局部组成型的互扩散系数模型

根据局部组成概念建立了混合物中互扩散系数与自扩系数的关系,并以分子集团迁移的概念建立了混合物中组分的自扩散系数的预测方法,由此预测二元系的自扩散系数和互扩散系数与实验结果符合良好,比经典的Ｈａｒｔｌｅｙ模型有了很大地改进。     

Measurement and correlation of mutual diffusion coefficients for styrene-butadiene rubber (SBR)-ethylbenzene systems

The mutual diffusion coefficients for styrene-butadiene rubber (SBR)-ethylbenzene systems were measured using a sorption apparatus with a quartz spring at 100 and 130°C for mass fractions of ethylbenzene ranging from 0 to 0.17. The mutual diffusion coefficients were correlated with good agreement by the free-volume theory.     

Measurement and correlation of mutual diffusion coefficients for polybutadiene-hydrocarbon systems

The mutual diffusion coefficients for polybutadiene-ethylbenzene and polybutadiene-n-nonane systems were measured by using a sorption apparatus with a quartz spring in the temperature region from 80 to 130°C and for mass fraction of hydrocarbon ranging from 0 to 0.27. The mutual diffusion coefficients were correlated with good agreement by the free-volume theory.     

Measurement and correlation of mutual diffusion coefficients for molten polystyrene-hydrocarbon systems

The mutual diffusion coefficients for three molten polystyrene(PS)-hydrocarbon systems—PS-in-xylene, PS-n-octane, and PS-n-nonane—were measured by using a sorption apparatus with quartz spring in the temperature region from 130 to 175°C and for mass fraction of hydrocarbon ranging from 0 to 0.15. The mutual diffusion coefficients were correlated with good agreement by the freevolume theory.     

非电解质溶液扩散系数的理论研究评述

许多过程都涉及扩散控制的传质,相应的扩散速率计算对过程工程的精确量化具有重要意义.本文简述了扩散速率的理论表述模型,并着重介绍了非电解质溶液内扩散系数的理论分析计算途径.分子动力学模拟正处于发展中,并用于估算自扩散系数,但进入实用化阶段尚需时日,唯象模型仍为最重要的理论计算手段.作为最常用的方法,由无限稀释浓度下的扩散系数以及合适的插值方法可计算特定浓度下的扩散系数;自由体积理论是半经验性模型,可以计算自扩散系数,并借助混合规则计算相互扩散系数;最后,对扩散系数的理论研究作了展望.     

Mutual diffusion and phase equilibrium in copolymers of nonyl acrylate and acrylic acid–diglycidyl ether of bisphenol A systems

The influence of the composition of statistical copolymers of nonyl acrylate with acrylic acid on the rate of mass transfer and phase equilibrium in solutions with diglycidyl ether of bisphenol A was studied. For these systems, the data on concentration dependencies of mutual diffusion coefficients and phase diagrams were obtained. The results were interpreted on the basis of the assumption about the effect of the effective concentration of nodes of the network of hydrogen bonds on the mutual diffusion and phase equilibrium. The dependencies of the mutual diffusion coefficients on the content of acrylic acid in the copolymers are described in terms of the free volume theory. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2353–2356, 1999     

Application of taylor dispersion technique to measure mutual diffusion coefficient in hexane + bitumen system

A novel approach with fewer technical and analytic limitations in liquid solvent‐bitumen diffusion studies is used in this article. The Taylor dispersion technique was selected for its convenient short run time experiments and reliable data analysis to find mutual diffusion coefficients in a hexane + bitumen mixture. For the first time, the infinite‐dilution molecular diffusion coefficients of bitumen in hexane were measured in both the presence and relative absence of asphaltene particles in the solution at atmospheric pressure and temperatures of 303.15, 310.15, and 317.15 K. The polydisperse nature of bitumen was clearly revealed. Results were compared with common predictive tools. Also, the asphaltene surface charge in the hexane precipitating solvent was demonstrated. Through concentration dependency investigations at atmospheric pressure and 303.15 K, it was determined that the mutual diffusion coefficients monotonically decrease as the viscosity of mixture increases within the studied 0–34% volumetric concentration of bitumen. The Taylor dispersion technique shows great potential for diffusion studies of liquid solvent‐bitumen systems. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2670–2682, 2014     

Self- and mutual diffusion coefficient equation for pure fluids, liquid mixtures and polymeric solutions

