Liquid multi-phase separation in solvent-polymer systems

In Simple Flory-Huggins solvent-polymer systems liquid three-phase separation occurs via a homogeneous double plait point. The conditions for three-phase separation in a system consisting of a solvent and two polydisperse polymer homologues are given. It is shown that in a simple Flory-Huggins solvent-polymer system four and more phase separation cannot occur. General conditions for a multicritical point are given.     

Phase equilibra of polystyrene/polybutadiene/tetrahydrofuran using gel permeation chromatography

Gel permeation chromatography using sequential differential refractive index and ultraviolet detectors has been successfully used to give the compositional analysis of conjugate phases in the incompatible system of polystyrene and polybutadiene with tetrahydrofuran as solvent. Application of this method to equilibrated samples yields tie lines, binodal curves, and plait points. The effects of molecular weights and molecular weight ratios on the slopes of the tie lines, the location of the binodal curve, and the depletion of second polymers from phases are discussed.     

Purification of wet process phosphoric acid by solvent extraction liquid-liquid equilibrium at 25 and 40°C of the system water-phosphoric acid-methylisobutylketone

Solubility and liquid-liquid phase equilibrium data are presented for the ternary system water-phosphoric acid-methyl isobutyl ketone at 25 and 40°C. Binodal curves, tie lines and distribution curves have been determined. Hand's method has been used to correlate tie lines and to calculate coordinates of plait points. The heterogeneous region at 40°C appeared to be slightly broader than that at 25°C, and the slopes of tie lines somewhat higher: the solubility of this system increases with decreasing temperature. The distribution curves indicated that methyl isobutyl ketone was an effective extractant for concentrated phosphoric acid solutions only.     

脉冲褶式滤芯在PTA输送系统中的应用

以脉冲褶式滤芯在几个化工厂气力输送系统改造中的应用为例,介绍了脉冲褶式滤芯及滤料的选用方法及工程应用,对我国今后化工装置的气力输送系统的设计和改造提供了一些经验和方法。     

SOLUBILITY AND TIE-LINE DATA FOR WATER + FORMIC ACID + METHYL ISOBUTYL KETONE TERNARY SYSTEM AT DIFFERENT TEMPERATURES

The solubility and tie-line data of the ternary system comprising water, formic acid, and methyl isobutyl ketone were experimentally determined at the temperatures 288.15, 298.15, and 308.15 K, and atmospheric pressure 101.3 kPa. The plait points were also determined using Treybal's method. The results indicate that formic acid distributes preferentially in MIBK compared to water. Experimental tie-line data were regressed with the NRTL model to obtain binary interaction parameters. It is found that the NRTL model correlates the present system satisfactorily with average root-mean-square deviation of 0.34%.     

Application of NRTL and uniquac models to liquid-liquid systems with halogen salts (Part I)

Binodal curves, tie lines, and plait points for benzene-halogen salt solutions-n-propanol systems were determined, and Othmer-Tobias equation was employed for a system without salt and Eisen-Joffe equation for systems with salt to test consistency. Halogen salt solutions were prepared with aqueous solution of 5% KF, 5% NaCl, 5% NaBr and5% Nal, respectively. Compositions of two splitting phases on liquid-liquid equilibria (L-L-E) condition were calculated and the parameters were estimated by correlating experimental tie lines with the NRTL and the UNIQUAC (or modified UNIQUAC) models. The effects of addition of four halogen salts (KF, NaCl, NaBr, Nal) to benzene-water-n-propanol system were considered.     

Improved method to calculate Hansen solubility parameters of a polymer

An improved method to calculate Hansen solubility parameters δ_d, δ_p and δ_h, as well as the radius of interaction sphere for a given polymer is presented, starting from the idea that the solvents which dissolve a polymer, form in the interior of its solubility range a system of material points, their ‘masses' being given by the unity normed intrinsic viscosities of the polymer in the considered solvents. The mass centre coordinates of the material points system represent in fact Hansen solubility parameters of the polymer, and the radius of interaction sphere the distance from this centre to the farthest point of material points system mentioned.     

