On the pressure correction of capillary melt rheology data

Dees, Marc; Mangnus, Marc; Hermans, Nicolaas; Thaens, Wouter; Hanot, A.-S.; Puyvelde, Peter Van

doi:10.1007/s00397-011-0529-2

Cited by 15 publications

(7 citation statements)

References 14 publications

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“…Cox and Merz first reported that steady shear viscosity correlates to complex viscosity as a function of angular frequency. Such behaviors in viscosities are observed in linear homopolymers as well Dees et al . Since a large number of polymer melts, such as linear amorphous homopolymers, would obey both the above conditions, this method can be quite useful in generating complete seven parameter Cross‐WLF data cards that can be used for better pressure predictions for their injection molding processes.…”

Section: Introductionmentioning

confidence: 76%

Determination of the pressure dependence of polymer melt viscosity using a combination of oscillatory and capillary rheometer

Raha¹,

Sharma²,

Senthilmurugan³

et al. 2019

Polymer Engineering & Sci

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For an accurate simulation of a high‐pressure injection molding process by using the CAE software, it is important to understand the pressure sensitivity of a polymer's melt viscosity. The current work describes a method for the determination of the pressure dependence parameter D3 of the Cross‐WLF model. It uses a combined rheological technique using both dynamic and capillary rheometers. Three grades of polycarbonate homopolymers were studied in this work and their complex viscosities were measured using a dynamic shear rheometer. The dynamic data were used to obtain six out of the seven parameters of the Cross‐WLF, except D3. A capillary rheometer fitted with a counter pressure chamber was further used to characterize the pressure dependence of the zero shear viscosity and to determine the D3 parameter. Finally, the derived parameters were validated by carrying out injection molding with a box tool and comparing the actual pressure profiles with simulation results using the Autodesk® MoldFlow® software. The validation results indicated that actual pressure profiles from the simulation were found to be less than 10% than that of injection molding. POLYM. ENG. SCI., 60:517–523, 2020. © 2019 Society of Plastics Engineers

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Section: Introductionmentioning

confidence: 76%

Determination of the pressure dependence of polymer melt viscosity using a combination of oscillatory and capillary rheometer

Raha¹,

Sharma²,

Senthilmurugan³

et al. 2019

Polymer Engineering & Sci

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show abstract

“…At this point, one might reasonably wonder whether or not the high-pressure effect on viscosity plays a minor role under the pressure conditions of these experiments. According to the Barus equation,

[ 58 , 59 ], the reciprocal of the pressure coefficient

may indicate a critical pressure

, above which the pressure dependence of viscosity cannot be neglected. Reported

values are

for PS,

for ABS, and

for PP [ 33 , 60 , 61 , 62 ], corresponding to pressure ranges of

for PS,

for ABS, and

for PP.…”

Section: Resultsmentioning

confidence: 99%

Retrieving Equivalent Shear Viscosity for Molten Polymers from 3-D Nonisothermal Capillary Flow Simulation

Wen¹,

Wang²,

Cyue³

et al. 2021

Polymers

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For highly viscous polymer melts, considerable fluid temperature rises produced by viscous heating can be a disturbing factor in viscosity measurements. By scrutinizing the experimental and simulated capillary pressure losses for polymeric liquids, we demonstrate the importance of applying a viscous heating correction to the shear viscosity, so as to correct for large errors introduced by the undesirable temperature rises. Specifically, on the basis of a theoretical derivation and 3-D nonisothermal flow simulation, an approach is developed for retrieving the equivalent shear viscosity in capillary rheometry, and we show that the shear viscosity can be evaluated by using the average fluid temperature at the wall, instead of the bulk temperature, as previously assumed. With the help of a viscous Cross model in analyzing the shear-dominated capillary flow, it is possible to extract the viscous heating contribution to capillary pressure loss, and the general validity of the methodology is assessed using the experiments on a series of thermoplastic melts, including polymers of amorphous, crystalline, and filler-reinforced types. The predictions of the viscous model based on the equivalent viscosity are found to be in good to excellent agreement with experimental pressure drops. For all the materials studied, a near material-independent scaling relation between the dimensionless temperature rise (Θ) and the Nahme number (Na) is found, Θ ~ Na0.72, from which the fluid temperature rise due to viscous heating as well as the resultant viscosity change can be predicted.

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“…Park et al investigated the pressure coefficient of melt viscosity using a high‐pressure sliding plate rheometer (HPSPR) and capillary rheometers with driven piston and nitrogen counter‐pressure to control the capillary exit pressure; they found that the pressure coefficient of viscosity, â , agreed fairly well with data from different laboratories and instruments. Dees et al investigated variances between rotational and capillary rheometry with respect to the effect of the mean pressure inside the capillary on the Cox‐Merx rule ; they found that the pressure coefficient obtained at constant shear stress and high pressures by the superposition method can provide accurate estimates of the pressure dependence.…”

Section: Discussionmentioning

confidence: 99%

“…The objective of the present study is to explore the factors affecting the observed transient response in the apparent viscosity behavior. The paper draws from the literature to provide a comprehensive analysis of variance in capillary rheometry including factors such as instrumentation errors, entrance and exit effects, polymer melt compressibility , pressure dependence of the viscosity , and polymer melt viscous heating that may significantly influence the transient behavior . Thus, the present investigation analyzes each physical phenomenon to estimate its contributions to the transient behavior and its quantitative effect on the model fidelity and coefficients.…”

Section: Introductionmentioning

confidence: 99%

Analysis of variance in capillary rheometry

et al. 2016

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The effect of deformation history (hysteresis) on transient capillary rheometric data was studied compared to conventional assumptions regarding steady state data. The factors studied were: the position instrumentation, the pressure instrumentation, entrance and exit effects, polymer melt compressibility, pressure dependence of the viscosity, and polymer melt viscous heating. Statistical analysis of variance was performed to statistically determine the sources of variance to specific degrees of confidence. The polymer melt compressibility, pressure dependence, and viscous heating were found to be statistically significant contributors of the observed variation at the 95% confidence level; the capillary length and instrumentation were not found to be significant. The results indicate that the transient behavior can vary the modeling of the apparent viscosity in a significant manner such that the model fidelity and model coefficients may vary substantially. Hence, polymer melt compressibility, pressure dependence, and viscous heating should be considered during rheological model fitting to increase model fidelity and predictive accuracy in end use. POLYM. ENG. SCI.,

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On the pressure correction of capillary melt rheology data

Cited by 15 publications

References 14 publications

Determination of the pressure dependence of polymer melt viscosity using a combination of oscillatory and capillary rheometer

Determination of the pressure dependence of polymer melt viscosity using a combination of oscillatory and capillary rheometer

Retrieving Equivalent Shear Viscosity for Molten Polymers from 3-D Nonisothermal Capillary Flow Simulation

Analysis of variance in capillary rheometry

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