Development of a Low Stress Creep Rheometer

低应力蠕变流变仪的开发

• 批准号: 9802793
• 负责人: Ralph Colby
• 金额: $ 14.5万
• 依托单位: Pennsylvania State Univ University Park
• 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: 1998-08-01 至 2001-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9802793&HistoricalAwards=false
• 关键词: Development; Low; Stress; Creep; Rheometer

9802793ColbyThere are many examples of fluids that are actually weak gels due to the presence of structure in the materials on length scales much larger than molecular dimensions. Below some critical yield stress, these structured fluids are solids, characterized by a modulus. In most cases, this modulus cannot be measured in commercially available rheological instrumentation because those rheometers cannot apply low enough stresses. However, by simply combining technologies that have been proven to work in various rheometers, it is possible to construct a creep rheometer capable of applying three orders of magnitude lower stress levels than "state of the art" commercial rheometers. This new rheometer will allow application of stresses below the yield stress, to measure the modulus of the unbroken structure. Application of stresses in the vicinity of the yield stress will allow detailed studies of yielding in structured fluids. This information is needed for needed for modeling the rheology of structured fluids, as the entire rheological response (even at high stresses) is due to structure breaking. Examples of such structured fluids that we are currently studying are: swollen gels, liquid crystal polymers, block copolymers, polyelectrolyte-surfactant complexes, suspensions, surfactant solutions and foods. The new rheometer will lead to breakthroughs in our understanding of each of these classes of materials because it will allow, for the first time, characterization of the linear response and the first departures from linear response. This rheometer is, therefore, vital to the long-term research and education plans of the Penn State Rheology Group.%%%***

9802793Colby 有许多流体的例子实际上是弱凝胶，因为材料中存在长度尺度远大于分子尺寸的结构。 在某些临界屈服应力以下，这些结构化流体是固体，其特征在于模量。 在大多数情况下，该模量无法在市售流变仪器中测量，因为这些流变仪无法施加足够低的应力。 然而，通过简单地结合已被证明适用于各种流变仪的技术，可以构建能够施加比“最先进的”商业流变仪低三个数量级的应力水平的蠕变流变仪。 这种新型流变仪将允许施加低于屈服应力的应力，以测量未破坏结构的模量。 在屈服应力附近施加应力将允许对结构流体中的屈服进行详细研究。 结构化流体的流变学建模需要此信息，因为整个流变响应（即使在高应力下）是由于结构破坏造成的。 我们目前正在研究的此类结构化流体的例子有：溶胀凝胶、液晶聚合物、嵌段共聚物、聚电解质-表面活性剂复合物、悬浮液、表面活性剂溶液和食品。 新的流变仪将在我们对每一类材料的理解上带来突破，因为它将首次允许线性响应的表征以及线性响应的首次偏离。 因此，该流变仪对于宾夕法尼亚州立大学流变学小组的长期研究和教育计划至关重要。%%%***