Flow Instabilities

Until now we have always considered stable flows that allow one to obtain products free of defects. However, it is well known that flows of molten polymers can lead to different types of instabilities, which generally limit the productivity of forming processes (Petrie and Denn, 1976; Larson, 1992; Koopmans, 2002; Hatzikiriakos and Migler, 2004; Vergnes, 2015). We will review these types of instability in this chapter.