Elongational Flow Behavior of Polymer Melts

Single polymer dynamics in an elongational flow.

The stretching of individual polymers in a spatially homogeneous velocity gradient was observed through use of fluorescently labeled DNA molecules. The probability distribution of molecular extension was determined as a function of time and strain rate. Although some molecules reached steady state, the average extension did not, even after a approximately 300-fold distortion of the underlying f...

Elastic instabilities in planar elongational flow of monodisperse polymer solutions

We investigate purely elastic flow instabilities in the almost ideal planar stagnation point elongational flow field generated by a microfluidic optimized-shape cross-slot extensional rheometer (OSCER). We use time-resolved flow velocimetry and full-field birefringence microscopy to study the behavior of a series of well-characterized viscoelastic polymer solutions under conditions of low fluid...

Nonlinear shear and elongational rheology of model polymer melts at low strain rates

We present new results for the low strain rate behavior of the steady-state planar shear and elongational viscometric functions of model polymer elts, computed by non-equilibrium molecular dynamics simulations. The chain lengths in our model polymer melts vary from N = 2 up to = 100 beads, the maximum value corresponding to approximately 57 Kuhn lengths (approximately equivalent to polyethylene...

Elongational Flows in Polymer Processing

Elongational Viscosity of Monodisperse and Bidisperse Polystyrene Melts

The startup and steady uniaxial elongational viscosity have been measured for two monodisperse 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 elongational viscosity vs. the elongational rate, ǫ̇, of about two times 3η0 whereas the bidisperse melts have a maximum of up to a fac...