Pressure-volume-temperature Data Research Articles

Pressure–volume–temperature data and surface tension of blends of poly(ethylene oxide) and poly(methyl acrylate) in the melt

AbstractThe pressure–volume–temperature behavior of miscible blends of poly(ethylene oxide) (PEO) and poly(methyl acrylate) (PMA) was studied over extended ranges of temperature and pressure. From pressure–volume–temperature data, the reduction parameters for the Flory‐Orwoll‐Vrij equation‐of‐state were determined. It was found that reduction parameters as well as density, thermal expansion coefficient, and isothermal compressibility vary with composition in a nonlinear manner. The surface tension of the blends in the molten state was measured over the whole composition range using the sessile drop method. The surface tension was found to display negative deviation from additivity pointing toward a remarkable surface excess of PMA. Moreover, surface tension displays a minimum in the range of low PEO content at weight fraction of ∼0.19. In addition, the temperature coefficient of surface tension shows negative deviation from linearity. It stays constant when PMA is in excess. Results are discussed in terms of equation‐of‐state thermodynamics. The minimum of surface tension can be well explained by weak self‐association of PEO in the bulk. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1893–1900, 2010

Online pressure–volume–temperature measurements of polypropylene using a testing mold to simulate the injection‐molding process

AbstractTo obtain accurate prediction of service performance and service life of polymers and to optimize the processing parameters, a modified online measurement was used to measure the pressure–volume–temperature (PVT) properties of polymers under certain processing conditions. The measurement was based on an injection molding machine, and it was used to obtain the PVT data of polymers directly with a special testing mold under normal processing conditions. The PVT properties of a semicrystalline polymer, polypropylene, were measured through both an online testing mold and a conventional piston–die dilatometer. The PVT properties were correlated by a modified two‐domain Tait equation of state. The differences between the two groups of PVT data measured were investigated, and relative differences, especially in the rubbery state because of different cooling or heating measuring modes and sample forms, were observed. Numerical simulations of injection‐molding processes were carried out by Moldflow software with both of the types of PVT data. The resulting online PVT data exhibited improvement in the accurate prediction of shrinkage and warpage. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

The temperature dependence of free volume in phenyl salicylate and its relation to structural dynamics: A positron annihilation lifetime and pressure-volume-temperature study

Positron annihilation lifetime spectroscopy (PALS) and pressure-volume-temperature (PVT) experiments were performed to characterize the temperature dependent microstructure of the hole free volume in the low molecular weight glass-former phenyl salicylate (salol). The PALS spectra were analyzed with the new routine LT9.0 and the volume distribution of subnanometer size holes characterized by its mean <v(h)> and standard deviation sigma(h) was calculated. Crystallization of the amorphous sample was observed in the temperature range above 250 K, which leads to a vanishing of the positronium formation. The positronium signal recovered after melting at 303 K. A combination of PALS with PVT data enabled us to calculate the specific density N(h)('), the specific volume V(f), and the fraction of holes f(h) in the amorphous state. From comparison with dielectric measurements in the temperature range above T(B)=265 K, it was found that the primary structural relaxation slows down with temperature, faster than the shrinkage of the hole free volume V(f) would predict, on the basis of the Cohen-Turnbull (CT) free volume theory. CT plots can be linearized by replacing V(f) of the CT theory by (V(f)-DeltaV), where DeltaV is a volume correction term. This was interpreted as indication that the lower wing of the hole size distribution contains holes too small to show a liquidlike behavior in their surroundings. Peculiarities of the relaxation behavior below T(B)=265 K and the possible validity of the Cohen-Grest free volume model are discussed.

