THE USE OF RHEOLOGY TO CHARACTERIZE THE BRANCHING STRUCTURE IN SPARSELY BRANCHED METALLOCENE CATALYZED POLYETHYLENE

摘要

A series of six commercial polyethylenes are investigated including four metallocene catalyzed (mc) PE resins having varying degrees of long-chain branching and narrow MWD and a LDPE and a LLDPE. The degree of branching (i.e. the number of long chain branches per 10,000 carbon atoms) is estimated via dilute solution light scattering measurements. However, whether the branching in the mc PE's is random or concentrated on a few chains cannot be assessed by means of dilute solution measurements. Shear and extensional viscosity measurements along with the use of molecular theory are employed to determine which is the most likely scenario.