Flow History – Morphology Development in Crystallizable Polymer Melts
-
A. J. McHugh
Abstract
Flow history-morphology interactions have been studied for three crystallizable polymers: high density polyethylene, poly(vinylidene fluoride), and polypropylene. Materials were extruded through an impinging channels film die which produces a mixed extensional and shearing flow field. Extrudate morphology was characterized by optical microscopy and x-ray diffraction. Stress fields during die flow were measured from flow birefringence and compared to calculations based on the power law model. Good quantitative agreement was found for the shearing stresses, however, large differences were observed between the measured and computed normal stresses along the symmetry axis of the flow where extensional gradients are also the highest. Extensional stresses on the order of 2.8·106, 1.4·106, and 3.9·105 dynes/cm2 were required to induce row-nucleated crystallization in the HDPE, PVF2, and polypropylene respectively. The respective stresses were found to decrease with increasing relaxation time in a non-linear fashion. An explanation for this behavior is presented based on the opposing tendencies of chain relaxation and oriented crystallization.
© 1990, Carl Hanser Verlag, Munich
Artikel in diesem Heft
- Contents
- Contents
- Original Contributions
- Innovative Extrusion Systems for Advanced Fiber and Film Extrusion
- Influence of Melting Zone and Melt Homogeneity on Extrusion and Injection Molding Processes
- Further Considerations of Simulation of Flow in Pin Barrel Extruders and in Screw Extruders with Sliced Flights
- Deformation Fields and Residence Time Distributions in Polymer Melt Flows
- Flow History – Morphology Development in Crystallizable Polymer Melts
- Rheological Studies on Solutions of Poly-p-phenylene Terephthalamide in H2SO4
- Instability Phenomena in Film Casting Process
- Influence of Stretching and Cooling Conditions in Cast Film Extrusion of PP Films
- Melt Strength Behavior of PE and its Relation to Bubble Stability in Film Blowing**
- Dynamics of Double Bubble Tabular Film Process for Producing Biaxially oriented Nylon 6 Film
- A Finite Difference Study of Roll Design in Calendering Processing
Artikel in diesem Heft
- Contents
- Contents
- Original Contributions
- Innovative Extrusion Systems for Advanced Fiber and Film Extrusion
- Influence of Melting Zone and Melt Homogeneity on Extrusion and Injection Molding Processes
- Further Considerations of Simulation of Flow in Pin Barrel Extruders and in Screw Extruders with Sliced Flights
- Deformation Fields and Residence Time Distributions in Polymer Melt Flows
- Flow History – Morphology Development in Crystallizable Polymer Melts
- Rheological Studies on Solutions of Poly-p-phenylene Terephthalamide in H2SO4
- Instability Phenomena in Film Casting Process
- Influence of Stretching and Cooling Conditions in Cast Film Extrusion of PP Films
- Melt Strength Behavior of PE and its Relation to Bubble Stability in Film Blowing**
- Dynamics of Double Bubble Tabular Film Process for Producing Biaxially oriented Nylon 6 Film
- A Finite Difference Study of Roll Design in Calendering Processing