Membrane formation via phase separation induced by penetration of nonsolvent from vapor phase. I. Phase diagram and mass transfer process

The isothermal phase diagram for poly(vinylidene fluoride)/dimethyl formamide/water system was derived. The binodal and spinodal were calculated based on the Flory–Huggins theory and the calculated binodal was approximately in agreement with the experimental data of the cloud points. The isothermal crystallization line was also obtained according to the theory of melting point depression. Mass transfer of the three components during membrane formation by the precipitation from the vapor phase has been analyzed. During this process, phase separation of the polymer solution is induced by the penetration of water vapor in the solution. The calculated result on the changes of the cast film weights indicated the good agreement with the experimental data. The time‐course of the polymer concentration profile in the film was calculated for various cases of different humidity of the vapor phase and different initial polymer concentration. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 159–170, 1999     

Liquid–liquid phase separation in polysulfone/polyethersulfone/N‐methyl‐2‐ pyrrolidone/water quaternary system

To construct a phase diagram of the polysulfone (PSF)/polyethersulfone (PES)/N‐methyl‐2‐pyrrolidone (NMP)/water quaternary system, cloud point measurements were carried out by a titration method. The miscible region in the PSF/PES/NMP/water quaternary system was narrow compared to the PSF/NMP/water and PES/NMP/water ternary systems. The binary interaction parameters between PSF and PES were estimated by water sorption experiments. The calculated phase diagram based on the Flory–Huggins theory fit the experimental cloud points well. In addition to the usual polymer–liquid phase separation, polymer–polymer phase separation, which resulted in a PSF‐rich phase and a PES‐rich phase, was observed with the addition of a small amount of nonsolvent. The boundary separating these two modes of phase separation could be well described and predicted from the calculated phase diagrams with the estimated binary interaction parameters of the components. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2113–2123, 1999     

Microporous anisotropic phase inversion membranes from bisphenol A polycarbonate: Effect of additives to the polymer solution

Phase inversion is a very flexible technique to obtain membranes with a large sort of morphologies. Membrane properties can vary greatly depending on the kind of polymer system used. Bisphenol A polycarbonate (PC) could be used as a phase inversion membrane base polymer, and presents very good properties. Nevertheless, very little information on membrane preparation using PC and the phase inversion process can be found in the literature. In this work flat‐sheet microporous membranes were obtained by the phase inversion process using the immersion precipitation technique. A new polymer system was studied, consisting of polycarbonate, N‐methyl‐2‐pyrrolidone as solvent, water as the nonsolvent, and an additive. The influence of some parameters on membrane morphology, such as polymer solution composition, exposition time before immersion into the precipitation bath, and the kind of additive was investigated. Precipitation was followed using light transmission experiments and membrane morphology was observed through Scanning Electron Microscopy (SEM). The viscosity and cloud points of all polymer solutions were also determined. The results were related to the studied synthesis parameters, using the basic principles of membrane formation by the phase inversion technique, looking forward to establishing criteria to control the morphology of flat‐sheet membranes using polycarbonate as the base polymer. The results showed that both additives were able to increase pore interconnectivity and even suppress macrovoid formation. The decrease in the miscibility region of the polymer system and increase in mass transfer resistance are found to be the determining factors during polymer solution precipitation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3085–3096, 2002     

Application of genetic algorithm in calculation of the phase behavior of binary and ternary polymer solutions

A genetic algorithm as an optimization procedure has been developed to predict the phase behavior of polymer solutions. The phase equilibrium diagrams of binary and ternary polymer solutions have been determined using the appropriate form of Flory–Huggins free-energy function for polymer solutions. A concentration and temperature dependent form of the interaction parameter has been used to reflect the effect of temperature and polymer properties in the free-energy form. The proposed genetic algorithm is applied to compare the phase behavior results of some typical polymer solutions with the results of the classical determination methods and then applied to some conventional ternary polymer solutions as polymer–solvent–nonsolvent systems. The proposed algorithm use a set of individual states as the initial chromosomes and uses the general rules as crossover, mutation, and with use of a fractional objective function determines the binodal points or the phase diagram boundaries of polymer solutions. The properties of an industrially relevant polymer solution, a polystyrene–cyclohexane solution, have been used to emphasize on the industrial application of the proposed algorithm. The algorithm has been used to predict the phase behavior of the two polymer–solvent–nonsolvent systems as polystyrene-butanone-methanol and polystyrene-butanone-propanol at three different temperatures and results show good agreement with the experimental observations. The algorithm also has the capability to predict both the concentration-independent and concentration-dependent interaction parameters among the different components. The genetic algorithm is an easy-to-use, state-of-art, and very fast optimization tool, and has very strong capability to solve nonlinear systems in chemical and polymer engineering topics.     

