间下，杨木（Populus sp。）和松木（Pinus nigra L.）木材在180°C和200°C的温度下对热改性的响应。在空气中5到7个小时，通过检查它们的物理和吸湿特性并相互比较这些物种的特性。具体而言，在这项研究中，检查了样品由于处理，质量，密度，平衡水分含量（EMC）和吸湿性（径向，切向和纵向溶胀和吸收百分比）而导致的质量损失。随着处理强度的增加，由于处理而引起的松木板和杨木板的质量损失也增加，这对应于水分的损失，以及由于木材降解而产生的化学成分（挥发提取物的蒸发，热降解产物的损失）等等。）。由于减少了水分的回收，热处理导致松树和杨树板原重量的回收率降低，这随着处理温度和持续时间的增加而更加明显。相对于相应的对照值，所有经过热处理的松树和杨树样品的EMC都降低了，即使在强度较低的处理中（180°C-3h），并且随着强度的提高，EMC进一步降低（20.73％-38.43）松树为％，白杨树为18.76％-49.20％）。热处理降低了松树的密度（0.76-20.24％）和杨树的密度（1.04-24.42％），并且随着处理强度的增加，记录到的减少量更大。在任何情况下，热处理后松木的吸湿性均得到改善。最密集的处理趋于稍微增加吸附和径向切向溶胀率，而未达到控制水平。关于白杨，所有处理，即使强度较低的处理，也都改善了木材的吸湿性，与对照样品相比，降低了吸附和切线-径向膨胀率。因此，证实了文献的结果，发现热处理改善了松树和杨树的吸湿性并进一步降低了相对于径向的切向膨胀水平，从而限制了木材的各向异性。

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