On Flow Characteristics of Dense Solutions in Screw Extruders

Abstract

With regards to the extrusion theories about high polymer solution, the characteristics of high polymer solution in extruders has been generally treated as the non-Newtonian fluide.However, when the flow properties of polymer solution, viscosity and pressure distribution in extruder are known, it is possible to introduce the Newtonian theory to analyse the behavior of polymer flow. Then, in order to calculate the viscosities by the eq (5), the relation between the drag flow and pressure gradient in the extruder can be measured by means of closing the out-let (exit end) of extruder, and from the formula (7), the viscosity values of polymer solutions at thevarious screw rotations (various shear rates) may be calculated, whose results are as shown in Fig (9).These viscosity values and the pressure gradients measured by the experimental pressure gauge, shown in Fig (3), are introduced to the general metering screw, Fig (4 As the next step, in order to measure the structural viscosity index of high polymer, the rotary visco-meter was deviced and the structural viscosity index, (n=1.55) )was obtained.By using this structural viscosisy index (n=1.55), the extrusion out-put is calculated in the case of the general non-Newtonian theory (power law), and its results are shown in Fig (16