The use of extensional rheometry to establish operating parameters for stretching processes

Abstract

Abstract This work describes a method of determining the limits of uniform extensibility, in terms of failure and fracture, from rheological tests in extensional flow. The limit of uniform stretching can be expressed in terms of the Weissenberg number for the process, as demonstrated by data for three chemically diverse polymers, polystyrene, poly(methyl methacrylate), and a polyester. The BKZ‐K model can be used to predict necking failure, as determined by the Considére criterion, and an empirical correlation can be derived for fracture.