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Title: Validation of a model for the cast-film process

Abstract

We have developed a model of the cast-film process and compared theoretical predictions against experiments on a pilot line. Three polyethylenes with a markedly different level of melt elasticity were used in this evaluation; namely, a high pressure low density polyethylene, LDPE, and two linear low density polyethylenes, LLDPE-1 and LLDPE-2. The final film dimensions of the LDPE were found to be in good agreement with 1-D viscoelastic stationary predictions. Flow field visualization experiments indicate, however, a 2-D velocity field in the airgap between the extrusion die and the chill roll. Taking this observation into account, evolutions of the free surface of the web along the airgap were recorded with LLDPE-2, our least elastic melt. An excellent agreement is found between these measurements and predictions of neck-in and edge bead with 2-D Newtonian stationary simulations. The time-dependent solution, which is based on a linear stability analysis, allows to identify a zone of draw resonance within the working space of the process, defined by the draw ratio, the Deborah number, and the web aspect ratio. It is predicted that increasing this latter parameter stabilizes the process until an optimum value is reached. Experiments with LLDPE-1 are shown to validate this uniquemore » theoretical result, thus allowing to increase the draw ratio by about 75%.« less

Authors:
 [1];  [2];  [3]
  1. Exxon Chemical Co., Baytown, TX (United States)
  2. Exxon Chemical Europe, Machelen (Belgium)
  3. Ecole des Mines de Paris, Sophia-Antipolis (France)
Publication Date:
OSTI Identifier:
602824
Report Number(s):
CONF-961108-
TRN: 98:001968-0009
Resource Type:
Conference
Resource Relation:
Conference: Annual meeting of the American Institute of Chemical Engineers (AIChE), Chicago, IL (United States), 10-15 Nov 1996; Other Information: PBD: 1996; Related Information: Is Part Of 1996 First joint topical conference on processing, structure and properties of polymeric materials; PB: 594 p.
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ASPECT RATIO; ELASTICITY; EXTRUSION; POLYETHYLENES; PROCESSING; STABILITY

Citation Formats

Chambon, F., Ohlsson, S., and Silagy, D. Validation of a model for the cast-film process. United States: N. p., 1996. Web.
Chambon, F., Ohlsson, S., & Silagy, D. Validation of a model for the cast-film process. United States.
Chambon, F., Ohlsson, S., and Silagy, D. Tue . "Validation of a model for the cast-film process". United States.
@article{osti_602824,
title = {Validation of a model for the cast-film process},
author = {Chambon, F. and Ohlsson, S. and Silagy, D.},
abstractNote = {We have developed a model of the cast-film process and compared theoretical predictions against experiments on a pilot line. Three polyethylenes with a markedly different level of melt elasticity were used in this evaluation; namely, a high pressure low density polyethylene, LDPE, and two linear low density polyethylenes, LLDPE-1 and LLDPE-2. The final film dimensions of the LDPE were found to be in good agreement with 1-D viscoelastic stationary predictions. Flow field visualization experiments indicate, however, a 2-D velocity field in the airgap between the extrusion die and the chill roll. Taking this observation into account, evolutions of the free surface of the web along the airgap were recorded with LLDPE-2, our least elastic melt. An excellent agreement is found between these measurements and predictions of neck-in and edge bead with 2-D Newtonian stationary simulations. The time-dependent solution, which is based on a linear stability analysis, allows to identify a zone of draw resonance within the working space of the process, defined by the draw ratio, the Deborah number, and the web aspect ratio. It is predicted that increasing this latter parameter stabilizes the process until an optimum value is reached. Experiments with LLDPE-1 are shown to validate this unique theoretical result, thus allowing to increase the draw ratio by about 75%.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1996},
month = {12}
}

Conference:
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