Measurements and modeling of PS/supercritical CO<sub>2</sub> solution viscosities

Lee, Minhee; Park, Chul; Tzoganakis, Costas

doi:10.1002/pen.11400

Cited by 157 publications

(122 citation statements)

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“…Since V is known, V 1 and V2 are not independent, and it suffices to know V1, or rather the ratio V 1/V, in order to find the separated free energy Fs in (15). The interface calculated using SCFT is actually three superposed contributions due to the three species in the present system.…”

Section: Theorymentioning

confidence: 99%

“…Carbon dioxide has main advantages of being non-toxic and having a relatively low critical point (T c=31C, Pc=7.376 MPa or 1070 psi). Although small amounts of carbon dioxide are added to the polymer process, dramatic changes result in physicochemical properties, such as glass transition temperature, viscosity, solubility and surface tension [15]. Particularly, the surface tension between polymer and gas phases has been emphasized because it significantly affects the foaming and morphology of final polymer products.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Temperature and Pressure on Surface Tension of Polystyrene in Supercritical Carbon Dioxide

et al. 2007

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This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry B, copyright 2007 © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see DOI: 10.1021/jp065851tThe surface tension of polymers in a supercritical fluid is one of the most important physicochemical parameters in many engineering processes, such as microcellular foaming where the surface tension between a polymer melt and a fluid is a principal factor in determining cell nucleation and growth. This paper presents experimental results of the surface tension of polystyrene in supercritical carbon dioxide, together with theoretical calculations for a corresponding system. The surface tension is determined by Axisymmetric Drop Shape AnalysisProfile (ADSA-P), where a high pressure and temperature cell is designed and constructed to facilitate the formation of a pendant drop of polystyrene melt. Self-consistent field theory (SCFT) calculations are applied to simulate the surface tension of a corresponding system, and good qualitative agreement with experiment is obtained. The physical mechanisms for three main experimental trends are explained using SCFT, and none of the explanations quantitatively depend on the configurational entropy of the polymer constituents. These calculations therefore rationalize the use of simple liquid models for the quantitative prediction of surface tensions of polymers. As pressure and temperature increase, the surface tension of polystyrene decreases. A linear relationship is found between surface tension and temperature, and between surface tension and pressure; the slope of surface tension change with temperature is dependent on pressure.

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Section: Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Temperature and Pressure on Surface Tension of Polystyrene in Supercritical Carbon Dioxide

et al. 2007

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“…Viscosities of polymer solutions have been measured with this viscometer previously [63][64][65][66][67]. Even though the instrument was the same, some changes were implemented in order to evaluate terminal velocity with greater reliability.…”

Section: G Viscosity Measurement Technique Used In the Present Studymentioning

confidence: 99%

High-Pressure Viscosity and Density of Polymer Solutions at the Critical Polymer Concentration in Near-Critical and Supercritical Fluids

Dindar

Kiran

2002

Ind. Eng. Chem. Res.

