Thermodynamic study of a water–dimethylformamide–polyacrylonitrile ternary system

Experimental cloud‐point data were obtained by cloud‐point titration. The phase diagram for a ternary system of water–dimethylformamide–polyacrylonitrile was determined by numerical calculation on the basis of the extended Flory–Huggins theory and was found to agree well with the cloud‐point data. To construct the theoretical phase diagram, three binary interaction parameters were obtained with different methods. The ternary phase diagram was used to investigate the mechanism of fiber formation. The skin–core structure and fingerlike pores in polyacrylonitrile fiber may be effectively eliminated if the composition of the spinning solution is properly chosen, and consequently, homogeneous polyacrylonitrile fiber with a bicontinuous structure and good mechanical properties can be obtained through the spinning process. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Alkanol removal from the apolar phase of a two-liquid phase bioconversion system. Part 2: Effect of fermentation medium on batch distillation

In two-liquid phase fermentations organic substrates and/or products are dissolved in an apolar phase while microorganisms are suspended in an aqueous medium. The effect of aqueous phase contaminants in the apolar phase on the separation of products from the apolar phase by batch distillation is described in this paper. Various amounts of polar phase, emulsified apolar phase and microorganisms normally present in the two-liquid fermentation medium were added to the organic phase. The recovery performance of a distillation unit in separating 1-octanol from such contaminated apolar phases was determined. Further, the bulk properties of the emulsified apolar phase, such as its composition, the nature and the stability of the emulsion were analysed. It was found that the distillation performance is very sensitive to the presence of fermentation media in the organic phase. The energy cost per kg product recovered was almost doubled for only small additions of fermentation impurities. The emulsified apolar phase was shown to be kinetically, but not thermally, stable. Based on these results a suitable apolar phase separation process before distillation can be developed, taking into account energy costs for phase separation and subsequent distillation, to optimize the overall downstream product purification process. © 1998 SCI     

Effect of longitudinal mixing on microbial growth in a multi-stage column bioreactor

The performance of a multi-stage column bioreactor for nonlimited microbial growth was studied. The back-flow model was employed to describe the flow pattern of the microbial suspension. Analytical solutions for calculating the microbial cell concentrations under steady-state and unsteady-state operations, with and without cells in feed, were obtained and the cell growth behavior was examined. Only when microbial cells were present in the feed and the reaction number was less than a critical number was a stable steady state achieved: the microbial cell concentration was then significantly affected by the extent of longitudinal mixing. In the absence of microorganisms in the feed, the steady state was not stable with either washout or nonlimited growth resulting.     

新溶剂体系对SBS生产工艺的影响

讨论了一种新溶剂体系对热塑性弹性体SBS工业生产工艺条件的影响，并与原应用纯环己烷溶剂的生产工艺进行比较。工业试生产结果表明，对SBS生产中溶剂精制工艺过程，应用新溶剂体系时精制塔系的气相压力增大，塔温降低，聚合反应单体质量分数在l8．0％～20．0％时对聚合反应与凝聚工艺控制没有影响，可较显著地提高装置生产能力，降低产品生产成本，同时其凝固点较低，有利于提高SBS生产体系对季节与地域的适应能力。     

Effect of polymer–clay interaction on solvent transport behavior of fluoroelastomer–clay nanocomposites and prediction of aspect ratio of nanoclay

Diffusion and sorption of methyl ethyl ketone and tetrahydrofuran through fluoroelastomer‐clay nanocomposites were investigated in the temperature range of 30–60°C by swelling experiments. Slightly non‐Fickian transport behavior was found for these nanocomposites, having variation of type of nanoclay and loading. Different transport parameters depend on the size and shape of the penetrant molecules. The results were used to study the effect of nanoclay on the solvent transport‐properties of nanocomposites and their interactions with solvents. The diffusion coefficient of methyl ethyl ketone at 30°C for neat rubber was 1.43 × 10^?8 cm² s^?1, while those of the unmodified and the modified clay filled samples at 4 phr loading were 0.24 × 10^?8 and 0.50 × 10^?8 cm² s^?1, respectively. At 8 and 16 phr loading of the unmodified clay, it was found to be 0.44 × 10^?8 and 0.64 × 10^?8 cm² s^?1, respectively. The samples were also reswelled after deswelling. Surprisingly, transport behavior became Fickian on reswelling. Interestingly, ratio of diffusion coefficients of the filled system to the neat system was found to be almost same for the first time swelling and reswelling experiments. The results showed that better polymer‐clay interaction in the case of the unmodified‐clay filled nanocomposites is responsible for enhanced solvent‐resistance property. From the permeation data, for the first time, aspect ratio of nanoclays in different composites was calculated and found to have good correlation with the morphology data obtained from transmission electron microscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Effect of mixing process on electromagnetic interference shielding effectiveness of nickel/acrylonitrile–butadiene–styrene composites

