The Effects of Molecular Structure on Polymer Viscoelastic Flow Functions in Steady and Time Dependent Simple Shearing Flow

稳态瞬态简单剪切流中分子结构对聚合物粘弹性流动函数的影响

• 批准号: 8616542
• 负责人: K. DeVries
• 金额: $ 11万
• 依托单位: University of Utah
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1987
• 资助国家: 美国
• 起止时间: 1987-04-01 至 1990-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8616542&HistoricalAwards=false
• 关键词: Effects; Molecular; Structure; Polymer; Viscoelastic

Research Summary: Flow function data for systematic variations in well-characterized polymer structures for a variety of shearing modes are critically needed for the development and evaluation of constitutive equations relating viscoelastic flow functions to polymer structure. The effect on the flow functions of molecular weight, weight distribution, stiffness, and complexity will be determined for linear polymers. Additionally, for branched polymers, the effects of branch number, length, and uniformity for star polymers, and branch distribution for comb and randomly branched polymers will be determined. The flow functions will include the viscosity, and especially the first and second normal stress differences, N1 and N2, and derived functions in steady shearing, oscillatory, stress growth and relaxation, and step strain deformations. Low compliance Weissenberg and Rheometries rheometers will be used in cone-plate and parallel plate shearing. Modification of constitutive equations, especially relaxation functions, will be studied. Technical Impact/Practical Applications: The complete flow function data will provide a basis for the formulation of realistic constitutive equations for use with the transport equations in the design of polymer production and processing equipment. Some applications follow: Extrudate Swell. The control of extrudate swell is critically important in such operations as the extrusion of plastic pipe, rods, and plastic vessel parisons. The rarely available ratio of N2 to N1 has been shown to be a major factor in extrudate swell. The proposed research will generate the required high shear-rate data and instrumentation to acquire such data. Wire Coating. Second normal stress difference and fluid dynamic forces act to center the wire in a coating of plastic. Dies designed to utilize these forces could reduce the average coating thickness, meet thickness specifications, and reduce material costs. The instrumentation developed by this proposal will make possible for the first time the acquirement of the required high shear-rate N2 data. Shaft Climbing on the shafts of mixers and reactors in the food and polymers or plastics industries must be managed. In one case, polymers climbed up the shaft and into the drive of a large mixer and forced a costly shutdown. With a knowledge of the ratio of N2 to N1 (currently rarely available), rod climbing can be predicted and mixers can be designed to avert the problems. Reverse Flow. In stirred tank polymer and biological reactors and mixers, significant normal stresses cause radially inward flow towards the mixer shafts (vs. radially outward). Mass and heat transfer and efficiency are importantly reduced by major changes in flow patterns. With a knowlege of the ratio of N2 to N1, reverse flow can be predicted and design measures taken to improve performance.

研究总结：系统变化的流函数数据 在用于各种 剪切模式是发展所急需的， 粘弹性流动本构方程的评价 聚合物结构的功能。 对流函数的影响 分子量，重量分布，刚度，和 将确定线性聚合物的复杂性。 此外，本发明还 对于支化聚合物，分支数、长度和 星星聚合物的均匀性和梳状聚合物的分支分布 和无规支化聚合物。 流动 函数将包括粘度，特别是第一个 和第二法向应力差N1和N2， 在稳定剪切、振荡、应力增长和 松弛和阶跃应变变形。 低顺应性 Weissenberg和Rheometries流变仪将用于锥板 和平行板剪切。 本构关系的修正 方程，特别是松弛函数，将被研究。 技术影响/实际应用：完整流程 功能数据将为制定 用于运输的实际本构方程 聚合物生产和加工设计中的方程 设备. 一些应用如下：挤出膨胀。 的 挤出物膨胀的控制在这种情况下是至关重要的 塑料管材、棒材、塑料管材 容器型坯。 N2与N1的比例很少， 显示出是挤出物溶胀主要因素。 拟议 研究将产生所需的高剪切速率数据， 仪器来获取这些数据。 电线涂层。 二 法向应力差和流体动力作用于中心 电线外面包了一层塑料。 模具设计利用这些 力可减小平均涂层厚度， 规格，并降低材料成本。 仪表 这一提议将首次使 获得所需的高剪切速率N2数据。 轴 爬上搅拌机和反应器的轴在食品和聚合物 或者塑料工业必须加以管理。在一个案例中，聚合物 沿着轴向上，进入大型搅拌机的驱动装置， 关机 了解N2与N1的比例（目前很少 可用），可以预测棒爬升并设计混合器 来避免这些问题 反向流动。 在搅拌罐中聚合物和 生物反应器和混合器，显著的正应力导致 径向向内流向混合器轴（相对于径向向外）。 质量和热传递以及效率被显著降低， 流动模式的重大变化。 知道了 N2至N1，可预测逆流并采取设计措施 以提高性能