RHEOTENS-MASTERCURVES AND DRAWABILITY OF POLYMER MELTS

In a Rheotens experiment, the tensile force needed for elongation of a n extruded filament is measured as a function of the draw ratio. For t hermo-theologically simple polymer melts, the existence of Rheotens-ma stercurves is proven. Rheotens-mastercurves are invariant with respect to changes in melt temperature. Also, for polymer melts with differen t average molar masses, but similar molar mass distribution and branch ing structure, Rheotens-mastercurves are invariant to changes in the a verage 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.