ASSESSING THE CONVERGENT FLOW-ANALYSIS AS A TECHNIQUE FOR CHARACTERIZING THE EXTENSIONAL FLOW OF POLYMER MELTS

In this work, Cogswell's convergent flow analysis of polymer melts at the die entry is experimentally assessed. The extensional flow curves of several polymers (high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polystyrene and poly(vinyl chloride)), as obtained by capillary and extensional rheometry, are compared. Additionally, the vortex angles calculated through the analysis are related to the values determined by flow visualization studies. The validity of the analysis was generally confirmed, although the quantitative predictions show considerable inaccuracy. © 1990.