Solvent and pH resistance of surface crosslinked chitosan/poly(acrylonitrile) composite nanofiltration membranes

The resistance of novel surface crosslinked Chitosan/poly(acrylonitrile) (PAN) composite nanofiltration (NF) membranes to pH and organic solvents was studied with respect to the effects of crosslinking parameters, namely, glutaraldehyde concentration and crosslinking time. The pH resistance was determined by permeation of aqueous acidic (pH 2.5) and basic (pH 11) solutions as well as swelling studies in the pH range of 2.5–11. The solvent resistance was determined by swelling, immersion, and permeation studies with several industrially important organic solvents, namely methanol, ethanol, iso‐propanol, methyl ethyl ketone, ethyl acetate and hexane. It was observed that the crosslinked composite membranes maintain the permeate fluxes for test solvents for 2 h of continuous operation without any significant change in flux. SEM studies on membrane samples after immersion as well as permeation with the above‐mentioned solvents indicated that the membrane morphology was maintained. The results are explained in terms of solvent–membrane polar and hydrophobic interactions, using solubility parameters of membrane and solvents and dielectric constants of solvents. Pure water flux and polyethylene glycol transmission data indicated that at pH 2.5 and 11, the membrane stability increased with increasing glutaraldehyde concentration and was much better at pH 11 than at pH 2.5. All surface crosslinked membranes showed reduced swelling between pH 4–10. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1782–1793, 2000     

Dielectric properties of an epoxy resin and its composite I. Moisture effects on dipole relaxation

Dipole relaxation dielectric loss behavior of a fiberglass–epoxy composite has been studied as a function of moisture uptake. A single widely distributed loss peak, centered at ?16°C for 10 kHz measurement, is observed in the dry composite. Very low moisture concentrations (<0.1%) interact with the composite, through either dipole pairing or by inducing chemical changes, to decrease loss intensity. At moisture concentrations from 0.1 to 1.4%, loss peak intensity generally increases with moisture uptake. Over this moisture concentration range water dipoles presumably relax in phase with the epoxy segments or side groups upon which they adsorb. Arrhenius relaxation activation energy decreases, and improved loss peak definition at increasing moisture concentrations is interpreted as indicating resin plasticization by adsorbed moisture. At moisture concentrations above 1.4%, the appearance of a second loss peak suggests formation of a new colloidal or weakly adsorbed moisture phase, as well as the saturation of primary adsorption sites.     

Spectroscopic changes induced by sonication of porphyrin-carbon nanotube composites in chlorinated solvents

We report the spectroscopic changes of tetraphenylporphyrin carbon nanotube composites in a variety of chlorinated solvents such as chloroform, dichloroethane and dichlorobenzene as a result of sonication. Detailed data analysis suggests that protonation of the porphyrin core nitrogen atoms occurs as a result of sonodegradation of the solvent molecules. Extreme care must be taken when working with carbon nanotube composite solutions in chlorinated solvents, as sonication is always employed to disperse the nanotubes. When working with molecules that are capable of acting as a base some amount of protonation is inevitable and this may dramatically change the physicochemical properties of the composite materials.     

Studies on syntheses and permeabilities of special polymer membranes, 32. New preparation method of cellulose membranes

The preparation of cellulose membranes from mixtures of cellulose, nonprotonic polar organic solvents, paraformaldehyde, and basic catalyst was studied. When dimethyl sulfoxide was used as casting solvent, the resulting membrane was the densest. An increase of an additional amount of triethyl amine used as basic catalyst gave denser membranes.     

