Real-time viscosity and density measurements of polymer melts using dielectric and ultrasound sensors fusion

Abstract

Ultrasound and dielectric measurements are used to measure the instantaneous density and viscosity of polymer melts during PVC extrusion process. The acoustic properties of the polymer melt, measured by a 2.25 MHz ultrasound transducer mounted on a special die adapter, are correlated to the melt density using pre-established theoretical models. In addition, a dielectric sensor, mounted on the opposite side of the die adapter, is used to measure the dielectric properties of the polymer melt, which are correlated to mechanical viscosity. The density and viscosity of the PVC melt were varied by varying the level of chemical blowing agent (AZO) and processing aid (K400) in the polymer compound. Strong correlations between the measured acoustic and dielectric parameters and the melt density and viscosity were found to be consistent with existing theoretical models.