未缠结聚合物溶液的粘弹毛细拉伸去润湿或VE-DeOh拉丝性
Viscoelastocapillary extensional De-Oh or VE-DeOh stringiness of unentangled polymer solutions
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- Department of Chemical Engineering, University of Illinois Chicago（伊利诺伊芝加哥大学化学工程系）
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中文总结 AI 辅助
本研究通过DoS和DiA流变测量法表征未缠结聚合物溶液的拉丝性，发现其与稳态末端拉伸粘度和拉伸松弛时间相关，并提出基于$Oh_E-De_E$图的定量比较框架。
中文摘要 AI 辅助
拉丝性（即形成长而细且持久的丝状物的倾向）的表征、控制和校准，对于通过滴注、喷射、喷涂或涂覆方式将聚合物溶液和配方转移到基材上的设计和应用至关重要，并用于制造纤维、膜或喷雾干燥产品。对于牛顿流体，提高剪切粘度会转化为拉丝性的增强，这在水滴与糖浆或甘油-水混合物的滴落过程中容易观察到。相比之下，即使具有相似剪切粘度的聚合物溶液，其拉伸流变学和表观拉丝性也可能存在显著差异。然而，目前尚无定量的拉丝性图谱、公式或标度，这促使了本研究。在本研究中，我们通过使用滴落至基材（DoS）流变测量法测定细丝寿命，以及使用滴落至空气（DiA）方法测定细丝长度和寿命，对比了一系列水性聚合物溶液的拉丝性。我们研究了聚合物化学性质和分子量对拉丝性的影响，并依靠DoS流变测量法来表征缩颈动力学和拉伸流变学响应。我们表明，拉丝性的增加分别与稳态末端拉伸粘度和拉伸松弛时间相关。最后，我们提供了一个框架，通过计算两个无量纲数$Oh_E$（使用稳态末端拉伸粘度）和$De_E$（使用拉伸松弛时间），绘制拉伸Ohnesorge-Deborah（$Oh-De$）图或$Oh_E-De_E$图，来比较不同聚合物溶液的拉丝性。
英文摘要
Characterization, control, and calibration of stringiness, the propensity to form long, thin, persistent threads, are key to the design and application of polymer solutions and formulations transferred to substrates by dropwise dispensing, jetting, spraying, or coating, and are used in manufacturing fibers, membranes, or spray-dried products. For Newtonian fluids, enhancing shear viscosity translates into increasing stringiness as can be easily perceived during dripping of water vs. sugar syrups or glycerol-water mixtures. In contrast, even polymer solutions with comparable shear viscosity can display a significant contrast in extensional rheology and apparent stringiness. However, there are no quantitative maps, formulas, or scales for stringiness, which motivates this study. In this contribution, we contrast the stringiness for a series of aqueous polymer solutions by determining the filament lifespan using dripping-onto-substrate (DoS) rheometry and filament length and lifespan in using dripping-into-air (DiA). We investigate the influence of polymer chemistry and molecular weight on stringiness and rely on DoS rheometry to characterize pinching dynamics and extensional rheology response. We show that an increase in stringiness correlates with steady, terminal extensional viscosity, and extensional relaxation time, respectively. Lastly, we provide a framework, which compares the stringiness of different polymer solutions through an extensional Ohnesorge-Deborah ($Oh-De$) plot or $Oh_E-De_E$ map, by computing the two dimensionless groups $Oh_E$ using steady, terminal extensional viscosity and $De_E$ using extensional relaxation time, respectively
