Structure and flow in solid/fluid/fluid systems: Model studies using immiscible polymer blends

本研究旨在对液-液-固混合物中流动诱导结构的发展进行全面研究，其中固体颗粒被两种不混相液体润湿起重要作用。在所选择的系统中，毛细力将远远强于热波动力，因此结构和流动特性将受到加工历史的强烈影响。本研究的总体假设是，以前未发现的流致结构将从粘性和界面张力之间的相互作用中出现。实验将使用两种熔融聚合物作为不混相流体相进行。其中一个相将通过简单地冷却混合物在期望的流动历史后固化。这种淬火将允许通过扫描电子显微镜进行详细的形态表征。利用原位光学成像、电子显微镜和流变学实验，将绘制颗粒的组成、流动历史和润湿性对结构和流变学的依赖关系。多相系统在各种工艺和产品中都很常见：食品、个人护理产品、石油开采等。目前对三元体系的结构和流动性质所知甚少。例如，连三元组成对粘度的影响这样的基本问题都不知道。这个项目将映射结构-加工-流变关系来解决这个问题。三元体系产生了各种各样的结构，从沙堡（由水半月板聚集在一起的颗粒），装甲气泡（表面挤满颗粒的气泡），bijels（两相连续的形态），液体弹珠（包裹着颗粒的水滴）等。该项目旨在提供毛细力在此类系统中的影响的统一视图。一名研究生和几名本科生将接受科学研究方面的培训。首席研究员还将在高中开展外联活动，向学生介绍多相材料的科学和技术。

1336311PI: VelankarThis research seeks to conduct a comprehensive study of flow-induced structure development in liquid-liquid-solid mixtures where wetting of the solid particles by the two immiscible liquids play an important role. Capillary forces will be far stronger than the thermal fluctuation forces in the chosen systems, and hence the structure and flow properties will be strongly influenced by the processing history. The overall hypothesis of this research is that previously-undiscovered flow-induced structures will emerge from the interplay between viscous and interfacial tension forces. Experiments will be conducted using two molten polymers as the immiscible fluid phases. One of the phases will be solidified by simply cooling the mixtures after the desired flow history. This quenching will allow detailed morphological characterization by scanning electron microscopy. Using in situ optical imaging, electron microscopy, and rheological experiments, the dependence of the structure and rheology on composition, flow history, and wettability of the particles will be mapped. Multiphase systems are common in a wide variety of processes and products: foods, personal care products, petroleum extraction, etc. Very little is known at present about the structure and flow properties of ternary systems. For instance, even a basic question such as the effect of ternary composition on viscosity is not known. This project will map the structure-processing-rheology relationships to address this issue. Ternary systems give rise to a wide variety of structures ranging from sand castles (particles held together by water menisci), armored bubbles (bubbles whose surface is jammed with particles), bijels (morphologies in which the two phases are continuous), liquid marbles (drops coated with particles), etc. This project aims to provide a unified view of the effects of capillary forces in such systems.One graduate student and several undergraduates will be trained in scientific research. The principal investigator will also conduct outreach at a high school level which introduces students to the science and technology of multiphase materials.