The stress in the startup of uniaxial elongational flow until steady state, followed by stress relaxation, has been measured for a narrow molar mass distribution polystyrene inelt with a molecular weight of 145 kg/mol. The experiments are conducted on a filament stretching rheometer, where a closed loop control of the midfilament diameter ensures controlled uniaxial extension. The closed loop control algorithm is extended to apply to the stress relaxation part of the experiment. It ensures a constant midfilament diameter, by controlling the motion of the end plates. By dividing the measured stress with the theoretically predicted stress from the Doi and Edwards model during relaxation, the stretch factors corresponding to each imposed stretch rate are obtained. These stretch factors converge to a unique envelope and eventually converge to unity for long times for all measured elongational rates. (C) 2008 The Society of Rheology.
Bibliographical noteCopyright (2008) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
- ENTANGLED POLYMERS
- ELONGATIONAL VISCOSITY
- RHEOLOGICAL PROPERTIES
- FAST FLOWS
- FILAMENT STRETCHING RHEOMETER
- CONSTITUTIVE EQUATION
Nielsen, J. K., Rasmussen, H. K., & Hassager, O. (2008). Stress relaxation of narrow molar mass distribution polystyrene following uniaxial extension. Journal of Rheology, 52(4), 885-899. https://doi.org/10.1122/1.2930872