Effect of ultrasound on the viscoelasticity and rheology of polystyrene extruded through a slit die

Abstract

AbstractThe rheological and processing behavior (melt fracture performance) of polystyrene extruded through a slit die is studied as a function of the ultrasound vibration intensity. The apparent viscosity reduces 29% and die pressure reduces 22% compared with that without ultrasound vibration. The viscosity of the melt decreases exponentially as ultrasound intensity increases and an Arrhenius equation fits the data well. Ultrasound vibration also leads to a decrease of the die swell ratio and a postponement of melts fracture. Characteristic relaxation times at the onset of melt fracture are calculated according to the hypothesis that the melt fracture behavior of a polymer is affected by a balance between its viscous (viscosity) and elastic properties (recoverable shear). Ultrasound vibration shortens the relaxation time of polystyrene molecular chains. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2907–2911, 2006