From melts mass distribution

Polymers in solution or as melts exhibit a shear rate dependent viscosity above a critical shear rate, ycrit. The region in which the viscosity is a decreasing function of shear rate is called the non-Newtonian or power-law region. As the concentration increases, for constant molar mass, the value of ycrit is shifted to lower shear rates. Below ycrit the solution viscosity is independent of shear rate and is called the zero-shear viscosity, q0. Flow curves (plots of log q vs. log y) for a very high molar mass polystyrene in toluene at various concentrations are presented in Fig. 9. The transition from the shear-rate independent to the shear-rate dependent viscosity occurs over a relatively small region due to the narrow molar mass distribution of the PS sample. 

Figure 10 J Compositional effects of melt on olivine/liquid mass distribution of Mn +. Reprinted from E. B. Watson, Geochimica et Cosmochimica Acta, 41, 1363-1374, copyright 1977, with kind permission from Elsevier Science Ltd., The Boulevard, Langford Lane, Kidlington 0X5 1GB, UK.

However all the samples heated in the presence of US-Y catalyst (polymer-to-catalyst mass ratio 2 1) showed a deviation from the original polymer molar mass distribution in the region of lower molar masses. In the first experiment, the polymer/US-Y-zeolite sample was exposed at a temperature of 378 K, which is below its melting point, for 120 min and then for 30 min at 418 K. No volatile products were initially observed, but traces of isobutane and isopentane were detected when the temperature was raised to 418 K. Although these conditions were much milder than in the equivalent experiment with pure polymer (curve number 2), the molar mass distribution, curve number 5 in Figure 7.5, was different from that of the original polymer. 

A special form of application results when gases are absorbed by the molten mass (enter into solution) or are stirred into the melt (mechanical distribution). The material expands and foams after exiting from the nozzle. The densities are reduced by about 100% compared to the compact adhesives. This type of adhesive application... 

Conti and Sorti [57] studied the relationship between molecular mass distribution and melt flow characteristics of poly (e-caprolactam). Samples of nylon-6 with different molecular masses and distributions were synthesized in order to check the predictions of flow theories. SEC was carried out in m-cresol at 112°C. Narrow-MMD polystyrenes were used for calibration. and were calculated from the chromatograms after correcting for skewness and... 

It should be noted that many of the parameters available from IFCI calculations are difficult to observe experimentally for instance, the actual water/melt mass ratio in the mixture region requires determination of the spatial distribution of the three-phase system. Another example is the calculation of a steam chimney forming in the mixture region, which has not been observed directly in experiments, although its presence has been suggested. It appears important to somehow measure the spatial variation of the three-phase mixture experimentally, both to verify the calculational results and to accurately determine the characteristics of the actual mixture region. 

It is well known that the linear viscoelastic properties of polymer melts and concentrated solutions are strong function of molecular structure, average molecular mass and molecular mass distribution (MWD). The relaxation time spectrum is a characteristic quantity describing the viscoelastic properties of polymer melts. Given this spectrum, it is easy to determine a series of rheological parameters. The relaxation time spectrum is not directly accessible by experiments. It is only possible to obtain the spectrum from noisy data. 

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