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The motivation for the determination of the viscosity of polymer solutions in dense fluids at the critical polymer concentration stems from the need to understand the factors that influence the time scale of phase separation in systems that undergo spinodal decomposition upon a pressure quench. In a recent investigation of PDMS + CO 2 and PE + n -pentane where molecular weights of the polymers and the critical polymer concentrations were comparable, significant differences were observed in the time evolution of new phase growth. Among the reasons that contribute to the difference in phase separation kinetics is the viscosity of the solutions. This thesis has been carried out to experimentally demonstrate the differences in viscosities of solutions at their critical polymer concentration. Specifically, the thesis focused on the high-pressure density and viscosity of solutions of poly(dimethylsiloxane) (M w = 93,700, M w /M n = 2.99) in supercritical carbon dioxide and of polyethylene (M w = 121,000, M w /M n = 4.3) in near-critical n -pentane. The measurements have been carried out a t the critical polymer concentrations, which is 5.5 wt % for solution of PDMS in CO 2 and 5.75 wt % for solution of PE in n -pentane. For PDMS + CO 2 system, the measurements were conducted at 55, 70, 85 and 100 o C and pressures up to 50 MPa. For iii PE + n-pentane system, the measurements were conducted at 140 and 150 o C and again up to 50 MPa. All measurements were conducted in the one-phase homogenous regions.At these temperatures and pressures, the viscosities were observed to be in the range from 0.14 mPa.s to 0.22 mPa.s for PDMS + CO 2 , and from 2.3 mPa.s to 4.6 mPa.s for PE + npentane systems. In both systems the viscosities increase with pressure and decrease with temperature. The temperature and pressure dependence could be described by Arrhenius type relationships in terms of flow activation energy (E # ) and flow activation volume (V # ) parameters. The flow activation energies in PDMS + CO 2 system were about 7 kJ/mol compared to about 18 kJ/mol for the PE + n -pentane system. The activation volumes were in the range 40-64 cm 3 /mol for PDMS + CO 2 system and 65-75 cm 3 /mol for the PE + n -pentane solution. The higher values of E # and V # represent the higher sensitivity of viscosity to temperature and pressure changes in the PE + n -pentane system. The viscosity d ata could also be correlated in terms of density using free-volume based Doolittle type equations. Density is shown to be an effective scaling parameter to describe T/P dependency of viscosity. The closed packed volumes suggested from density correlations were found to be around 0.33 cm 3 /g for the PDMS and 0.48 cm 3 /g for the PE systems. Comparison of the viscosity data in these systems with the data on the kinetics of pressure-induced phase separation confirms that the slower kinetics in the PE + n-pentane stems from the higher viscosity in this solution compared to the PDMS + CO 2 system, despite the similarity in the molecular weight of the polymer a...

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“…Adequate melt viscosity is necessary to maintain sufficient melt pressure in the die and to prevent premature foaming [1]. In this context, it has to be considered that the dissolved blowing agent (BA) can act as plasticizer, which causes a considerable reduction in the viscosity of the polymer melt [2][3][4][5]. If melt pressure is lower than the solubility pressure required for complete dissolution of the BA in the melt, early nucleation and premature foaming in the die can occur, causing poor morphology and surface quality of the foam [1,6,7].…”

Section: Introductionmentioning

confidence: 99%

Extensional Flow Properties of Externally Plasticized Cellulose Acetate: Influence of Plasticizer Content

et al. 2013

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Elongational flow properties of polymer melts are very important for numerous polymer processing technologies such as blown film extrusion or foam extrusion. Rheotens tests were conducted to investigate the influence of plasticizer content on elongational flow properties of cellulose acetate (CA). Triethyl citrate (TEC) was used as plasticizer. Melt strength decreases whereas melt extensibility increases with increasing plasticizer content. Melt strength was further studied as a function of zero shear viscosity. The typical draw resonance of the Rheotens curve shifts to higher drawdown velocity and the amplitude of the draw resonance decreases with increasing TEC content. With respect to foam extrusion, not only are melt strength and melt extensibility important but the elongational behavior at low strain rates and the area under the Rheotens curve are also significant. Therefore, elongational viscosity as well as specific energy input were calculated and investigated with respect to plasticizer content. Preliminary foam extrusion tests of externally plasticized CA using chemical blowing agents confirm the results from rheological characterization.

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Measurements and modeling of PS/supercritical CO₂ solution viscosities

Cited by 157 publications

References 33 publications

Effect of Temperature and Pressure on Surface Tension of Polystyrene in Supercritical Carbon Dioxide

Effect of Temperature and Pressure on Surface Tension of Polystyrene in Supercritical Carbon Dioxide

High-Pressure Viscosity and Density of Polymer Solutions at the Critical Polymer Concentration in Near-Critical and Supercritical Fluids

Extensional Flow Properties of Externally Plasticized Cellulose Acetate: Influence of Plasticizer Content

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Measurements and modeling of PS/supercritical CO2 solution viscosities

Cited by 157 publications

References 33 publications

Effect of Temperature and Pressure on Surface Tension of Polystyrene in Supercritical Carbon Dioxide

Effect of Temperature and Pressure on Surface Tension of Polystyrene in Supercritical Carbon Dioxide

High-Pressure Viscosity and Density of Polymer Solutions at the Critical Polymer Concentration in Near-Critical and Supercritical Fluids

Extensional Flow Properties of Externally Plasticized Cellulose Acetate: Influence of Plasticizer Content

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Measurements and modeling of PS/supercritical CO₂ solution viscosities