EXTRUDATE SWELL AND ISOTHERMAL MELT-SPINNING ANALYSIS OF LINEAR LOW-DENSITY POLYETHYLENE USING THE WAGNER CONSTITUTIVE EQUATION

The rheological behaviour of a linear low density polyethylene melt is studied using a wide range of techniques: shear and elongational stre ss growth at constant strain rate, steady shear flow, extrudate swell and isothermal melt spinning. The analysis of the behaviour is based o n the Wagner constitutive equation which appears to be suitable. Moreo ver, the extrudate swell and the isothermal spinning are simulated by taking into account. the past shear and elongation deformation in the reservoir, the contraction and the die of a capillary rheometer. For t his purpose, the Finger deformation tensor is evaluated using a Protea n coordinate system. This approach is shown to be very useful to rest the validity of the constitutive equation and to determine its charact eristic parameters. (C) 1997 Elsevier Science B.V.