An investigation on modelling and measurements of transient elongational rheology of polymer melts by SER testing platform

AbstractTransient elongational rheology of PP is investigated experimentally. A specifically designed fixture consisting of two drums mounted on a TA Instruments ARES rotational rheometer was used to measure the transient uniaxial extensional viscosity of two commercial grades polypropylene in the molten state. The Hencky strain was varied from 0.003 to 2 s-1 and the temperature was fixed at 180 oC. The measurements show that the steady state elongational viscosity was reached at the measured Hencky strains for polypropylene. Eslami and Grmela have recently introduced a reptation diffusion term arising from the intermolecular chain forces into the rigid FENE-P dumbbells model. The same approach has been used in this study to interpret the transient rheological data in both shear-free and simple shear flows.

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Recovery of Realistic Polymer Melts after Simple Shear Flows

Macromolecules ◽

10.1021/ma00117a024 ◽

1995 ◽

Vol 28 (13) ◽

pp. 4540-4547 ◽

Cited By ~ 2

Author(s):

Ulrik Borgbjerg ◽

Juan J. de Pablo

Keyword(s):

Simple Shear ◽

Shear Flows ◽

Polymer Melts

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The rheology of non-dilute dispersions of highly deformable viscoelastic particles in Newtonian fluids

Journal of Fluid Mechanics ◽

10.1017/jfm.2014.687 ◽

2014 ◽

Vol 763 ◽

pp. 386-432 ◽

Cited By ~ 6

Author(s):

Reza Avazmohammadi ◽

Pedro Ponte Castañeda

Keyword(s):

Steady State ◽

Simple Shear ◽

Shear Flows ◽

Rheological Behaviour ◽

Time Dependent ◽

Simple Shear Flow ◽

Average Particle ◽

Special Cases ◽

Constitutive Properties ◽

Extensional Flows

AbstractWe present a model for the rheological behaviour of non-dilute suspensions of initially spherical viscoelastic particles in viscous fluids under uniform Stokes flow conditions. The particles are assumed to be neutrally buoyant Kelvin–Voigt solids undergoing time-dependent finite deformations and exhibiting generalized neo-Hookean behaviour in their purely elastic limit. We investigate the effects of the shape dynamics and constitutive properties of the viscoelastic particles on the macroscopic rheological behaviour of the suspensions. The proposed model makes use of known homogenization estimates for composite material systems consisting of random distributions of aligned ellipsoidal particles with prescribed two-point correlation functions to generate corresponding estimates for the instantaneous (incremental) response of the suspensions, together with appropriate evolution laws for the relevant microstructural variables. To illustrate the essential features of the model, we consider two special cases: (i) extensional flow and (ii) simple shear flow. For each case, we provide the time-dependent response and, when available, the steady-state solution for the average particle shape and orientation, as well as for the effective viscosity and normal stress differences in the suspensions. The results exhibit shear thickening for extensional flows and shear thinning for simple shear flows, and it is found that the volume fraction and constitutive properties of the particles significantly influence the rheology of the suspensions under both types of flows. In particular, for extensional flows, suspensions of particles with finite extensibility constraints are always found to reach a steady state, while this is only the case at sufficiently low strain rates for suspensions of (less realistic) neo-Hookean particles, as originally reported by Roscoe (J. Fluid Mech., vol. 28, 1967, pp. 273–293) and Gao et al. (J. Fluid Mech., vol. 687, 2011, pp. 209–237). For shear flows, viscoelastic particles with high viscosities can experience a damped oscillatory motion of decreasing amplitude before reaching the steady state.

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Effects of chain length and polydispersity on shear banding in simple shear flow of polymeric melts

Soft Matter ◽

10.1039/d0sm00669f ◽

2020 ◽

Vol 16 (28) ◽

pp. 6468-6483 ◽

Cited By ~ 2

Author(s):

Mahdi Boudaghi-Khajehnobar ◽

Brian J. Edwards ◽

Bamin Khomami

Keyword(s):

Steady State ◽

Shear Rate ◽

Shear Flow ◽

Chain Length ◽

Simple Shear ◽

Polymer Melts ◽

Shear Banding ◽

Simple Shear Flow ◽

Polydisperse Polymer ◽

Transient And Steady State

Transient and steady-state shear banding are demonstrated for polydisperse polymer melts as functions of applied shear rate.

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Observation and Analysis of Carbon Black Agglomerate Dispersion in Simple Shear Flows

International Polymer Processing ◽

10.3139/217.910098 ◽

1991 ◽

Vol 6 (2) ◽

pp. 98-102 ◽

Cited By ~ 9

Author(s):

S.-P. Rwei ◽

S. W. Horwatt ◽

I. Manas-Zloczower ◽

D. L. Feke

Keyword(s):

Carbon Black ◽

Simple Shear ◽

Shear Flows ◽

Agglomerate Dispersion

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Kinetics of dispersion for sparse agglomerates in simple shear flows: Application to silica agglomerates in silicone polymers

Chemical Engineering Science ◽

10.1016/s0009-2509(96)00338-7 ◽

1996 ◽

Vol 51 (23) ◽

pp. 5193-5204 ◽

Cited By ~ 29

Author(s):

Fabrice Bohin ◽

Ica Manas-Zloczower ◽

Donald L. Feke

Keyword(s):

Simple Shear ◽

Shear Flows ◽

Silicone Polymers ◽

Kinetics Of

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Numerical study of electric field effects on the deformation of two-dimensional liquid drops in simple shear flow at arbitrary Reynolds number

Journal of Fluid Mechanics ◽

10.1017/s0022112009006442 ◽

2009 ◽

Vol 626 ◽

pp. 367-393 ◽

Cited By ~ 32

Author(s):

STEFAN MÄHLMANN ◽

DEMETRIOS T. PAPAGEORGIOU

Keyword(s):

Steady State ◽

Shear Flow ◽

Electric Field ◽

Electric Fields ◽

Simple Shear ◽

Simple Shear Flow ◽

Physical Parameters ◽

Shear Stresses ◽

Two Dimensional ◽

Liquid Drops

The effect of an electric field on a periodic array of two-dimensional liquid drops suspended in simple shear flow is studied numerically. The shear is produced by moving the parallel walls of the channel containing the fluids at equal speeds but in opposite directions and an electric field is generated by imposing a constant voltage difference across the channel walls. The level set method is adapted to electrohydrodynamics problems that include a background flow in order to compute the effects of permittivity and conductivity differences between the two phases on the dynamics and drop configurations. The electric field introduces additional interfacial stresses at the drop interface and we perform extensive computations to assess the combined effects of electric fields, surface tension and inertia. Our computations for perfect dielectric systems indicate that the electric field increases the drop deformation to generate elongated drops at steady state, and at the same time alters the drop orientation by increasing alignment with the vertical, which is the direction of the underlying electric field. These phenomena are observed for a range of values of Reynolds and capillary numbers. Computations using the leaky dielectric model also indicate that for certain combinations of electric properties the drop can undergo enhanced alignment with the vertical or the horizontal, as compared to perfect dielectric systems. For cases of enhanced elongation and alignment with the vertical, the flow positions the droplets closer to the channel walls where they cause larger wall shear stresses. We also establish that a sufficiently strong electric field can be used to destabilize the flow in the sense that steady-state droplets that can exist in its absence for a set of physical parameters, become increasingly and indefinitely elongated until additional mechanisms can lead to rupture. It is suggested that electric fields can be used to enhance such phenomena.

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