Characterization of glow‐discharge–treated cellulose acetate membrane surfaces for single‐layer enzyme electrode studies

Cellulose acetate membranes (CA) were modified by means of plasma polymerization of ethylene diamine (EDA) and n‐butylamine (n‐BA). The motivation for this work was the application of a modified membrane for the single‐layer enzyme electrode. A tubular reactor with the external radiofrequency (13.56 MHz) excitation was used. Surface modification was performed at 5, 10, and 15 W power (at 27 Pa working pressure) for 5, 10, 15 min. Modified surfaces were characterized in detail by FTIR–ATR, XPS (ESCA), contact angle, and enzyme immobilization activity. The best treatment results were obtained for EDA with 5 W and 30 min and 15 W and 10 min. These results are discussed using surface analysis data. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1341–1352, 2001     

脂肪酶改性醋酸纤维的性能研究

采用脂肪酶Lipex 100L对醋酸纤维进行脱乙酰化处理,改善纤维的吸湿、染色等性能;通过脂肪酶处理残液的紫外光谱分析、反应液pH值变化以及染料对纤维的吸附量、回潮率、取代度测试等方法,分析酶处理后反应液中水解产物的产生和纤维表面官能团的变化.结果表明:脂肪酶处理醋酸纤维后,反应液中有水解产物乙酸存在,醋酸纤维的回潮率...     

Ion‐plasma modification of polyvinylchloride microfiltration membranes

Here we present how the surface and some filtration properties of PVC microfiltration membranes are affected by controlled and well‐defined modification by ion‐plasma treatment in the kinetic region of the high voltage (HVGD) or normal glow discharge (NGD) in air. The surface energy and work of adhesion of the samples were calculated from the contact angle with both polar (H₂O) and nonpolar (CH₂I₂) liquid measurement data. The surface morphology was observed by SEM and the surface chemical composition was analyzed by ESCA. The trans‐membrane water flux, the average pore size, and the pore‐size distribution as well as the “bubble point” were used to control the effect of the ion‐plasma treatment on the filtration properties of the PVC microfiltration membranes. Two characteristic regions of the ion‐plasma treatment in air were found in our experiments where the surface properties and filtration characteristics of the membranes are extremely changed: at a pressure of 10–15 Pa in the region of the HVGD and at a pressure of 100–120 Pa in the region of the NGD. It was shown that the ion‐plasma treatment in air is an effective technological method for regulation of some important surface and filtration properties of PVC microfiltration membranes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2433–2440, 2003     

Surface modification of polypropylene membrane by low‐temperature plasma treatment

Microporous polypropylene membranes were low temperature plasma treated with acrylic acid and allylamine. Parameters of plasma treatment were examined and optimized for the enhancement of membrane performance properties. Excess power damaged the membrane surface and excess monomer flow rate increased the reactor pressure to interfere with the glow discharge. Longer plasma treatment time resulted in even more plasma coating and micropore blocking. The contact angle with water decreased and wettabilities increased with the increase of plasma treatment time. Deposition of the plasma polymer on the membrane surface was confirmed by FTIR/ATR spectra of the treated surface. In determining the flux, the hydrophilicity of the surface played a role as important as that of the micropore size. Adequate plasma treatment could enhance both water flux and solute removal efficiency. Results from the BSA (bovine serum albumin) solution test confirmed that fouling was greatly reduced after the plasma treatment. The BSA solution flux through the plasma‐treated membranes depended on pH, whereas pH variation had no serious effects on the untreated membrane. Modification of the surface charge by the plasma treatment should exert a substantial influence on the adsorption and removal of BSA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1555–1566, 2001     

乙酸纤维素的应用及改性研究现状

随着污染问题及资源短缺问题的日益严重,乙酸纤维素作为纤维素的重要衍生物之一,具有良好的加工性能及可生物降解性能,近年来一直备受关注。本文系统介绍了乙酸纤维素在服装纺织、烟用滤嘴及膜材料等方面的应用,分析了目前乙酸纤维素应用中存在的问题。同时从共混改性、纳米及纳米复合改性、表面改性等方面对乙酸纤维素的改性技术的研究进展进行了综述,最后展望了乙酸纤维素的发展前景,指出开发简单易行能够工业化的改性技术及制备出可再生的生物降解材料研究是乙酸纤维素改性今后的主要发展方向。     

