| Titre : |
The prediction of sharkskin instability observed during film blowing |
| Type de document : |
texte imprimé |
| Auteurs : |
R. P. G. Rutgers, Auteur ; N. Clemeur, Auteur ; J. Husny, Auteur |
| Année de publication : |
2002 |
| Article en page(s) : |
p. 214-222 |
| Note générale : |
Bibliogr. |
| Langues : |
Anglais (eng) |
| Index. décimale : |
668.9 Polymères |
| Résumé : |
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. |
| Note de contenu : |
- INTRODUCTION : Characteristics of sharkskin - Film blowing die geometry - Non-isothermal conditions in the film blowing die - Numerical simulation of film blowing
- Materials and experimental methods : Materials - Conditions for film production - Surface instability characterisation
- Numerical modelling
- RESULTS AND DISCUSSION : Characterisitics of surface instability on blown films - Surface roughness in relation to optical properties - Effect of processing temperature on the instability - Development of the surface instability as a function of flow rate - Gap width dependence of the instability - Numerical prediction of viscoelastic annular extrusion - Predicted flow fields near the Die exit - Correlation between onset of instability and simulated tensile exit stresses |
| DOI : |
10.3139/217.1691 |
| En ligne : |
https://drive.google.com/file/d/1pt1JuhXFlV7ZRRlYqNh04eMvhuriX884/view?usp=drive [...] |
| Format de la ressource électronique : |
Pdf |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=15996 |
in INTERNATIONAL POLYMER PROCESSING > Vol. XVII, N° 3 (09/2002) . - p. 214-222
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