Ultrasound Measurement of Two-Filler Concentrations in Polypropylene Compounds. Part 2: On-Line Calibration

An ultrasound system capable of measuring the concentration levels of two fillers, glass fibres and mica flakes, in polypropylene blends during extrusion compounding, has been successfully developed. The system is capable of operating under harsh conditions of the extruder settings while efficiently measuring the acoustic properties of the polymer melt. The attenuation and time-of-flight measurements of 1 MHz ultrasound waves propagating continuously through the polymer stream, prior to exiting the extrusion die, are used to characterise the morphology of the polymer blend and to determine the relative concentrations of blend additives. Prior work on the static calibration of the ultrasound set-up (Part 1) has been used to evaluate the real-time performance of the system. The ultrasound measurements showed a good match with the laboratory analysis.