This article reports the effect of the mixing process on the electromagnetic interference (EMI) shielding effectiveness of nickel/acrylonitrile–butadiene–styrene (ABS) composites. Nickel in either powder or filament form was used as the filler material. It was mixed with ABS by two mixing processes: one was the Brabender‐mixing method, in which nickel was mixed in the polymer melt by a strong shear at high temperatures, and the other was a simple dry mixing method performed in a centrifugal ball mill. Our results showed that the dry‐mixing method could produce EMI shielding effectiveness of 36 dB at the 3 vol % nickel filaments level. In contrast, we need 20 vol % nickel powder to exhibit some shielding effectiveness for the Brabender method. After the nondestructive X‐ray examination and four‐point probe resistivity measurements, we concluded that better EMI shielding effectiveness could be achieved when the mixing method provided a state of uniformity on the macroscale, but not on the microscale. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 128–135, 2005     

Effect of methanol addition on water–CO2–diethanolamine system: Influence on CO2 solubility and on liquid phase speciation

The aim of this study is the characterisation of VLE and chemical equilibria for the system CO₂/diethanolamine (DEA)/H₂O/methanol. The effect of MeOH composition has been studied using four compositions (from 0 to 30 wt% of methanol with a fixed composition (30 wt%) of DEA), the measurement being made at T = 298.15 K and at various CO₂ loadings (from 0.2 to 0.8). An original experimental device was used. This device combines a FT-IR spectroscopy analysis of the liquid phase with a VLE measurement cell.The data base obtained, including the new solubility data and the liquid phase composition, allows the modelling of the system CO₂/DEA/H₂O/methanol using an electrolyte equation of state [Fürst, W., Renon, H., 1993, Representation of excess properties of electrolyte solutions using a new equation of state, AIChE J, 39(2): 335–343] representing the equilibrium properties of the system and the liquid phase speciation.     

Alkanol removal from the apolar phase of a two-liquid phase bioconversion system. Part 1: Comparison of a less volatile and a more volatile in-situ extraction solvent for the separation of 1-octanol by distillation

Biocatalytic systems can be used for the regio- and stereospecific synthesis of oxidized alkanes and aromatic compounds, such as aliphatic and aromatic alcohols, aldehydes and epoxides. These reactions are typically carried out in two-liquid phase media. The biocatalyst is usually a natural microorganism, often a Pseudomonas, or a genetically altered host, a Pseudomonas or E. coli recombinant typically, which grows in the aqueous phase, while the substrate and product are present in an organic bulk phase. Oxidation products formed in these systems must be purified after separation of the two liquid phases. We have evaluated the performance of distillation for the separation of the product 1-octanol by examining a more volatile (octane) and a less volatile (hexadecene) in-situ extraction system. The separation performance of the two systems has been compared based on recovery efficiency, energy cost and number of required process units. Results showed that a less volatile extractant compared favorably in terms of number of product separation unit steps, decreased operating and energy cost to the use of a more volatile extraction solvent. In addition, a major disadvantage of the more volatile in-situ extraction process was the coloring of the bottom product of the first distillation step, in which the product is contained in this case. Such modifications can be implemented into an upstream and downstream process of bioconversions to improve the overall system and to reduce downstream processing cost. © 1998 SCI     

Particle paths in three-dimensional flow fields as a means of study: Opposing jet mixing system

Particle paths can provide a tool for the analysis of mixing process. As an example, we will consider an opposing jet mixing system. Experimental, full-field, time-revolved, velocity vector data have been obtained using three-dimensional particle tracking velocimetry (PTV) technique. Using this field as a basis, hypothetical particles are injected anywhere and at any time into the field. The particles are then tracked as they move under the influence of the velocity field. The injected hypothetical particles can be neutrally buoyant or given a different density than the fluid. Color graphical representation of the results cannot be conveniently reported here; however, examples are provided in an equivalent gray-level coding. A more thorough presentation is possible by using color. These are provided at the URL (Uniform Resource Locator, i.e., the address for a location on the Internet) cited in Zhao and Brodkey [Y. Zhao, R.S. Brodkey, Particle paths in three-dimensional flow fields as a means of study: opposing jet mixing system, . See item on Paper to be published in a Special Issue of Powder, 1997].     

