Viscosity transient elongational

The inclusion of internal viscosity raises considerably the free-energy storage capacity of a rapidly deforming macromolecule as compared to the idealized Hookean spring model and could play a decisive role in mechanochemical reactivity in transient elongational flow. 

It is expected, however, that the Gaussian representation is inadequate in transient elongational flow, even if the chain is only weakly deformed. During a fast deformation, the presence of non-equilibrium effects, like internal viscosity , noncrossability and self-entanglements will stiffen the molecular coil which is now capable of storing a much larger amount of elastic energy than that predicted from Eq. (113). 

Laun HM and Schuch H (1989) Transient elongation viscosities and drawability of polymer melts. J Rheol 33 119-75. 

Figure 9 shows the predictions of the Wagner model compared to experimental data for transient elongational viscosity of LD. These have been calculated according to ... 

Nguyen TQ, Kausch HH (1990) Effects of solvent viscosity on polystyrene degradation in transient elongational flow. Macromolecules 23 5137-5145... 

Micic, R, S. N. Bhattacharya, and G. Field. 1998. Transient elongational viscosity of LLDPE/LDPE blends and its relevance to bubble stability in the film blowing process. Polymer Engineering and Science 38 1685-1693. 

This represents the solid lines in Fig. 1, which shows data for three concentrations (500, 250 and 100 wppm) each of the fresh and shear degraded solutions. The parameters that govern the viscosity function in (11) also strongly influence other predicted response functions such as normal stress behavior, elongational viscosity, transient response, etc. 

Laun, H. M., and Schuch, H. (1989) Transient elongational viscosities and drawability... 

Nanophase separation of block copolymer melts introduces interesting rheological behavior. For example, the transient elongational viscosity behavior of a triblock copolymer of styrene and olefins was found to be strongly dependent on the initial orientation of the cylindrical domains [103]. 

Traditionally, tack properties of a PSA have been correlated to their linear rheological behavior, such as elastic and loss modulus [1-3]. While this type of phenomenological analysis provides many clues for the practical design of PSA, it is intrinsically limited by the fact that a tack experiment involves large strains and transient behaviors of the PSA, which cannot be easily predicted by either viscosity (shear, elongational) or any other small strain steady-state dynamical property. The simple observation of the debonding of a PSA tape from a solid... 

Laun, H. M. 1989. Transient Elongational Viscosities and Drawa-biUty of Polymer Melts. J. RheoL, 33(1), 119. 

Fig 5. Elongational viscosity transients of PP-g-MA/ Nanocor F30P composite atlSOC. 

It shoiild be noted that this is the exact derivation of equation (3). These models are usually referred to quasi-linear models and display qualitatively correct predictions of typical phenomena of elongational flows such as the occurrence of the strain-hardening effect in transient extension. Nevertheless the predicted elongational viscosity is never boimded in the long time range and a steady state value can only be expected for small elongation rates. Moreover, the shear behaviour remains unrealistic as compared to the experiment, especially because of constant predicted viscosity and first normal... 

This chapter is devoted to the molecular rheology of transient networks made up of associating polymers in which the network junctions break and recombine. After an introduction to theoretical description of the model networks, the linear response of the network to oscillatory deformations is studied in detail. The analysis is then developed to the nonlinear regime. Stationary nonhnear viscosity, and first and second normal stresses, are calculated and compared with the experiments. The criterion for thickening and thinning of the flows is presented in terms of the molecular parameters. Transient flows such as nonhnear relaxation, start-up flow, etc., are studied within the same theoretical framework. Macroscopic properties such as strain hardening and stress overshoot are related to the tension-elongation curve of the constituent network polymers. 

The limiting value for vanishing e is exactly three times as large as the shear viscosity (9.73) T]o in the Umit of small shear rate im) = 3> o- Hence, Trouton s rule, ix = iri, which is known to hold at any elongational rate for Newtonian fluids, holds for our transient network with arbitrary P(r) in the limit of small strain rate. 

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