混合溶剂体系中葫芦[6]脲溶解度的测定

以NaCl水溶液作为基础溶剂,选取EtOH、DMSO、DMF 3种有机溶剂与之混合作为溶剂,通过紫外分光光度法测定了葫芦[6]脲(CB[6])在不同比例含量混合溶剂中的溶解度。结果表明,随着有机溶剂的加入,CB[6]的溶解度不断减小。在DMF/NaCl水溶液混合体系中,CB[6]的溶解度降低是最大的,而且在体积比5:5,CB[6]的溶解度是几个混合体系中最小的。对于DMSO/NaCl水溶液混合体系,DMSO比例超过1/2时,对CB[6]溶解度影响增大。EtOH/NaCl水溶液混合体系对CB[6]溶解度影响是最小的,说明极性较小的有机溶剂对CB[6]溶解度的影响较小。     

Nanofiltrationsmembranen für Trennprobleme in organischen Lösungen

Nanofiltration Membranes for Separation Problems in Organic Solutions . Nanofiltration based on rejection and flux features intermediate between those ultrafiltration and reverse osmosis is one of the technically and scientifically interesting membrane processes with a great future. Moreover, most commercial available nanofiltration membranes are only suitable for separation processes in aqueous solutions. A small number of composite membranes with a highly cross-linked selective layer show a technically interesting resistance towards organic solvents, such as ketones, esters, ethers or alcohols. The present article describes such nanofiltration membranes used for separation of low molecular weight chemical compounds from polar or nonpolar solvents, but also for the removal of organic compound from aqueous solutions. Methods of manufacturing and modifying such solvent stable composite membranes are shown, as are the conditioning of membranes and examples of industrial application.     

环境友好型脱漆剂的制备

以苯甲醇(BA)、二丙二醇丁醚(DPNB)和二甲基亚砜(DMSO)等为主溶剂制备环境友好型脱漆剂,采用单因素试验法研究了有机溶剂、促进剂、缓蚀剂以及封闭剂等助剂对脱漆效率的影响。试验结果表明:以BA、DPNB和DMSO为主溶剂,异丙醇(IPA)为助溶剂,表面活性剂AR-10和十二烷基苯磺酸钠(LAS)复配,复配有机酸为促进剂,微晶蜡为封闭剂,氨基磺酸与有机羧酸醇铵盐类缓蚀剂复配。当复合主溶剂的用量范围为60%～70%,m(DMSO)∶m(DPNB)=8∶6,m(AR-10)∶m(LAS)=1∶0.8,复配用量为2.5%～3%,异丙醇用量为5%～l0%,复配有机酸用量为7.5%～10%,微晶蜡用量为2.5%～3%时,脱漆效率最高。其组成均为低挥发性的物质,符合绿色化学"高效、洁净、经济、环保"的要求。     

Experimental study on dielectric relaxation in alfa fiber reinforced epoxy composites

Investigation on dielectric properties and behavior of thermoset epoxy composite based on cellulosic fibers has been carried on. Dielectric spectra were measured in the frequency range 0.1 Hz–100 kHz and at temperature intervals from ambient to 200°C. For the composite, four relaxations processes were identified, namely the orientation polarization imputed to the presence of polar water molecules in Alfa fiber, the α mode relaxation associated with the glass transition of the epoxy resin matrix, the relaxation process associated with conductivity occurring as a result the carriers charges diffusion noted for high temperature above glass transition and low frequencies, and interfacial or Maxwell‐Wagner‐Sillars relaxation that is attributable to the accumulation of charges at the Alfa fibers/epoxy resin interfaces. Dielectric relaxation analysis revealed evolution in water relaxation and it is thus concluded that the chemical treatment of the fiber can strongly influence the dielectrical properties and interfacial polarization processes in composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Reactions of conjugated fatty acids. III. Kinetics of the Diels-Alder reaction

Summary The kinetics of a Diels-Alder-type reaction between diethylazodicarboxylate andt,t-9,11-octadecadienoic acid has been studied in various solvent systems and with acidic catalysts. The rate of the reaction was found to vary as follows: a) the reaction rate is faster in polar solvents than in nonpolar solvents; b) addition of acidic catalysts to nonpolar solvents increases the rate of the reaction, and acidic catalysts appear to have no effect on the rate of reaction in polar solvents; c) when compatibility can be maintained, addition of water to polar solvent systems appears to increase the reaction rate in proportion to the amount of water added. The reaction follows second-order or pseudo second-order kinetics. Probably it is more complex than the over-all reaction kinetics indicate. Certain reactions were studied at two temperatures, and information on activation energy of the reaction has been obtained. Presented at fall meeting, American Oil Chemists’ Society, Philadelphia, Pa., Oct. 10–12, 1955.     

