In–line Ultrasonic Melt Flow Measurement of Polypropylene with Different Fillers

Pulsed Wave Velocimetry (PWV) is an ultrasonic technique for measuring velocity profiles in flowing liquids. We already demonstrated that PWV can be used to obtain velocity profiles of polypropylene melt, flowing in capillary dies with channel depths less than 2 mm. The required ultrasound transducer with large bandwidth (which is restricted to operating temperatures below 50 °C) is coupled to the hot melt using a temperature buffer, which serves as acoustic waveguide, but decouples transducer and melt thermally. In this contribution, we show results obtained in-line during the extrusion of glass-fiber-filled polypropylene as well as talcum-filled polypropylene at various feed rates.