SGER: Re-Examining the Basic Description of Polymer Entanglement in Flow

SGER：重新审视流动中聚合物缠结的基本描述

• 批准号: 0603951
• 负责人: Shi-Qing Wang
• 金额: --
• 依托单位: University of Akron
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-05-01 至 2008-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0603951&HistoricalAwards=false
• 关键词: SGER; Re; Examining; Basic; Description

SGER: Re-examining the basic description of polymer entanglement in flowTECHNICAL SUMMARYThe proposed research aims to clarify the nature of nonlinear flow behavior of entangled polymers. Description of chain entanglement in flow and its influence on the observed rheological properties have been predicated on the premise that a homogenous shear field is established in steady state in any common rheometric instruments, which employ a cone-plate assembly. Some recent work appears to offer new insight into how chains may disentangle in simple shear and to question the basic foundation of polymer rheology. Experiments will be carried out to reveal the velocity profiles associated with the various standard rheological tests. Specifically, a particle-tracking velocimetric method will be implemented in conjunction with conventional rheometric measurements. Both monodisperse and polydisperse entangled solutions will be studied in this manner in the nonlinear flow regime that will be probed using both controlled-strain and controlled-stress protocols. After the role of molecular weight distribution (MWD) is established in terms of how MWD affects the characteristics of the velocity profile, the focus will be shifted onto model entangled melts that can be used to depict the flow characteristics of a host of important commercial polymers such as polyethylene and polystyrene. Since the velocity profile has never been determined previously for entangled polymers, the knowledge accumulated over the past decades concerning their basic flow characteristics has remained essentially untested. The exploratory nature of this proposed research lies in its activities that open up this black box for the first time and critically examine the widely accepted assumption of homogenous flow with the goal to either find support for or evidence against the basic underlying assumption in polymer rheology and to provide a phenomenological foundation for a new theoretical description.NON-TECHNICAL SUMMARYThe world-wide annual production of plastics and rubber materials (i.e., polymers) has long exceeded that of steel in terms of volume. They all undergo one process before coming into use by consumers in various forms as final products (from milk containers to water bottles, from car bumpers to plastic grocery bags): heated up and melted to flow like honey and to be formed into different shapes. The proposed research questions the basic understanding of how these polymers undergo processing to become commercial products. A realistic description of the processing to result from the proposed research could enhance the efficiency of polymer processing in terms of energy savings and potentially improve the performance of items produced from polymeric materials. Equally important, the proposed research will provide rigorous and potentially unorthodox training to students, allowing them to conduct research critically instead of simply following an established paradigm. In other words, there is an attractive opportunity to foster the next-generation scientists capable of thinking independently and out of the box.

SGER：重新审视流动中聚合物缠结的基本描述技术摘要所提出的研究旨在阐明缠结聚合物非线性流动行为的本质。 流动中的链缠结及其对观察到的流变性质的影响的描述是基于在任何采用锥板组件的常见流变仪器中在稳态下建立均匀剪切场的前提。 最近的一些工作似乎为链如何在简单剪切下解开提供了新的见解，并对聚合物流变学的基本基础提出了质疑。 将进行实验以揭示与各种标准流变测试相关的速度分布。 具体来说，粒子跟踪测速方法将与传统的流变测量结合实施。 单分散和多分散纠缠溶液都将以这种方式在非线性流态中进行研究，并使用受控应变和受控应力协议进行探测。 在根据分子量分布 (MWD) 如何影响速度分布特征确定分子量分布 (MWD) 的作用后，重点将转移到缠结熔体模型上，该模型可用于描述许多重要商业聚合物（例如聚乙烯和聚苯乙烯）的流动特性。 由于以前从未确定过缠结聚合物的速度分布，因此过去几十年积累的有关其基本流动特性的知识基本上尚未经过测试。 这项拟议研究的探索性在于其活动首次打开了这个黑匣子，批判性地检验了广泛接受的均匀流动假设，目的是找到支持或反对聚合物流变学基本假设的证据，并为新的理论描述提供现象学基础。 非技术摘要全球塑料和橡胶材料（即聚合物）的年产量长期以来一直在增长。 就体积而言，超过了钢材。 它们都经过一个过程，然后以各种形式作为最终产品（从牛奶容器到水瓶，从汽车保险杠到塑料杂货袋）被消费者使用：加热并熔化，像蜂蜜一样流动并形成不同的形状。 拟议的研究质疑对这些聚合物如何经过加工成为商业产品的基本理解。 拟议研究对加工过程的真实描述可以提高聚合物加工在节能方面的效率，并有可能提高聚合物材料生产的产品的性能。 同样重要的是，拟议的研究将为学生提供严格且可能非正统的培训，使他们能够批判性地进行研究，而不是简单地遵循既定的范式。 换句话说，这是培养能够独立思考、跳出框框的下一代科学家的诱人机会。