Methylcellulose (MC), a methoxy-substituted cellulose ether, is widely used as a rheology modifier, binder, and water-retention agent in a variety of food, pharmaceutical, construction, and consumer applications. While soluble in water at low temperatures, MC reversibly transitions to a turbid hydrogel upon heating or upon the addition of NaCl, due to the formation of a fibrillar network. These complex MC solutions and gels experience a range of flow conditions in industrial processes, including shear and extensional flows. While the shear rheological behavior has been well characterized for many MC solutions, the extensional rheological behavior is often more challenging to characterize, particularly for solutions with lower molecular weights, relaxation times, and viscosities. Filament stretching using a flow-focusing microfluidic device is a promising method to resolve extensional properties of lower molecular weight and lower viscosity polymeric solutions, and it is used here to characterize MC solutions at varying NaCl concentrations. The flow-driven apparent extensional viscosity can be calculated from transient filament diameter thinning behavior of 1 wt% MC with a molecular weight of 150 kg/mol. The apparent extensional viscosity increased as the concentration of NaCl increased, from 0.947 ± 0.005 Pa s to 15.1 ± 0.6 Pa s between 0 and 8 wt% NaCl, respectively. The increase in apparent extensional viscosity is attributed to the presence of fibrils in the MC solutions containing NaCl annealed at room temperature, as demonstrated with cryogenic transmission electron microscopy. The study of the extensional behavior of this commercially relevant polymer should enable new ways to process MC, such as fiber spinning and extrusion.

中文翻译：

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纤维状甲基纤维素水溶液的微流丝细化

甲基纤维素（MC）是一种甲氧基取代的纤维素醚，被广泛用作各种食品，药品，建筑和消费类应用中的流变改性剂，粘合剂和保水剂。虽然MC在低温下可溶于水，但由于形成纤维状网络，在加热或加入NaCl后可逆地转变为浑浊的水凝胶。这些复杂的MC溶液和凝胶在工业过程中会经历一系列流动条件，包括剪切流和拉伸流。尽管对于许多MC溶液已经很好地表征了剪切流变行为，但表征所需的拉伸流变行为通常更具挑战性，特别是对于分子量，松弛时间和粘度较低的溶液而言。使用聚流微流体装置进行长丝拉伸是解决较低分子量和较低粘度的聚合物溶液的拉伸性能的一种有前途的方法，在这里用于表征NaCl浓度变化时的MC溶液。流动驱动的表观拉伸粘度可以由分子量为150kg / mol的1wt％MC的瞬时长丝直径稀化行为来计算。当NaCl浓度增加时，表观拉伸粘度增加，分别从0％和8 wt％NaCl之间的0.947±0.005 Pa s增至15.1±0.6 Pa s。如通过低温透射电子显微镜所证实的，表观拉伸粘度的增加归因于在包含在室温下退火的NaCl的MC溶液中原纤维的存在。