Anomalous rheological behavior of polyethylene melts in the gross melt fracture regime in the capillary extrusion: Effect of long‐chain branching

Abstract

During a capillary extrusion with several different polyethylenes, we observe an abnormal rheological behavior. The nominal viscosity of some polyethylene melt in the gross melt fracture regime does not change with the temperature. Several metallocene-catalyzed linear low density polyethylene are investigated. Among them, polyethylenes, which have long-chain branches in their main chain, show this abnormal rheological behavior. By capillary extrusion experiments with various dies of different L/D ratios, it is inferred that the abnormal rheological behavior is originated in the die land, not die entrance nor die exit. From various experiments, we notice that this abnormal phenomenon may be used to detect long-chain branch of PE.

The influence of long chain branches of LLDPE on processability and physical properties

“…Nevertheless, the most sensitive method is the rheological method. Small levels of LCB, such as 1LCB / 10.000C affect the rheological behavior of the polymer [6,12] . LCB has distinct effects on different rheological quantities (zero shear-rate viscosity -η 0 -and strain hardening).…”

Effects of long chain branching on melt fractures in capillary extrusion of metallocene‐catalyzed linear low‐density polyethylene melts

“…Recently, we have been conducting capillary extrusion experiments with various metallocene catalyzed polyethylenes 13, 21, 24, 25. We observed very interesting rheological behaviors for these materials.…”