Photografting of N‐isopropylacrylamide and glycidyl methacrylate binary monomers on polyethylene film: Effect of mixed solvent consisting of water and organic solvent

Photografting (λ > 300 nm) of N‐isopropylacrylamide (NIPAAm) and glycidyl methacrylate (GMA) binary monomers (NIPAAm/GMA) on low‐density polyethylene film (thickness = 30 μm) was investigated at 60°C using mixed solvent consisting of water and an organic solvent such as acetone. Xanthone was used as a photoinitiator by coating it on the film surfaces. A maximum percentage of grafting was observed at a certain concentration of acetone in the mixed solvent, which was commonly observed for both ratios of NIPAAm/GMA, 8/2 and 7/3. Based on the photografting of NIPAAm/GMA on xanthone‐coated film, monomer reactivity ratios of NIPAAm (r₁) and GMA (r₂) were calculated using the Fineman–Ross method. The values were 0.31 ± 0.1 and 4.8 ± 0.2 for the water solvent system, while they were 0.96 ± 0.1 and 4.9 ± 0.1 for the mixed solvent system. NIPAAm/GMA‐grafted films with a homogeneous distribution of grafted chains were formed by photografting using water and mixed solvents. The NIPAAm/GMA‐grafted films exhibited temperature‐responsive characters, whereas the grafted films showed a reversible change in the degree of swelling between 0 and 50°C, respectively. Epoxy groups in the grafted poly(NIPAAm/GMA) chains could be aminated with ethylenediamine in N,N′‐dimethylformamide at 70°C for 3 h. Complexes of the aminated NIPAAm/GMA‐grafted chains with cupric ion exhibited catalytic activity for the decomposition of hydrogen peroxide at 20 to 50°C. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2469–2475, 2005     

Influence of a surfactant or salt on phase inversion in a water–oil pipe flow

Phase inversion experiments have been performed with a water–oil flow through a pipe to study the effect of the addition of a surfactant or of salt on the critical dispersed phase volume fraction (at the point of phase inversion). The addition of a surfactant caused a small change in the critical volume fraction, but the general form of the ambivalence region in the inversion map remained the same. The influence of salt was negligible.     

混合室直径对带喷射器的跨临界CO2热泵性能影响

通过在跨临界CO₂系统中引入喷射器是回收系统节流损失的有效手段。实验研究了混合室直径分别为1.2、1.4、1.6 mm时,对带喷射器的跨临界CO₂热泵整体性能以及喷射器自身性能的影响。整个实验中热水进口温度、蒸发温度不变,热水出口温度作为比较基准,在实验中为变量。结果表明,混合室直径对压缩机排气温度影响较小,而其对压缩机排气压力影响较大,当混合室直径为1.6 mm时,压缩机排气压力最小;当混合室直径为1.6 mm时,系统制热系数最高。     

Photografting of methacrylic acid on polyethylene film: Effect of mixed solvents consisting of water and organic solvent

Photografting of methacrylic acid (MAA) on linear low‐density polyethylene film (thickness = 30 μm) was investigated at 60°C in mixed solvents consisting of water and organic solvent with xanthone as the photoiniator. The organic solvents examined were acetone, methanol, tetrahydrofuran, and dioxane. A maximum percentage of grafting was observed at a certain concentration of organic solvent in the mixed solvent, depending on the nature of the organic solvent. Distribution of the grafted chains in the resultant MAA‐grafted film, which was examined by scanning electron microscopy and attenuated total‐reflection IR spectroscopy, was largely influenced by the use of the mixed solvent. The grafted samples swelled in the alkaline region and shrank in acidic medium, showing a pH‐responsive character. The extent of the pH‐responsive function was closely related to the location of grafted chains, which could be controlled by proper choice of the composition of organic solvent in the mixed solvent. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2454–2461, 2002     

Single and two-phase flows in a horizontal pipe with a Kenics static mixer: Effect of pressure drop on mixing

