ELONGATIONAL BEHAVIOR OF POLYMER MELTS IN CONSTANT ELONGATION-RATE, CONSTANT TENSILE-STRESS, AND CONSTANT TENSILE FORCE EXPERIMENTS

The extensibility of polymer melts is of great practical importance for polymer processing. On the basis of a single-integral constitutive equation with a straindepent memory functional verified for two similar well-characterized LDPE melts, predictions are made on material behaviour in uniaxial extension under constant strain-rate, tensile stress, and tensile force conditions. It is found that experiments at constant tensile force are more adequately described by assuming purely viscous response of the polymer melts than by assuming Maxwell-model type of behaviour. © 1979 Dr. Dietrich Steinkopff Verlag.