Huang, Qian1; Rasmussen, Henrik K.3; Skov, Anne Ladegaard5; Hassager, Ole1
1 Department of Chemical and Biochemical Engineering, Technical University of Denmark2 The Danish Polymer Centre, Department of Chemical and Biochemical Engineering, Technical University of Denmark3 Department of Mechanical Engineering, Technical University of Denmark4 Manufacturing Engineering, Department of Mechanical Engineering, Technical University of Denmark5 Centre for oil and gas – DTU, Center, Technical University of Denmark
The extensional dynamics of two low-density polyethylene melts Lupolen 3020D and Lupolen 1840D, both showing a stress overshoot in start-up of uniaxial extension [Rasmussen, H. K., J. K. Nielsen, A. Bach, and O.Hassager, 'Viscosity overshoot in the start-up of uniaxial elongation of low density polyethylene melts,' J. Rheol. 49(2), 369-381 (2005)], have been further investigated in stress relaxation and reversed flow. After the overshoot, the stress relaxation has a remarkably faster decrease of the transient stress than when the relaxation is initiated before the overshoot. The measurements from the reversed flow also show that the melts appear less elastic after the overshoot. Multi mode versions of the pom-pom and interchain pressure model fit the data quantitatively up to the stress maximum, but neither model captures the qualitative behavior after the maximum.
Journal of Rheology, 2012, Vol 56, Issue 6, p. 1535-1554