Detection of low levels of long‐chain branching in polydisperse polyethylene materials

Abstract

Abstract Creep experiments have been applied to probe the zero‐shear viscosity, η 0 , of polyethylene chains directly and precisely in a constant‐stress rheometer at 190°C. Such experiments, when combined with precise measurements of the weight‐average molecular weight, M w , calibrated relative to linear chains of high‐density polyethylene, are shown to provide a very sensitive approach to detect low levels (0.005 branches per 1000 carbons) of long‐chain branching (LCB). This detection limit is shown to be insensitive to whether the molecular weight distribution (MWD) breadth, M w / M n , rises from about two to ten. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011