Crystallization and Orientation Development in Melt Spinning Isotactic PP of Varying Tacticity
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D. Choi
Abstract
We investigated the effects of tacticity on crystallization and orientation development in melt spinning isotactic polypropylene (iPP) through air. Melt-spun fibers were characterized by wide-angle X-ray diffraction (WAXD), birefringence and differential scanning calorimetry (DSC). The melt-spun fibers usually exhibited the monoclinic α-crystalline form, but the mesomorphic form was found under certain processing conditions. The mesomorphic structure was formed more readily in low tacticity fibers. We found certain amounts of hexagonal β-crystalline form in all of the α-form fiber samples. The amouns were generally negligibly small, but the low tacticity fibers spun at high draw-down ratios exhibited significant amounts of β-form crystals. At low spinline stress levels, some low tacticity fibers exhibited lower birefringence and chain orientation than high tacticity fibers due to a less perfect crystal structure. At certain high spinline stress levels, low tacticity fibers exhibited much higher birefringence and chain-axis orientation levels than expected. This was attributed to a reduction in epitaxial lamellar branching (a*-axis oriented group in bimodal orientation). However, the extent of lamellar branching in low tacticity fibers appeared to increase again at higher stress levels. This led to a significant decrease in birefringence and crystalline orientation.
© 2002, Carl Hanser Verlag, Munich
Artikel in diesem Heft
- Editorial
- Touchstones of Polymer Processing
- Twin Screw Extrusion and Compounding
- Residence Time Distribution Curves of Screw Elements in Twin-Srew Extruder
- Rheological Effect of Zinc Surfactant on the TESPT-Silica Mixture in NR and S-SBR Compounds
- Optimization of Processing Conditions for Polymer Twin-Screw Extrusion
- Fibers and Film
- The Prediction of Sharkskin Instability Observed during Film Blowing
- Tensile Strength Characteristics of Polymer Melts
- Biaxially Oriented PP Films Using the Double Bubble Process
- Fiber and Film
- Crystallization and Orientation Development in Melt Spinning Isotactic PP of Varying Tacticity
- Extrusion Coating
- Extrusion Coating with Metallocene-Catalysed Polyethylenes
- Injection Molding
- Design Sensitivity Analysis Applied to Injection Molding for Optimization of Gate Location and Injection Pressure
- Three-dimensional Numerical Modeling of Co-injection Molding
- Residual Stress and Warpage Models for Complex Injection Molded Parts
- Blow Molding
- Investigation of Design Parameters and Novel Design of Petaloid PET Bottles
Artikel in diesem Heft
- Editorial
- Touchstones of Polymer Processing
- Twin Screw Extrusion and Compounding
- Residence Time Distribution Curves of Screw Elements in Twin-Srew Extruder
- Rheological Effect of Zinc Surfactant on the TESPT-Silica Mixture in NR and S-SBR Compounds
- Optimization of Processing Conditions for Polymer Twin-Screw Extrusion
- Fibers and Film
- The Prediction of Sharkskin Instability Observed during Film Blowing
- Tensile Strength Characteristics of Polymer Melts
- Biaxially Oriented PP Films Using the Double Bubble Process
- Fiber and Film
- Crystallization and Orientation Development in Melt Spinning Isotactic PP of Varying Tacticity
- Extrusion Coating
- Extrusion Coating with Metallocene-Catalysed Polyethylenes
- Injection Molding
- Design Sensitivity Analysis Applied to Injection Molding for Optimization of Gate Location and Injection Pressure
- Three-dimensional Numerical Modeling of Co-injection Molding
- Residual Stress and Warpage Models for Complex Injection Molded Parts
- Blow Molding
- Investigation of Design Parameters and Novel Design of Petaloid PET Bottles
