New expressions for non-randomness in equation-of-state models

Panayiotou, Costas

doi:10.1016/j.fluid.2005.08.019

Cited by 14 publications

(22 citation statements)

References 15 publications

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“…An evolution of classical compressible LF theories used to describe the thermodynamics of amorphous rubbery polymer–penetrant mixtures, consisted in introducing modifications to the SL theory by accounting for the for non-random distribution of components and of free volume. The NRLF approach adopted here belongs to this class of models and is derived from the NRHB model [ 17 , 18 , 19 , 20 , 21 ] by dropping out the terms related to specific interactions. We address here only the specific case of a binary system made of a polymer and a low molecular weight penetrant.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Modelling Sorption Thermodynamics and Mass Transport of n-Hexane in a Propylene-Ethylene Elastomer

et al. 2021

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Optimization of post polymerization processes of polyolefin elastomers (POE) involving solvents is of considerable industrial interest. To this aim, experimental determination and theoretical interpretation of the thermodynamics and mass transport properties of POE-solvent mixtures is relevant. Sorption behavior of n-hexane vapor in a commercial propylene-ethylene elastomer (V8880 VistamaxxTM from ExxonMobil, Machelen, Belgium) is addressed here, determining experimentally the sorption isotherms at temperatures ranging from 115 to 140 °C and pressure values of n-hexane vapor up to 1 atm. Sorption isotherms have been interpreted using a Non Random Lattice Fluid (NRLF) Equation of State model retrieving, from data fitting, the value of the binary interaction parameter for the n-hexane/V8880 system. Both the cases of temperature-independent and of temperature-dependent binary interaction parameter have been considered. Sorption kinetics was also investigated at different pressures and has been interpreted using a Fick’s model determining values of the mutual diffusivity as a function of temperature and of n-hexane/V8880 mixture composition. From these values, n-hexane intra-diffusion coefficient has been calculated interpreting its dependence on mixture concentration and temperature by a semi-empiric model based on free volume arguments.

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Section: Theoretical Backgroundmentioning

confidence: 99%

Modelling Sorption Thermodynamics and Mass Transport of n-Hexane in a Propylene-Ethylene Elastomer

et al. 2021

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“…An evolution of classical compressible LF theories used to describe the thermodynamics of amorphous rubbery polymer-penetrant mixtures, consisted in introducing modifications to the SL theory by accounting for the for non-random distribution of components and of free volume and for the presence of specific interactions between neighboring molecules. The non-random hydrogen-bonding theory (NRHB) is a model belonging to this class of approaches [15][16][17][18][19]. In the present context, in view of the absence of hydrogen bonding and other specific interactions in the system under investigation, the contribution related to specific interactions has been omitted in the description of the model equations.…”

Section: Modeling Sorption Thermodynamics By Nrhb Approachmentioning

confidence: 99%

Modelling Sorption Thermodynamics and Mass Transport of n-Hexane in a Propylene-Ethylene Elastomer

Tammaro¹,

Lombardi²,

Scherillo³

et al. 2021

Preprint

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Optimization of post polymerization devolatilization process of polyolefin elastomers (POE) is of considerable industrial interest. To this aim, experimental determination and theoretical interpretation of the thermodynamics and mass transport properties of POE-solvent mixtures is relevant. Sorption behaviour of n-hexane vapour in a commercial propylene-ethylene elastomer (V8880 VistamaxxTM from ExxonMobil) is addressed here, determining experimentally the sorption isotherms at temperatures ranging from 115 to 140 °C and pressure values of n-hexane vapour up to 1 atm. Sorption isotherms have been interpreted with the Non-Random-Hydrogen-Bonding Equation of State model retrieving, from data fitting, the value of the binary interaction parameter for the n-hexane/V8880 system. Both the case of temperature-independent and of temperature-dependent binary interaction parameter have been considered. Sorption kinetics was also investigated at different pressures and has been interpreted using a Fick’s model determining values of the mutual diffusivity as a function of temperature and of n-hexane/V8880 mixture composition. From these values, n-hexane intra-diffusion coefficient has been calculated interpreting its dependence on mixture concentration and temperature by a semi-empiric model based on free volume arguments.

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“…Significant improvement of the classic compressible lattice fluid theories to describe rubbery polymer–penetrant mixture thermodynamics was obtained by accounting for the nonrandomness distribution of all contactsincluding the nonrandom distribution of free volume hole sitesand for highly specific forces, like hydrogen bonding, between neighboring molecules. A relevant example of this class of approaches is the nonrandom hydrogen bonding (NRHB) model, − that has been used in this study. In view of the absence of hydrogen bonding and other specific interactions in the case of the polystyrene–toluene system, the contribution to model equations related to hydrogen bonding has been omitted here.…”

Section: Introductionmentioning

confidence: 99%

Modeling Retrograde Vitrification in the Polystyrene–Toluene System

et al. 2018

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Atactic polystyrene, as reported in a recent contribution by our group, displays a marked change in glass transition when exposed to toluene vapor due to plasticization associated with vapor sorption within the polymer. The dependence of the glass transition temperature of the polymer-penetrant mixture on the pressure of toluene vapor is characterized by the so-called "retrograde vitrification" phenomenon, in that, at a constant pressure, a rubber to glass transition occurs by increasing the temperature. In this contribution, we have used a theoretical approach, based on the nonrandom lattice fluid thermodynamic model for the polymer-toluene mixture, to predict the state of this system, i.e., rubbery or glassy, as a function of fluid pressure and system temperature. The experimentally detectable glass transition is assumed to be a kinetically affected evidence of an underlying II order thermodynamic transition of the polymer mixture. On the basis of this hypothesis, the Gibbs-Di Marzio criterion, stating that equilibrium configurational entropy is zeroed at the glass transition, has been applied to locate the transition. The working set of equations consists of the expression of configurational entropy obtained from the adopted lattice fluid model equated to zero, coupled with the equation expressing the phase equilibrium between the polymer phase and the pure toluene vapor phase in contact and with the equations of state for the two phases. Theoretical predictions are in good qualitative and quantitative agreement with the experimental results previously obtained gravimetrically performing "dynamic" sorption experiments, which represent a neat example of the occurrence of so-called "type IV" glass transition temperature vs pressure behavior. The peculiar retrograde vitrification phenomenon and the glass transition temperature vs pressure envelope determined experimentally are well described by the proposed theoretical approach.

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New expressions for non-randomness in equation-of-state models

Cited by 14 publications

References 15 publications

Modelling Sorption Thermodynamics and Mass Transport of n-Hexane in a Propylene-Ethylene Elastomer

Modelling Sorption Thermodynamics and Mass Transport of n-Hexane in a Propylene-Ethylene Elastomer

Modelling Sorption Thermodynamics and Mass Transport of n-Hexane in a Propylene-Ethylene Elastomer

Modeling Retrograde Vitrification in the Polystyrene–Toluene System

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