Effect of cellulose acetate/cellulose triacetate ratio on reverse osmosis blend membrane performance

Surface functionalization and modification including the grafting process are effective approaches to improve and enhance the reverse osmosis (RO) membrane performance. This work is aimed to synthesize grafted/crosslinked cellulose acetate (CA)/cellulose triacetate (CTA) blend RO membranes using N-isopropylacrylamide (N-IPAAm) as a monomer and N,N-methylene bisacrylamide (MBAAm) as a crosslinker. The morphology of these membranes was analyzed by scanning electron microscopy and their surface roughness was characterized by atomic force microscopy. The performance of these membranes was evaluated through measuring two major parameters of salt rejection and water flux using RO unit at variable operating pressures. It was noted that the surface average roughness obviously decreased from 148 nm for the pure CA/CTA blend membrane with 2.5% CTA to 110 nm and 87 nm for the grafted N-IPAAm and grafted/crosslinked N-IPAAM/MBAAm/CA/CTA-RO membranes, respectively. Moreover, the contact angle decreased from 51.98° to 47.6° and 43.8° after the grafting and crosslinking process. The salt rejection of the grafted CA/CTA-RO membrane by 0.1% N-IPAAm produced the highest value of 98.12% and the water flux was 3.29 L/m²h at 10 bar.     

Surface modification of poly(ether sulfone) ultrafiltration membranes by low‐temperature plasma‐induced graft polymerization

Low‐temperature helium plasma treatment followed by grafting of N‐vinyl‐2‐pyrrolidone (NVP) onto poly(ether sulfone) (PES) ultrafiltration (UF) membranes was used to modify commercial PES membranes. Helium plasma treatment alone and post‐NVP grafting substantially increased the surface hydrophilicity compared with the unmodified virgin PES membranes. The degree of modification was adjusted by plasma treatment time and polymerization conditions (temperature, NVP concentration, and graft density). The NVP‐grafted PES surfaces were characterized by Fourier transform infrared attenuated total reflection spectroscopy and electron spectroscopy for chemical analysis. Plasma treatment roughened the membrane as measured by atomic‐force microscopy. Also, using a filtration protocol to simulate protein fouling and cleaning potential, the surface modified membranes were notably less susceptible to BSA fouling than the virgin PES membrane or a commercial low‐protein binding PES membrane. In addition, the modified membranes were easier to clean and required little caustic to recover permeation flux. The absolute and relative permeation flux values were quite similar for the plasma‐treated and NVP‐grafted membranes and notably higher than the virgin membrane. The main difference being the expected long‐term instability of the plasma treated as compared with the NVP‐grafted membranes. These results provide a foundation for using low‐temperature plasma‐induced grafting on PES with a variety of other molecules, including other hydrophilic monomers besides NVP, charged or hydrophobic molecules, binding domains, and biologically active molecules such as enzymes and ribozymes. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1699–1711, 1999     

Protein separation by cellulose acetate/sulfonated poly(ether imide) blend ultrafiltration membranes

A process for purifying aqueous solutions containing macromolecular proteins such as bovine serum albumin (BSA), egg albumin (EA), pepsin, and trypsin has been investigated. Protein removal from food and biorelated industrial waste streams are gaining increased visibility due to environmental concern and saving precious materials. Ultrafiltration (UF) processes are largely being applied for protein separation from aqueous streams. In this work, an attempt has been made to separate the valuable proteins using cellulose acetate (CA)/sulfonated poly(ether imide) (SPEI) blend UF membranes prepared in the absence and presence of the additive, polyethyleneglycol (PEG600) in various compositions. The blend membranes were subjected to the determination of pore statistics and molecular weight cut‐off (MWCO). Porosity and pore size of the membranes increased with increasing concentrations of SPEI and PEG600 in the casting solution. Similarly, the MWCOs of the blend membranes ranged from 20 to greater than 69 kDa, depending on the various polymer blend compositions. Surface morphology of the blend membranes were analyzed using scanning electron microscopy. Studies were carried out to find the rejection and permeate flux of proteins. On increasing the concentration of SPEI and PEG600, the rejection of proteins is decreasing, whereas the permeate flux has an increasing trend. The effect of hydrophilicity of SPEI on fouling of protein for CA/SPEI blend membranes was also discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of quench medium on the structure and gas permeation properties of cellulose acetate membranes

