The instability mechanism for two elastic liquids being co-extruded

Hinch, E. J.; Harris, Oliver; Rallison, J. M.

doi:10.1016/0377-0257(92)80030-2

Cited by 85 publications

(71 citation statements)

References 3 publications

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“…If the outer fluid is more elastic, then long waves are unstable, and the sinuous mode is the more unstable for long waves [3] but can be overtaken by the varicose mode at some wavenumber of order unity. The modes have the same behaviour for very short waves.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…Since the long-wave stability characteristics are reversed by interchanging the core and annulus ( [3,5]) short and long wave limits are fundamentally different from one another. In most cases, the short waves are unstable, and, having finite growth rates, are predicted to grow faster than the long waves, whose growth rate is small.…”

Section: Discussionmentioning

confidence: 99%

“…The fundamental mechanism of the elastic instability (as shown in [3]) is that the tilting of this interface exposes the jump in Σ 11 and this drives a perturbation flow which may in its turn cause the perturbation to grow.…”

Section: Base Statementioning

confidence: 99%

“…For long wavelength disturbances Hinch et al [3] provide a mechanism for, and calculation of, the growth of disturbances resulting from normal stresses. This operates only when the annulus is more elastic than the core, and has zero growth rate as the wavelength tends to infinity.…”

Section: Introductionmentioning

confidence: 99%

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Short wave instability of co-extruded elastic liquids with matched viscosities

Wilson

Rallison

1997

Journal of Non-Newtonian Fluid Mechanics

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The stability of channel flow of coextruded elastic liquids having matched viscosities but a jump in elastic properties is studied. Inertia and surface tension are neglected. A short wave disturbance is found, confined near the interface, whose growth rate is independent of wavelength. For dilute Oldroyd-B fluids this disturbance is unstable for any non-zero jump in normal stresses, and has a maximum growth rate for intermediate levels of elasticity in the two fluids. When one or other fluid is highly elastic the growth rate falls. In the concentrated limit (a UCM fluid), the disturbance is unstable only for a finite range of normal stress jumps, and is restabilised if one fluid is much more elastic than the other. Because the short wave disturbance is localised, the results apply for any steadily sheared interface across which the normal stress jumps. The results are confirmed for moderate parameter values by means of a full numerical solution for a three-layer planar flow.

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Section: Numerical Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Base Statementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Short wave instability of co-extruded elastic liquids with matched viscosities

Wilson

Rallison

1997

Journal of Non-Newtonian Fluid Mechanics

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“…Hinch et al [17] proposed a physical mechanism to explain how a jump in primary normal stress difference can cause instability whenever there is no jump in viscosity across the interface. It is important to note that the shear rate is not constant throughout thickness and a relevant parameter is rather the ratio between the viscosity and elasticity estimated at the interface.…”

Section: Introductionmentioning

confidence: 99%

Role of the interphase in the flow stability of reactive coextruded multilayer polymers

Lamnawar

Maazouz

2009

Polymer Engineering & Sci

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Coextrusion technologies are commonly used to produce multilayered composite sheets or films for a large range of applications from food packaging to optics. The contrast of rheological properties between layers can lead to interfacial instabilities. Important theoretical and experimental advances regarding theses defects have, during the last decades, been made using a mechanical and numerical approach. This study deals with the influence of the physicochemical affinity between the neighboring layers on interfacial instabilities for functionalized incompatible polymers. It was experimentally confirmed, in this case, that weak disturbance can be predicted by considering an interface of nonzero thickness (corresponding to an interdiffusion/reaction zone interphase) instead of a purely geometrical interface between the two reactive layers. According to the rheological investigations, an experimental strategy was here formulated to investigate the parameters that controlled the stability of the reactive multilayer flows. The role of the viscosity ratio, elasticity ratio, and layer ratio of the stability of the interface was also investigated coupling to the reaction rate/compatibilization phenomenon. Hence, based on this analysis, guidelines for a stable coextrusion of reactive functionalized polymers can be provided coupling the classical parameters and the physicochemical affinity at the polymer/polymer interface. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

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Films, Manufacture

Mount¹

2002

Encyclopedia of Polymer Science and Technology

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This article describes the methods and materials used in the commercial manufacture of polymer film products. Techniques for cast and oriented films using a variety of film‐making equipment are discussed and explained. The manufacturing process is broken down into a series of critical process steps to describe the function of each in the film‐making process and the impact of each on the film properties produced. Both extrusion and solvent‐based casting methods are described and a description of film‐finishing processes is given.

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The instability mechanism for two elastic liquids being co-extruded

Cited by 85 publications

References 3 publications

Short wave instability of co-extruded elastic liquids with matched viscosities

Short wave instability of co-extruded elastic liquids with matched viscosities

Role of the interphase in the flow stability of reactive coextruded multilayer polymers

Films, Manufacture

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