Correlating Rheological Experiments, TEVP Models, and Microstructure with Small Angle Light Scattering

Matthew J Armstrong,André M Pincot

doi:10.4236/ojfd.2022.121002

Abstract

The existence of an evolving microstructure in a 2.9 vol% fumed silica in paraffin oil and polyisobutylene is demonstrated experimentally and via rheological modeling during steady state and large amplitude oscillatory shear flow. The continuously evolving, rebuilding, and breaking down of the microstructure is shown, and correlated through the rheology experiments, thixo-elastovisco-plastic modeling, and small angle light scattering (SALS). All elements are then connected via a global, stochastic optimization algorithm that will provide parameter estimation with a “best-fit” of the steady state and transient data using the well-known Modified Delaware Thixotropic Model, allowing for the comparison of SALS results with experimental values.

Highlights

We demonstrate the use of the full soft matter interrogation technique, consisting of simultaneous use of rheological and scattering data along with modeling, and parameter estimation to interrogate a complex material’s microstructure
We started by demonstrating that comparing Af calculated using neutron scattering data and simultaneously using the Modified Delaware Thixotropic Model (MDTM) to predict λ was possible, and useful to make relevant correlations of how the flow field affects both measures of a material’s microstructure [1] [2] [11]-[17] [37] [38]
This method was subsequently applied to 2.9 vol% fumed silica in paraffin oil and PIB

Summary

Introduction

We demonstrate the use of the full soft matter interrogation technique, consisting of simultaneous use of rheological and scattering data along with modeling, and parameter estimation to interrogate a complex material’s microstructure. The fitting of the model parameters to the steady state rheological data is accomplished with a novel parallel tempering algorithm [1] [2] [4]. Steady state and large amplitude oscillatory shear (LAOS) scattering and rheological data from the TA Instruments DHR-3 stress-controlled rheometer is wielded to make structural connections between. Marty’s number, M' (akin to an inverse Bingham number), and viscosity measurements from steady state and LAOS are used to facilitate discussion of key structure development and evolution under flow. The scattering measurement methods are discussed, and it is demonstrated that it can be used to calculate structural features under varying flow conditions. Discussion of neutron scattering experiments for our model thixotropic material, 2.9 vol% fumed silica in paraffin oil and polyisobutylene, are included. The scattering, modeling, and rheology data is interpreted [1] [5] [6] [7]

Objectives

Methods

Results

Conclusion