The velocity profiles of molten polymers during laminar flow

Otter, J. L. den; Wales, J. L. S.; Schijf, J.B.

doi:10.1007/bf01976437

Cited by 32 publications

(6 citation statements)

References 5 publications

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“…Galt and Maxwell (1964) measured veloci only in the developed flow region in circular g ass capillaries by a tracer particle technique. Den Otter et al (1967) performed experiments similar to those of Galt and Maxwell in rectangular slit geometry. Gogos and Maxwell ( 1966) measured velocity profiles of molten polyethylene near the exit of a circular glass capillary but with questionable accuracy (den Otter et al, 1967;Whipple, 1974).…”

Section: Elastic Recovery Conceptmentioning

confidence: 99%

Velocity distributions in die swell

Whipple¹,

Hill²

1978

AIChE Journal

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\ SLIT n ADJUSTABLE 3 MM GHT INTERRUPTER u -CAMERA Fig. 2. Die cross section and light path. A, B, C = velocity curve fit parameters A~A = cross-sectional area at section lA, Figure 8 Aw = interfacial area between sections 1A and 2, Figure 8 B = die swell, ratio of die and extrudate area or widths K = ratio of average square to the square of the average of the velocity pa = atmospheric pressure Re = Reynolds number, u D p /~ 8 , = transverse velocity component vy = axial velocity component 1A = average of the square of the velocity in the 1 direction at section 1A

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Section: Elastic Recovery Conceptmentioning

confidence: 99%

Velocity distributions in die swell

Whipple¹,

Hill²

1978

AIChE Journal

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“…They observed that only a fraction (around +) of the particles 'at the wall' were motionless; the rest moved with an apparent slip velocity of around 10% of the centreline velocity. The inference of slip in this study was questioned by den Otter et al (1967), who observed that the large size of the particles and the photographic technique used by Galt & Maxwell cast doubt on the assumption that velocities 'at the wall' were being probed. In the studies of den Otter, Wales & Schijf, who used 5-20 pm dust particles as probes, no evidence of slip was found in melts of polyethylene and poly(dimethylsi1oxane).…”

Section: Introductionmentioning

confidence: 72%

Direct measurements of slip in sheared polymer solutions

Archer

Larson

Chen³

1995

J. Fluid Mech.

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We report direct measurements of slip flow during and after plane-Couette shearing of poly(styrene) solutions between glass surfaces. Slip is studied by visualizing the microscopic motions of micron-sized silica spheres suspended in the solutions. Slip velocities as large as 4 μm s−1 are observed during shear, and recoil displacements of as much as 80 μm are observed at the glass surfaces after the driving surface stops moving. Significant slip is observed when the Weissenberg number $\lambda\dot{\gamma}$ exceeds 0.5 or so, where λ is the relaxation time and $\dot{\gamma}$ the shear rate. The magnitude of the slip correlates strongly with the fluid's birefringence, indicating that slip is induced by polymer stress or orientation. Away from the centre of the sample, toward the free edges, a secondary flow is observed, which appears to be driven by a normal-stress imbalance at these edges.

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“…By contrast, den Otter et a1. 39,40 found no slippage a t the walls of glass slits during flow of high-and low-density polyethylene and of poly(dimethylsiloxane) in the melt fracture region. The report of Maxwell and Galt41 that wall slippage did occur was thought to be in error because of the large particle sizes of the tracer particles used in this work.…”

Section: Discussionmentioning

confidence: 99%

A study of melt density of flowing linear polyethylene

Rudin

Chang

1978

J. Appl. Polym. Sci.

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SynopsisLinear polyethylene was extruded from a capillary rheometer with the driving piston operated at fixed speed and at fixed pressure. Apparent viscosity and melt density were measured in both extrusion modes. Apparent density decreased at shear rates approaching the melt fracture region in fixed piston-speed operation. Flow of other polymer melts was essentially incompreaeible in fiied piston-speed operation, and all polymers exhibited incompressible flow in fixed-pressure extrusion. The oscillating portion of the flow curve of linear polyethylene reflects alternating periods in which the polymer exits faster and slower than the rate at which the advancing piston clears the rheometer reservoir. Linear polyethylene behaves differently from most other polymers in fixed piston-speed extrusion and during melt fracture because of the existence of a more extensive entanglement network in the melt. It is suggested that melt fracture in general results from a tensile failure of the entanglement network, which may occur at the die inlet and in the orifice.

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The velocity profiles of molten polymers during laminar flow

Cited by 32 publications

References 5 publications

Velocity distributions in die swell

Velocity distributions in die swell

Direct measurements of slip in sheared polymer solutions

A study of melt density of flowing linear polyethylene

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