The flow behavior of nanocrystalline cellulose (CNC) hydrogels in the presence of a monovalent electrolyte (NaCl) as a function of CNC and salt concentration is explored using a variety of linear and nonlinear rheological tests. We have first observed an apparent “slip yield stress” at small wall shear stress values that is mainly due to the onset of solidlike slippage of the hydrogels before their true yielding and deformation. This flow regime and the “slip yield stress” can be eliminated using a sandpaper of an optimum grit size. At higher wall shear stress values, two yielding points for the CNC/salt network are seen in strain sweep tests due to network disruption and cluster deformation that depend on the concentration of both CNC (1–5 wt. %) and electrolyte (0–100 mM). The first yield stress is due to yielding and flow of clusters, while the second one is due to breakage of clusters to small flocs and individual fibers. These yielding stresses were obtained by a variety of tests including strain amplitude sweep, creep, and steady shear, and their values are compared confirming their existence. Rheo-SALS (small angle light scattering) measurements confirmed structural changes as the scattering patterns change from isotropic to highly anisotropic with an increase of deformation and rate of deformation. Moreover, confocal laser scanning microscopy and polarized microscopy images confirm the gradual breakup of clusters to smaller ones and eventually to nearly individual fibers with an increase in the applied shear strain and rate.

中文翻译：

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纳米晶纤维素 (CNC) 有吸引力的凝胶的产生

纳米晶纤维素 (CNC) 水凝胶在单价电解质 (NaCl) 存在下的流动行为作为 CNC 和盐浓度的函数使用各种线性和非线性流变测试进行了探索。我们首先观察到在小壁面剪切应力值下明显的“滑动屈服应力”，这主要是由于水凝胶在真正屈服和变形之前开始发生固体状滑动。使用最佳粒度的砂纸可以消除这种流动状态和“滑动屈服应力”。在较高的壁面剪切应力值下，由于网络中断和簇变形取决于 CNC (1-5 wt. %) 和电解质 (0- 100 毫米）。第一屈服应力是由于团簇的屈服和流动，而第二个是由于簇破碎成小絮状物和单根纤维。这些屈服应力是通过各种测试获得的，包括应变振幅扫描、蠕变和稳定剪切，并比较它们的值以确认它们的存在。Rheo-SALS（小角光散射）测量证实了结构变化，因为随着变形和变形速率的增加，散射模式从各向同性变为高度各向异性。此外，共聚焦激光扫描显微镜和偏光显微镜图像证实，随着施加的剪切应变和速率的增加，簇逐渐分解为较小的簇，并最终分解为几乎单个的纤维。这些屈服应力是通过各种测试获得的，包括应变振幅扫描、蠕变和稳定剪切，并比较它们的值以确认它们的存在。Rheo-SALS（小角光散射）测量证实了结构变化，因为随着变形和变形速率的增加，散射模式从各向同性变为高度各向异性。此外，共聚焦激光扫描显微镜和偏光显微镜图像证实，随着施加的剪切应变和速率的增加，簇逐渐分解为较小的簇，并最终分解为几乎单个的纤维。这些屈服应力是通过各种测试获得的，包括应变振幅扫描、蠕变和稳定剪切，并比较它们的值以确认它们的存在。Rheo-SALS（小角光散射）测量证实了结构变化，因为随着变形和变形速率的增加，散射模式从各向同性变为高度各向异性。此外，共聚焦激光扫描显微镜和偏光显微镜图像证实，随着施加的剪切应变和速率的增加，簇逐渐分解为较小的簇，并最终分解为几乎单个的纤维。Rheo-SALS（小角光散射）测量证实了结构变化，因为随着变形和变形速率的增加，散射模式从各向同性变为高度各向异性。此外，共聚焦激光扫描显微镜和偏光显微镜图像证实，随着施加的剪切应变和速率的增加，簇逐渐分解为较小的簇，并最终分解为几乎单个的纤维。Rheo-SALS（小角光散射）测量证实了结构变化，因为随着变形和变形速率的增加，散射模式从各向同性变为高度各向异性。此外，共聚焦激光扫描显微镜和偏光显微镜图像证实，随着施加的剪切应变和速率的增加，簇逐渐分解为较小的簇，并最终分解为几乎单个的纤维。