Equations of state for polyamide-6 and its nanocomposites. II. Effects of clay

The pressure-volume-temperature (PVT) dependencies of polyamide-6 and its nanocomposites (polymeric nanocomposites) were measured at temperatures T = 300–600 K and pressures P = 0.1–190 MPa, thus spanning the range of molten and “solid” phases. The Simha-Somcynsky (S-S) cell-hole equation of state (EOS) was used for describing the molten region. At Tg(P) ≤ T ≤ Tm(P), the “solid” phase is a mixture of the liquid polyamide-6 with dispersion of crystals. Accordingly, the PVT behavior in this region was described as a combination of the S-S EOS for the liquid phase and the Midha-Nanda-Simha-Jain (MNSJ) EOS for the crystalline one. These two theories based on different models yielded two sets of the characteristic reducing parameters, P*, T*, V* and the segmental molecular weight, Ms. Incorporation of 2 and 5 wt % clay increased P* and reduced T* and V*, but the effects were small. Fitting the combination of S-S and MNSJ EOS' to isobaric “solid” phase data yielded the total crystallinity, Xcryst, and the correcting excess specific volume, ΔVm,c. Both parameters were sensitive to pressure, P, and the clay content, w—the former increased with P and w, whereas the latter decreased. The raw PVT data were numerically differentiated to obtain the thermal expansion and compressibility coefficients, α and κ, respectively. At T Tm, the opposite effect was observed, most likely owing to the excess of intercalant in the polymeric nanocomposites samples. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 966–980, 2009

Analysis of ionic liquid PVT behavior with a Modified Cell Model

High pressure pure component pressure–volume–temperature (PVT) properties of ionic liquids are summarized and analyzed with a Modified Cell Model (MCM) that uses characteristic parameters, T*, V* and P*. The model was found to provide good fits of 28 different ionic liquid PVT data consisted with 14 types cation and 10 types anion over a wide range of temperatures (278–473 K) and pressures (0.1–200 MPa). The characteristic parameters of the model could be correlated with simple functions of the Bondi van der Waals volume for the cation and anion of each ionic liquid. Generalized parameters for MCM with the van der Waals volume are proposed that allow calculation of ionic liquid densities at high pressures to within an average deviation of 1.9%.

Measurements and calculations of hydrocarbon mixtures liquid density by simple cubic equations of state

The continuing importance of pressure-volume-temperature (PVT) property calculations of reservoir fluids mixtures in design of equipments used for storage, transportation and separation processes need considerable experimental and theoretical attempts to present a simple, accurate and theoretical based equation of state to replace the existing empirical based equations of state. The first author and his co-workers previously presented two parameters cubic theoretical based equation of state (MMM). This equation was used in PVT and vapour-liquid-equilibrium (VLE) calculations of pure and fluid mixtures. The comparisons for the different pure and mixture fluids calculations indicated the advantages of this equation of state over the well-known empirical-based two parameters cubic equation of state (RK EOS). In this study, PVT data for binary, ternary, quaternary and multicomponent oil mixtures at the different temperature and ambient pressure are measured, and reported. The measured PVT data were compared with those obtained by using the simple cubic equations of state. The calculated results by MMM EOS are compared with SRK and PR EOSs which are the commonly used three parameters cubic EOSs in the oil and gas calculations. The comparisons indicate that, although the SRK and PR EOSs needs an additional parameter (acentric factor, ω), the MMM equation of state is more accurate than both SRK and PR equations for the PVT calculations of oil mixtures.

The relative placement of linear viscoelastic functions in amorphous glassy polymers

A procedure is described and analyzed for the determination of the relative placement of linear viscoelastic functions and their relative relaxation∕retardation spectra for a commercial polycarbonate (LEXAN GE). The complete set of viscoelastic functions in creep and relaxation was obtained from two simple experimental data, namely the linear viscoelastic response in shear and the pressure volume temperature (PVT) behavior. The dimensionless bulk compliance was extracted from PVT data showing that it coincides with the memory function appearing in the Kovacs, Aklonis, Hutchinson, Ramos phenomenological theory [Kovacs, A. J., J. J. Aklonis, J. M. Hutchinson, and A. R. Ramos, J. Polym. Sci., Polym. Phys. Ed. 17, 1097 (1979)]. Our results are compared with the relevant literature data obtained on different polymers and show that polycarbonate fulfills simultaneously the responses features concerning the relative placement of the bulk and shear moduli [Kono, R. J., Phys. Soc. Jpn. 15, 4 (1960)], the shapes of...

