DYNAMIC RHEOLOGICAL

In order to reconciliate high-frequency dynamic rheological data with theory, Cerf proposed an additional internal viscosity term which should be mainly molecular weight independent [37] ... 

The effect of oxidative irradiation on mechanical properties on the foams of E-plastomers has been investigated. In this study, stress relaxation and dynamic rheological experiments are used to probe the effects of oxidative irradiation on the stmcture and final properties of these polymeric foams. Experiments conducted on irradiated E-plastomer (octene comonomer) foams of two different densities reveal significantly different behavior. Gamma irradiation of the lighter foam causes stmctural degradation due to chain scission reactions. This is manifested in faster stress-relaxation rates and lower values of elastic modulus and gel fraction in the irradiated samples. The incorporation of O2 into the polymer backbone, verified by IR analysis, conftrms the hypothesis of... 

Wang, W. and Zheng, Q. The Dynamic Rheological Behavior and Morphology of Nylon/Elastomers Blends, J. Mater. Set Lett. 40, 2005. 

Dynamic Rheological Properties of the Reconstituted Milks During the Coagulation Kinetics... 

Kinetics of Gelation Studied by Dynamic Rheological Measurements... 

The pulse mode experiments were conducted by placing the sample between the quartz plates and exposing it to 30 second bursts of UV radiation. Dynamic rheological tests were then applied to the sample and this process was repeated until the sample had passed its gel point and became highly cross-linked. 

For the continuous mode, we utilized a dynamic rheological technique, Fourier transform mechanical spectroscopy (FTMS) (77,75), which provided a powerful method for monitoring, simultaneously, the evolving dynamic moduli at several frequencies during the course of photo-cross-linking. In this technique, an oscillatory strain, y, was applied to the sample, such that... 

Dynamic rheological measurements have recently been used to accurately determine the gel point (79). Winter and Chambon (20) have determined that at the gel point, where a macromolecule spans the entire sample size, the elastic modulus (G ) and the viscous modulus (G") both exhibit the same power law dependence with respect to the frequency of oscillation. These expressions for the dynamic moduli at the gel point are as follows ... 

Activation Energy. The gel times, determined by dynamic rheological tests, can also be utilized to calculate an apparent activation energy. We can obtain the gel times over the temperature range of interest and if the extent of reaction at these temperatures are constant, an apparent activation energy can be determined. First, the polymerization reaction can be represented by a generalized kinetic expression of the type (24)... 

S. R. Raghavan, J. Hou, G.L. Baker, and S.A. Kahn Colloidal Interactions between Particles with Tethered Nonpolar Chains Dispersed in Polar Media Direct Correlation Between Dynamic Rheology and Interaction Parameters. Langmuir 16, 1066 (2000). 

Dynamic rheometers have been widely used to study the viscoelastic characteristics of liquid, solid, and semi-solid foods. However, to our knowledge, very few studies on the rheological characteristics of potato flesh using dynamic rheometry have been carried out. The dynamic rheological behavior of potato tubers may be helpful to have a quick idea about potato texture and... 

The viscoelastic properties of polypropylene melts containing magnesium hydroxide fire retardant fillers have been studied using parallel plate dynamic rheology [36]. In this work the filler variants differed in particle size, surface area and morphology, ranging from approximately spherical particles formed... 

The solid-like properties may be measured by non-destructive dynamic rheology analysis or by destructive methods using a Penetrometer, Jelly Tester, Instron instruments, or other types of texture analyzers. The latter methods are the most useful due to their simplicity and speed. Texture analysis of whippable emulsion must always be compared with the amount of air incorporated into the foam, which is known as percentage overrun and is calculated as follows ... 

Wu G, Asai S, Sumita M, Hattori T, Higuchi R, Washiyama J (2000) Estimation of flocculation structure in filled polymer composites by dynamic rheological measurements. Colloid Polym Sci 278 220-228... 

Fig. 3.1 Examples of simple, viscometric, shear-flow rheometer geometries, la, 2a and 3 are steady while lb and 2b are dynamic rheological property... 

The viscoelastic response of polymer melts, that is, Eq. 3.1-19 or 3.1-20, become nonlinear beyond a level of strain y0, specific to their macromolecular structure and the temperature used. Beyond this strain limit of linear viscoelastic response, if, if, and rj become functions of the applied strain. In other words, although the applied deformations are cyclic, large amplitudes take the macromolecular, coiled, and entangled structure far away from equilibrium. In the linear viscoelastic range, on the other hand, the frequency (and temperature) dependence of if, rf, and rj is indicative of the specific macromolecular structure, responding to only small perturbations away from equilibrium. Thus, these dynamic rheological properties, as well as the commonly used dynamic moduli... 

The linear viscoelastic models (LVE), which are widely used to describe the dynamic rheological response of polymer melts below the strain limit of the linear viscoelastic response of polymers. The results obtained are characteristic of and depend on the macromolecular structure. These are widely used as rheology-based structure characterization tools. 

In addition to the microstructural geometrical features described above, macroscopic, dynamical, rheological properties of the suspensions are derived by Brady and Bossis (1985). Dual calculations are again performed, respectively with and without DLVO-type forces. When such forces are present, an additional contribution (the so-called elastic stress) to the bulk stress tensor exists. In such circumstances, the term (Batchelor, 1977 Brady and Bossis, 1985)... 

Yoo, B. and Rao, M. A. 1996. Creep and dynamic rheological behavior of tomato concentrates effect of concentration and finisher screen size. J. Texture Stud. 27 451-459. 

---