Assessment of LDPE Melt Strength by Use of Rheotens Mastercurves
-
A. Bernnat
Abstract
In a Rheotens test, the tensile force needed for elongation of an extruded filament is measured as a function of the draw ratio. In this way, the melt strength can be assessed, which is an important property in many polymer processes like fibre spinning, film blowing, and blow moulding. Several LDPE grades with different melt index and polymerised by both tubular and autoclave reactor technology were investigated. It is demonstrated that to assess melt strength, Rheotens tests have to be compared at constant extrusion pressure, while comparison at constant mass flow rate can be highly misleading. At constant extrusion pressure, Rheotens curves are invariant not only with respect to temperature but also with respect to average molar mass, and polymer grades with similar branching structure and molar mass distribution fall onto a common mastercurve. Two distinct and different Rheotens mastercurves were found for grades produced by tubular versus autoclave reactor technology, indicating distinct differences in the branching structure. Irrespective of the processing conditions, all LDPE melts investigated fail by brittle fracture, and a true rupture stress in the range of 1 to 2 MPa was found.
© 2000, Carl Hanser Verlag, Munich
Articles in the same Issue
- Editorial
- Third of a Series: Pioneering Polymer Industry Developments — The First Successful Mathematical-Computer Modeling of A Complex Industrial Process: Toyobo and Melt Spinning
- Screw Extrusion / Mixing
- Polymer Flow Velocity in the Helical Channel in Dependence of a Coordinate System
- Non-Isothermal Transient Startup of A Starved Flow Modular Co-Rotating Twin Screw Extruder
- Numerical Simulations and Experiments in a Double-Couette Flow Geometry
- Dynamic Analysis of Melting in Injection Extruder
- Extrusion Die
- Production of Pipe with Uniform Wall Thickness: How to Compensate for Gravity Sag
- Fiber and Film
- Assessment of LDPE Melt Strength by Use of Rheotens Mastercurves
- Molding
- Analysis of Flow and Heat Transfer in Liquid Composite Molding
- Solidification Criterion on Shrinkage Predictions for Semi-crystalline Injection Moulded Samples
- Polymer Melt Rheology at High Shear Rates
- Factors Affecting the Stability of Gas Penetration in Gas Assist Injection Molded Bifurcation Parts
- Transient Polymer Flow Rate in Injection Mold Filling
- Flow Analysis of Injection-Press Molding Process
- Properties of Injection Molded In Situ Composites Based on PPS and a Melt Processable Glass
- A New Approach in Offline-Optimization of the Injection Molding Process
Articles in the same Issue
- Editorial
- Third of a Series: Pioneering Polymer Industry Developments — The First Successful Mathematical-Computer Modeling of A Complex Industrial Process: Toyobo and Melt Spinning
- Screw Extrusion / Mixing
- Polymer Flow Velocity in the Helical Channel in Dependence of a Coordinate System
- Non-Isothermal Transient Startup of A Starved Flow Modular Co-Rotating Twin Screw Extruder
- Numerical Simulations and Experiments in a Double-Couette Flow Geometry
- Dynamic Analysis of Melting in Injection Extruder
- Extrusion Die
- Production of Pipe with Uniform Wall Thickness: How to Compensate for Gravity Sag
- Fiber and Film
- Assessment of LDPE Melt Strength by Use of Rheotens Mastercurves
- Molding
- Analysis of Flow and Heat Transfer in Liquid Composite Molding
- Solidification Criterion on Shrinkage Predictions for Semi-crystalline Injection Moulded Samples
- Polymer Melt Rheology at High Shear Rates
- Factors Affecting the Stability of Gas Penetration in Gas Assist Injection Molded Bifurcation Parts
- Transient Polymer Flow Rate in Injection Mold Filling
- Flow Analysis of Injection-Press Molding Process
- Properties of Injection Molded In Situ Composites Based on PPS and a Melt Processable Glass
- A New Approach in Offline-Optimization of the Injection Molding Process
