Figure 8. Effects of (a) feed rate and (b) screw rotational speed on the temperature of the kneading section. The screw rotational speed was set to 88 rpm to determine the effect of the feed rate. The feed rate was set to 1.0 kg/h to determine the effect of the screw rotational speed.
The effects of the feed rate and the screw rotational speed are shown in Figure 8. The simulation results showed a higher temperature than the experimental results. Their average discrepancy was 1.6 °C. The numerical simulation tended to be at a higher temperature because the temperature sensor was not immersed in the resin; it was located in the barrel at a distance of 1 mm from the resin. The experimental data involved the effect of heat resistance of the barrel so that the temperature of the simulation was higher than that in the experiment.
The resin distribution on the twin screws in the numerical simulation is compared with that from the experimental result. The experimental result was obtained by capturing an optical photograph when the TSE stopped, and the screws were pulled out from the barrel. As the resin used is polypropylene—a semi-crystalline polymer—the color of the area filled with the resin was white.
Figure 9 shows the optical photograph of the resin distribution and the contour plot of the numerical simulation result. The numerical simulation indicates that the resin exists on the pushing side of the full-flight screw and the kneading section. The trailing side of the full-flight screw is empty. The area where the resin exists in the experiment corresponds to that in the simulation. The resin distribution observed in the experiments and simulation agree well qualitatively.