The Prediction of Sharkskin Instability Observed during Film Blowing
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R. P. G. Rutgers
Abstract
The characteristics of sharkskin surface instability for linear low density polyethylene are studied as a function of film blowing processing conditions. By means of scanning electron microscopy and surface profilometry, is it found that for the standard industrial die geometry studied, sharkskin only occurs on the inside of the film bubble.
Previous work suggests that this instability may be due to critical extensional stress levels at the exit of the die. Isothermal integral viscoelastic simulations of the annular extrusion process are reported, and confirm that the extensional stress at the die exit is large enough to cause local melt rupture. However, the extensional stress level at the outer die wall predicts melt rupture of the outside bubble surface also, which contradicts the experimental findings.
A significant temperature gradient is expected to exist across the die gap at the exit of the die, due to the external heating of the die and the low conductivity of the polymer melt. It is shown that a gradient of 20°C is required to cause sharkskin to only appear on the inner bubble surface.
© 2002, Carl Hanser Verlag, Munich
Articles in the same Issue
- 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
Articles in the same Issue
- 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
