Collaborative Research: EAGER Proposal on Non-Homogeneous Flow Fields in Nonlinear Rheology: A Challenge to Current Paradigms?

合作研究：关于非线性流变学中非均匀流场的迫切建议：对当前范式的挑战？

• 批准号: 0934312
• 负责人: Gareth McKinley
• 金额: $ 2.5万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-01 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0934312&HistoricalAwards=false
• 关键词: Collaborative; Research; EAGER; Proposal; Non

TECHNICAL SUMMARYThe present EAGER proposal is a collaborative effort among four U.S. institutions (Texas Tech University, Massachusetts Institute of Technology, Cornell University and Illinois Institute of Technology) and one foreign institution (Technical University of Eindhoven in the Netherlands). The technical goal is to detail the limits of validity of reported flow instabilities in entangled polymer melts and solutions. The flow of polymer fluids in conventional rheometers is generally assumed to be nearly viscometric and stable. When instability or secondary flows occur, it is generally acknowledged that such measurements cannot be used to determine material parameters. This is important in any experimental challenge to, e.g., a molecular theory such as the reptation model of polymer chain dynamics. According to a new set of results that has appeared in the literature, the basis for the experimental verification of the reptation theory is, in fact, based upon experiments from non-homogeneous flows. If this is true, it changes the paradigm for the dynamics of polymer fluids in nonlinear deformation regimes. However, much of the community is skeptical of these results and there are multiple reports in the literature of contradictory results. Hence, it is paramount to establish the range of both flow conditions (rate and magnitude of shear) and material parameters (e.g., entanglement density) for which such observations are correct and the range where errors may have been made and to do so in a way that the results are accepted by the community at large. The present proposal is constructed to do this. The groups collaborate through an innovative set of student teams having one representative from at least three institutions for all experiments. Success of the work is defined as achieving an interlaboratory consensus of the flow profiles in polymer solutions and melts. Objectivity is developed by having multiple labs with multiple students performing each type of experiment so that ?neutral eyes? have the major influence in the examination of experimental data. Three types of experiments will be performed, each will be performed in at least two labs and one will be performed in all labs. The experiments are particle tracking velocimetry, confocal microscopy fluorescence dye velocimetry and macroscopic parallel plate-cone and plate comparisons of nonlinear properties. NON-TECHNICAL SUMMARYThe major paradigm of polymer rheology is the reptation theory. Because reptation is the present paradigm for polymer flow, it is widely used in industrial settings to understand how to change molecular parameters in making advances in polymer processing. There are several offshoots to reptation theory as well that are beginning to be adopted in industry. Yet, recent work has appeared that is being strongly advanced to challenge this paradigm. It has reported strong flow instabilities which would invalidate the reptation theory in the regime relevant to polymer processing. Hence establishing whether or not the reported flow instabilities occur in industrially relevant ranges of flow rates is important. The present proposal brings together collaborators from four U.S. and one foreign university (Texas Tech University, Massachusetts Institute of Technology, Cornell University and Illinois Institute of Technology,Technical University of Eindhoven in the Netherlands) with the goal of establishing the range of experimental conditions where such flow instabilities occur. Because the general community has not uniformly accepted the reported results, the present collaboration will provide both repeat (for validation purposes) and novel experimentation to establish the range over which the reported results are relevant and how they impact the current understanding of polymer nonlinear rheology and its basis in molecular (reptation) theory. The present proposal does this. In addition, because of its structure as a collaborative work through an innovative set of student teams having one representative from at least three institutions for all experiments. All students will participate in the collaboration with the Technical University of Eindhoven.

本EAGER提案是四个美国机构（德克萨斯理工大学、马萨诸塞州理工学院、康奈尔大学和伊利诺伊理工学院）和一个外国机构（荷兰埃因霍温技术大学）之间的合作努力。 技术目标是详细说明缠结聚合物熔体和溶液中报告的流动不稳定性的有效性限制。 聚合物流体在常规流变仪中的流动通常被假定为接近粘度测定和稳定。当出现不稳定或二次流时，一般认为这种测量不能用于确定材料参数。 这在任何实验挑战中都很重要，例如，分子理论，如聚合物链动力学的爬行模型。 根据一组新的结果，已出现在文献中，爬行理论的实验验证的基础上，事实上，从非均匀流的实验为基础。 如果这是真的，它改变了聚合物流体在非线性变形机制的动力学范式。 然而，社区中的许多人对这些结果持怀疑态度，文献中有多份关于矛盾结果的报告。因此，最重要的是建立流动条件（剪切速率和剪切幅度）和材料参数（例如，纠缠密度），这种观察是正确的，错误的范围可能已经作出，并这样做的方式，结果是由社会普遍接受。 本提案就是为了做到这一点而提出的。 这些小组通过一套创新的学生团队进行合作，其中至少有三个机构的一名代表参加所有实验。成功的工作被定义为实现实验室间的共识，在聚合物溶液和熔体的流动剖面。 客观性是由多个实验室与多个学生进行每种类型的实验，使？中性的眼睛？对实验数据的检验有重大影响。 将进行三种类型的实验，每种实验将在至少两个实验室进行，一种将在所有实验室进行。 实验包括粒子跟踪测速、共焦显微荧光染料测速和宏观平行板-锥和板非线性特性的比较。 聚合物流变学的主要范式是蠕动理论。由于蠕动是目前聚合物流动的范例，它被广泛用于工业环境中，以了解如何改变分子参数，使聚合物加工的进步。 爬行理论的几个分支也开始在工业中被采用。然而，最近的工作似乎正在大力推进，以挑战这一范式。它已经报道了强烈的流动不稳定性，这将使爬行理论在聚合物加工相关的制度。 因此，确定所报告的流动不稳定性是否发生在工业相关的流速范围内是重要的。本提案汇集了来自四所美国大学和一所外国大学（德克萨斯理工大学、马萨诸塞州理工学院、康奈尔大学和伊利诺伊理工学院、荷兰埃因霍温技术大学）的合作者，目的是建立发生这种流动不稳定性的实验条件范围。 由于一般社区还没有统一接受报告的结果，目前的合作将提供重复（验证目的）和新的实验，以建立报告结果相关的范围，以及它们如何影响目前对聚合物非线性流变学的理解及其在分子（爬行）理论中的基础。 目前的建议就是这样做的。此外，由于其结构是通过一组创新的学生团队进行协作，其中至少有三个机构的一名代表参与所有实验。 所有学生都将参加与埃因霍温技术大学的合作。