Viscoelastic properties components

In a fundamental sense, the miscibility, adhesion, interfacial energies, and morphology developed are all thermodynamically interrelated in a complex way to the interaction forces between the polymers. Miscibility of a polymer blend containing two polymers depends on the mutual solubility of the polymeric components. The blend is termed compatible when the solubility parameter of the two components are close to each other and show a single-phase transition temperature. However, most polymer pairs tend to be immiscible due to differences in their viscoelastic properties, surface-tensions, and intermolecular interactions. According to the terminology, the polymer pairs are incompatible and show separate glass transitions. For many purposes, miscibility in polymer blends is neither required nor de-... 

In the molten state polymers are viscoelastic that is they exhibit properties that are a combination of viscous and elastic components. The viscoelastic properties of molten polymers are non-Newtonian, i.e., their measured properties change as a function of the rate at which they are probed. (We discussed the non-Newtonian behavior of molten polymers in Chapter 6.) Thus, if we wait long enough, a lump of molten polyethylene will spread out under its own weight, i.e., it behaves as a viscous liquid under conditions of slow flow. However, if we take the same lump of molten polymer and throw it against a solid surface it will bounce, i.e., it behaves as an elastic solid under conditions of high speed deformation. As a molten polymer cools, the thermal agitation of its molecules decreases, which reduces its free volume. The net result is an increase in its viscosity, while the elastic component of its behavior becomes more prominent. At some temperature it ceases to behave primarily as a viscous liquid and takes on the properties of a rubbery amorphous solid. There is no well defined demarcation between a polymer in its molten and rubbery amorphous states. 

The SAS data files that wera created as a results of the operations noted earlier have the important property that all three viscoelatic properties have either been measured or interpolated to the same temperature. Therefore one can merge data sets for different polymers by temperature (a SAS data set manipulation) and then perform blend calculations on the data quite simply in SAS. For example, one can calculate the expected viscoelastic properties of a blend from the pure components and their volume fraction using the equations of Uemura and Takaynagi (8). 

This customized function also circumvents the intractability problem pertinent to (19). Unlike the area function discussed previously to relate the physical properties of carbon black to the overall viscoelastic properties of the composite [229], the function introduced here is unique because it is a dimensionless quantity. Thus, it represents the property better and is devoid of any significant bias arising out of the differences in magnitudes of the constituting components. 

Prest,W.M., Jr., Porter,R.S. The effect of high-molecular-weight components on the viscoelastic properties of polystyrene. Polymer J. (Japan) 4,154-162 (1973). 

The results of measurements of the dependencies G (w,t) for three circular frequencies w0 = 27tf0, wi= 4rcwo, and w2 = 16jtwo are shown in Fig. 3.1. The lack of coincidence in the shapes of die time dependencies of the dynamic modulus components for different frequencies is obvious. This phenomenon is especially true for G", because the position of the maximum differs substantially along the time axis. In the most general sense, this reflects the contributions of the main relaxation mechanisms of the material to its measured viscoelastic properties. 

Jenkinson IR (1993) Bulk-phase viscoelastic properties of seawater. Oceanol Acta, 16 317-334 Jenkinson IR, Biddanda BA (1995) Bulk-phase viscoelastic properties of seawater relationship with plankton components. J Plankton Res 17 2251-2274 Jenkinson IR, Wyatt T, Malej T (1998) How viscoelastic effects of colloidal biopolymers modify rheological properties of seawater. In Emri I, Cvelbar R (eds) Proceedings of the 5th European Rheology Conference, Portoroz, Slovenia, September 6-11, 1998, Progress and Trends in Rheology 5 57-58... 

Gliadin. Gliadin is that portion of the gluten proteins that is soluble in 70% aqueous ethanol. It comprises approximately 35 to 40% of the flour proteins. Gliadin imparts the viscous component to the viscoelastic properties of gluten. 

The variation of wood with chemical modification should be caused by the number and nature of introduced side chains because the treatment is an introduction of new side chains into wood substance. Thus, on the basis of viscoelastic properties, the effects of both factors on the mobility of wood components molecules are examined. 

The low shear rheology measurements also show a rapid increase in the viscoelastic properties (modulus and zero shear viscosity) with increase of bentonite concentration above the gel point (> 30 g dm bentonite). Several models have been proposed to account for the elastic properties of concentrated dispersions, of which that originally proposed by van den Tempel (25) and later developed by Papenhuizen (26) seems to be the most appropriate for the present system. According to this model, if the interaction energy minimum between adjacent particles is sufficiently negative, a three-dimensional network structure may ensue, giving an elastic component. Various models can be used to represent the three dimensional structure, the simplest of which would be either an ideal network where all particles are... 

The attenuation and velocity of acoustic energy in polymers are very different from those in other materials due to their unique viscoelastic properties. The use of ultrasonic techniques, such as acoustic spectroscopy, for the characterization of polymers has been demonstrated [47,48]. For AW devices, the propagation of an acoustic wave in a substrate causes an oscillating displacement of particles on the substrate surface. For a medium in intimate contact with the substrate, the horizontal component of this motion produces a shearing force. In such cases, there can be sufficient interaction between the acoustic wave and the adjacent medium to perturb the properties of the wave. For polymeric materials, attenuation and velocity of the acoustic wave will be affected by changes in the viscoelastic behavior of the polymer. 

Blend morphology commonly depends on the weight fraction and viscoelastic properties of each component, the interfacial tension between components, the shape and sizes of the discontinuous phase, and the fabrication conditions and setup. Most rheological experiments applied to homogeneous melts can also be similarly applied to these immiscible blends [55,63,88,89]. The viscoelastic properties arising from these studies should be labeled with a subscript apparent since the equations used to translate rheometer transducer responses to properties incorrectly assume that the material is homogeneous. Nevertheless, these apparent properties are often found to be excellent metrics of fabrication performance. 

Jenkinson, I. R., andBiddanda, B. A. (1995). Bulk-phase viscoelastic properties of seawater relationship with plankton components. J. Plankton Res. 17(12), 2251—2274. 

Kokini, J. L. and Plutchok, G. J. 1987. Viscoelastic properties of semisolid foods and their biopolymeric components. Food Technol. 41(3) 89-95. 

Cubic liquid crystalline systems have been described as clear, stiff gelsJ As such, they show shear thinning after an apparent yield stress has been exceeded. The viscoelastic properties are also typical for the gel character a broad linear viscoelastic range and a frequency-independent elastic component, which is considerably higher than the viscous component, are observed. ... 

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