Equations of state for polyamide‐6 and its nanocomposites. 1. Fundamentals and the matrix

AbstractThe pressure‐volume‐temperature (PVT) surface of polyamide‐6 (PA‐6) was determined in the range of temperature T = 300–600 K and pressure P = 0.1–190 MPa. The data were analyzed separately for the molten and the noncrystalline phase using the Simha‐Somcynsky (S‐S) equation of state (eos) based on the cell‐hole theory. At Tg(P) ≤ T ≤ Tm(P), the “solid” state comprises liquid phase with crystals dispersed in it. The PVT behavior of the latter phase was described using Midha‐Nanda‐Simha‐Jain (MNSJ) eos based on the cell theory. The data fitting to these two theories yielded two sets of the Lennard‐Jones interaction parameters: ε*(S‐S) = 34.0 ± 0.3 and ε*(MNSJ) = 22.8 ± 0.3 kJ/mol, whereas v*(S‐S) = 32.00 ± 0.1 and v*(MNSJ) = 27.9 ± 0.2 mL/mol. The raw PVT data were numerically differentiated to obtain the thermal expansion and compressibility coefficients, α and κ, respectively. At constant P, κ followed the same dependence on both sides of the melting zone near Tm. By contrast, α = α(T) dependencies were dramatically different for the solid and molten phase; at T &lt; Tm, α linearly increased with increasing T, then within the melting zone, its value step‐wise decreased, to slowly increase at higher temperatures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 299–313, 2009

PVT Behavior of Thermoplastic Poly(styrene-co-acrylonitrile)-Modified Epoxy Systems: Relating Polymerization-Induced Viscoelastic Phase Separation with the Cure Shrinkage Performance

The volume shrinkage during polymerization of a thermoplastic modified epoxy resin undergoing a simultaneous viscoelastic phase separation was investigated for the first time by means of pressure-volume-temperature (PVT) analysis. Varying amounts (0-20%) of poly(styrene-co-acrylonitrile) (SAN) have been incorporated into a high-temperature epoxy-diamine system, diglycidyl ether of bisphenol A (DGEBA)-4,4'-diaminodiphenyl sulfone (DDS) mixture, and subsequently polymerized isothermally at a constant pressure of 10 MPa. Volume shrinkage is highest for the double-phased network-like bicontinuous morphology in the SAN-15% system. Investigation of the epoxy reaction kinetics based on the conversions derived from PVT data established a phase-separation effect on the volume shrinkage behavior in these blends. From subsequent thermal transition studies of various epoxy-DDS/SAN systems, it has been suggested that the behavior of the highly intermixed thermoplastic SAN-rich phase is the key for in situ shrinkage control. Various microscopic characterizations including scanning electron microscopy, atomic force microscopy, and optical microscopy are combined to confirm that the shrinkage behavior is manipulated by a volume shrinkage of the thermoplastic SAN-rich phase undergoing a viscoelastic phase separation during cure. Consequently, a new mechanism for volume shrinkage has been visualized for the in situ polymerization of a thermoplastic-modified epoxy resin.

Free volume of molten and glassy polystyrene and its nanocomposites

AbstractThe Pressure‐Volume‐Temperature (PVT) dependencies of polystyrene‐based clay‐containing nanocomposites (CPNC) were determined in the glassy and molten state. The PVT data in the melt were fitted to the Simha‐Somcynsky (S‐S) lattice‐hole equation‐of‐state (eos), yielding the free volume quantity, h = h(T, P), and the characteristic reducing parameters, P*, V*, T*. The data within the glassy region were interpreted considering that the latter parameters are valid in the whole range of independent variables, than calculating h = h(T, P) from the experimental values of V = V(T, P). Next, the frozen free volume fraction in the glass was computed as FF = FF(P). In the molten state the maximum reduction of free volume was observed at wsolid ≈ 3.6–wt % clay, amount sufficient to adsorb all PS into solidified layer around organoclay stacks. In the vitreous state FF increased with clay content from 0.6 to 1.6—this is the first time FF ≫ 1 has been observed. The highest value was determined for CPNC with the highest clay content, w = 17.1 wt %, thus well above wsolid. The derivative properties, compressibility, κ, and the thermal expansion coefficient, α, depend on T, P, and w. Plots of κ versus T indicate the presence of two secondary transitions, one at Tβ/Tg ≈ 0.9 ± 0.1 and other at TT/Tg = 1.2 ± 0.1. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2504–2518, 2008

