Stress Induced Crystallization in Elongational Flow
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F. H. M. Swartjes
Abstract
Stress-induced crystallization is studied in an extensional flow device (a cross-slot flow cell) for an isotactic Polypropylene (iPP) by measuring the micro-structure that develops after flow. Birefringence and Wide Angle X-ray experiments were performed. The birefringence experiments with flow below the melting temperature showed the occurrence of a fiber-like structure around the outflow centerline and, later in time, of ‘streamlines’. The latter are explained by the influence of shear gradients close to the optical windows. The WAXS experiments also showed the fiber-like structure around the outflow centerline, having orientations in the (110), (040) and (130) reflections, with a width of about 80 μm. This dominance of the elongational flow around the stagnation line could not be observed in experiments with flow above and subsequent crystallization below the melting temperature.
Structure development in this cell was numerically predicted using the Leonov and the extended Pompom (XPP) model. The oriented structures can be predicted. Moreover, process conditions are found with less influence of the (unwanted) shear gradients. Finally, it was concluded that the strain hardening behavior in the Leonov model over-estimates the first component of the Finger tensor, and thus the number of flow-induced nuclei. Therefore it is recommended to use the extended Pompom model as a more realistic basis for a quantitative flow-induced crystallization model.
© 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
