INSTABILITY PHENOMENA IN FILM BLOWING PRO CESS - A LINEAR-STABILITY ANALYSIS

Instability phenomena leading to unacceptable product often occurs in the film blowing process. After having studied the steady-state soluti on (Andrianarahinjaka and Micheau, 1994), we now rum To the actual sta bility aspect. We perform a linear stability analysis leading to an ei genvalue problem. By means of a pattern problem: the stretching of a f lat film we first clarify the matter of spurious eigensolutions genera ted by the discretization. Then we define a methodology of computing t he eigenvalues. Computations emphasize the predominance of the way of controlling the process on rheology and cooling.