Using NMR To Study The Pore Distribution And Moisture Changes Of Laminated Bambo

Changes in ambient temperature and humidity can lead to variations in the pore structure of laminated veneer bamboo,which in turn affects the adsorption and release of moisture from the material.The study of the moisture movement and pore distribution of laminated veneer bamboo allows the optimisation of its processing and use conditions,and improves the processing and application efficiency of laminated veneer bamboo.This study focuses on laminated veneer bamboo as the research subject and utilizes nuclear magnetic resonance technology to monitor the moisture content of laminated veneer bamboo during the drying and moisture absorption processes.The T₂ relaxation distribution curves are analysed to investigate the effect of ambient temperature and humidity on the moisture migration and pore distribution of laminated veneer bamboo,which provides theoretical basis and data support for the modification of laminated veneer bamboo and the improvement of drying process.Finally,the fibre saturation point of laminated veneer bamboo is determined using low temperature NMR techniques,extrapolation and mechanical testing.The main research content and achievements are as follows:（1）Analysing the T2 relaxation distribution curves of laminated veneer bamboo at different environmental temperatures and humidity revealed some rules.Depending on the relaxation time,the water in laminated veneer bamboo is divided into strongly bound water,weakly bound water and free water.Under the same temperature conditions,the equilibrium moisture content of laminated bamboo decreases exponentially with decreasing relative humidity.As the temperature rises,the drying rate of weakly bound water is lower than the drying rate of free water.（2）The pore distribution of laminated veneer bamboo at different temperatures is measured using nuclear magnetic resonance techniques.The results show that:The porosity of laminated veneer bamboo is approximately 53%;The pores within laminated veneer bamboo are divided into cell wall pores and cell lumen pores depending on where the water is present.The cell wall pore size range is concentrated in the range of 0.01 to 0.11μm and the cell lumen pore size range is concentrated in the range of 1 to 40μm;The maximum pore size of the cell wall and cell lumen increases with the increase of temperature.The maximum pore size of the cell wall decreases with decreasing relative humidity.（3）The fibre saturation point of laminated veneer bamboo is determined using low temperature NMR techniques and extrapolation,and the relationship between fibre saturation point and mechanical properties is verified using mechanical tests.The results show that:The fibre saturation point of laminated veneer decreases as the temperature rises.When the moisture content is lower than the fibre saturation point of laminated veneer bamboo,the mechanical properties of laminated veneer bamboo decrease exponentially with increasing moisture content.When the moisture content is higher than the fibre saturation point of laminated veneer,the change in mechanical properties tends to level off.