A Model for Adhesive Failure of Viscoelastic Fluids During Flow

Lau, Hon Chung; Schowalter, W. R.

doi:10.1122/1.549888

Cited by 77 publications

(33 citation statements)

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“…Polymer melts [14] Constitutive instability Many-valued shear stress [79] Constitutive instability Predicts hysteresis loop [59] Junctions are assumed between wall/polymer interface as well as in the bulk of the polymer fluid. Junctions are described by kinetic equation describing a reaction between bonded and free macromolecules at the interface Prediction of the temperature dependence of wall-slip velocities.…”

Section: Reference Approach Predictionmentioning

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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Section: Reference Approach Predictionmentioning

confidence: 99%

Slipping fluids: a unified transient network model

Joshi

Lele

Mashelkar

2000

Journal of Non-Newtonian Fluid Mechanics

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“…Using an activation rate theory first proposed by Lau and Schowalter (1986), we derived an expression for the slip velocity valid in the low-flow-rate branch of the flow curve:…”

Section: Slip Velocity On Low-flow-rate Branch Of Flow Curvementioning

confidence: 99%

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

Hatzikiriakos

Dealy

1992

Journal of Rheology

193

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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“…(9), (10), and (12), Eq. (9) can be rewritten as (13 ) Following Lau and Schowalter (1986), we interpret the specific rate constants in terms of activation rate theory in order to assess the effect of pressure on the slip velocity. While these constants are also functions of temperature, the principal effect of temperature is included in the present model through the function 11 (T) as described above.…”

Section: B Pressure Dependencementioning

confidence: 99%