Rheology structural changes

Small temperature variations (+5°C) can change the phase structure of the paste dramatically, resulting in undesired rheological structures like gels. Good temperature control is therefore key in neutralization reactions. 

Beekmans F, "Rheology and Changes in Structure of Thermotropic Liquid Crystalline Polymers", PhD Thesis, Delft, 1997. 

Morris, E. R. 1998. Segregative interactions in biopolymer co-gels, in Phase/State Transitions in Foods Chemical, Rheological and Structural Changes, eds. M. A. Rao and R. W. Hartel, pp. 111-156, Marcel Dekker, Inc., NY. 

While rheological measurements are wonderfully quantitative, they are usually poor qualitative probes of fluid structure. This is because in rheological experiments, the structural changes responsible for the measured relaxation behavior remain hidden. Thus, rheometry is often most useful when supplemented by other experimental methods that characterize fluid structure and flow-induced structural changes. Some of the most useful methods are microscopy, light, x-ray, and neutron scattering, and polarimetry. 

At low concentration of the second polymer, blends have dispersed-phase morphology of a matrix and dispersed second phase. As the concentration increases, at the percolation threshold volume fraction of the dispersed pase, ([) = 0.16, the blends structure changes into co-continuous. Full co-continuity is achieved at the phase inversion concentration, ( ). The morphology as well as the level of stress leads to different viscosity-composition dependencies (for more details see Chapter 7. The Rheology of Polymer Alloys and Blends ). 

Time-dependent rheological properties reflect the nature of a system s structure and can be due to viscoelasticity, structural changes, or both (Cheng and Evans, 1965 Harris, 1972). Structure breakdown can result in a decrease in the viscosity of a substance. It occurs in emulsions, suspensions, and sols. The characterization of the time-dependent flow properties of food systems is important for process design and control, for product devel-... 

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