Huang Yan-hui, Fei Ben-hua, Zhao Rong-jun
Guang Pu Xue Yu Guang Pu Fen Xi. 2015 Dec;35(12):3356-9.
Study on the modified mechanism of wood cell walls, it is very important for improving treatment reagents, optimizing treatment technology, and enhancing wood density, mechanical properties, dimensional stability, and so on. Samples of plantation Chinese fir were treated gradually with synthesized water-soluble low-molecular-weight phenol formaldehyde (PF) resins under vacuum and pressure. The correlated physical and chemical properties of the treated and untreated reference samples were determined by X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FTIR), and nuclear magnetic resonance spectrometer(NMR) (Using method of Cross Polarization/Magic Angle Spinning for continuous testing) with high precision and resolution. The results showed that, after treated with water-soluble low-molecular-weight PF resin, the average values of crystallinity from the treated samples were decreased obviously, and the average reduction rate was 12.67%, 11.91% and 6.26%, respectively. Comparing water-soluble, low-molecular-weight PF resin modified Chinese fir with untreated reference samples, no new chemical shifts and characteristic peaks of functional groups from esters, ethers, etc. were present by using FTIR and ¹³C NMR spectrum. It was considered that there was no distinct chemical reaction between the water-soluble low-molecular-weight PF resin and Chinese Fir cell walls. But water-soluble low-molecular-weight PF resin could enter into the structure relatively loose, large size spaces, relatively area large amorphous regions in cell walls of Chinese fir tracheids, and form physical filling, which resulting in the decreasing of relative crystallinity. This study has important reference value for the development of new wood modification reagents and the optimization of wood modification process. The findings also provide important theoretical foundation for further proving the modification mechanisms of wood cell walls and enriching the modified theories of wood cell walls.
研究木材细胞壁的改性机理，对于改进处理剂、优化处理工艺以及提高木材密度、力学性能、尺寸稳定性等具有重要意义。以人工林杉木为试样，在真空和压力条件下，用合成的水溶性低分子量酚醛（PF）树脂对其进行逐步处理。采用具有高精度和高分辨率的X射线衍射仪（XRD）、傅里叶变换红外光谱仪（FTIR）和核磁共振仪（NMR）（采用交叉极化/魔角旋转方法进行连续测试）测定处理后和未处理的参考试样的相关物理和化学性质。结果表明，经水溶性低分子量PF树脂处理后，处理试样的结晶度平均值明显降低，平均降低率分别为12.67%、11.91%和6.26%。通过FTIR和¹³C NMR光谱比较水溶性低分子量PF树脂改性杉木与未处理的参考试样，未发现酯、醚等官能团有新的化学位移和特征峰。认为水溶性低分子量PF树脂与杉木细胞壁之间没有明显的化学反应。但水溶性低分子量PF树脂能够进入杉木管胞细胞壁中结构相对疏松、尺寸较大的空间以及相对面积较大的无定形区域，形成物理填充，从而导致相对结晶度降低。本研究对新型木材改性剂的开发和木材改性工艺的优化具有重要参考价值。研究结果也为进一步阐明木材细胞壁的改性机理和丰富木材细胞壁的改性理论提供了重要的理论基础。