Review Of PVT Correlations For Crude Oils

Reservoir fluid physical property values constitute an integral part of the data required for comprehensive study of the reservoir and for optimal design of oil recovery and production schemes. More specifically, Pressure-Volume-Temperature (PVT) data corresponding to the reservoir fluid are needed to validate the well test property and to provide meaningful interpretation. In the absence of laboratory measured PVT data, property correlations are used for property estimation. Various PVT correlations have been published over the years, which used data from limited geographical areas, sometimes assumed to be global and differing fluid characteristics. Because of variation in the crude compositions, geographical, and petrophysical conditions of the operating environments, these correlations cannot acclaim universal applicability. This paper attempts to give comprehensive review of existing PVT correlations and models in the literature, indicating geographical region, accuracies as well as the nature of these correlations. Using these correlations from other regions would have implications such as poor fluid property estimations, poor reservoir performance studies, as well as uncertainty in reserve estimations in the Niger Delta. Keywords: PVT Correlations, PVT Data, Reservoir Fluid Properties, Fluid Property EstimationGlobal Journal of Pure and Applied Sciences Vol. 14 (3) 2008: pp. 331-338

Determining the pressure dependency of the viscosity using PVT data: A practical alternative for thermoplastics

The relation between Pressure–Volume–Temperature (PVT) and rheological behaviour of several polymers including polypropylene, poly(methyl methacrylate), polyamide, polycarbonate, polystyrene and polystyrene/polycarbonate blends was studied. Pressure–viscosity coefficient b = ( ∂ ln η 0 / ∂ P ) was calculated by means of a revisited version of the Miller equation that accounts for pressure and temperature effect on Newtonian viscosity through the activation energy of flow and PVT parameters. Pressure–temperature dependent viscosities experimentally determined using pressure chamber capillary rheometry allow us to check the approach of the Miller equation. Incorporating the pressure effect in the Carreau–Yasuda model for η ( γ ˙ ) allows establishing the viscosity curves of thermoplastics over a wide range of shear rates and pressures.

Improved Fluid Characterization for Miscible Gas Floods

Summary Equations of state (EOSs) are typically tuned to black-oil pressure/volume/temperature (PVT) data such as constant volume-depletion, constant-composition-expansion, differential-liberation, and separator tests. Other PVT data more appropriate for gas injection could include multicontact and swelling tests and slimtube tests. The standard method of tuning, however, does not typically incorporate important displacement parameters, such as the minimum miscibility pressure (MMP), minimum miscibility enrichment (MME), or the likely compositions that result in a reservoir from condensing-vaporizing (CV) displacements. This paper demonstrates an improved reservoir-fluid-characterization procedure for miscible gas floods that can represent the interaction of flow and phase behavior more accurately. We demonstrate the approach for two displacements, an 11-component CO2 flood and a 12-component enriched-gas flood. The method-of-characteristic (MOC) theory is used to determine the MME (or MMP) of both lumped and unlumped models. The results show that by tuning to the calculated MME/MMP, fewer pseudocomponents are required to characterize the fluid than with conventional tuning methods. For the cases studied, fluids lumped to as few as four or five pseudocomponents can provide a good match to the composition profiles and oil recoveries of the unlumped models.

