Shear and Extensional Rheology of Nanoclays and Nanotubes in Polymer Melts and Solutions

该基金为纳米粘土/聚合物和碳纳米管/聚合物复合材料的非线性流变学、颗粒取向和结构发展的综合表征提供资金，包括剪切和延伸，以及纳米复合材料过程控制和优化的模拟工具的开发。聚合物纳米复合材料表现出显著增强的性能，包括增强的强度、刚度、阻隔性和耐热性，而冲击强度没有显著损失。两种类型的纳米颗粒，自然产生的层状纳米粘土和合成的碳纳米管，在改善热塑性和热固性聚合物的机械和电学性能方面表现出希望。然而，这些改进伴随着加工成本：少量添加高表面积体积比的纳米粘土和纳米管会显著增加聚合物熔体和溶液的粘度和弹性，使聚合物纳米复合材料产品的挤出和注射成型复杂化。此外，加工对纳米颗粒取向和结构发展的影响，从而对产品材料的性能性能的影响，还不是很清楚。随着所提出的聚合物纳米复合材料的综合流变学和结构表征，以下问题将得到解决：填充超大宽高比纳米颗粒的熔体和溶液的剪切和拉伸粘度是多少？在不同长宽比的管和盘之间，它们对纳米粒子几何形状的依赖是什么？剪切和伸展流动中的颗粒取向和结构发育情况如何？应力/应变/结构的过程建模可以开发哪些模型？纳米颗粒在拉伸流中排列到什么程度？纳米管和纳米粘土的弹性性能与聚合物熔体和溶液的粘弹性之间、纳米颗粒浓度与溶液的粘弹性之间、取向和结构发育与粘弹性之间的关系是什么？纳米颗粒在拉伸和剪切时的流向特性是什么？管和血小板的流向结构是否有很大的不同？

This grant provides funding for the comprehensive characterization of the non-linear rheology, particle orientation, and structure development of nanoclay/polymer and carbon nanotube/polymer composites, in both shear and elongation, and the development of simulation tools for control and optimization of processes for nanocomposites. Polymer nanocomposites exhibit significantly enhanced performance properties, including increased strength, stiffness, barrier properties, and heat resistance, without a significant loss in impact strength. Two types of nanoparticles, naturally occurring layered nanoclays and synthesized carbon nanotubes, show promise in improving the mechanical and electrical properties of thermoplastic and thermoset polymers. However, these improvements come with a cost in processing: small additions of the high surface-area-to-volume-ratio nanoclays and nanotubes have been observed to significantly increase the viscosity and elasticity of polymer melts and solutions, complicating the extrusion and injection molding of polymer nanocomposite products. In addition, the effect of processing on nanoparticle orientation and structure development, and hence performance properties of the product materials, is not well understood. With the proposed comprehensive rheological and structural characterization of polymer nano-composites, questions such as the following will be addressed: What are the shear and extensional viscosities of melts and solutions filled with extremely large aspect ratio nanoparticles? What are their dependencies on nanoparticle geometry, varying between tubes and discs of different aspect ratios? What is the particle orientation and structure development in shear and extensional flow? What models can be developed for process modeling of stress/strain/structure? To what degree do nanoparticles become aligned in an extensional flow? What are the correlations between elastic properties of nanotubes and nanoclays and the viscoelasticity of the polymer melts and solutions, between nanoparticle concentration and viscoelastic properties of solutions, between orientation and structure development and viscoelastic properties? What are the flow-aligning properties of the nanoparticles in extension and shear, and do the tubes and platelets have very different flow-aligning structures?