Rheological Characterization of Polymer Additives for Mist Control and Drag Reduction

Citation

Lhota, Red C. (2022) Rheological Characterization of Polymer Additives for Mist Control and Drag Reduction. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/wav1-4t47. https://resolver.caltech.edu/CaltechTHESIS:05262022-231652129

Abstract

Long flexible polymers in solution at low concentrations strongly change the extensional properties of fluids due to chain stretching that resists flow, while their compact conformation in shear has weak effects. This dramatic difference between their effects on extension and shear is desirable in a variety of applications--controlling drop size in sprayed mists, reducing drag in turbulent flow, and preventing rebound in drop impact. Traditional long covalent polymers, however, are not practical in many applications because they undergo mechanical degradation, i.e. chain scission, under strong flow conditions. Megasupramolecular polymer systems, consisting of long end-associative telechelic polymers that assemble in solutions into multi-million molecular weight supramolecules, meet this practical need. Through association, they act like traditional covalently-bonded polymers in extension, while reversibly dissociating under the strong flows that cause scission for those long polymers.

This thesis examines the interplay of flow and degradation that imposes an upper-bound on useful lengths of invididual end-associative chains (how long is too long) (Chapters 2 and 3); the quiescent coil size that affects the onset of stretching in fluids of interest (water and polyalphaolefin lubricant) (Chapters 2 and 4); rheological approachs to detect variations in the degree of end-functionalization that affect formation of ultra-long supramolecules (Chapter 5); and the changes to turbulent flow when long polymers are present at low concentration (Chapter 2). Ultimately, the audience who might enjoy this thesis is limited by barriers of rheological jargon. In the pursuit of broader rheological and overall scientific understanding, I describe evidence-based pedagogical techniques and my approach to implementing them in chemical engineering and polymer physics classrooms (Chapter 6).

Thesis Files