Integrally skinned asymmetric cellulose acetate membranes made by the wet phase inversion for removal of CO₂ from natural gas were investigated. The membrane was cast with the membrane-forming systems of cellulose acetate–acetone and quench media, such as methanol, ethanol and isopropanol, respectively, without heat-treating and multistage exchange process. By means of evaluation on separating characteristics of the membrane for CO₂/CH₄, observation of morphologies by scanning electron photomicrographs and analysis of the phase diagrams on the membrane-forming systems, it has shown that the membrane-forming system of cellulose acetate–acetone–methanol is quite suitable to prepare integrally skinned asymmetric cellulose acetate membranes for gas separation with good selectivity CO₂/CH₄ = 30 and flux coefficient = 2.4 × 10⁻⁵ cm³/cm² − s − cm Hg. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1269–1276, 1998     

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.     

Studies on cellulose acetate‐carboxylated polysulfone blend ultrafiltration membranes. III

Enhancement of the hydrophilicity in polymeric membrane materials results in membranes with higher flux and better membrane characteristics. Hence, polysulfone was carboxylated and ultrafiltration membranes were prepared from blends of cellulose acetate and carboxylated polysulfones having various degrees of carboxylation with a total polymer concentration of 20 wt % in casting solution and at different blend polymer compositions. The effects of degree of carboxylation on membrane characteristics such as compaction, pure water flux, and membrane hydraulic resistance (R_m) have been investigated. The influence of the polymer concentration in the blend solution on the performance of blend membranes at various blend polymer compositions has also been investigated and compared with that of blend membranes prepared from blends of cellulose acetate and polysulfone or carboxylated polysulfone with a total polymer concentration of 17.5 wt %. Further, the solute rejection performance of the membranes has also been investigated by subjecting the membranes to metal ion permeation studies using polyelectrolyte‐enhanced ultrafiltration. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 976–988, 2005     

The use of the simplex method to characterize dry cellulose acetate membranes for gas separations

The normal and log-normal distributions are used to describe the pore size distribution of dry asymmetric cellulose acetate membranes for CO₂/CH₄ separations. Various optimization techniques are implemented to determine the distribution parameters R and σ as well as the constants A₁, and A₂, related to pore structure and surface transport. respectively. By using the Simplex method, a unique solution for the characterization parameters is easily obtained irrespective of the starting search point. The permeation data of helium was used to characterize the membranes and determine the flow parameters which can be used to predict the performance of those membranes in separating CO₂/CH₄ mixtures.     

Pesticides removal performance by low‐pressure reverse osmosis membranes

Pressure driven techniques (viz. reverse osmosis and nanofiltration) have the potentiality to remove the pesticides from water. The observations revealed that pesticides removal mostly depends upon the molecular weight (size exclusion) and hydrophobicity (log P) of the pesticides. Interfacial polymerization of m‐phenylene diamine (MPD) and trimesoyl chloride (TMC) on the polysulfone membranes impart the salt rejection property in it. It is shown that with the greater salt rejection property, the performance removal of pesticides also is in increasing trend. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3575–3579, 2006     

醋酸纤维素的降解性研究进展

介绍了醋酸纤维素的生物降解、水解、光解的降解机理与研究现状,并对影响醋酸纤维素降解速率的因素进行了探究。从现有研究中可知,影响醋酸纤维素降解速率的主要因素为醋酸纤维素自身的分子结构（如取代度、取代度分布及结晶性等）,物理改性、化学改性及增塑改性会通过改变醋酸纤维素的分子结构,进而影响醋酸纤维素的降解性能。最后,总结了醋酸纤维的应用领域,并做出了展望。     

An environment‐friendly thermal insulation material from cellulose and plasma modification

Cellulose aerogels were prepared by combining the NaOH/thiourea/H₂O solvent system and the freeze‐drying technology. Hydrophobic aerogels were obtained with the cold plasma modification technology. The results showed that cellulose aerogel had good heat insulation performance, while the main factors affecting thermal conductivity were density and porosity. Thermal conductivity decreased with the decrease of density and the increase of porosity. It could be as low as 0.029 W/(m K). Cellulose aerogel adsorbed moisture easily. The moisture adsorption had a significant influence on the heat insulation performance of aerogel. After conducting hydrophobic modification using CCl₄ as plasma, cellulose aerogel was changed from hydrophilic to hydrophobic and water contact angle was as high as 102°. Hydrophobic modification did not affect the heat insulation performance of aerogel. This work provided a foundation for the possibility of applying cellulose aerogels in the insulating material field. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3652–3658, 2013     

