Phase transition behavior of water in original, heat-treated and acetylated poplar woods
Phase transition behavior of water in original, heat-treated and acetylated poplar woods
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DOI：
10.1016/j.indcrop.2023.117899
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发表时间：
2024-02
影响因子：
5.9
通讯作者：
Shuyang Cao;Jingbo Shi;Youming Dong;Huijun Dong;Jianxiong Lv;Changlei Xia;Sohrab Rahimi
中科院分区：
文献类型：
--
作者：
Shuyang Cao;Jingbo Shi;Youming Dong;Huijun Dong;Jianxiong Lv;Changlei Xia;Sohrab Rahimi
热改性和乙酰化改性是提高白杨人工林木材附加值的重要手段。水在改性木材中的相变行为对于预测改性木材产品的物理、机械和生物降解性能是必不可少的，但尚未得到充分的研究。采用差示扫描量热仪（DSC）分析了白杨原料、乙酰化处理和热处理后木材中水的液-固相变行为。详细研究了水分含量（MC）、不同处理（热处理和乙酰化处理）和样品尺寸（固体与粉末）对相变行为的影响。在5 °C/min的加热或冷却速率下，从− 85-25 °C范围内发生的峰中清楚地观察到水的冻结和融化。定义了具有不同形状和位置的四种不同峰类型，以表征木材中的自由水和结合水相变行为。从固体样品中揭示了更多的峰细节。随着含水率的降低，白杨木材样品中水的冻结温度和融化温度均降低，这可能是由于含水率较低时孔隙尺寸较小所致。改性方法，尤其是乙酰化处理，显著降低了白杨的吸湿性和纤维饱和点，进而显著影响改性木材的结合水相变行为。改性木材中的冻结结合水在冷却时似乎更稳定，并且它们在较高温度下倾向于熔化。
Heat and acetylation modifications are often required to increase the added values of planted poplar woods. The phase transition behavior of water in modified woods is essential in predicting the physical, mechanical, and biodegradable properties of modified wood products but has not been fully explored. In the present study, the differential scanning calorimeter (DSC) was used to analyze the liquid-solid phase transition behavior of water in original, acetylated, and heat-treated poplar wood samples. The effects of moisture content (MC), different treatments (heat and acetylation treatments), and sample size (solid vs. powder) on the phase transition behavior were investigated in detail. The freezing and melting of water were clearly observed from peaks that occurred in the range of − 85–25 °C at a heating or cooling rate of 5 °C/min. Four different peak types with different shapes and positions were defined to characterize the free and bound water phase transition behavior in wood. More peak details were revealed from solid samples. Both freezing and melting temperatures of water in poplar wood samples were lowered with the decrease in MC, possibly resulting from the smaller pore size at lower MC. The modification methods, especially acetylation, reduced the hygroscopicity and associated fiber saturation point (FSP) of poplar wood samples remarkably, which further affected the bound water phase transition behavior of modified wood significantly. The freezing bound water in modified wood seemed to be more stabilized when subjected to cooling, and they tended to melt at higher temperatures.