Paper Number
AR25                         My Program 

Session
Applied Rheology for Industrial Applications

Title
Fighting bad rheometry: Lessons from compliance limits and protorheology

Presentation Date and Time
October 22, 2025 (Wednesday) 1:30

Track / Room
Track 4 / Peralta + Lamy

Authors (Click on name to view author profile)

  1. Hossain, Mohammad Tanver (University Of Illinois Urbana-champaign, Mechanical Science and Engineering)
  2. Tiwari, Ramdas (University of Illinois Urbana-Champaign, Mechanical Science and Engineering)
  3. Macosko, Christopher W. (University of Minnesota, Chemical Engineering and Materials Science)
  4. McKinley, Gareth H. (Massachusetts Institute of Technology, Mechanical Engineering)
  5. Ewoldt, Randy H. (University Of Illinois Urbana-champaign, Mechanical Science and Engineering)

Author and Affiliation Lines (in printed abstract book)
Mohammad Tanver Hossain1, Ramdas Tiwari1, Christopher W. Macosko2, Gareth H. McKinley3 and Randy H. Ewoldt1
1Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL 61801; 2Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455; 3Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139

Speaker / Presenter 
Ewoldt, Randy H.

Keywords
experimental methods; applied rheology; gels; industrial applications; methods; networks; rheometry

Text of Abstract

Rheological data are only as trustworthy as the tools and interpretations that generate them. This talk integrates insights from two recent studies [1,2] that identify and address distinct but complementary challenges in rheological measurement and inference.

The first challenge arises from instrument compliance artifacts, which can systematically depress apparent viscoelastic moduli below their true values. This risk is especially important with curing systems on a rotational rheometer, as well as with dynamic mechanical analysis (DMA) devices. We present a framework for identifying and avoiding such errors using operational limit lines, G_{max} and E_{max}, that enable immediate visual assessment of data credibility and error estimation, even without access to raw displacement or force data. These limit lines also provide a proactive tool for experimental design, instrument selection, and retrospective data evaluation.

The second challenge emerges in the broader and less controlled domain of protorheology, where informal or opportunistic observations are used to infer rheological properties. While protorheology offers accessibility, creative insight, and a sanity check for rheometric data, it also carries significant risks of misinterpretation, e.g. confusing viscosity with elasticity, flow time with relaxation time, or capillary pinning with yield stress. With several realistic examples, we illustrate how to avoid these pitfalls and apply protorheological reasoning responsibly.

Together, these two perspectives reinforce a central message: good rheology requires not just good data, but vigilance against both instrumental artifacts and interpretive overreach. By applying operational limit lines and critically evaluating assumptions, we can avoid common errors and enable more reliable insights into rheological behavior.

[1] Hossain, Macosko, McKinley, Ewoldt (2025). DOI: 10.1007/s00397-024-01481-9
[2] Hossain, Tiwari, and Ewoldt (2024). DOI: 10.1016/j.cocis.2024.101866