The influence of organic solvents on transphosphatidylation by phospholipase D from peanut in anhydrous organic solvents

Phospholipase D (PLD) is widely used for the transphosphatidylation of phospholipids, which is conventionally performed in biphasic systems. The influence of organic solvents on transphosphatidylation by peanut PLD in anhydrous organic solvents was studied and, for the first time, compared to that of a biphasic system in this paper. The results demonstrated that PLD activity from peanut was influenced by solvents of different polarity in anhydrous organic solvents, and the influence tendency of organic solvents (diethyl ether, chloroform, methylenechloride) on transphosphatidylation by peanut PLD in anhydrous organic solvents was the same as that in a biphasic system consisting of water and a hydrophobic organic solvent.     

Sorption and desorption behavior of water and organic solvents from graphite oxide

The sorption-desorption of water and different organic solvents (methanol, 1-propanol, benzene, chloroform and carbon tetrachloride) from the vapor phase in graphite oxide (GO) was studied. Changes observed in the GO interlayer distance, initially due to solvent uptake, were subsequently monitored during desorption by means of time-resolved X-ray diffraction so providing desorption kinetics. A limiting geometric stability in the GO interlayer distance was envisaged, corresponding to an expansion of about 60%, with an intercalation of about 45 mL of solvent/100 g of GO. Specific desorption kinetics behavior was found for each solvent to be related to their chemical nature and geometry. Finally, from this study it was also found that the layer distortions of GO, when exposed to water and organic solvent vapors, occurred in a lesser extent than that found when the intercalation occurred from the liquid solvents.     

不同有机溶剂对新疆油砂沥青的组成性质影响

油砂作为一种非常规石油资源,越来越受到人们的重视。油砂沥青的含量和性质对其开发有着重要的影响。有机溶剂抽提可以测定油砂沥青的含量。本文研究了3种溶剂对新疆油砂的抽提能力,并对不同溶剂抽提得到的新疆油砂沥青进行了性质分析。结果表明,新疆油砂含油率（甲苯测）为11.75%,属于中品位油砂矿;甲苯、氯仿和石油醚3种不同溶剂对新疆油砂沥青进行抽提,发现3种溶剂抽提能力的大小关系为氯仿＞甲苯＞石油醚;抽提过程中,氯仿表现出对胶质和沥青质较强的萃取能力,而石油醚对沥青质的萃取能力几乎为0,采用氯仿可以更准确地测定油砂沥青的含量。氯仿抽提得到新疆油砂沥青及其组分的杂原子含量和分子量高于甲苯和石油醚抽提的。由红外谱图发现,氯仿抽提得到的油砂沥青的含氧、含硫官能团的吸收峰强度大于甲苯和石油醚抽提的,表明氯仿对油砂沥青中极性物质的抽提能力更强。     

