Representation of polymer mixing status during extrusion based on the model of ultrasonic reflection at screw

In the process of ultrasonic in-line monitoring the polymer mixing status, the screw structure has significant impacts on the ultrasonic echoes. The standard deviation of normalised ultrasonic attenuation coefficient is got by using correction methods based on the model of ultrasonic reflection at screw, which can be used to determine the status of polymer compounding. The model of ultrasonic reflection at screw, which is composed of the model of screw structure and the model of reflection attenuation ratio coefficient, is established by using the ultrasonic propagation time and amplitude for monitoring the pure polymer. Then the model is used to remove the impacts of the screw structure during polymer extrusion. The normalised ultrasonic attenuation coefficient is regarded as the characteristic, to determine the polymer mixing status. The results show that this method is effective and stable for monitoring the inline mixing processes of LDPE/CaCO3 and LDPE/BaSO4 compounds in the single screw extruder.