Development of a Rheology Die and Flow Characterization of Gas-Containing Polymer Melts
Sprache des Titels:
Deutsch
Original Kurzfassung:
We present a novel measurement die for characterizing the flow behavior of gas-containing
polymer melts. The die is mounted directly on the injection-molding cylinder in place of the mold
cavity and thus enables near-process measurement of viscosity (i.e., under the conditions that
would be present were a mold attached). This integration also resolves the issue of keeping gascontaining
polymer melts under pressure during measurement to prevent desorption. After thermal
characterization of the die, various correction approaches were compared against each other to
identify the most suitable one for our case. We conducted measurements using polypropylene in
combination with two different chemical blowing agents. Increasing the blowing-agent content to up
to 6% revealed an interestingly low influence of gases on melt viscosity, which was confirmed by
elongational viscosity measurements. For verification, we compared our results to corresponding
measurements taken on a high-pressure capillary rheometer and found that they were in excellent
agreement. Our die cannot only be used for rheological characterization. Combined with ultrasound
sensors, it provides an innovative way of measuring the volumetric flow rate. This development
represents an important step in improving the sustainability of gas-containing polymer processing.