Polymer Flow Instability: A Review and Analysis

Boudreaux, Edwin; Cuculo, John A.

doi:10.1080/00222357608064314

Cited by 30 publications

(4 citation statements)

References 63 publications

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“…These instabilities are generally designated under the generic English term \melt fracture" (Tordella, 1956), even though we will see later that this term may be sometimes maladapted. Anyway, extrusion defects have been the subject of various reviews in the literature for over forty years (Dennison, 1967;Tordella, 1969;Bialas and White, 1969;Petrie and Denn, 1976;Boudreaux andCuculo, 1977 -1978;Denn, 1990Larson, 1992;Hatzikiriakos and Migler, 2004;Koopmans et al, 2011).…”

Section: Introductionmentioning

confidence: 98%

Extrusion Defects and Flow Instabilities of Molten Polymers

Vergnes

2015

International Polymer Processing

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International audienceWhen certain critical conditions are exceeded, the flow of a polymer melt becomes unstable, giving rise to particular phenomena that are the subject of this review. These instabilities are a vital industrial problem, as they are the key to productivity of extrusion processes. Indeed, their onset leads to unacceptable products and is thus the upper limit of the processing conditions. They are also a fascinating scientific problem because, although studied and discussed for more than half a century, they are still not fully understood and their mechanisms are still sometimes controversial. In the present literature review, we present an overview of the studies carried out for fifty years, as well as our own opinion on the underlying mechanisms.3-2

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Section: Introductionmentioning

confidence: 98%

Extrusion Defects and Flow Instabilities of Molten Polymers

Vergnes

2015

International Polymer Processing

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“…After this early observation, several research groups investigated the phenomenon in various other polymers. Many terms have been used in the literature (as mentioned in the review of Boudreaux and Cuculo) to describe extrudate distortion, namely melt fracture, elastic turbulence, waviness, ripples, sharkskin, etc. The various details of sharkskin distortion phenomenon, as investigated by several research groups, have been reviewed extensively. ,,− In this section, we will summarize only some of the key observations.…”

Section: Introductionmentioning

confidence: 99%

“…After this early observation, several research groups investigated the phenomenon in various other polymers. Many terms have been used in the literature (as mentioned in the review of Boudreaux and Cuculo 6 ) to describe extrudate distortion, namely melt fracture, elastic turbulence, waviness, ripples, sharkskin, etc. The various details of sharkskin distortion phenomenon, as investigated by several research groups, have been reviewed extensively.…”

Section: Introductionmentioning

confidence: 99%

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A Geometrical Solution to the Sharkskin Instability

Pol

Joshi

Tapadia

et al. 2006

Ind. Eng. Chem. Res.

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We study the effect of die exit divergence on the sharkskin behavior, both experimentally as well as through the use of computational fluid dynamics (CFD) simulations. Sharkskin or surface fracture is known to occur immediately after the die exit, because of the large elongational deformation that a polymer melt experiences as it exits the die. We show that the diverging taper at the die exit postpones or completely removes the occurrence of sharkskin. The corresponding CFD simulations of an equivalent K-BKZ fluid show that the taper at the die exit significantly reduces the severity of the elongational flow, thereby reducing the normal stresses as the polymer melt leaves the die. We believe that, in an extrusion operation, the provision of a diverging taper at the die exit is one of the potential measures by which sharkskin instability can be eliminated on an industrial scale.

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Flow visualization of cellulose acetate–acetone solutions

Boudreaux

Cuculo

1979

J of Applied Polymer Sci

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SynopsisThe flow behavior of four cellulose acetate-acetone solutions varying from 20.00% to 28.18% solids concentration was observed using flow visualization techniques a t 24°C with an industrial-type dry spinning system. Fibrous particulate matter entraimd in the solutions and crossed polars revealed the streamlines and the birefringence due to flow in glass spinnerets. The streamlines of the four solutions were radially convergent at all obtainable throughputs. The crossed polars revealed a cone of birefringence with the order of the interference colors decreasing upstream of the capillary inlet. The intensity and extent of birefringence varied somewhat with concentration and throughput. Except for kneeing, the emerging extrudates were undeformed. The kneeing was not a result of flow instability a t the capillary inlet but was due to another, undetermined instability. A separate study of the kneeing revealed both a concentration dependence and hysteresis. The birefringence of the emerging extrudates was a function of both concentration and throughput, and it yielded some information about the structure of the solutions.

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Polymer Flow Instability: A Review and Analysis

Cited by 30 publications

References 63 publications

Extrusion Defects and Flow Instabilities of Molten Polymers

Extrusion Defects and Flow Instabilities of Molten Polymers

A Geometrical Solution to the Sharkskin Instability

Flow visualization of cellulose acetate–acetone solutions

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