Study on the melt entry flow characteristics in axisymmetric dies with abrupt contraction by a visualization technique

Wong, A. C.-Y.; Jiang, Lanyue

doi:10.1016/s0142-9418(01)00013-7

Cited by 11 publications

(7 citation statements)

References 13 publications

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“…As for the latter case, experimental results by Dennison [11] and Binding [12] suggested, by visualizing the flow patterns for different types of polymer melts near the die entrance, that there were some secondary or stagnant flows observed for PS melt, but were not seen with LLDPE melt. Further work by Wong and Jaing [13] described that a polymer melt exhibiting secondary flows was bound to be more elastic, and thus resulting in greater swelling at the die exit. The above reasons should explain why the extrudate swell ratio for the PS melt was greater than that for the LLDPE melt found in this work.…”

Section: Measurements and Calculationsmentioning

confidence: 99%

“…It was believed that the flow with greater vortices was likely to exhibit higher elastic character and greater swelling. Since this dimensionless vortex size was related to molecular orientations of the extrudates [13], the greater the vortex size the greater the molecular orientations as the melt entered the die, thus the increased extrudate swell at the die exit. This may be the reason why the differences in extrudate swell ratio in the circular and slit channels were more pronounced in the case of PS melt, as mentioned earlier.…”

Section: Figures 3(a) and 3(b) Show The Variations Inmentioning

confidence: 99%

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Extrudate swell behavior of PS and LLDPE melts in a dual die with mixed circular/slit flow channels in an extrusion rheometer

Sombatsompop

O-Charoen

2003

Polymers for Advanced Techs

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Extrudate swell behaviors of polystyrene (PS) and linear low-density polyethylene (LLDPE) melts in a dual channel die, having mixed circular/slit flow channels, in a constant shear rate rheometer were examined. The extrudate swell ratio for PS melt was observed to be higher than that for LLDPE melt for all cases, this being associated with the differences in molecular structures that could be described in terms of power law indexes and secondary flows near the die entrance. In single channel die, the extrudate swell of both PS and LLDPE melts in circular flow channel die was greater than that in slit flow channel, whereas, in dual channel die the slit channel exhibited a higher extrudate swell ratio, the results being explained by revealing the flow patterns of the melt in the barrel and die of the rheometer. It was found that the dimensionless size of the vortex flows near the entrance, and the extent of disentanglement of molecular chains on entering the die were the important factors for the differences in the extrudate swell ratios of the melts at the die exit influenced by the die designs used.

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Section: Measurements and Calculationsmentioning

confidence: 99%

Section: Figures 3(a) and 3(b) Show The Variations Inmentioning

confidence: 99%

Extrudate swell behavior of PS and LLDPE melts in a dual die with mixed circular/slit flow channels in an extrusion rheometer

Sombatsompop

O-Charoen

2003

Polymers for Advanced Techs

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“…To examine predictive ability of Equation (20) for the vortex length ratio, the experimental data of Wong and Jiang are adopted: The vortex length ratio of the extrusion grade low density polyethylene (LDPE) (160 AS, Escorene Co., USA) is conducted by the visualization technique at 185 °C. The non‐Newtonian index is 0.373 and the pipe contraction ratio is 3.1 in the measure of the shear flow.…”

Section: Methodsmentioning

confidence: 99%

“…. Figure shows the Bagley correction factor at different shear rate for LDPE melt, where the Bagley correction factor (

e_{0}

) is an important parameter characterizing the energy stored in the convergent flow and given by

Δ P_{e n t} true/ 2 η_{s} \overset{γ}{true}

. Figures depict that apparent shear viscosity and entrance pressure drop at different apparent shear rate for HDPE A, HDPE B, and LLDPE melts, respectively …”

Section: Methodsmentioning

confidence: 99%

“…Based on the shear experimental data of Wong and Jiang, the predicted vortex length ratio calculated from the proposed Equation (20) is compared with the visualization experimental data of LDPE melt. Figure shows the comparison between measured vortex length ratio and prediction for LDPE melt, and the friction coefficient is 0.17.…”

Section: Experimental Verification and Equation Comparisonmentioning

confidence: 99%

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Comparison of Different Approaches for Analyzing Converging Flows for Polymer Fluids

Yang

Zhu

Qin

et al. 2015

Macromol. Mater. Eng.

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Entrance converging flow of the circular pipe was analyzed to reveal the flow mechanism and optimize the pipe geometry in entrance converging region. Based on the principle of minimum energy, different equations involving entrance converging flow were proposed by considering the friction effect and introducing the elongational rate of Cogswell's analysis, and then the predicted vortex length ratio and elongational viscosity were compared with the experimental data of different polymer melts. In final, the predictive ability of the proposed equations, Cogswell's equations, Binding's equations, and Gibson's equations was discussed. It was found that the predicted vortex length ratio and elongational viscosity of the proposed equations were close to the experimental results. Based on the shear flow measurement of polymer fluids, it was demonstrated that the proposed equations were helpful to optimize the geometry in the pipe contraction region and evaluate the elongational viscosity.

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Relation between interfacial wave instability and tensile strength of two-layer polymer structure: An experimental study

Ranjbaran

2010

Chin J Polym Sci

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Study on the melt entry flow characteristics in axisymmetric dies with abrupt contraction by a visualization technique

Cited by 11 publications

References 13 publications

Extrudate swell behavior of PS and LLDPE melts in a dual die with mixed circular/slit flow channels in an extrusion rheometer

Extrudate swell behavior of PS and LLDPE melts in a dual die with mixed circular/slit flow channels in an extrusion rheometer

Comparison of Different Approaches for Analyzing Converging Flows for Polymer Fluids

Relation between interfacial wave instability and tensile strength of two-layer polymer structure: An experimental study

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