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Multiplicities and instabilities in film blowing
Author(s) -
Cain John J.,
Denn Morton M.
Publication year - 1988
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760282303
Subject(s) - bubble , viscoelasticity , rotational symmetry , newtonian fluid , mechanics , steady state (chemistry) , thermodynamics , materials science , infinitesimal , blow molding , physics , mathematics , mathematical analysis , composite material , chemistry , mold
The mechanics of the blown film process are studied for Newtonian and viscoelastic models of the polymer melt. Multiple solutions of the governing equations are possible even for the Newtonian fluid, with the existence of more than one steady‐state bubble profile for a given set of operating parameters; steady axisymmetric solutions vanish suddenly at critical combinations of operating variables. Several types of instabilities exist, including one that is analogous to “draw resonance.” The stability of the bubble to infinitesimal disturbances depends on the set of operating parameters that is controlled; control of the bubble inflation pressure is much less stable than control of the amount of inflating air, for example. Heat transfer is stabilizing.