Phase behaviors of polymer blend(PEO–PPO) electrolyte/LiCF3SO3 systems in lithium battery

Polymer blend (poly(ethylene oxide) (PEO)–poly(propylene oxide) (PPO)) systems with two different mole ratios, complexed with LiCF₃SO₃ salt, have been characterized at various temperatures and compositions using a thermo‐optical analysis (TOA) technique. We also developed a new melting point depression theory based on the modified perturbed hard sphere chain model to interpret phase behavior of polymer blend electrolyte systems. The obtained results show that the eutectic points move toward higher T_m and lower weight fraction of salt with decreasing PEO mole ratio and also indicate that the mole ratio of PEO–PPO for each polymer blend plays an important role in determining the eutectic point of the polymer blend system. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2314–2319, 2005     

甲苯-正己烯-二甲基亚砜液-液平衡数据的测定与关联

裂解汽油是含有烯烃的重要芳烃资源,二甲基亚砜(DMSO)能够从高烯烃含量组分中选择性萃取芳烃,测定相应体系液-液平衡是裂解汽油中的芳烃萃取过程研究开发的理论基础。测定了常压下293.15、298.15、303.15 K时甲苯-正己烯-DMSO体系液-液平衡数据,获得了三元体系的相图和褶点,并采用Hand方程和NRTL方程进行关联。体系中甲苯对正己烯选择性系数为2～6,表明DMSO萃取分离甲苯和正己烯理论上可行。通过体系液-液平衡关联获得了NRTL方程模型参数,利用NRTL模型对该体系进行计算,计算值与实验值的平均偏差较小,说明NRTL模型适用于该体系的液-液平衡。     

Barrier properties of polypropylene/organoclay nanocomposites

Polypropylene/clay nanocomposites are attractive candidates for applications requiring good barrier properties because of the inherent features of the polymer matrix. To assess their potential, systematic research relating the barrier performance to the structural characteristics of polypropylene/montmorillonite samples has been conducted. The nanocomposites have been tested in the presence of helium, water vapor, toluene, and methanol, and the unmodified matrix has been found to exhibit better properties than its mixtures with the compatibilizer and/or clay. The method for the interpretation of the results proposed in this study considers the composition of the samples, the morphology of the semicrystalline polymer matrix, and the state of dispersion/exfoliation of the clay layers, along with the specific interactions between the solvent molecules and the system components. In this way, several points have been identified for understanding and improving the performance of the nanocomposites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 618–625, 2007     

Analysis of the moisture sorption behavior of amorphous drug–polymer blends

Hydrophobic drugs are often formulated with hydrophilic polymers to form miscible blends called amorphous solid dispersions. The interaction of moisture with these blends is an important topic, both from stability as well as processing perspectives. In this study, the moisture sorption profiles of four different drug–polymer blends, [felodipine–poly(vinylpyrrolidone) (PVP), indomethacin–PVP, felodipine–hypromellose (HPMC), and felodipine–hypromellose acetate succinate (HPMCAS)] were experimentally determined at 25°C, and analyzed using various mathematical models. It was found that the moisture sorption profiles of the drug–polymer blends could not be reconstructed using the weight‐averaged sum of the moisture sorbed by each of the components. Application of the Flory–Huggins model for ternary systems to extract drug–polymer interaction parameter (χ₂₃) values using known values of water–drug and water–polymer interaction parameters led to ambiguous conclusions about the systems' thermodynamics. χ₂₃ values extracted for felodipine–PVP and indomethacin–PVP using this model ranged from ?9.6 to 26.9 and ?20.4 to 22.0, respectively. It is thought that the presence of specific drug–polymer interactions changed the water–drug and the water–polymer interactions in the system. Combined with the mathematically small contribution from the term encompassing χ₂₃ to the predicted amount of moisture sorbed by the drug–polymer blends, it was concluded that this method cannot be used to unambiguously determine drug–polymer interaction parameters in solid dispersions. Instead, a model with a mean interaction parameter (χ_1,23) that considers the drug and the polymer in the blend as a single unit was found to better describe the changing affinity of water for the solid matrix with a change in composition or polymer type. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Determination of Critical Aggregation Concentration in the Poly-(vinylpyrrolidone)–Sodium Dodecyl Sulfate System by Capillary Electrophoresis

