Velocity profiles polymer flow studies

A quite different approach to rheo-NMR was taken by Xia and Callaghan [12], in an NMR microscopy measurement of the velocity profile of a high molecular weight polymer solution flowing through a capillary. In this study anomalous polymer diffusion was found at a radius within the pipe at which the local shear rate exceeded... 

Whipple s careful experimental study of the velocity profile in the region before and after the capillary exit is an initial step in answering some of these needs. He found that polymer melts anticipate the swelling phenomenon, in that, just before the exit, axial decelerations and radial velocity components are observed. Thus the exit velocity profile is not the same as in the fully developed region and the flow there is not viscometric.4... 

For viscous solutions, the assumptions of plug flow are not strictly valid. If the velocity profile is not flat, polymer solution near the tube wall will move more slowly than that near the center of the tube. Since the slow-moving polymer near the wall remains in the reactor longer, it will polymerize to a higher conversion (or extent of reaction) than the bulk material. This higher conversion will then compound the viscosity problem. Studies on the effect of this deviation from plug flow in tubular polymerization have to be carried out by Hamer and Ray [4,5]. 

The study of polymerization in a tubular reactor involves simultaneous consideration of the velocity profile, heat release and conduction, as well as the kinetics of the polymerization. This work was undertaken to determine the effect of this type of reactor upon the molecular weight distribution of the polymer produced. The system studied was the copolymerization of an elastomer from ethylene, propylene, and 1,4-hexadlene In solution using Ziegler catalysis. Laminar flow polymerization similar to previously described work involving polymerization of sytrene in tubular reactors (1, 2, was analyzed, but the numerical... 

One of the most interesting and fruitful approaches to the theoretical study of the non-isothermal flow of polymer melts has been suggested by Merzhanov and coworkers 82 84), which reduced the set of equations for the flow to the well-known equation of thermal explosion. The authors obtained the profiles of temperature and velocity for the case of stationary flow. However, the thermal explosion was founda5) to become feasible at too high velocities v lOm/s which could hardly be attained at low-pressure injection moulding of polymers. 

In the study, the mathematical model of the polymer melt flows in the extrusion process of plastic profile with metal insert was developed and the complex melt rheological behavior was simulated based on the finite element method. The melt flow characteristic in the flow channel was analyzed. The variation of the melt pressure, velocity, viscosity and stress versus different metal insert moving rate was investigated. Some suggestions on its practical manufacturing control were concluded based on the simulation results. 

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