Extensional rheology of polypropylene melts from the Rheotens test

In recent years the Rheotens melt strength test has emerged as one of the most important tools for comparing the drawability of polymer melts. This paper examined whether a reliable set of test conditions could be obtained to determine a true and accurate melt strength of a polymer. The influence of various extrusion and drawing parameters on the extensional theological performance of two polypropylenes are discussed. Using this knowledge an attempt was made to estimate the transient extensional viscosity from the Rheotens test. An analytical Wagner model in the linear region of the Rheotens test was used for the first time to calculate the transient extensional viscosity from the Rheotens test. These results were compared to the transient extensional viscosity obtained from a constant strain rate Rheometrics melt extensional rheometer (RME). The results agree within measurement accuracy with those measured from an RME. Consequently, the viscosity determined from the Rheotens experiment can be used to estimate transient extensional viscosity. The influence of different Rheotens test conditions on transient extensional viscosity are also discussed. (C) 2001 Elsevier Science B.V. All rights reserved.