POWRE: Rheology and Microstructure of Dilute Surfactant Systems in Complex Flows

POWRE：复杂流动中稀释表面活性剂体系的流变学和微观结构

• 批准号: 9753157
• 负责人: Lynn Walker
• 金额: $ 8.02万
• 依托单位: Carnegie-Mellon University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-01-01 至 1999-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9753157&HistoricalAwards=false
• 关键词: POWRE; Rheology; Microstructure; Dilute; Surfactant

Surfactants, or surface active agents, pervade almost every aspect of our daily lives. Biological functions, healthcare products, cleaning materials, paints and many other products and processes rely on the unique properties of these molecules. Many of these solution properties arise from the fact that surfactants aggregate in solution, forming a myriad of structures with different properties. The ability to control aggregate structure requires a fundamental knowledge of the influence of system parameters. Although this understanding exists for equilibrium situations, the changes in structure caused by external forces, such as flow, are not well studied. Flow is a pertinent variable as most surfactant-based systems are subject to flow in application, transport and processing. Thread-like micelles, or one-dimensional aggregates, form in a number of surfactant solutions. In the case of dilute solutions of rod-like (stiff) micelles with low levels of added salt, a transition to a shear-thickened state has been observed and fairly well characterized. A qualitative understanding of the shear-induced transition exists both at a macroscopic and structural level and this understanding is becoming more quantitative. Most studies have focused on simple shear fields and Couette rheometry. The influence of flow fields other than shear has not been studied, yet information from these types of studies are required for a complete understanding of the phenomenon. In this proposed research, the intent if to simultaneously probe macroscopic flow behavior and microstructural changes in more complex flow fields. Initial thrusts will involve inhomogeneous shear flow. The study will then extend to flow fields with increasing levels of elongation to begin to understand the influence of strong flows. Long term goals include the study of elongational flows, both at the macroscopic and microstructural levels. Results from this research will provide information necessary for the development of struct ure based constitutive equations for these micellar solutions, verify the potential of these fluids n specific engineering applications (such as drag reduction) and answer specific questions about the nature of the shear-induced transition which cannot be elucidated with shear alone.

表面活性剂，或表面活性剂，几乎渗透到我们日常生活的各个方面。 生物功能、保健产品、清洁材料、油漆和许多其他产品和工艺都依赖于这些分子的独特性质。 这些溶液性质中的许多是由于表面活性剂在溶液中聚集，形成具有不同性质的无数结构的事实。 控制骨料结构的能力需要对系统参数的影响有基本的了解。 虽然这种理解存在于平衡的情况下，但由外力（如流动）引起的结构变化并没有得到很好的研究。 流动是一个相关的变量，因为大多数基于表面活性剂的系统在应用、运输和加工过程中都会流动。 线状胶束或一维聚集体在许多表面活性剂溶液中形成。 在棒状（硬）胶束与低水平的添加盐的稀溶液的情况下，已观察到的剪切增稠状态的过渡，并相当好地表征。 对剪切诱导转变的定性理解存在于宏观和结构水平上，并且这种理解正变得更加定量。 大多数研究都集中在简单的剪切场和Couette流变仪。 流场的影响，而不是剪切尚未研究，但从这些类型的研究信息需要一个完整的理解的现象。 在这项拟议的研究中，如果同时探测宏观流动行为和微观结构的变化，在更复杂的流场的意图。 初始推力将涉及不均匀的剪切流。 然后，研究将扩展到伸长水平增加的流场，以便开始了解强流的影响。 长期目标包括在宏观和微观结构水平上研究拉伸流动。 从这项研究的结果将提供必要的信息，为这些胶束溶液的结构为基础的本构方程的发展，验证这些流体在特定的工程应用（如减阻）的潜力，并回答具体的问题，剪切诱导的过渡的性质，不能单独与剪切阐明。