Electrospinning of polylactide and its composites with carbon nanotubes

Electrospinning of the biodegradable polylactide (PLA) and its composites containing carbon nanotubes (CNTs) was studied in terms of solution concentrations and solvents effects as well as CNT loadings. The results reveal that the PLA fibers obtained from the solutions using the mixed solvents of chloroform/assistant solvent (v/v 3/1) show better morphologies than those from the solutions using chloroform as the single solvent. This is due to the synergistic effect by the improved conductivity and altered viscosity with addition of assistant solvent. Moreover, the surface structure of fibers depends on the volatility of assistant solvents strongly. Using volatile acrylonitrile or acetone as the assistant solvents, the columned fibers with porous surface structure are obtained; while the flat fibers with fluted surface are formed using nonvolatile dimethyl sulfoxide as the assistant solvents. As for electrospinning of the PLA/CNT composites, the morphology of obtained fibers is closely related to the dispersion of CNTs in the fibers. At low loading levels, the CNTs can be well embedded in the PLA matrix and oriented along the fiber axis, forming nanowire structure. At high loading levels, the CNTs are mainly dispersed as entangled bundles along the fiber axis, and as a result, the obtained fibers show tortuous or misshaped morphologies. Compared with that of the neat PLA fibers, the overall morphologies of the composite fibers are more or less degraded because the presence of some small CNT aggregates in the solutions easily leads to the formation of beaded fiber structure during electrospinning. The conductivity of the obtained composite fiber mats was further studied in terms of CNT loadings. POLYM. COMPOS., © 2011 Society of Plastics Engineers.     

Effect of filler geometry on the diffusion and transport behavior of aromatic solvents and commercial oil through nitrile rubber nanocomposites

The diffusion and transport behavior of nitrile rubber nanocomposites was studied with respect to different types of filler and also different types of solvents. The nitrile rubber nanocomposites showed considerable variations in the molecular transport owing to the tortuosity of path, decreased segmental mobility, and difference in particle geometry. As the matrix under consideration is polar, the behavior of the filled systems in aniline was also studied with a view to understand the polar–polar interaction between the filled matrix and the solvent. The oil repellency as a result of filler addition in the matrix was investigated by studying oil uptake of the nanocomposites. In all these investigations, it has been observed that the filler geometry played an important role in controlling the molecular transport through the polymer matrix. The layered silicate‐filled system showed better solvent resistance and hence minimum solvent uptake in polar and nonpolar solvents and better oil repellency followed by titanium dioxide and calcium phosphate filled systems. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Hydrazinodeoxycellulose for collection of metal ions from aqueous solution

We measured ellipsometrically the adsorption of polystyrene and polymethylmethacrylate on high-vacuum-vapoured chromium-, platinum- and gold-mirrors from various solvents under variation of the molecular weight of polymers. For both polymers we find an increase in thickness and adsorbed amount with an increase in polymer-concentration of solution. The concentration of the adsorbed polystyrene-film decreases, the concentration of the adsorbed polymethylmethacrylate-film increase with the polymer concentration of solution. Molecules of high molecular weight produce bigger thicknesses and adsorbed amounts than molecules of low molecular weight. With increasing polarity of the adsorbent we find an increase of thickness and amount of the adsorbed layer and a decrease of concentration. An increasing polarity of the solvent results in a decrease of thickness and amount and in an increase of concentration of the adsorbed layer. In saturation the polystyrene-molecules adsorb in the conformation of statistical coils. For the polar PMMA-molecules we find a divergent behaviour of the adsorption as a result of the strong interactions between the polar polymer-segments.     

溶剂对刮涂法制备P3HT:PCBM活性层薄膜形貌及光电性能的影响

选用2种混合溶剂氯仿+四氢化萘和二氯苯+氯仿配制活性液,通过刮涂法制备了P3HT∶PCBM活性层,研究了不同溶剂物化参数对P3HT∶PCBM活性层薄膜形貌及其组装电池光电性能的影响。应用显微图像分析仪、紫外可见分光光度计和台阶仪对P3HT∶PCBM活性层薄膜形貌进行了表征;采用X-射线衍射仪和紫外可见分光光度计分别测试了P3HT∶PCBM活性层的晶型结构和吸收光谱;在AM 1.5G、100mW/cm2光照下,测试了电池的光电性能。结果表明:采用二氯苯+氯仿(9∶1)混合溶剂较氯仿+四氢化萘(19∶1)混合溶剂制备的薄膜具有良好的均一性、平滑度、晶体结构,长吸收波长,用其组装的大面积(4cm2)柔性有机太阳能电池光电转换效率提高37%。     

