The interpretation of rate curves arising from membrane permeation studies

The evaluation of rate curves arising from the permeation of salicylic acid through human and pig skin is discussed. The approaches based upon steady state and time lag analyses are commented on in comparison with a more complete mathematical model.
Some model zeolite/polystyrene membranes are also discussed.
Interprétation des courbes découlant d'études de perméabilité des membranes     

High‐rate hydrogen separation using an MIEC oxygen permeable membrane reactor

In this study, we propose using mixed ionic‐electronic conducting (MIEC) oxygen permeable membrane to separate hydrogen via the water splitting reaction. To do that, steam was fed to one side of the membrane (side I) and a low‐purity hydrogen was fed to the other side (side II). Oxygen from water splitting on side I permeates through the membrane driven by an oxygen chemical potential gradient across the membrane to react with the low‐purity hydrogen on side II. After condensation and drying, high‐purity hydrogen is acquired from side I. Thus, the hydrogen separation process is realized based on the fact that the low‐purity hydrogen is consumed and high‐purity hydrogen is acquired. We achieved a high hydrogen separation rate (13.5 mL cm^?2 min^?1) at 950°C in a reactor equipped with a 0.5‐mm‐thick Ba_0.98Ce_0.05Fe_0.95O_3‐δ membrane. This research proofed that it is feasible to upgrade hydrogen purity using an MIEC oxygen permeable membrane. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1278–1286, 2017     

Polycarbonate/silica nanocomposite membranes: Fabrication,characterization, and performance evaluation

Polycarbonate/silica nanocomposite membranes at low silica loading were fabricated by solution blending and solvent evaporation technique. The functionalized silica nanoparticles used were synthesized by co‐condensing hydrolyzed tetraethylorthosilicate with 3‐aminopropyl trimethoxysilane in the sol–gel process. The membranes morphology, composition, surface, structure, thermal and mechanical properties were analyzed by the standard characterization techniques. The gas permeation tests were conducted in four‐channel permeation cells. Field emission scanning electron microscopy results reveal that membranes above 3 wt % silica content formed distinguishable voids and agglomerates. Fair distribution of silica nanoparticles and absence of residual solvents were observed by energy dispersive X‐ray and thermogravimetric analysis. Fourier transform infrared spectroscopy spectra confirmed the presence of new functional groups (N? H) and (O? H) bonds. The X‐ray diffraction pattern revealed the polymer‐particle interactions, the formation of rigidified polymer chain, and nanostructured silicon crystals. Further, the thermogravimetric analysis results revealed thermal stability enhancement while differential scanning calorimetry results of increased glass transition temperatures confirmed the presence of rigidified polymer chain. Furthermore, enhancements in mechanical strength of the membranes were observed. Moreover, at all feed pressures, increased CO₂, N₂, and CH₄ gas permeation was observed. At 6 bar feed pressure, the CO₂/N₂ and CO₂/CH₄ ideal selectivities of PC membranes with 3 wt % silica loading have increased from 19.2 to 38.0 and 29.2, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45310.     

Study on diffusion and flow of benzene, n-hexane and CCl4 in activated carbon by a differential permeation method

In this paper the diffusion and flow of carbon tetrachloride, benzene and n-hexane through a commercial activated carbon is studied by a differential permeation method. The range of pressure is covered from very low pressure to a pressure range where significant capillary condensation occurs. Helium as a non-adsorbing gas is used to determine the characteristics of the porous medium. For adsorbing gases and vapors, the motion of adsorbed molecules in small pores gives rise to a sharp increase in permeability at very low pressures. The interplay between a decreasing behavior in permeability due to the saturation of small pores with adsorbed molecules and an increasing behavior due to viscous flow in larger pores with pressure could lead to a minimum in the plot of total permeability versus pressure. This phenomenon is observed for n-hexane at 30°C. At relative pressure of 0.1-0.8 where the gaseous viscous flow dominates, the permeability is a linear function of pressure. Since activated carbon has a wide pore size distribution, the mobility mechanism of these adsorbed molecules is different from pore to pore. In very small pores where adsorbate molecules fill the pore the permeability decreases with an increase in pressure, while in intermediate pores the permeability of such transport increases with pressure due to the increasing build-up of layers of adsorbed molecules. For even larger pores, the transport is mostly due to diffusion and flow of free molecules, which gives rise to linear permeability with respect to pressure.     

