Wall slip of molten high density polyethylenes. II. Capillary rheometer studies

Hatzikiriakos, Savvas G.; Dealy, John M.

doi:10.1122/1.550313

Cited by 363 publications

(204 citation statements)

References 23 publications

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“…Temperature measurements at the die exit showed a discrepancy of about 20°C between shear rates of 3 and 15 s -1 ( Figure 6), whereas the shear heating induced temperature variations measured on the capillary rheometer remain lower than 2°C. This shear heating, which is important in industrial configurations, should generate more slip [16][17][18]. On the other hand, the results are presented vs. shear rate and not shear stress.…”

Section: Piv Measurements 311 Simple Flowsmentioning

confidence: 99%

“…Rheological measurements were carried out on a rheograph (Göttfert) using 0.5 and 1 mm capillary dies with a L/D ratio of 20. Wall slip was determined using the classical Mooney's method [17,18]. For a capillary flow, it is based on Equation (1): (1) where V s is the slip velocity, γ · A the apparent shear rate (calculated from flow rate Q and die radius R by Equation (2)) and γ · A,S the apparent shear rate corrected for slip, which is only a function of the wall shear stress (τ w ).…”

Section: Methodsmentioning

confidence: 99%

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Characterization of extrusion flow using particle image velocimetry

Fournier¹,

Lacrampe²,

Krawczak³

2009

Express Polym. Lett.

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Abstract. The aim of this study was the characterization of polymer flows within an extrusion die using particle image velocimetry (PIV) in very constraining conditions (high temperature, pressure and velocity). Measurements were realized on semi-industrial equipments in order to have test conditions close to the industrial ones. Simple flows as well as disrupted ones were studied in order to determine the capabilities and the limits of the method. The analysis of the velocity profiles pointed out significant wall slip, which was confirmed by rheological measurements based on Mooney's method. Numerical simulations were used to connect the two sets of measurements and to simulate complex velocity profiles for comparison to the experimental ones. A good agreement was found between simulations and experiments providing wall slip is taken into account in the simulation.

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Section: Piv Measurements 311 Simple Flowsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Characterization of extrusion flow using particle image velocimetry

Fournier¹,

Lacrampe²,

Krawczak³

2009

Express Polym. Lett.

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show abstract

“…Slip of polymer melts is explained by flow induced chain detachment/desorption and chain disentanglement. According to Hatzikiriakos & Dealy's experiments with sliding plate and capillary rheometers [17,18], wall slip occurs when the shear stress exceeds a critical stress, which is around 0.1MPa for Polyethylene. The various experimental methods of determining wall slip velocity can be found in an excellent review by Hatzikiriakos [19].…”

Section: Wall Slipmentioning

confidence: 99%

Characterization of thermo-rheological behavior of polymer melts during the micro injection moulding process

Zhang

Gilchrist

2012

Polymer Testing

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A bstract: In-line process monitoring and rheological characterization can help to understand the behavior of polymer melt flows during manufacturing and to make injection molding a measurable process for manufacturing high quality parts. This work developed an in-line rheology measurement system using a slit die attached to a micro injection molding machine. A series of dog-bone mold inserts was used to form the slit die with thickness ranging from 600µm to 200µm. Two combined pressure and temperature sensors were embedded into the slit die to measure the pressure drop. Based on the slit flow model, it was found that the viscosity of Pebax melts depends on the slit thickness in the actual injection molding process. The competing effects of wall slip and non-isothermal conditions will determine the melt viscosity. The plastication induced thermo-mechanical history can also influence polymer viscosity, although it is neglected in conventional rheology measurements.

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“…When the velocity meets the requirement u > u c , we can not say that all the lubricant molecules on the surface occur to slip. Some of the literatures [23,[27][28][29][30] have proposed a simple criterion to distinguish whether wall slip effect has occurred on the solid-liquid interface through theoretical and experimental researches. When the interface tension of the lubricant medium becomes bigger than that of the friction pair material, namely, adhesion fracture occurs before the cohesive fracture of molecular bonds, then the wall slip is very likely to happen.…”

Section: Theoretical Basis Of Wall Slipmentioning

confidence: 99%

Theoretical and experimental research on the friction coefficient of water lubricated bearing with consideration of wall slip effects

Xie

Rao

Liu

et al. 2015

Mechanics & Industry

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-Researches of the nature of friction coefficient of water lubricated bearing are carried out in this paper. Based on the experimental results of composite material bearing under hydrodynamic lubrication by water, we calculate the Stribeck curves as the function of load and speed, deviate the modified Reynolds equation considering wall slip effects in Cartesian coordinate system, put forward the essential model of friction coefficient, the composition of friction coefficient and essential changing correlation between them. Numerical results are in good agreement with experimental results, which verifies existence of wall slip. Researches indicate that there is always an appropriate working condition which friction coefficient is minimum. Comparison of the theoretical and experimental results shows that they are consistent on the overall trend but still exist some deviations under certain operating conditions. Reasonable explanations are given to illustrate the correctness of theoretical model. Key words:Water lubricated bearing / nature of friction coefficient / wall slip effect / solid contact effect and fluid viscous effect / experimental research

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Wall slip of molten high density polyethylenes. II. Capillary rheometer studies

Cited by 363 publications

References 23 publications

Characterization of extrusion flow using particle image velocimetry

Characterization of extrusion flow using particle image velocimetry

Characterization of thermo-rheological behavior of polymer melts during the micro injection moulding process

Theoretical and experimental research on the friction coefficient of water lubricated bearing with consideration of wall slip effects

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