The rheological behavior of flexible-chain polymers in the region of high shear rates and stresses, the critical process of spurting, and supercritical conditions of their movement at T &gt; Tg

Vinogradov, G. V.; Protasov, V. P.; Dreval, V. E.

doi:10.1007/bf01333875

Cited by 84 publications

(44 citation statements)

References 32 publications

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“…Pearson and Petrie (1968), Schowalter (1988), and Renardy (1990) examined the stability of simple shear of a viscoelastic liquid with wall slip, but they did not find an instability of a type that could explain oscillatory shear. Vinogradov et al (1984) proposed that at the upper critical stress the melt is in a "forced high elastic state" and cannot sustain further deformation. This rheological transformation, he argued, explains the jump to a high-slip, high-flow regime.…”

Section: Rheological Explanations Of Oscillatory Flowmentioning

confidence: 99%

Role of slip and fracture in the oscillating flow of HDPE in a capillary

Hatzikiriakos

Dealy

1992

Journal of Rheology

195

123

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Certain polymers exhibit two distinct branches in their capillary flow curves (wall shear stress versus apparent wall shear rate). This gives rise to oscillatory flow in constant-piston-speed rheometers and to flow curve hysteresis in controlled-pressure rheometers. These curious phenomena have attracted considerable interest over a period of many years, but their basic mechanisms are still the subject of debate. Building on previous work we have developed a model that predicts all the essential features of the curves of pressure and flow rate versus time in the oscillatory flow regime. Fluid compressibility and the second branch of the flow curve are necessary features of the model, but fluid elasticity is found not to be an essential element. While our macroscopic measurements do not prove it conclusively, our data lead us to believe that on the high-flow-rate branch of the flow curve there is slip along a cylindrical fracture surface near the wall. The jump to the high-flow branch occurs when this fracture occurs, at an upper critical value of the shear stress, while the jump back to the low-flow branch occurs when adhesion is established at the fracture surface at a lower critical shear stress.

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Section: Rheological Explanations Of Oscillatory Flowmentioning

confidence: 99%

Role of slip and fracture in the oscillating flow of HDPE in a capillary

Hatzikiriakos

Dealy

1992

Journal of Rheology

195

123

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“…The flow anomalies due to wall slip observed in extrusion of polymer melts are in many ways similar to those in polymer solutions. For example, Vinogradov [21] reported flow-rate enhancement and diameter-dependent flow curves for extrusion of polybutadine. Pressure-drop oscillations and rough extrudate surface (melt fracture) are well known phenomena that occur in controlled flow extrusion.…”

Section: Introductionmentioning

confidence: 99%

Slipping fluids: a unified transient network model

Joshi

Lele

Mashelkar

2000

Journal of Non-Newtonian Fluid Mechanics

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Wall slip in polymer solutions and melts play an important role in fluid flow, heat transfer and mass transfer near solid boundaries. Several different physical mechanisms have been suggested for wall slip in entangled systems. We look at the wall slip phenomenon from the point of view of a transient network model, which is suitable for describing both, entangled solutions and melts. We propose a model, which brings about unification of different mechanisms for slip. We assume that the surface is of very high energy and the dynamics of chain entanglement and disentanglement at the wall is different from those in the bulk. We show that severe disentanglement in the annular wall region of one radius of gyration thickness can give rise to non-monotonic flow curve locally in that region. By proposing suitable functions for the chain dynamics so as to capture the right physics, we show that the model can predict all features of wall slip, such as flow enhancement, diameter-dependent flow curves, discontinuous increase in flow rate at a critical stress, hysteresis in flow curves, the possibility of pressure oscillations in extrusion and a second critical wall shear stress at which another jump in flow rate can occur. #

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“…This model is not completely satisfactory: discontinuous rates of deformation have not been observed in the flow domain by experimenters, when macroscopic slip phenomena appear [39,25,24]. This leads us to argue that we have reached a possible limit of such differential models when a discontinuous rate of deformation appears.…”

Section: Poiseuille Flowsmentioning

confidence: 98%

Efficient simulation of nonlinear viscoelastic fluid flows

Saramito

1995

Journal of Non-Newtonian Fluid Mechanics

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This paper presents a new and efficient method for computing the flow of a non-Newtonian fluid. The approach is based on two independent concepts:Time-dependent simulation of viscoelastic flow: A new decoupled algorithm, presented in P. Saramito, Simulation numerique d'ecoulements de fluides viscoelastiques par eRments finis incompressibles et une methode de directions alternees; applications, These de l'Institut National Polytechnique de Grenoble, 1990 and P. Saramito, Numerical simulation of viscoelastic fluid flows using incompressible finite element method and a 0-method, Math. Modelling Num. Anal., 35 (1994) 1-35. enables us to split the major difficulties of this problem, and to solve it more efficiently. Moreover, this scheme is of order two in time, and can be used to obtain stationary flows in an efficient way.Conservative finite element method: this method combines the incompressible Raviart Thomas element, the discontinuous Lesaint Raviart element, and a finite volume element method. It satisfies exactly the mass conservation law, and leads to an optimal size for the nonlinear system in terms of the total degree of freedom versus the mesh size.We apply our numerical procedure to the Phan-Thien-Tanner model with a classical benchmark: the four to one abrupt contraction. The numerical solutions exhibit good behavior, especially near the singularity, in the vicinity of the re-entrant corner. The numerical experiments present the main features of such flows: vortex development and overshooting of the velocity profile along the axis of symmetry in the entry region.

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The rheological behavior of flexible-chain polymers in the region of high shear rates and stresses, the critical process of spurting, and supercritical conditions of their movement at T > Tg

Cited by 84 publications

References 32 publications

Role of slip and fracture in the oscillating flow of HDPE in a capillary

Role of slip and fracture in the oscillating flow of HDPE in a capillary

Slipping fluids: a unified transient network model

Efficient simulation of nonlinear viscoelastic fluid flows

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