Paper Number
PO41 

Session
Poster Session

Title
Quantifying thixotropy using step-rate tests and kinetic structure-based constitutive modeling

Presentation Date and Time
October 13, 2021 (Wednesday) 6:30

Track / Room
Poster Session / Ballroom 1-2-3-4

Authors (Click on name to view author profile)

  1. Sen, Samya (University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering)
  2. Lu, Xinyu (PPG Industries)
  3. Wang, Chao (PPG Industries)
  4. Ewoldt, Randy H. (University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering)

Author and Affiliation Lines (in printed abstract book)
Samya Sen1, Xinyu Lu2, Chao Wang2 and Randy H. Ewoldt1
1Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801; 2PPG Industries, Allison Park, PA

Speaker / Presenter 
Sen, Samya

Keywords
experimental methods; colloids; emulsions; gels; non-Newtonian fluids; polymer blends; suspensions

Text of Abstract
Complex rheological phenomena like thixotropy pervade fluid-based industrial materials, including paints, coatings, adhesives, and sealants, among others. The objective of the current work is to develop and assess fast methods to measure thixotropic rheological properties of these complex fluid systems. The proposed test conditions use step shear tests and simulate the mechanical shearing history that these fluids would typically undergo during either processing or application. The thixotropic recovery and breakdown data are analyzed using structure kinetics-based constitutive equations that use a superposition of two different stretched exponentials for modeling the thixotropic transients, which is an ad-hoc modification of the mathematical model originally proposed by Wei et al. (J. Rheol., 2018). This method is effective in both fitting and predicting the thixotropic behavior of many application relevant materials under typical processing and testing conditions. Using the techniques developed here would give the user a handle on low-dimensional, easily accessible thixotropic material properties such thixotropic timescales, degrees of stress and viscosity changes due to shearing. One will be able to quantify both viscoelastic and thixotropic properties and their relative importance in material behavior.