基于TD-NMR的PMMA木塑复合材吸湿和吸水研究

Study on Moisture Absorption and Water Absorption of PMMA Wood-plastic Composites Based on TD-NMR

本研究采用时域核磁共振(TD-NMR)技术探究聚甲基丙烯酸甲酯(PMMA)木塑复合材在吸湿与吸水过程中水分的状态和自旋-自旋弛豫(T_(2))特征.并比较PMMA木塑复合材的阻湿率和拒水率,分析PMMA木塑复合材的阻湿和防水性能与原理.研究对象为浸渍甲基丙烯酸甲酯(MMA)单体聚合生成的PMMA木塑复合材.首先对绝干的PMMA木塑复合材进行核磁共振T_(2)检测,然后分别进行吸湿和吸水实验,并每隔一段时间测定试件质量及其T_(2)信号量.结果表明:PMMA木塑复合材的吸湿率和吸水率低于未处理材,具有良好的阻湿和防水性能,且MMA浸渍浓度为100%,浸渍时间为24 h时,在温度为(40±0.2)℃相对湿度为(96.4±0.4)%恒温恒湿环境下木塑复合材吸湿率低于15%,常温下吸水试件的吸水率低于30%.PMMA木塑复合材的吸湿率和吸水率明显降低,T_(2)峰面积也逐渐减小.这说明木塑复合材内部的PMMA起到了防止水分进入的作用.

In this study,time-domain nuclear magnetic resonance(TD-NMR)technology was employed to explore the moisture state and spin-spin relaxation(T_(2))characteristics of polymethyl methacrylate(PMMA)wood-plastic composites during the moisture absorption and water absorption process.The moisture resistance and water repellency of PMMA woodplastic composites were compared and analyzed.The experimental samples were PMMA wood-plastic composite material produced by impregnated methyl methacrylate(MMA)monomer polymerization.Firstly,the NMR T_(2)test was carried out on the dry PMMA wood-plastic composite,and then the moisture absorption and water absorption experiments were carried out respectively,and the mass of the specimen and its T_(2)signal were measured at intervals.The results showed that the moisture absorption rate and water absorption rate of PMMA wood-plastic composite were lower than those of untreated wood,and PMMA had good moisture resistance and water resistance.When the impregnation concentration of MMA was 100%and the impregnation time reached 24 h,the moisture absorption rate of wood-plastic composites was lower than 15%under the constant temperature of(40±0.2)℃and relative humidity of(96.4±0.4)%,and the water absorption rate of waterabsorbing specimens at room temperature was lower than 30%.At the same impregnation time,with the increase of impregnation concentration of MMA,the moisture absorption rate and water absorption rate of PMMA wood-plastic composites decreased significantly,and the T_(2)peak area decreased gradually.This indicates that the PMMA inside the woodplastic composite material contributes to preventing water from entering.