Transport properties are important information not only for industrial equipment design but also for many research areas. While there is a well-developed theory for gases at low densities, there is no established theory to calculate diffusion coefficients for dense fluids, especially for polymeric solutions. Recently, a database of 96 self-diffusion coefficient data points were obtained from molecular dynamics (MD) simulations for freely jointed Lennard-Jones chains (LJC) with lengths of 2, 4, 8 and 16 at reduced densities ranging from 0.1 to 0.9 and in the reduced temperature interval of 1.5 to 4. These data were used to develop an equation that correlates MD self-diffusion coefficient points with an overall absolute average deviation of 15.3%. The aim of this work is to show that this equation can be used to calculate diffusivities of pure liquids and liquid mixtures, including polymeric solutions. The proposed equation is used for correlating self-diffusion coefficients for 22 pure real substances and then for predicting mutual diffusion coefficients for 12 binary liquid mixtures. The proposed equation is also used to calculate mutual diffusion coefficients for polymeric systems as: polystyrene-toluene at 110 °C, poly(vinyl acetate)-toluene at 35 °C, and poly(vinyl acetate)-chloroform at 35 and 45 °C. Results show that the model developed here seems to be a promising approach for correlating mutual diffusion coefficients not only for small-molecule systems but also for polymer-solvent systems. One advantage of the equation proposed here is that the parameters have physical meaning and most of them can be estimated without any information on binary diffusion data.     

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.     

Prediction of mass diffusivity of CO2 into bitumen

The infinite dilution and mutual diffusion coefficients for the CO₂/bitumen system were predicted using existing correlations. Out of seven semi-empirical correlations tested, the Umesi-Danner correlation was found to be best suited for the prediction of gas-liquid infinite dilution diffusion coefficient. For the mutual diffusion coefficient, Teja's method based on the generalized corresponding states principle was successfully used. The predictions are compared with the limited CO₂/bitumen diffusivity data available in the literature.     

A principle of equivalent states for liquid transport properties

A principle of equivalent states for liquid transport properties is developed for binary liquid systems. Under the assumption that the activity and viscosity corrected mutual diffusion coefficient is a function of the solution molar volume, working equations are developed for the concentration dependence of the binary mutual diffusion coefficients. The results apply to binary liquid systems for which the coefficient of thermal expansion is independent of composition and for which the difference in activation free energies for viscous flow and diffusion is also independent of composition. The results are tested with available data to show that the binary mutual diffusion coefficient can be predicted from the infinitely dilute values and the solution viscosity and thermodynamics for a large number of liquid systems.     

Hydraulic permeation of liquids through swollen polymeric networks. I. Poly(vinyl alcohol)–water

Poly(vinyl alcohol) membranes were prepared by crosslinking with terephthalaldehyde. Hydraulic permeation of water through this network structure was measured as a function of pressure for temperatures ranging from 18° to 35.8°C. The data were analyzed via a previously developed solution–diffusion theory for hydraulic permeation to give mutual diffusion coefficients. The activation energy for diffusion was found to be 6.5 kcal/mole which compared to the value of 4.3 kcal/mole for viscous flow of water indicates an influence of polymer–liquid interaction on the energetics of the diffusion process.     

Dynamic light-scattering studies of poly(γ-benzyl α, l-glutamate)–benzyl alcohol system

We report the concentration and temperature dependencies of the diffusion coefficients obtained from dynamic light-scattering studies for the poly(γ-benzyl α, l-glutamate)-benzyl alcohol (PBLG–BA) system. These studies were made at dilute and semidilute polymer concentrations, mainly in the isotropic phase. The measured translational and rotational diffusion coefficients in dilute solutions are consistent with predictions based on wormlike chain models. The mutual diffusion coefficient in semidilute solutions shows a marked deviation from scaling predictions, demonstrating the strong coupling between the translational and rotational motions. The measured time evolution of the scattered intensity after the PBLG–BA system is suddenly quenched into the gel phase demonstrates that aggregation is a significant mechanism in the formation of the gel phase.     

Correlations for prediction of diffusion in liquids

Based on an extensive experimental data collection (about 1925 points), empirical correlations for the estimation of binary liquid diffusion coefficients have been developed. The new correlations for organic mixtures and for aqueous solutions (including dissolved gases) require only well known and simple parameters like the viscosity of the solvent and the molar volumes of solute and solvent at the normal boiling point. They are shown to predict the limiting diffusion coefficients with the same or sometimes better accuracy than established correlations which make use of additional parameters. The concentration dependence of the mutual diffusion coefficients can be estimated from the knowledge of the two limiting diffusion coefficients and thermodynamic data. Established equations are investigated and classified for different groups of systems e.g. nonpolar + nonpolar, nonpolar + polar and polar + polar liquid mixtures.     