Effect of the miscibility between a silane and a sizing agent on silanol condensation

The miscibility between a hydrolyzed silane coupling agent, which had chemically nonreactive organofunctional groups such as propyl groups, and a film‐forming polymer [poly(vinyl acetate) PVAc] and its effect on silanol condensation were studied. A mixture consisting of a silane hydrolyzate and PVAc obtained from an alcoholic aqueous solution was investigated with Fourier transform infrared spectroscopy and size exclusion chromatography. Hydrogen bonding between the SiOH groups of the silane and the C?O groups of PVAc and silanol condensation affected by PVAc were examined. The hydrogen bonding and condensation reaction were influenced by the miscibility between the organofunctional group of the silane and PVAc. The miscibility of each system was estimated from the calculated Hildebrand solubility parameter of the organofunctional group. A correlation between the miscibility and the integrated absorbance of the hydrogen‐bonded C?O, obtained by least‐squares curve fitting, was established. On the basis of the molecular weight of the silane and the number of hydrogen‐bonded C?O groups, a micellelike phase was proposed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 589–598, 2003     

玻璃膜用于气体分离的研究

本文介绍了分离气体的玻璃膜的制备工艺和特性，采用二种工艺制备了玻璃分离膜；多孔玻璃毛细管膜和沸石一多孔玻璃（陶瓷）复合膜。初步探讨了孔径分布，气体温度，后处理等对多孔玻璃膜和复合膜气体透过率和气体分离率的影响，结果表明，所制备的多孔玻璃膜的孔径在２ｎｍ以下时，分离膜具有较高的分离能力，复合膜可通过ＳｉＣＬ４再涂膜处理提高其气体分离率。     

MULTICOMPONENT POLYMER/SOLVENTS EQUILIBRIA: AN EVALUATION OF FLORY-HUGGINS THEORY FOR CROSSLINKED PDMS NETWORKS SWELLED BY BINARY MIXTURES

The prediction of equilibrium volume fractions of solvents mixtures in a polymer network is of utmost importance for processes dealing with polymeric materials (e.g. chromatographic and membrane processes). Up to now, few studies have studied the ability of existing theories to predict experimental multicomponent sorption data in polymers; this work intends to achieve that purpose on model liquid mixtures in contact with silicone rubber (polydimethylsiloxane). The equilibrium volume fractions of three liquid mixtures (chloroform/toluene; ethanol/toluene; ethanol/2-butanol) in crosslinked PDMS samples have been determined experimentally at 40^°C. Results are compared to predictions by the Flory-Huggins theory applied to ternary mixtures (one polymer and two liquids) with constant interaction parameters and negligible elastic contribution. Solvent/polymer interaction parameters have been determined by swelling the crosslinked samples in pure liquids, while liquid/liquid interaction parameters have been estimated from liquid/vapor equilibrium data. It is shown that the Flory-Huggins theory offers good predictions in the case of good (chloroform, toluene) and fair (2-butanol) PDMS solvents, while significant discrepancies are obtained with a non solvent (ethanol). Implications in ternary diagrams simulation and possible prediction improvements, based on non constant interaction parameters, are discussed.     

Effect of F/P and OH/P molar ratios and condensation viscosity on the structure of phenol‐formaldehyde resol resins for overlays—A statistical study

A two‐level full factorial experimental design with three variables, formaldehyde‐to‐phenol (F/P) molar ratio, hydroxyl‐to‐phenol (OH/P) molar ratio, and condensation viscosity was implemented to determine the effect of the variables on the structure of phenol‐formaldehyde resol resins for paper overlay impregnation. Ten resins were prepared with F/P molar ratios between 1.9 and 2.3, OH/P molar ratios between 0.09 and 0.13, and condensation viscosities between 60 and 180 mPa s. The effect of these three independent variables on the chemical structure was analyzed by ¹³C‐NMR spectroscopy, on the molecular weight distribution by gel permeation chromatography, and on the reactivity by differential scanning calorimetry. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2942–2948, 2004     

RHEOLOGICAL CHARACTERIZATION OF PYROLYTIC WOOD DERIVED OILS: EXISTENCE OF A COMPENSATION EFFECT

Detailed rheological study was made for sixteen pyrolytic wood derived oils provided by different laboratories and obtained from a wide range of liquefaction processes. Molecular characterization of these oils has been performed through gel permeation chromatography (GPC) and intrinsic viscosity [η] measurements.

All pyrolytic wood derived oils exhibit an essentially Newtonian behavior in the range of shear rate examined (10^-1 to 10³s^-1). The variation of viscosity with temperature follows an Arrhenius-type relationship. GPC chromatograms and [ η] measurements have shown the existence of a Mark-Houwink relationship between [ η] and molecular weights of the pyrolytic oils with a Mark-Houwink exponent of the order of 0.58 when tetrahydrofuran (THF) is used as solvent. Therefore the pyrolytic oils despite the diversity of the liquefaction processes all belong to a same family. Moreover, a compensation effect has been found. Because of the Newtonian character of these oils, the compensation effect allows the determination of the temperature dependence of viscosity from only one measurement of viscosity at a given temperature     

用表面渗透法检测高温工程陶瓷的热震性能

本文介绍依据热弹性理论,利用表面渗透法测量高温工程陶瓷材料的热震性能。对几种有代表性的高温工程陶瓷材料进行测试,并将结果与热震后测弯曲强度、依据热弹性理论计算的R、R′进行对比。本方法有简易、可靠、热震裂纹及分布可直接观察等特点。