Improved Spinnability of Metallocene Polyethylenes by Using Processing Aids
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R. Vogel
Abstract
Melt spinning is a polymer processing technique that is strongly influenced by the extensional flow behaviour of polymer melts. Therefore only a few polymeric materials are usable for this kind of processing with sufficient take-up speeds. When approaching critical conditions of deformation most polymers show either fibre break in the molten state either by a brittle cohesive rupture or a ductile failure. During the melt spinning of pure and modified metallocene poylethylenes additional flow instabilities occur within the spinning die. Namely, wall slip, ‘sharkskin’ and pressure oscillations (gross fracture) may be obtained dependending on the volume flow rate. Pressure oscillations lead to diameter oscillations of the melt extrudate, which create local increase of tensile stress in the spin line. This effect immediately causes fiber break in the spinline.
Therefore, melt spinning of polyethylenes was only possible up to a critical molecular weight or its relating melt viscosity. The limitation of the molecular weight restricts the mechanical properties of the melt spun fibres. This paper reports on an attempt to find out appropriate processing aids for suppressing ‘sharkskin’ effects and pressure oscillations in an attempt to overcome the limitation of a critical molecular weight. At first, the critical conditions for the onset of flow instabilities for higher molecular weight polymers were analysed. Further experiments concerned with the use of processing aids for melt spinning of metallocene polyethylenes of higher molecular weights. A combination of boron nitride powder and a fluoroelastomer was found to be an effective processing aid for this process.
© 2003, Carl Hanser Verlag, Munich
Articles in the same Issue
- Contents
- Contents
- Editorial
- Polymorphic and Crystal Structures from Crystallization in Polymer Processing
- Compounding/Screw Extrusion
- Flow Properties and Morphology of PC/LCP Blends Affected by the Addition of Glass Fiber and Resulted Mutual Influences
- Modeling Filler Dispersion along a Twin-Screw Extruder
- Characterisation of Finite Length Composites
- Single Screw Extrusion of Natural Fibre Reinforced Thermoplastics (NFRTP)
- Fiber and Film
- A New Method to Determine the Filament Force Tension within the Fibre Formation Zone
- Diameter Profile Measurements for CO2 Laser Heated Drawing Process of PET Fiber
- Stress Induced Crystallization in Elongational Flow
- Improved Spinnability of Metallocene Polyethylenes by Using Processing Aids
- Melt Spinning of Reactive Extruded and/or Blended Polymer Fibers by Means of an Online Coupled Twin Screw Extruder
- Cast Film Problem: A Non Isothermal Investigation
- Rotational Molding
- Effect of Processing History on the Sintering of Ethylene Copolymers
- Injection Molding
- Five Geometric Principles for Injection Molding
- Modelling of Residual Stresses and Warpage in Sandwich Injection Moulding
Articles in the same Issue
- Contents
- Contents
- Editorial
- Polymorphic and Crystal Structures from Crystallization in Polymer Processing
- Compounding/Screw Extrusion
- Flow Properties and Morphology of PC/LCP Blends Affected by the Addition of Glass Fiber and Resulted Mutual Influences
- Modeling Filler Dispersion along a Twin-Screw Extruder
- Characterisation of Finite Length Composites
- Single Screw Extrusion of Natural Fibre Reinforced Thermoplastics (NFRTP)
- Fiber and Film
- A New Method to Determine the Filament Force Tension within the Fibre Formation Zone
- Diameter Profile Measurements for CO2 Laser Heated Drawing Process of PET Fiber
- Stress Induced Crystallization in Elongational Flow
- Improved Spinnability of Metallocene Polyethylenes by Using Processing Aids
- Melt Spinning of Reactive Extruded and/or Blended Polymer Fibers by Means of an Online Coupled Twin Screw Extruder
- Cast Film Problem: A Non Isothermal Investigation
- Rotational Molding
- Effect of Processing History on the Sintering of Ethylene Copolymers
- Injection Molding
- Five Geometric Principles for Injection Molding
- Modelling of Residual Stresses and Warpage in Sandwich Injection Moulding