Prediction of mutual diffusion coefficients for polymer–solvent systems

A new equation is proposed for relating solvent self‐diffusion coefficients and mutual diffusion coefficients for polymer–solvent systems. The formulation of the new equation avoids a friction‐coefficient formalism, and hence the new equation does not require the thermodynamic properties of the polymer–solvent system. A comparison has been made of the predictions of the proposed equation with experimental data for the benzene–rubber system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3195–3199, 2000     

Measurement of concentration profiles using confocal Raman spectroscopy in multicomponent polymeric coatings—model validation

Concentrations of the solvents were measured using confocal laser Raman Spectroscopy for two ternary systems, poly(styrene)—tetrahydrofuran—p‐xylene and poly(methyl methacrylate)—ethylbenzene—tetrahydrofuran, during drying at room temperature. The concentrations were compared with predictions of drying models, which utilize several existing theories for mutual diffusion coefficients for polymer solvent systems. Of the nine free volume parameters required to predict diffusion coefficients of binary systems, four for each of the four pairs studied here were estimated as suggested by the literature. Estimation was done by minimizing the difference between predictions of the model and experimental weight loss data for each binary pair. It is found that the predictions of the models which include cross term diffusion coefficients are in better agreement with measured concentrations than those which ignore the cross terms. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

丙烯酸聚氨酯涂料成膜过程(Ⅰ)溶剂扩散系数的估算

采用傅里叶变换红外光谱（FTIR）测定了不同时间下丙烯酸聚氨酯涂料体系成膜聚合物的固化度及固化反应速率常数,并将该体系按二元聚合物-溶剂体系进行简化处理,在Vrentas-Duda自由体积理论模型的基础上,利用Di-Benedetto方程关联了溶剂的扩散系数与涂膜的固化度,建立了涂膜中溶剂扩散系数的预测模型.结果表明,本涂膜体系中溶剂扩散系数是溶剂浓度、干燥时间的函数.     

Novel ion-containing reverse osmosis membranes. II. Reverse osmosis properties

The reverse osmosis properties of ion-containing membranes prepared by ⁶⁰Co mutual irradiation grafting of 2-vinylpyridine to poly(3,3-bis(chloromethyl)oxetane) (polyoxetane, Penton) followed by quaternization with methyl bromide are presented. In general, the volumetric fluxes varied linearly with pressures up to 55 atm. Katchalsky's treatment of membrane permeability was used to analyze the data. Membrane constants and diffusion coefficients of water and sodium chloride were determined with membranes containing different volume fractions of water. The diffusion coefficients of water in the membranes were of the same order of magnitude as the self-diffusion coefficient of water (～3 × 10^?5 cm²/s). The diffusion coefficients of sodium chloride in the membrane were of the order of 10^?7 cm²/s. The diffusion coefficients increased with hydration, and the salt rejections were markedly affected by the external salt concentrations. The apparent energies of activation for the volumetric flux were calculated in distilled water and in 0.5% sodium chloride solution.     

硬球理论用于液相扩散系数的关联

<正>硬球理论的基础是Maxwell－Boltzman的统计力学理论,最早由Chapman等将该理论应用于研究稀薄气体的传递性质。在稠密流体中,必须考虑分子碰撞频率大幅度增加的影响因素。 Dymond等认为该影响与分子接触径向分布函数g(σ)有关,并以此计算了     

Diffusion of solvent from a cast cellulose acetate solution during the formation of skinned membranes

The transport of solvent out of a cast cellulose acetate (CA) solution into the coagulation bath during membrane formation is treated as a diffusion process. From the increase of solvent concentration in the bath with time (solvent leaching experiments) an overall solvent diffusion coefficient has been calculated. In size these coefficients compare well to mutual pseudo-binary solvent-non-solvent diffusion coefficients determined by means of a classical boundary broadening method applied to ternary solutions with fixed CA concentration, but with a gradient in solvent-nonsolvent composition. Since binary polymer-solvent interdiffusion coefficients are at least one order of magnitude lower, it is concluded that the diffusion of solvent into the coagulation bath is essentially a pseudo-binary solvent-non-solvent diffusion process. Combination of experimental results with model calculations for the effect of a thin dense skin on the diffusion of solvent out of the sublayer shows that the casting-leaching diffusion coefficient can be used to describe the out-diffusion of solvent from the layer under the skin provided that the relative skin resistance is not too high, or that the skin thickness is small.