Single and two-phase flows pressure drops through a Kenics static mixer were investigated, for liquid and gas Reynolds numbers ranging from 8110 < Re_L < 18 940 to 1730 < Re_G < 8680, respectively. New friction factor correlations were established for single and two-phase flows, showing better agreement than those available in the literature. Dissipated energy and characteristic time constants were estimated from experimental data. For instance, a dissipated energy with a maximum value of 510 W/kg was calculated in two-phase flow with the drift-flux model. The dispersed phase reduced the characteristic mixing times and its influence was more important than the continuous phase for all the characteristic mixing time investigated. Furthermore, the macroscopic characteristic mixing time was shown to be the governing mixing process for almost all gas and liquid flow rates explored.     

Effect of extraction and enzymatic esterification of ethanol on glucose consumption by two Saccharomyces cerevisiae strains: a comparative study

Extractive alcoholic fermentations of high glucose concentrations (300 and 400 g dm^?3) using a flocculent (saké) and a non‐flocculent (DER24) Saccharomyces cerevisiae strain were compared. The introduction of a Rhizomucor miehei lipase, in the extractive fermentations of 300 g dm^?3 of glucose, increased the ethanol extraction due to its esterification with oleic acid, allowing complete glucose consumption at an organic solvent/fermentation medium phase ratio of 1. In these conditions, an increase of ethanol yield was observed. Total glucose consumption was also obtained in enzymatic extractive fermentations of 400 g dm^?3 of glucose, but only when oleic acid was added at the exponential growth phase. From the comparison of the extractive fermentation performances obtained using the two yeast strains it was observed that the flocculent strain led to a lower glucose metabolisation rate. This behaviour was related to the highest diffusional limitations that occur in the presence of flocs. The developed processes showed that the association of alcoholic fermentation with enzymatic extraction led to the reduction of inhibitory effects as well as to the simultaneous production of fatty esters which are compounds with several commercial applications. © 2001 Society of Chemical Industry     

Dehydrogenation of 11α‐hydroxy‐16α, 17‐epoxyprogesterone by encapsulated Arthrobacter simplex cells in an aqueous/organic solvent two‐liquid‐phase system

BACKGROUND: Arthrobacter simplex cells immobilised in sodium cellulose sulfate/poly‐dimethyl‐diallyl‐ammonium chloride microcapsules were used for the microbial dehydrogenation of 11α‐hydroxy‐16α,17‐epoxyprogesterone to 11α‐hydroxy‐16α,17α‐epoxypregn‐1,4‐diene‐3,20‐dione in an aqueous/organic solvent two‐liquid‐phase system, which is a key reaction in the production of glucocorticoid pharmaceuticals. The aim of the study was to establish a suitable aqueous/organic solvent two‐liquid‐phase system for performing semi‐continuous production in an airlift loop reactor by encapsulated A. simplex cells with the addition of suitable surfactants to achieve a higher yield of the product. RESULTS: n‐Hexane was selected as the most suitable organic solvent. In optimised Tween‐80 emulsion feed mode the conversion in the airlift loop reactor was as high as 97.54% when the time of reaction was 2 h, and the reaction time was greatly shortened. In semi‐continuous production the cultivation with immobilised cells was carried out for five batches in total. The conversion in each batch was above 95% and the enzymatic activity still remained quite high after five batches of biotransformation. CONCLUSION: The results showed that performing the conversion by this method shortened the reaction time and increased the productivity, thus demonstrating the great potential of the method for the dehydrogenation of 11α‐hydroxy‐16α,17‐epoxyprogesterone. Copyright © 2008 Society of Chemical Industry     

Polypropylene–wood fiber composites: Effect of treatment and mixing conditions on mechanical properties

Polypropylene/wood fiber composites were prepared at three different temperatures: 170°C, 180°C, and 190°C. The surface of wood fibers was modified through the use of silane coupling agents and/or coating with polypropylene or maleated polypropylene. The fiber coating was performed by propylene polymerization in the presence of wood fibers or by immersion in an o-dichlorobenzene polypropylene (or maleated polypropylene) solution. Tensile and three-point bending tests were performed in order to evaluate the adhesion between matrix and wood fibers. Evidence shows that 180°C is the best mixing temperature, while the use of vinyl-tris (2-methoxy ethoxy) silane with or without maleated polypropylene coating is the best surface treatment. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1227–1235, 1997