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: 0934600
• 负责人: Lynden Archer
• 金额: $ 2.5万
• 依托单位: Cornell University
• 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 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0934600&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.

技术摘要当前的急切提议是美国四个机构（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）和一家外国机构（荷兰埃因霍温技术大学）的合作努力。 技术目标是详细介绍纠缠聚合物熔体和溶液中报告的流量不稳定性的有效性限制。 通常认为传统流变仪中聚合物流体的流动几乎是粘度且稳定的。当出现不稳定性或次要流时，通常认为不能使用此类测量来确定材料参数。 这在任何实验性挑战中都很重要，例如分子理论，例如聚合物链动力学的振兴模型。 根据文献中出现的一系列新结果，实际上，基于非均匀流的实验，对起伏理论的实验验证的基础。 如果这是真的，它会改变非线性变形方案中聚合物流体动力学的范例。 但是，社区的大部分内容都对这些结果持怀疑态度，并且文献中有许多矛盾结果的报道。因此，建立流动条件（剪切的速率和幅度）和材料参数（例如纠缠密度）的范围至关重要，这些范围是正确的，并且可能已经犯了错误，并以社区在整个社区所接受的结果而进行的范围。 目前的建议是为此而构建的。 这些小组通过一组创新的学生团队合作，其中一名来自至少三个机构的代表进行所有实验。这项工作的成功被定义为在聚合物溶液和熔体中取得了实验室间的共识。 客观性是通过有多个学生执行每种实验的多个实验室来发展的客观性，以使眼睛中性？在检查实验数据中具有主要影响。 将执行三种类型的实验，每种实验将在至少两个实验室中进行，并且将在所有实验室中进行。 实验是粒子跟踪速度法，共聚焦显微镜荧光染料速度法和非线性特性的宏观平行板锥和板比较。 非技术总结聚合物流变学的主要范式是起伏理论。由于振兴是当前聚合物流量的范式，因此它被广泛用于工业环境中，以了解如何在聚合物加工方面更改分子参数。 在行业中也开始采用几种销售理论的分支。然而，最近的工作似乎已经有了很强的进步来挑战这一范式。它报告了强大的流动不稳定性，这将使与聚合物加工有关的制度中的仓库理论无效。 因此，确定报告的流量不稳定性是否在流速的工业相关范围内发生很重要。本提案汇集了来自美国四所大学（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州荷兰技术大学）的合作者，目的是确定发生这种流动不便的一系列实验条件。 由于一般社区尚未统一接受报告的结果，因此目前的合作将提供重复（出于验证目的）和新颖的实验，以确定报告结果相关的范围以及它们如何影响当前对聚合物非线性流变学及其在分子（回复）理论中的理解。 目前的提议做到了这一点。此外，由于其作为合作工作的结构，通过一组创新的学生团队，其中一名来自至少三个机构的代表进行所有实验。 所有学生将与埃因霍温技术大学合作。