Capillary flow of linear polyethylene melt: sudden increase of flow rate

Weill, A.

doi:10.1016/0377-0257(82)80021-9

Cited by 29 publications

(7 citation statements)

References 5 publications

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“…On the other hand, if in the high-flow-rate part of the cycle the extrudate was smooth, the low-flow-rate material may be described as (relatively) "rough," because of the presence of sharkskin. Weill (1980) described his extrudates as exhibiting sharkskin as the pressure was rising and as being "rough" during the stage of decreasing pressure. He also observed a third, very smooth segment of each cycle, which he called a "plug," a phenomenon also observed by Bergem (1976).…”

Section: Extrudate Appearancementioning

confidence: 99%

“…This would have an effect on the flow rate that would be very similar in appearance to that of wall slip. The jump from a flow with a monotonic variation of shear rate with r to one with a discontinuity would produce a sudden increase in the flow rate that could explain the spurt effect (Weill, 1980;Uhland, 1919;Hunter and Slernrod, 1983).…”

Section: Rheological Explanations Of Oscillatory Flowmentioning

confidence: 99%

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

Hatzikiriakos

Dealy

1992

Journal of Rheology

196

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: Extrudate Appearancementioning

confidence: 99%

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

196

123

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“…Without going deeper into the mechanisms behind the appearane of polymer extrudates, we only note an interesting similarity between the two-period appearance of polymer melt extrudates and the combined pulsating and transversally oscillating (spiralling) flow reported in this paper. In both cases, the higher frequency component appears only during a part of the slower oscillation [1,11,43]. It may be noted that the ideas about the origin of the instabilities observed in extrudates are rather diverging.…”

Section: Final Remarksmentioning

confidence: 96%

“…It may be noted that the ideas about the origin of the instabilities observed in extrudates are rather diverging. While some authors associate them with the entry flow, others claim stickslip phenomena [12] or relaxational oscillations [11,43] as responsible. In the latter case, the frequencies are found to depend on the volume of the reservoir upstream from the capillary.…”

Section: Final Remarksmentioning

confidence: 97%

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Electrical fluctuations and entry flow instabilities during capillary flow of aqueous poly (ethylene oxide) solutions

Hedman

Kubát

1986

Rheol Acta

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Capillary flow of poly(ethylene oxide) solutions generates voltage fluctuations (noise) between electrodes placed on both sides of the capillary. The noise has a 1/f ~ type spectral distribution, the value of ~ increasing with ?) (shear rate) to a limiting level. Within certain ~ ranges, two sets of harmonic peaks appear in the spectra. It is demonstrated that these peaks are retated to the frequency components of the instabilities in the entry flow region. The lower frequency set of harmonics corresponds to axial oscillations (pulsations) of the flow, while the higher frequency peaks are associated with the transverse oscillation of the stream lines in the vicinity of the entry. The corresponding frequencies were measured by visual counting and by spectral analysis of laser light transmitted through the entry region during injection of a coloured solution.The noise measurements were carried out using both platinum and reversible Ag/AgC1 electrodes. In the latter case the streaming potential was also measured; its variation due to pressure fluctuations in the instable flow region appears to provide a plausible explanation of flow-induced noise phenomena as observed in elastic solutions.

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Stability of the interface between two dynamic phases in capillary flow of linear polymer melts

McLeish

1987

J Polym Sci B Polym Phys

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Results of previous work1 on a theoretical explanation of the “spurt effect” in polymer melt flow are extended. A modified Doi—Edwards liquid is shown to support axisymmetric traveling waves on an interface between high and low shear‐rate phases in capillary flow. The stability of these perturbations is found to be governed by normal stress effects and may be related to certain types of melt fracture. Observed effects of varying the capillary length are explained qualitatively.

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Capillary flow of linear polyethylene melt: sudden increase of flow rate

Cited by 29 publications

References 5 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

Electrical fluctuations and entry flow instabilities during capillary flow of aqueous poly (ethylene oxide) solutions

Stability of the interface between two dynamic phases in capillary flow of linear polymer melts

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