COMPARISON OF THREE METHODS TO MEASURE THE ELONGATIONAL VISCOSITY OF POLYMER MELTS: ENTRY FLOW, FIBER SPINNING AND UNIAXIAL ELONGATION

摘要

The melt viscosity of three commercial polyolefines (LDPE, LLDPE and HDPE) was measured in uniaxial elongational flow at constant extension rate, as well as by the Rheotens and the Entry Flow Methods. The melts showed the same MFI but differed in their extensional properties, reflecting the differences in their molecular structure. The indirect methods could also give meaningful estimates for the extensional viscosity of polymer melts, if the amount of accumulated extensional strain in each case was taken into consideration.