Uniaxial Elongational Viscosity of High Molecular Weight High Density Polyethylene Melts

Extensional properties of high molecular weight high density polyethylene(HDPE) were studied. Uniaxial elongational viscosity was measured under constant strain rate. The following conclusions were obtained.(1)Time-temperature superposition could be applied to the elongational viscosity at a constant strain at different temperatures.(2)The samples which show a remarkable strain-hardening during deformation had a good processability, i.e. narrow distribution of bottle thickness, for the blow molding.(3)Order of the magnitude of steady shear viscosity did not agree with that of maximum elongational viscosity at the same strain rate.(4)Shear relaxation modulus at non-linear region could not be separated with the terms of strain and modulus during long time period. Transient elongational viscosity calculated was good fit with experimental viscosity behavior by introducing short time process.