Viscoplastic‐elastic modeling of tubular blown film processing

Abstract

Abstract The blown film process has been modeled through the transition from liquidlike to solidlike behavior at the freeze line. A new constitutive equation has been developed that, when incorporated into the the kinematic and dynamic equations that describe the process, for the first time yields qualitatively correct predictions of all process variables. It is suggested that the demarcation between liquidlike behavior and solidlike behavior be altered from the conventional, kinematically based constraint, dr / dz = O, to a rheologically based constraint, the plastic‐elastic transition (PET). The results are qualitive in nature since the material is modeled as an elastic solid above the PET instead of as a viscoelastic material. The model is tested using the polystyrene data of Gupta (1981).