High pressure capillary rheometry of polymeric fluids

Couch, M.; Binding, D.M.

doi:10.1016/s0032-3861(99)00865-4

Cited by 74 publications

(58 citation statements)

References 11 publications

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“…6A (intercepts of fits with the pressure axis), the entrance pressure drop increases with increasing exit pressure. These results are in agreement with orifice data by Couch and Binding (2000) and Sorrentino and Pantani (2009) in which was shown that the orifice pressure drop increases with increases exit pressure at constant shear rates.…”

Section: Bagley Plots At Elevated Exit Pressuressupporting

confidence: 92%

“…However, obtaining Bagley plots in measurements obtained with acounter pressure chamber in which the exit pressure differs from atmospheric pressure is not straightforward. Therefore, to correct capillary data, measurements are sometimes conducted using an orifice as az ero-length capillary (Couch and Binding, 2000;Sorrentino and Pantani, 2009). The measured orifice pressure drop directly provides an estimate for the entrance pressure drop for acapillary at acertain shear rate and upstream pressure.…”

Section: Introductionmentioning

confidence: 99%

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On the Pressure Dependency of the Bagley Correction

Puyvelde

Vananroye

Hanot

et al. 2013

International Polymer Processing

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The effect of pressure on the viscosity of polymer melts is an often forgotten parameter due to the inherent difficulty to measure this quantity. Different experimental approaches have already been undertaken in literature in the past. Apopular methodology to measure the pressure dependence of the viscosity is to use ac apillary rheometer equipped with a counter pressure chamber in which the exit pressure can be controlled. In order to process the data, one of the key elements is the Bagley correction that is required to determine the correct entrance pressure at as pecific shear rate. In all analysis approaches presented in literature on data at controlled exit pressure, the Bagley correction was always determined at atmospheric exit pressure, disgarding possible effects of an enhanced exit pressure. In this paper, an ew analytical approach is presented that for the first time allows for ad irect assessment of the entrance pressures obtained when capillary measurements are performed with controlled counter pressures. It is demonstrated, using polycarbonate, that the entrance pressure correction needed to obtain correct viscosity values under pressure is significantly different than the one needed to correct measurements performed at atmospheric exit pressure. 1I ntroductionAlready in 1957, Maxwell and Jung demonstrated that the apparent viscosity of abranched polyethylene melt increased exponentially with pressure (Maxwell and Jung, 1957). This dependency has important consequences for polymer processing operations. For instance, under typical injection molding conditions, at pressures of the order of several tens of MPa, neglecting the increase of viscosity with pressure can lead to incomplete cavity filling and/or longer processing times. With a growing demand on product performance and accuracy, in combination with the availability of sophisticated numerical simulations, an accurate incorporation of pressure effects is more and more required. Nevertheless, the pressure effect on viscosity is often ignored and the amount of experimental data is still relatively limited. The latter is due to the inherent difficulty in performing accurate measurements of the pressure effect as was reviewed by for instance Goubert et al. (2001) and more recently by Cardinaels et al. (2007).Since the pioneering work of Maxwell and Jung, arange of analysis procedures and experimental devices has been discussed in literature, which can be categorized into indirect and direct methods. Indirect methods to determine the pressure dependence of the viscosity are typically based on the principle of free volume and use the temperature dependency of viscosity and an equation of state for the polymer (the pressure-volume-temperature behavior) to determine the pressure sensitivity of the viscosity (e. g. Utracki, 1983Utracki, , 1985Utracki and Sedlacek, 2007). Regarding the direct methods, two approaches exist. The first one requires no special instruments but is based on the non-linearities in the Bagley plots, obtained either with capillary...

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Section: Bagley Plots At Elevated Exit Pressuressupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

On the Pressure Dependency of the Bagley Correction

Puyvelde

Vananroye

Hanot

et al. 2013

International Polymer Processing

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“…HDPE measurements for high shear rate leads to high pressure values up to 60 MPa. At such a pressure level, dissipative heating and pressure dependent viscosity are no longer negligible [5]. Dissipative heating decreases the viscosity, whereas the rise of pressure enhances the viscosity.…”

Section: Flow Hypothesismentioning

confidence: 99%

Polymer rheology at high shear rate for microinjection moulding

2010

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International audienceIn this paper, we present the rheology of a high-density polyethylene for microinjection moulding. At high flow rate, pressure becomes high enough so that shear heating and pressure-dependence of the viscosity cannot be neglected. Moreover, spurt and chaotic defects related to wall slip were encountered. Nevertheless, we used classical data processing. We obtained viscosity at high shear rate which is lower than the viscosity obtained with the Carreau-Yasuda extrapolation of the moderate shear rate data. In order to discuss the origin of this difference, we developed a flow numerical simulation in the capillary where we take into account pressure and temperature dependent viscosity. The relative importance of these phenomena and their coupling is presented. Then, injection moulding experiments were carried out in a plaque mould. Different moulding parameters were tested. A three dimensional injection moulding numerical simulation, using Rem3D software, was carried out. The quality of the different sets of rheological data is assessed by comparing computed and measured pressure

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“…Furthermore an investigation of pressure affected viscosity employing modified rheometers and followed by evaluation of flow behavior by the help of pressure coefficient using some mathematical models could be employed. The pressure coefficient was incorporated into several nonlinear models such as Barus-Arrhenius combination [8][9], White-Metzner [10], Cross-Vogel [11], modified power law [12], WLF equation [13] and Carreau-Yasuda [1,14]. The accuracy and reliability of different techniques available for determination of pressure influence has been reported by Goubert et al [15] and H. E. Park et.…”

Section: Introductionmentioning

confidence: 99%

On Pressure Affected Shear Viscosity of Poly(Lactic) Acid

Piyamanocha¹,

Sedláček²,

Sáha³

et al. 2011

AIP Conference Proceedings

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Abstract. Evaluation of pressure coefficient of polymer melt viscosity has become important parameter taken into account for flow behavior prediction in polymer processing simulation software. In this paper, the pressure coefficient of biodegradable polymers, poly(lactic) acid (PLA), was investigated. A capillary rheometer equipped with back pressure device controlling pressure in polymer melt during flow was employed for experiments. Pressure sensitivity was evaluated through pressure coefficient calculated via fitting of obtained viscosity data by the help of Carreau-Yasuda model. It was found that pressure coefficient of PLAs is strongly affected by the internal structure of tested polymer.

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High pressure capillary rheometry of polymeric fluids

Cited by 74 publications

References 11 publications

On the Pressure Dependency of the Bagley Correction

On the Pressure Dependency of the Bagley Correction

Polymer rheology at high shear rate for microinjection moulding

On Pressure Affected Shear Viscosity of Poly(Lactic) Acid

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