Thermal equation of state of natural chromium spinel up to 26.8 GPa and 628 K

A pressure–volume–temperature data set has been obtained for natural chromium spinel, using synchrotron X-ray diffraction with a resistance heated diamond-anvil cell (RHDAC). The unit cell parameter of the chromium spinel was measured by energy dispersive X-ray diffraction up to pressures of 26.8 GPa and temperatures of 628 K. No phase change has been observed. The observed P–V–T data were fit to the high-temperature Birch-Murnaghan equation of state, with V0 fixed at its experimental value, yields K0 = 209 ± 9 GPa, (∂K/∂T)P = −0.056 ± 0.035 GPa K−1, and α0 = 7±1 × 10−5 K−1. The temperature derivative of the bulk modulus (∂K/∂T)P of chromium spinel is determined here for the first time. The obtained K0 is slightly higher than the previous results of synthetic spinel. We suggest that Fe2+–Mg2+ substitution is responsible for the high bulk modulus of chromium spinel.

Measurement of the PVT property of PP/CO 2 solution

The pressure–volume–temperature (PVT) data for polymer/gas solutions is an important fundamental property of which accurate measurement has not been reported until recently. The diffusivity, solubility and surface tension are critical physical properties of polymer/gas systems for understanding and controlling polymer processing such as foaming, blending, extraction reaction and so on. However, the determination of these properties relies on accurate PVT data as a prerequisite. In this study, we have developed a new methodology for measuring the PVT properties of polymer melts saturated with high-pressure gas at elevated temperatures. This paper presents a description of the methodology, including the experimental apparatus design and data analysis. A case study on neat polypropylene (PP) density measurement and determination of PP/CO 2 solution volume swelling was presented to elucidate and verify the methodology at high-pressure and high-temperature conditions.

Comparison of the Performance of Empirical Models Used for the Prediction of the PVT Properties of Crude Oils of the Niger Delta

A review of the literature has revealed the lack of a formal analysis of the performance of empirical methods for the prediction of pressure volume temperature (PVT) properties of Niger delta crude oils. This study presents an assessment of the predictive accuracy of five bubble-point pressure (P b ) correlations and five bubble-point oil formation volume factor (B ob ) correlations against a large measured PVT data bank from Niger Delta crude oils. Statistical analysis techniques were used to evaluate the performance and the accuracy of the commonly used empirical models for estimating PVT properties of Niger crude oil in order to guide designers and operators in selecting the best correlations for their particular applications. Agreement between calculated and measured P b and B ob values for the various models was very poor. The model predictions of P b and B ob can be different from the measured values by 56% and 242%, respectively. Development of improved models for predicting the PVT properties of Niger delta crude oils is urgently required.

The free volume in two untreated, pressure-densified, and CO2 gas exposed polymers from positron lifetime and pressure-volume-temperature experiments

AbstractChanges in the microstructure of the free volume and its temperature dependence in ethylene-norbornene copolymer and bisphenol-A polycarbonate due to densification under pressure and swelling with CO2 gas have been examined using positron annihilation lifetime spectroscopy (PALS) and pressurevolume- temperature (PVT) experiments. Employing the Simha-Somcynsky equation of state the specific hole free and occupied volumes were estimated. From the PALS spectra analyzed with the new routine LT9.0 the size distribution of subnanometre holes and its mean and mean dispersion were calculated. Above Tg, the dispersion mirrors the thermal fluctuations in the free volume. From comparison of PALS and PVT data the specific number of holes was estimated. It was found that the occupied volume has a constant and identical compressibility in the glassy and rubbery state. It shows no memory for the history of the glass and mirrors only the pressure and temperature during the measurement. The change in the total volume due to the pre-treatments of the polymers occurs exclusively in the hole free volume Vf and the relative change in Vf is one order of magnitude larger than in the total volume. PALS data show that the mean hole size and its dispersion in the glassy state is decreased due to densification and increased due to swelling. PVT data show that the volume changes are frozen in the polymer glasses and that, when heating the samples, the volume begins to recover at temperatures ca. 50 K in gas swollen and 20 K in densified polymers below Tg. The PALS data show a corresponding behaviour.

