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

University Of Pittsburgh, Pittsburgh PA

Investigators

Abstract

1336311 PI: Velankar This 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.