Failure of Polymer Gum Gels Close to their Critical Strain

Polymer gels prepared from synergistic blends of xanthan and konjac gums exhibit remarkable flow characteristics. Creep measurements indicate that when the applied stress results in a deformation of the gel in excess of the critical strain, the gel rapidly fails and flows; when the applied stress results in a deformation far less than the critical strain, the gel only slowly creeps. Remarkably, when the applied stress results in a deformation close to the critical strain, the gel slowly creeps for an extended ‘incubation’ time at which point it catastrophically fails and flows. In fact, there is a power-law relationship between the applied stress and the ‘incubation’ time. Although similar behavior is reported in materials ranging from ketchup to waxy crude oil, surprisingly little is understood about the creeping behavior of materials close to their critical strain. We have looked to structural kinetic models, which balance the rate of structure formation and stress-induced structure break down, as a way to generalize the problem. These approaches should have broad application to a variety of industries and technologies.

Matthew Lynch, Proctor & Gamble Company

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