Restructuring time and deformation history effect in restructuring process after yield behavior of α-gel O/W emulsion

Autor: Yukinobu Sugihara, Yasunori Sato, Ippei Homma, Tsutomu Takahashi
Rok vydání: 2021
Předmět:
Zdroj: Rheologica Acta. 60:409-421
ISSN: 1435-1528
0035-4511
DOI: 10.1007/s00397-021-01278-0
Popis: An interesting aspect of the yielding behavior of soft matter is the repetitive nature of the yielding phenomenon. In creams and gels, once the yielding phenomenon occurs, the structure recovers after a certain period of time, and the same yielding property is shown again. The time required for the yield properties to recover in yield stress fluids is one of their most important rheological properties. In this study, the time evolution of the rheological properties of an α-gel during the structural recovery process after the onset of yielding behavior was experimentally measured. A stress sweep test was used as the flow to initiate yielding, and the effect of the experimental parameters of the stress sweep, which determine the deformation history, on the structural recovery process was investigated. To realize this purpose, we used a rheometer that can instantly switch the control mode from a stress-controlled sweep test to a strain-controlled oscillation test. The α-gel used is a typical yield stress fluid that exhibits slip yielding and true yielding. The process of restructuring after the onset of true yielding can be divided into three time regions: (1) the region affected by stress relaxation, (2) the region where the storage and loss moduli fluctuate violently, and (3) the region where the storage and loss moduli increase uniformly and gradually. Yield stress recovery is related to region (3). The recovery process of each modulus in region (3) can be well approximated by an experimental equation expressed as a product of an exponential function and an attenuation function. In particular, for the recovery of the storage modulus, a strong correlation was found between the representative time of the attenuation function and the maximum applied stress in the stress sweep test.
Databáze: OpenAIRE
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