Molecular Orientation in Polycarbonate Induced by Cooling Stresses
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R. Wimberger-Friedl
Abstract
The origin of the maximum of the birefringence at the surface of injection-molded polymer products is discussed. By systematic variation of the molding conditions with polycarbonate, it is shown that the maximum at the surface not only depends on the filling, but even more so on the packing conditions. The birefringence at the surface is equal in the flow direction and transverse to it. The height scales with the cavity pressure during compression and packing. This cannot be explained by stresses due to the classical fountain flow at the flow front. Instead, the dominating contribution comes from transient deviatoric stresses induced by the compression of the vitrifying polymer in combination with wall adhesion. The pressure-induced stress history in the vitrifying polymer leads to molecular orientation and residual stresses giving a birefringence maximum at the surface.
© 1996, Carl Hanser Verlag, Munich
Articles in the same Issue
- Contents
- Contents
- Editorial
- First in a Series: Pioneers of Polymer Processing: Thomas Hancock – The First Polymer Processing Innovator
- Mixing
- The Extensional Flow Mixer, EFM
- Reactive Extrusion
- Continuous Polymerization of Caprolactam-Polyether Sulfone Solutions in a Twin Screw Extruder to Form Reactive Polyamide–6/Polyether Sulfone Blends and Their Melt Spun Fibers
- Biodegradable Poly(Lactic Acid) with High Molecular Weight
- Acceleration of Chemical Reaction in Reactive Extrusion Accompained by Devolatilization
- Fibers and Films
- Viscous-Elastic Effects in a PA 6 Melt – Cause of Unevennesses in Melt-Spun Yarns**
- Gear Pump Performance in Polypropylene Filament Yarn Uniformity
- Molding
- Physically-Based Model of Thermoplastics Injection Molding for Control Applications
- Effect of Pressure and Shear Stress on Crystallization Behaviors in Injection Molding
- The Crystallinity of PVC and its Effect on Physical Properties**
- Molecular Orientation in Polycarbonate Induced by Cooling Stresses
Articles in the same Issue
- Contents
- Contents
- Editorial
- First in a Series: Pioneers of Polymer Processing: Thomas Hancock – The First Polymer Processing Innovator
- Mixing
- The Extensional Flow Mixer, EFM
- Reactive Extrusion
- Continuous Polymerization of Caprolactam-Polyether Sulfone Solutions in a Twin Screw Extruder to Form Reactive Polyamide–6/Polyether Sulfone Blends and Their Melt Spun Fibers
- Biodegradable Poly(Lactic Acid) with High Molecular Weight
- Acceleration of Chemical Reaction in Reactive Extrusion Accompained by Devolatilization
- Fibers and Films
- Viscous-Elastic Effects in a PA 6 Melt – Cause of Unevennesses in Melt-Spun Yarns**
- Gear Pump Performance in Polypropylene Filament Yarn Uniformity
- Molding
- Physically-Based Model of Thermoplastics Injection Molding for Control Applications
- Effect of Pressure and Shear Stress on Crystallization Behaviors in Injection Molding
- The Crystallinity of PVC and its Effect on Physical Properties**
- Molecular Orientation in Polycarbonate Induced by Cooling Stresses
