Rheology master curve

Figure 26.6 Melt rheology master curve for ES20 and ES60 at various melt indices (Ml)...

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... 

Fig. 10. Rheological master curve of PI-3(reference temperature Tr =230 K) of the real imaginary parts of the shear modulus.

The rate at which the transition from cohesive to interfacial failure occurs is strongly correlated with the frequency at which the transition from rubbery to flow behavior occurs in the linear viscoelastic properties. The second transition from smooth to unsteady peel is related to the frequency at which the transition from rubbery to glassy behavior occurs in the viscoelastic properties. More quantitative connections between the rheological master curves and the peel master curves will be explored in Section 5. 

The first line of the description within each quadrant indicates the regions of the rheological master curve within which the debonding and bonding frequencies fall, respectively. 

Correlation between peel master curves and rheological master curves... 

Finally we compare the temperature dependencies reported for the structural relaxation and the self-motion of hydrogens studied by NSE. For PI, the shift factors used for the construction of the master curve on Q,T) (Fig. 4.17) are identical to those observed for the structural relaxation time [8]. This temperature dependence also agrees with DS and rheological studies. The case of PIB is more complex [ 147]. The shift factors obtained from the study of Teif(Q>T) (Fig. 4.14b) reveal an apparent activation energy close to that reported from NMR results (-0.4 eV) [136]. This temperature dependence is substantially weaker than that observed for the structural relaxation time (=0.7 eV, coinciding with rheological measurements) in the same temperature range (see Fig. 4.20). 

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 ... 

A master curve of the rheological conditions applicable during spreading of lipophilic preparations with force on the skin using a method similar to that of Wood (1968) showed that the range of acceptable apparent viscosity was about 3.9 poise to 11.8 poise, with an optimum value of approximately 7.8 poise (Barry and Grace, 1972). The preferred region was approximately bounded by shear rates 400-700 s and shear stress 2,000-7,000 dyne cm (200-700 Pa, respectively). 

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. 

The principle of time-temperature superposition is that there is a temperature-shift factor that allows all data to be plotted on a master curve. This presupposes that there is no change in mechanism during the reaction, so that Equation (3.8) applies (Prime, 1997b). Such superposition processes are regularly used in rheology and the WLF equation is routinely applied when the system is above temperature Tg. When the system is controlled by... 

The effect of overall molecular weight or the number of blocks on rheological properties for the samples from the second fractionation can be illustrated as a plot of reduced viscosity vs. a function proportional to the principal molecular relaxation time (Figure 2). This function includes the variables of zero shear viscosity, shear rate, y, and absolute temperature, T, in addition to molecular weight, and allows the data to be expressed as a single master curve (10). All but one of the fractions from the copolymer containing 50% polystyrene fall on this... 

Our method, then, provides a rheological criterion for measuring the effect of a graft copolymer on a continuous matrix. As was discussed above, the master curves relative to a reference temperature and rubber content ... 

Over the years, dynamic testing has become the preferred method of testing the rheological behavior of the multiphase systems. For example, Nishi et al. [1981] carried out careful studies on the dynamic behavior of PS/PVME. The specimens were cast at temperatures either below or above the lower critical solution temperature, LCST = 95°C. While those prepared at T < LCST (single-phase system) showed superposition of dynamic data onto a master curve, the ones that were cast at T > LCST did not. 

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