摘要
The extensional viscosity of three polyethylenes(LDPE,LLDPE and HDPE)melts was measured in-uniaxialelongational flow at a constant extension rate,as well asby the process of fiber spinning"Rheotens"and the entryflow methods.The melts showed the same melt flowingindex(MFI)but differed in their extensional viscositiesand attenuating forces,reflecting the differences in theirmolecular structures.The indirect methods could alsogive meaningful estimates for the extensional viscosity ofthe polymer melts,if the amount of the accumulated ex-tensional strain in each case was taken into consider-ation.
The extensional viscosity of three polyethylenes (LDPE, LLDPE and HDPE) melts was measured in uniaxial elongational flow at a constant extension rate, as well as by the process of fiber spinning 'Rheotens' and the entry flow methods. The melts showed the same melt flowing index (MFI) but differed in their extensional viscosities and attenuating forces, reflecting the differences in their molecular structures. The indirect methods could also give meaningful estimates for the extensional viscosity of the polymer melts, if the amount of the accumulated extensional strain in each case was taken into consideration.