高分子稀溶液中溶剂对分子特性与流变性能的影响

本文研究了不同溶剂对离子性和非离子性高分子稀溶液的分子构型和流变性能的影响.在部分水解的聚丙烯酰胺水溶液中加入无机盐,测量并计算了分子扩张因数,特征粘度与盐浓度、盐离子价数、溶液pH值的关系.同时使用不同的有机溶剂测量聚丁烯溶液的Maxwell模型松弛时间和分子扩张因数.研究表明,高分子稀溶液可藉调整溶剂性质的方法以达到期望的流变特性.     

Desorption Behaviour of Regular Adsorbed Polyampholytic Layers

The desorption behaviour of the diblock polyampholyte PMAA-b-PDMAEMA, poly(methacrylic acid)-block-poly((dimethylamino)ethyl methacrylate), preadsorbed on silicon substrates was investigated under the influence of several desorption agents. The investigated polyampholyte is known to adsorb in regular structures directly from aqueous solutions onto silicon substrates. While the adsorption process is mainly determined by electrostatic interactions, two kinds of desorption mechanism should be assumed. The first mechanism is based on changed electrostatic conditions caused for instance by a strong change in pH of the aqueous solution. The other mechanism is observed after treatment with hydrophobic organic solvent, which leads to the desorption of hydrophobic adsorbed polyampholyte chains, while the electrostatically attached ones will not be influenced. To complete the desorption experiments with organic solvents also adsorption experiments from analogous polyampholytic solutions in the same organic solvents were performed. The amount of polymer at the substrate surface after adsorption or desorption experiments was determined using ellipsometry. Atomic force microscopy (AFM) was used to investigate the surface topography of dried samples after the desorption process.     

Improvement of interfacial adhesion between oxide ceramic nanoparticles and epoxy resin by wet-jet milling

Although ceramic/polymer composites are useful for various applications, such as sensors, electronics, automobiles, and aerospace, the aggregation of nanoparticles can lead to the degradation of the mechanical and functional properties of the composites. To mitigate this, the interfacial adhesion between epoxy resin and the oxide ceramic nanoparticles γ-aluminum oxide (Al₂O₃), silicon dioxide, and magnesium oxide was strengthened by wet-jet milling (WJM) treatment without a chemical modifier. The WJM treatment of the slurry containing nanoparticles and epoxy resin led to the good adsorption of epoxy resin onto the nanoparticle surface, which significantly improved the mechanical properties of the composites. Throughout this process, the amount of epoxy resin adsorbed on the nanoparticle surface and the composite mechanical properties increased with increasing WJM processing pressure, owing to the increased contact between the nanoparticles and epoxy resin droplets and the reduced droplet size. Furthermore, poor solvent was found to be effective for the dispersal of the nanoparticles because the epoxy resin droplets in the slurry were more stable on the nanoparticle surfaces than those in the solvent. When Al₂O₃ nanoparticles were used as a filler, the amount of epoxy resin adsorbed increased from 3.7 to 70.6 mg g⁻¹, and the composite tensile strength increased from 67.1 to 100.3 MPa in poor solvent and under high WJM processing pressure. This optimized WJM treatment will lead to improvements in the mechanical and functional properties of various composite materials.     

EXTRACTION OF TRIS(MALONATO) CHROMATE(III) BY SOLUTIONS OF ALIQUAT-336 IN VARIOUS ORGANIC SOLVENTS

Abstract

The extraction of tris(raalonato) chromate(III) by solutions of Aliquat-336 in various organic solvents such as n-pentane, n-heptane, cyclohexane, chloroform, carbon tetrachloride, o-xylene,benzene, toluene, nitrobenzene and nitromethane has been studied. The effect of the organic solvent on the extraction is correlated with their solubility parameters by application of the theory of regular solutions. The solubility parameter of the extracted species is reported.