We introduce an alternative separation method, i.e., capillary electrophoresis to examine the polymer/surfactant interaction. The migration behavior of the poly-(vinylpyrrolidone)–sodium dodecyl sulfate (PVP–SDS) model system was screened under a high electrical field for seven different PVP initial concentrations. From the electrophoretic mobilities of formed polymer–surfactant species, the critical aggregation concentration (CAC) of SDS for PVP was determined. The CAC value in the present study was very well matched with the CAC values of this system reported by alternative methods. A strong interaction between polymer and SDS under CAC concentration was observed and the independence of CAC on polymer concentration was experimentally demonstrated.     

A new approach to determine rheological percolation of carbon nanotubes in microstructured polymer matrices

We demonstrate the rheological percolation of carbon nanotubes (CNTs) in microstructured polymer matrices. Polymer/CNT composites are fabricated from polycarbonates with different molecular weights to diversify the microstructures, which vary with the polymer radius of gyration and entanglements. We propose a model for the dispersion of CNTs in polymer matrices, which explains the electrical and rheological properties. The percolation theory represented by a power–law relation cannot account for the rheological percolation of CNTs in this work. Therefore, we investigate the crossover points to provide a quantitative indication of the rheological percolation threshold of nanofillers in polymer matrices. For the first time, the rheological percolation threshold is determined experimentally with this definition. The effects of molecular weight and shear viscosity of the medium on the percolation of CNTs are demonstrated separately.     

Estimation of diffusion coefficients for trace amounts of solvents in glassy and molten polymers

Two methods based on the free-volume theory of transport are developed for the estimation of diffusion coefficients for trace amounts of solvents in amorphous polymers. The first method uses diffusivity data for a polymer–solvent system above the glass transition temperature to estimate the temperature dependence of the mutual diffusion coefficient below this temperature. In the second method, mutual diffusion coefficients are estimated for a particular polymer–solvent system both above and below the glass transition temperature using no diffusivity data for the system. The predictions of the proposed theory are compared with diffusivity data for the n-pentane–polystyrene and ethylbenzene–polystyrene systems.     

Effect of cationic surfactant addition on the drag reduction behaviour of anionic polymer solutions

Although extensive research work has been carried out on the drag reduction (DR) behaviour of polymers and surfactants alone, little progress has been made on the synergistic effects of combined polymers and surfactants. In this work, the interactions between drag‐reducing anionic polymer (copolymer of acrylamide and sodium acrylate, referred to as PAM) and drag‐reducing cationic surfactant (octadecyltrimethylammonium chloride, OTAC) are studied. Solutions are prepared using both deionised (DI) water and tap water. The measurement of the physical properties such as electrical conductivity and viscosity are used to determine the surfactant–polymer interactions. The addition of surfactant to the polymer solution has a significant effect on the properties of the system. The critical micelle concentration (CMC) of the mixed surfactant–polymer system is found to be different from that of the surfactant alone. With the addition of surfactant to a polymer solution, a substantial decrease in the viscosity occurs. The observed changes in the viscosity of mixed polymer–surfactant system are explained in terms of the changes in the extension of polymeric chains, resulting from polymer–surfactant interactions. The anionic PAM chains tend to collapse upon the addition of cationic OTAC. The pipeline flow behaviour of PAM/OTAC mixtures is found to be consistent with the bench scale results. The DR ability of PAM is reduced upon the addition of OTAC. At low concentrations of PAM, the effect of OTAC on the DR behaviour is more pronounced. The DR behaviour of polymer solutions is strongly influenced by the nature of water (DI or tap). © 2011 Canadian Society for Chemical Engineering     

Laboratory studies on solvent extraction of low-temperature tar oils by aqueous sodium salicylate

The use of aqueous saturated sodium salicylate for the extraction of tar acids from a low-temperature tar fraction is discussed. Solubility and equilibrium data for the system:neutral oil-tar acids-aqueous sodium salicylate when plotted on a ternary diagram showed two types of curves: an ordinary bite type and another a loop containing solid and liquid phases. The tie-line data agree with most of the empirical relationships reported in the literature. The plait point for the system had a tar acid concentration of 47%. The results have been compared with the earlier data for the system: phenol-α-methylnaphthalene-aqueous sodium salicylate.