Pressure–volume–temperature (PVT) measurements of ionic liquids ([bmim +][PF 6−], [bmim +][BF 4−], [bmim +][OcSO 4−]) and analysis with the Sanchez–Lacombe equation of state

Pressure–volume–temperature measurements of the pure ionic liquids 1-butyl-3-methyl-imidazolium hexafluorophosphate ([bmim +][PF 6 −]), 1-butyl-3-methyl-imidazolium tetrafluoroborate ([bmim +][BF 4 −]), 1-butyl-3-methyl-imidazolium octylsulfate ([bmim +][OcSO 4 −]) were performed with a metal bellows apparatus at temperatures from 313 to 473 K and at pressures up to 200 MPa. The pressure–volume–temperature data were used to determine parameters of the Sanchez–Lacombe equation of state, which was used to calculate the hard core volume and free volume of ionic liquids. It was found that the hard core volume of the ionic liquid was related with anion size and was slightly smaller than the van der Waals volume estimated with Bondi methods. The free volumes of [bmim +][PF 6 −] and [bmim +][BF 4 −] calculated with the Sanchez–Lacombe equation of state showed a similar pressure dependence and were close to each other (ca. 10–14 cm 3/mol) whereas the values for [bmim +][OcSO 4 −] were much higher (ca. 18–25 cm 3/mol) over the range of pressure.

Empirical Equations for Estimating ADE of Crude Oils

There has been an increasing interest in the construction of asphaltene deposition envelope (ADE) to determine a safe zone of operation during oil production. Equations of state are usually used for calculations of ADE; however, the method requires tuning some experimental Pressure Volume Temperature (PVT) data of the reservoir fluid. The objective of this study is to develop a simple, accurate, and reliable empirical equation for estimating the ADE by determining the upper and lower onset pressures as well as the saturation pressures. Three simple empirical equations are developed to calculate these onset pressures of several crude oils. Experimentally measured compositions, saturation, and onset pressures of 33 crude oil samples, primarily from the Middle East, at different temperatures were used to develop the equations. Another set of compositions and upper saturation and lower onset pressures of different crude oil samples from the literature were used to test the accuracy of the empirical equations. The results were also compared with equations of state predictions. The results indicate that the method is accurate, valid, reliable, and eliminates the splitting and characterizing of the heavy fraction, which is necessary for the equations of state predictions. The method is useful for estimating the ADE of crude oils where experimental data is not available.

Density measurement of polymer/CO2 single‐phase solution at high temperature and pressure using a gravimetric method

AbstractThe densities of two polymer/CO2 single‐phase solutions, poly(ethylene glycol) (PEG)/CO2 and polyethylene (PE)/CO2, were measured at temperatures higher than melting temperature of the polymer under CO2 pressures in the range 0–15 MPa using a newly‐proposed gravimetric method. A magnetic suspension balance (MSB) was used for the density measurement under the high pressure CO2: A thin disc‐shaped platinum plate was submerged in the considered polymer/CO2 single‐phase solution in the MSB high‐pressure cell. The weight of the plate was measured while keeping CO2 pressure and temperature in the sorption cell at a specified level. Since the buoyancy force exerted on the plate by the polymer/CO2 solution reduced the apparent weight of the plate, the density of the polymer/CO2 solution could be calculated by subtracting the true weight of the plate from its measured weight. Experimental results showed that the density of PE/CO2 solution increased with the increase of CO2 pressure and the density of PEG/CO2 solution decreased with the increase of CO2 pressure. To differentiate the effect of CO2 dissolution in polymer from that of mechanical pressure, the density of polymer/CO2 solution was compared with the density of neat polymer under the given mechanical pressure, which was calculated using the Sanchez–Lacombe equation of state and Pressure–Volume–Temperature data of the polymer. The comparison could elucidate that the dissolution of CO2 in polymer reduced density of both PEG/CO2 and PE/CO2 systems but the degree of CO2 induced‐density reduction was different between two polymer/CO2 systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007