On the Limitations of Shear Induced Crystallization in Polypropylene Melts
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S. Liedauer
Abstract
Recently, the mechanism of shear induced crystallization in melts of isotactic industrial polypropylene has been unravelled for sufficiently high rates of shear [1]. This was achieved with the aid of, what we called, short term shearing. This shearing was applied in a rectangular duct of large aspect ratio. The development of crystallization subsequent to this short term shearing was monitored with the aid of the growing optical retardation. Other traits of this process could be deduced from the cross-sections of the samples extracted from the duct after complete solidification. Mainly one of these traits is the subject of the present paper. As with injection molding, highly oriented areas are found in the cross-sections. The laws governing the limitations of these areas are discussed. In other words, the dependence of the thickness of the layers on the previous shear rate and shearing time is described with the aid of a model containing the relaxation times of threadlike (liquid) precursors. These relaxation times are assumed to depend on the size of the precursors: The larger these precursors have grown the more stable they are assumed. Nucleation and growth are considered as statistical processes.
© 1995, Carl Hanser Verlag, Munich
Artikel in diesem Heft
- Contents
- Contents
- Editorial
- Fifteenth in a Series: Ikegai Corporation: From Engine Lathes to Twin Screw Extruders
- Die Extrusion
- Analysis of Polymer Flow through Coathanger Melt Distributors
- Viscosity and the Formation of Die Drool at the Polymer-Metal Interfaces
- Flow Implications in the Processing of Tetrafluoroethylene/Hexafluoropropylene Copolymers
- Reactive Processing
- Thermal/Peroxide Induced Degradation and Maleation of Polypropylene by Reactive Extrusion
- Fibers and Films
- Biaxially Oriented Polyethylene Films by Compression of Injection Moldings
- Tubular Film Blowing
- Tubular Film Blowing
- Molding
- Elastic Calculation of Residual Stresses in Injection Molding
- On the Limitations of Shear Induced Crystallization in Polypropylene Melts
- Structure and Properties of Injection Moldings of β-Crystal Nucleator-Added Polypropylene
- Study on the Performance of Cooling Systems in Precision Injection Molds
- Measurement of Planar Orientation of Fibers for Reinforced Thermoplastics Using Image Processing
- Welding
- Dynamics and Structure Development in Spin Welding of Polyvinylidene Fluoride Cylindrical Rods
Artikel in diesem Heft
- Contents
- Contents
- Editorial
- Fifteenth in a Series: Ikegai Corporation: From Engine Lathes to Twin Screw Extruders
- Die Extrusion
- Analysis of Polymer Flow through Coathanger Melt Distributors
- Viscosity and the Formation of Die Drool at the Polymer-Metal Interfaces
- Flow Implications in the Processing of Tetrafluoroethylene/Hexafluoropropylene Copolymers
- Reactive Processing
- Thermal/Peroxide Induced Degradation and Maleation of Polypropylene by Reactive Extrusion
- Fibers and Films
- Biaxially Oriented Polyethylene Films by Compression of Injection Moldings
- Tubular Film Blowing
- Tubular Film Blowing
- Molding
- Elastic Calculation of Residual Stresses in Injection Molding
- On the Limitations of Shear Induced Crystallization in Polypropylene Melts
- Structure and Properties of Injection Moldings of β-Crystal Nucleator-Added Polypropylene
- Study on the Performance of Cooling Systems in Precision Injection Molds
- Measurement of Planar Orientation of Fibers for Reinforced Thermoplastics Using Image Processing
- Welding
- Dynamics and Structure Development in Spin Welding of Polyvinylidene Fluoride Cylindrical Rods
