基于时域核磁共振技术的木材吸湿过程研究

Moisture Sorption in Wood Studied by Time Domain Nuclear Magnetic Resonance

木材吸湿会对其力学性能和尺寸稳定性产生影响,深入了解木材吸湿过程中水分状态的变化有重要意义.利用时域核磁共振(TD-NMR)技术,以美国黄杨木和红橡木作为研究对象,对木材吸湿过程中水分状态和弛豫特性进行研究.结果显示:吸湿过程的前4h,两种木材试件结合水峰面积迅速增大,自由水峰面积无明显增长,说明在吸湿初期,增加的水分主要以结合水为主;在达到吸湿平衡后,红橡木试件内自由水峰面积约为黄杨木试件内自由水峰面积的2倍,这是由于与黄杨木相比,红橡木管孔孔径较大,因此在吸湿过程中,红橡木的自由水吸湿速度较快,吸湿量大于黄杨木.

The mechanical properties and dimensional stability of wood are influenced by moisture sorption. Understanding changes of the state of water during wood sorption has great significance. In this study, the state and relaxation property of water in American yellow poplar and red oak during the sorption process were investigated by time-domain nuclear magnetic resonance（TD-NMR）. It was found that, in both species, the peak area of bound water increased rapidly during the first 4 hours of the sorption process, while the peak area of free water showed no obvious change. These results suggested that water amount increases in the early sorption stage could mainly be attributed to bound water. Under the equilibrium condition of moisture sorption, the peak area of free water in red oak doubled that in American yellow poplar, likely due to the pore aperture of former is bigger than the later, providing more space for absorbed free water. It was also observed that the amount and rate of free water sorption were higher in red oak than in American yellow poplar.