Method of Processing Ultrasonic In-line Monitoring Signals in Polymer Mixing Extrusion to Determine Mixing State

The polymer mixing status along a screw channel has significant impacts the quality of the polymer extrusion process. The development of the techniques for monitoring the polymer mixing status is highly desirable for controlling polymer extrusion results. Therefore, we developed a system equipped with ultrasonic probes for fast data acquisition capability and carried out extrusion experiments on different polymers. Results show that the amplitude of the resulting ultrasonic signals is affected by the mixing status of the polymers; these results can be used to monitor the polymer mixing process along the extruder channel. In this study, we use both rank and low pass filtering to correct amplitude differences in acquired raw signals that arise due to the influence of temperature. We employ the correlation coefficient method to ensure that our comparison of the amplitudes of the acquired signals is reflected from the same screw position. Subsequently, we define signal fluctuation coefficients to investigate the polymer's mixing state. The results show that this method is highly effective for monitoring the inline mixing processes of polymers.