Equilibration time, viscoelastic

The Equilibration Time in Viscoelastic Systems. When working with viscoelastic detergent systems we should be aware that the systems may need rather long times to reach equilibrium. The time can be of the order of days, sometimes longer. In order to obtain reproducible... 

The dynamic properties for the reptation model just described are obtained by solving the equations 71,72,73,74 and the linear viscoelastic properties are solved from the relationship between the stress and the chain orientation function (63). Without going into detail, the results for times longer than the tube equilibration time but shorter than the reptation time are... 

Various techniques have been developed to measure surface and interfacial tensions of liquids and melts and an early extensive discussion was presented by Padday [118]. In principle, aU the standard techniques can be used to measure the surface and/or interfacial tension of polymer liquids and melts however, due to the high viscosity and viscoelastic character of the polymers, only a few methods are suitable. In general, equilibrium static techniques seem completely satisfactory. Due to the high equilibration times involved with polymeric materials, it has not been possible to demonstrate that pull, detachment, or bubble pressure measurements can always be made slowly enough to yield accurate results with highly viscous liquids. Extensive reviews on the suitability of the various methods applied to polymeric systems have been given by Frisch et al. [119], Wu [10, 120], Koberstein [121], Anastasiadis [122], Xing et al. [123], and Demarquette [124]. 

This quantity has many uses. For example, to is approximately the time required for final equilibration of flow-induced stress in the liquid. As shown below, to also locates the onset of nonlinear viscoelastic response in steady-shear flows. 

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