浸渍改性材干燥过程中水分迁移与树脂固化交互作用机制研究

Resin impregnation, as one of the suitable methods for modification of fast-growing wood, gives us a series of desired performance change with respect to the physical-mechanical properties. However, resin impregnation retards the moisture transfer within wood during drying, causing longer drying time and more drying defects. The interaction mechanisms between moisture transfer and resin curing during drying of modified wood remained unknown, which influenced the drying schedule's optimization and restricted the industrial application of the resin modification technology for fast-growing wood. Low molecular weight resin impregnated poplar wood (Populous tomentosa) is used in this research. With the help of low field nuclear magnetic resonance, differential scanning calorimetry and other technical means, the influence of resin curing on the water relaxation properties and moisture migration will be revealed by studying the free water and bound water relaxation properties and space-time distribution in different layer and structure of resin modified wood during drying. The effect of water on resin curing and the resin curing process during moisture migration of modified wood will be revealed by studying the resin curing characteristic and the in situ response of mechanical properties of impregnated wood during resin curing process. Finally, the dynamic interaction mechanism of moisture transfer and resin curing during the drying process of modified wood can be revealed. This project is helpful to provide theoretical support for the research of high efficiency drying technology of resin impregnated wood. In addition, this research will also make a breakthrough in solving the technical problems that seriously restrict the high quality and efficient utilization of fast-growing timber in China.

树脂浸渍改性是实现人工林速生材提质增值的重要手段，但树脂浸渍材干燥存在时间长、质量差、效率低的技术难题，干燥过程中水分迁移和树脂固化交互作用机制尚不清楚，导致浸渍材干燥基准制定缺乏科学依据，严重制约了速生材树脂浸渍改性技术的工业化应用。本项目拟以低分子量树脂浸渍杨木为研究对象，采用低场核磁共振、差示扫描量热等技术手段，研究浸渍材干燥过程中自由水和和吸着水弛豫性质以及在不同层位不同组织结构中的时空分布，阐明树脂固化对水分弛豫性质及其迁移特性的影响规律；研究干燥过程中树脂固化特性及树脂固化过程中浸渍材力学性能的原位响应，揭示水分对树脂固化的影响机理，解明浸渍材水分迁移过程中的树脂固化历程；从而最终揭示浸渍材干燥过程中水分迁移与树脂固化的动态交互作用机制，为树脂浸渍材高效干燥技术研究提供理论支撑。这一研究也将为解决严重制约我国人工林速生木材高质高效利用的技术难题实现重要理论突破。

低分子量树脂浸渍改性是实现人工林速生材提质增值的重要手段，但树脂浸渍导致“木材-水分”体系变为“木材-树脂-水分”体系，干燥过程中面临水分与树脂双重相态变化，水分迁移蒸发与树脂缩聚固化交互作用机制尚不清楚，导致浸渍材干燥基准制定缺乏科学依据，严重制约了速生材树脂浸渍改性技术的工业化应用。本课题以低分子量三聚氰胺-尿素-甲醛共缩聚树脂溶液（MUF）浸渍毛白杨木材为研究对象，通过低场核磁共振CPMG、SE-SPI、GR-HSE脉冲序列等技术，阐明了MUF树脂浸渍材干燥过程中自由水与吸着水弛豫特性，从宏观与微观层次解译了其水分迁移规律。运用差示扫描量热（DSC）等方法，系统研究了干燥过程中MUF树脂溶液的固化特性以及MUF树脂浸渍材的固化特性，并通过固化反应动力学模型得到了浸渍材中树脂时间-温度-固化度函数、等温条件下固化度变化曲线以及固化度为0.99时树脂固化温度-固化时间关系曲线。采用MSE-CPMG脉冲序列、动态热机械分析（DMA）等手段，从宏观与微观层次探明了干燥过程中MUF树脂浸渍材多尺度力学性能对水分迁移蒸发与树脂固化反应的响应规律。基于上述研究，最终揭示了浸渍材干燥过程中水分迁移与树脂固化的动态交互作用机制。研究成果为树脂浸渍材的高效干燥技术研究以及树脂浸渍改性技术研究提供了重要理论支撑。