On the initiation of melt fracture



The importance of (τ11 − τ22)/τ12 (sometimes called the Weissenberg number) in determining the onset of melt fracture is examined using classical linearized hydrodynamic stability analysis. The constitutive relation used is that proposed by Bird and Carreau. It is shown that simple shearing flow of a viscoelastic fluid becomes unstable at a critical value of the Weissenberg number. Implications with regard to polymer processing are discussed.