Polymer rheology master curve

The rheological properties and associated melt-processing characteristics of ethylene-co-styrene polymers, including solid-state DMS, melt strength, and pressure-volume-temperature (PVT) data, have been reported by Kaijala and coworkers (59,60). Rheological master curves were generated via time-temperature... 

Figure 5.13. (a) Rheological master curves of selected commercially available polymers which approach each other at 300 rad/s and 500 Pa.s, and (b) degree of dispersion derived from LM for composites with 1 vol% MWCNTs (prepared at the same shear level) plotted versus the effective Hamaker constant... 

We have seen in the previous sections that viscoelastic scaling, employing the scaling factor ac, produces master viscosity curves for polymer-gas solutions that are identical to the master curve for the pure polymer. This means that the effect of dissolved gas on the rheology of polymer melts can be described entirely by the variation of ac with gas content. We have not, of course, demonstrated that all polymer-gas systems follow this scaling beha-... 

If this question can be answered in the affirmative, then dimensionless relationships where Q is used as the key parameter for the MMD (e.g. in rheological master graphs) will have a general validity. If not - one can hardly expect any generally valid set of master curves (e.g. viscosity versus shear rate) even for one polymer ... 

Dynamic melt rheology studies were carried out on PE/EMA and PE/EMA-salt in order to better understand the role of EMA-salt as a compatibilizer in the PE/EMA/PA system. The tlme-ten jerature superposition principle was applicable in all cases for G. Also, G super master curves were constructed for blends of PE/EMA and PE/EMA-salt when the EHA and EMA-salt are derived from the same parent polymer. Superposition of G" was possible for all blends containing EMA in the free acid form, but not for those in the salt form, with the extent of deviation from superposability being a function of EMA-salt concentration. 

Lohr, J.J., Yield Stress Master Curves for Various Polymers below Their Glass Transition Temperatures , J. of Rheology, vol. 9, Issue 1, March... 

Further, in the case of nylon it has been shown [103] that the presence of metal halides, too, does not alter the shape and position of the master curve, as can be seen from Fig. 4.45. Metal halides cannot be termed as fillers or diluents because their effects are much more pronounced than those expected of fillers or diluents. In fact, they could be better described as reactive additives because of their capability of interacting with the active amide-group sites along the nylon chain. Thus, it is obvious that any changes that occur in the rheological characteristics of the polymer due to the addition of reactive or inert fillers/ diluents are implicitly reflected in the MFI value as well. 

The utility of the master curves presented in Chapters 4 and 5 is obvious in the sense that the individual curves for any grade of polymer at any temperature of interest can be merely readout and replotted by knowing the appropriate MFI value. However, the easier method is to use equations which fit the master curve and regenerate data by mere substitution of the MFI value. In order to do this, rheological models have been suggested in Chapter 6. 

Using a unification technique introduced and developed by the authors, rheological data on a very large number of polymers are concisely presented. None of the books currently available dealing with rheology of polymer melts has made use of the master curve approadi to present unified curves for each generic type of polymer hence, the treatment in this book represents a distinct departure from the standard mode of presentation. 

The fifth chapter upgrades the master rheogram in the low-shear-rate region where coalescence is impaired by differences in the molecular-weight distribution of the polymers. Further, extensions of the unification tedinique are discussed to establish the parameters for obtaining master curves for other rheological parameters such as normal stress difiference, complex viscosity, storage modulus, and extensional viscosity. 

The General Rheological Model [87] was basically developed for master curves of viscosity versus shear rate for polymer melts using the melt-flow index (MFI) as a normalizing parameter. It can be written in a general form applicable to any viscosity versus shear rate curve of a polymer melt simply by putting MFI as unity to give... 

The presented command sequences in Chapter 7 for developing the spreadsheet program are given only for viscosity versus shear rate curves. The step-by-step procedure is very simple and needs to be extended for other rheological parameters once master curves are established for a long list of polymers. 

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