Rheotens-Mastercurves and Drawability of Polymer Melts

M. H. WAGNER
Institut für KW1Ststo!.tJtech1Wlogfe
Untversitdt Stuitgart
D- 70 199 Stuttgart. Germany
and
V. SCHULZE Md A. GÖTI'FERT
Göttfert Werkstoff-Pnlftnaschinen GmbH
D- 74722 Buchen. Gemlany

In a Rheotens experiment. the tensile force needed for elongation of an extruded filament Is measured as a functlon of the draw ratio. For thermo-rheologically simple polymer melts. the existence ofRheotens-mastercurves is proven. Rheotens mastercurves are invariant with respect to changes in melt temperature. Also. for polymer melts with different average molar masses. but similar molar mass distribution and branching structure. Rheotens-mastercurves are invariant to changes in the average molar mass. It is shown. by testing Several polyethylenes with different molar mass distribution and different long-chain branching. that Rheotens-mastercurves allow a direct and quantitative assessment of the drawability of polymer melts under actual processing conditions. i.e. under the action of a constant tensile force and including the effects of the rheological prehistory in the extrusion die.