Elongational viscosity of monodisperse and bidisperse
polystyrene melts

Jens Kromann Nielsen 1,Henrik Koblitz Rasmussen 2 and Ole Hassager
The Danish Polymer Centre
Department of Chemical Engineering
Department of Manufacturing Engineering and Management
Technical University of Denmark
DK-2800 Kgs. Lyngby, Denmark

Gareth H. McKinley
Hatsopoulos Microfluids Laboratory
Department of Mechanical Engineering
Massachusetts Institute of Technology
Cambridge, Massachusetts 02139, USA

The startup and steady uniaxial elongational viscosity have been measured for two monodis-
perse polystyrene melts with molecular weights of 52 kg/mole and 103 kg/mole, and for three
bidisperse polystyrene melts. The monodisperse melts show a maximum in the steady elon-
gational viscosity vs. the elongational rate, ÿ o, of about two times 3η0 whereas the bidisperse
melts have a maximum of up to a factor of 7 times the Trouton limit of 3η0. The Wiest
model which incorporates anisotropic drag and finite extensibility may be used to interpret
the results in molecular terms.