The extensional properties of semidilute aqueous methylcellulose (MC) solutions have been characterized. Pure aqueous MC solutions are shear-thinning liquids at room temperature. With the addition of 8 wt % NaCl, a fraction of MC self-assembles into long fibrils, which modify the rheological properties of the original MC solution. Capillary Breakup Extensional Rheometry (CaBER) was used to characterize salt-free and 8 wt % NaCl solutions of MC at room temperature. The salt-free solutions exhibit only power-law behavior whereas solutions with NaCl exhibit both power-law and elastic regimes. As MC concentration increases, the extensional relaxation time also increases strongly, from 0.04 s at 0.5 wt % to 4 s at 1 wt %. In addition, the apparent extensional viscosity rapidly increases as a function of increasing MC concentration, from 40 Pa·s at 0.5 wt % to 1300 Pa·s at 1 wt %. This behavior is attributed to the presence of fibrils in the MC solutions containing NaCl.

中文翻译：

---

含有原纤维的甲基纤维素溶液的拉伸流动行为

已经表征了半稀释的甲基纤维素 (MC) 水溶液的拉伸特性。纯 MC 水溶液在室温下是剪切稀化液体。添加 8 wt% NaCl 后，一部分 MC 自组装成长原纤维，从而改变了原始 MC 溶液的流变特性。毛细管断裂拉伸流变仪 (CaBER) 用于表征室温下 MC 的无盐和 8 wt% NaCl 溶液。无盐溶液仅表现出幂律行为，而含有 NaCl 的溶液则表现出幂律和弹性状态。随着 MC 浓度的增加，拉伸弛豫时间也大幅增加，从 0.5 wt% 的 0.04 s 增加到 1 wt% 的 4 s。此外，表观拉伸粘度随着 MC 浓度的增加而迅速增加，从 0 时的 40 Pa·s 开始。5 wt% 至 1300 Pa·s 在 1 wt%。这种行为归因于在含有 NaCl 的 MC 溶液中存在原纤维。