Flow behavior of sparsely branched metallocene-catalyzed polyethylenes

摘要

The dramatic effect of chain architecture on the melt flow behavior of polyethylenes is well established. The advant of metallocene and other constrained-geometry catalysts now allows the precise control of molecular weight, branch content, and branch distribution. In the present study, the rheological responses of three different metallocene-catalyzed polyethylenes are analyzed. Despite similarities in their shear properties, the differences in transient extensional viscosities can be attributed to the presence of sparse long-cain branches and/or high molecular weight fractions. Melt fracture observations as wel as full-field flow birefringence measurements are collected to further corroborate this idea.