Center for Materials Processing and Tribology, Purdue University, West Lafayette, IN 47907, USA.
Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012, India.
J R Soc Interface. 2021 Dec;18(185):20210483. doi: 10.1098/rsif.2021.0483. Epub 2021 Dec 1.
Diffusion of water into plant materials is known to decrease their mechanical strength and stiffness but improve formability. Here, we characterize water diffusion through areca palm leaf-sheath-a model plant material, with hierarchical structure, used in eco-friendly foodware. The diffusion process is studied using mass gain measurements and imaging of water transport. By treating the areca sheath as homogeneous ensemble, and incorporating effects of material swelling due- to water absorption, a factor typically neglected in prior studies, the diffusion coefficient for water is estimated as (6.5 ± 2.2) × 10 mm s. It is shown that neglecting the swelling results in gross underestimation of . Microstructural effects (e.g. fibre, matrix) on the diffusion are characterized using imaging of the water transport at high resolution. The observations show that the water diffuses an order of magnitude faster in the matrix (8.63 × 10 mm s) than in the fibres (7.19 × 10 mm s). This non-uniformity is also reflected in the swelling-induced strain in the leaf, mapped by image correlation. Lastly, we vary salt concentration by controlled additions of NaCl and note a non-monotonic dependence of the diffusion on concentration. Implications of the results for improving foodware manufacturing processes and product life are discussed.
水向植物材料的扩散会降低其机械强度和硬度，但会提高其可成形性。在这里，我们通过质量增益测量和水传输成像来研究水在鱼尾葵叶鞘中的扩散过程，鱼尾葵叶鞘是一种具有层次结构的模型植物材料，用于环保型食品容器。将鱼尾葵鞘视为均匀的整体，并考虑到由于吸水引起的材料膨胀的影响（这在先前的研究中通常被忽略），估计水的扩散系数为（6.5 ± 2.2）× 10 mm s。结果表明，忽略膨胀会严重低估 。使用高分辨率的水传输成像来研究微观结构（例如纤维、基质）对扩散的影响。观察结果表明，水在基质中的扩散速度比纤维中快一个数量级（8.63 × 10 mm s 比 7.19 × 10 mm s）。这种非均匀性也反映在叶片的膨胀引起的应变中，通过图像相关映射来表示。最后，我们通过控制添加 NaCl 来改变盐浓度，并注意到扩散对浓度的依赖性是非单调的。讨论了这些结果对改进食品容器制造工艺和产品寿命的影响。
