Chemical, water vapour sorption and ultrastructural analysis of Scots pine wood thermally modified in high-pressure reactor under saturated steam
Chemical, water vapour sorption and ultrastructural analysis of Scots pine wood thermally modified in high-pressure reactor under saturated steam
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DOI：
10.1007/s10853-017-1714-1
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发表时间：
2018-02
影响因子：
4.5
通讯作者：
M. Kymäläinen;Selim Ben Mlouka;T. Belt;V. Merk;Ville Liljeström;T. Hänninen;Tuuli Uimonen;M. Kostiainen;Lauri Rautkari
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文献类型：
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作者：
M. Kymäläinen;Selim Ben Mlouka;T. Belt;V. Merk;Ville Liljeström;T. Hänninen;Tuuli Uimonen;M. Kostiainen;Lauri Rautkari
木材的热改性可改善尺寸稳定性，并增加木材的最终用途。据报道，与更传统的热改性方法相比，饱和蒸汽下的改性导致更高的性能。 本研究分析了在高压反应器中饱和水蒸气条件下，樟子松热改性后的化学和超微结构变化，以及对水蒸气的吸附性能。其目的是揭示重要的化学和吸附相关的变化，木材在饱和蒸汽下改性。讨论了纤维素的化学组成、水蒸气吸附性能、纤维素羟基的可及性和浓度以及细胞壁的演变。在180 °C的温度下，观察到明显的泡孔壁分层和变形。在纳米尺度上，结果表明微纤丝束打开，这导致更高的表面积，理论上也导致更高的可及性。然而，在平衡水分含量和可及性的提取和未提取的样品都观察到，但减少不太明显，在提取的样品，因此得出结论，提取物和降解产物在热改性过程中起着重要的作用，通过阻塞孔隙，从而降低可及性和减少吸附的热改性样品。提取后滞后行为的变化也支持这一结果。
Thermal modification of wood results in improved dimensional stability and increases the end-use possibilities of wood. Modification under saturated steam is reported to result in higher performance when compared to more traditional thermal modification methods. This study analyses the chemical and ultrastructural changes, as well as water vapour sorption properties of Scots pine modified thermally in a high-pressure reactor under saturated steam. The aim is to reveal important chemical and sorption-related changes in wood modified under saturated steam. Chemical composition, water vapour sorption properties, accessibility and concentration of cellulosic hydroxyl groups, as well as evolution of cell wall are discussed. At a temperature of 180 °C, clear cell wall delamination and distortion were observed. In nanoscale, the results indicated opening of microfibril bundles, which leads to higher surface area and theoretically, a higher accessibility. However, a decrease in the equilibrium moisture content and accessibility of both extracted and unextracted samples were observed, but the decrease was less obvious in extracted samples.Hence, it was concluded that extractives and degradation products play an important role during thermal modification by blocking porosity and therefore decreasing accessibility and reducing sorption of thermally modified samples. The changes in hysteresis behaviour after extraction also support this outcome.