Small stress (<1 Pa) can dramatically disrupt gelation.
We report that during temperature-induced gelation, applied shear stress (even below 1 Pa) dramatically changes the gel temperature and the resulting mechanical properties of aqueous methylcellulose (MC). This can lead to catastrophic inaccuracy in relating rheological properties to expected performance if stress-dependent gelation is not considered, e.g. with retention of surface coating in the presence of gravitational stress or extrusion-based 3D printing that must resist gravitational loading.
We use rotational rheometers for the experimental study and a filament network mathematical model to relate the measured properties to microstructural features.
This work was supported by Corporate R&D at The Dow Chemical Company. Since the completion of this grant, the Pharma Solutions business of Dow, to which this work was aligned, has moved to International Flavors & Fragrances (IFF).
FULL CITATION: Nelson, A. Z., Y. Wang, Y. Wang, A. S., Margotta, R. L. Sammler, A. Izmitli, J. S. Katz, J. Curtis-Fisk, Y. Li, and R. H. Ewoldt, “Gelation under stress: impact of shear flow on the formation and mechanical properties of methylcellulose hydrogels,” Soft Matter, Advance Article (2022). DOI link