STUDY OF THE LINEAR-STABILITY OF THE DRAW ING OF A NEWTONIAN FILM

This paper focuses on the prediction of the instability phenomenon occ urring in the polymer film casting process. This instability appears t o be periodic fluctuations of the thickness and the width of the film. We built a model able to predict both fluctuations. This model is one -dimensional, Newtonian, isothermal and assumes a uniform section of t he film across its width. The nonstationary resolution implements the linear stability method and enables us to obtain a critical curve. The importance of a dimensionless parameter, called the aspect ratio, has been shown. At first the increase in this parameter stabilizes the dr awing process but then it destabilizes it.