Surface characterization of PET nonwoven fabric treated by He/O2 atmospheric pressure plasma

The surface of polyethyleneterephthalate (PET) nonwoven fabric was modified by He/O₂ atmospheric pressure plasma treatment, varying plasma exposure time. The plasma treated PET surfaces have been analyzed to investigate the chemical nature and morphology of surface by X‐ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The change of wettability was measured depending on plasma exposure time. XPS results indicated the presence of oxygen‐based functional groups on the PET nonwoven fabric surface after plasma treatment and oxygen content increased as exposure time increased. The mean roughness increased after 30 s exposure and further increase in exposure to 60 s led to decrease of the roughness and then again increase. The root mean square roughness followed the similar trend to mean roughness. The average difference in height, Rz, increased after plasma exposure for 30 s, while it slightly decreased after 60 s exposure. Despite of redeposition, the Rz of 90 s exposed sample increased more than two times compared with those of 30 and 60 s exposed. Wettability increased progressively up to 10 times after 90 s exposure compared with the untreated. It is attributed to the increases of hydrophilicity and surface roughness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

超临界CO_2法制备乙酸纤维素微孔膜

以超临界CO2为非溶剂,丙酮和N, N-二甲基甲酰胺（DMF）为溶剂,制备了乙酸纤维素（CA）微孔膜,采用扫描电镜表征膜的微观形态并测定了膜的纯水通量,考察了溶剂与CO2的亲和性、CA质量分数、成膜压力、成膜温度、保压时间和卸压速度等因素对膜形态及性能的影响。实验结果表明,以丙酮为溶剂可制备出表观形态均一完整的膜;随着CA质量分数的增加,膜孔径变小,膜的水通量迅速降低;随着成膜压力、成膜温度的升高,膜水通量均先增加后减小;保压时间及卸压速度对膜水通量的影响较小。当CA质量分数为10 %时,在成膜压力为15 MPa,成膜温度为45 ˚C,保压45 min,快速卸压的操作条件下,微孔CA膜的水通量可达30 L·m-2·min-1。     

Biodegradation behavior of acid‐containing cellulose acetate film in soil

The biodegradation behavior of various cellulose acetate (CA; degree of substitution = 2.5) films that contain acids was examined by a laboratory soil burial test to clarify the effects of additives on the biodegradability of CA. The biodegradation rate of the CA films containing polyphosphoric acid, phosphoric acid, and p‐toluenesulfonic acid increased compared to that of the nonadditive CA film. CA films containing mandelic acid and maleic acid showed a small tendency to increase. Conversely, CA films containing adipic acid did not affect the biodegradability of CA. A similar experiment was carried out with a sterilization system. The acid‐containing CA film, which showed an accelerated biodegradation rate, was chemically deacetylated by contact with water in the environment and was consequently converted to a lower degree of acetyl group substitution matter that had higher biodegradability. An IR analysis suggested that this deacetylating ability of acids is correlated with the intensity of their interaction with the acetyl group of CA. In the biodegradation process, the contact efficiency of acids to CA was considerably lowered by the elution of internal acids with time. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 466–473, 2005     

Adsorption properties of cyclic compounds on cellulose acetate

The interaction between solutes and semipermeable membranes is an important factor for the membrane‐separation process. As an extension to previous works, we studied the adsorption properties of cyclic compounds on cellulose acetate, a material commonly used for semipermeable membranes, in aqueous solution systems by high‐performance liquid chromatography (HPLC). Cycloalcohols, cycloethers, amino acids, heterocyclic aromatic compounds, and nucleosides were used in this study. The logarithm of the capacity factor (log k′) for these compounds was linearly correlated with the logarithm of 1‐octanol/water partition coefficients (log K_o/w) as well as noncyclic compounds. Cyclic compounds were relatively retained more than were noncyclic compounds in spite of their hydrophilic properties, which indicates the structural effects of the solute molecule on the adsorption. Although noncyclic compounds were retained mainly by hydrophobic interaction, the retention of cyclic compounds was suggested to be controlled by their inclusion within the micropore in cellulose acetate. The adsorption of heterocyclic aromatic compounds was not influenced only by ionic dissociation but also by tautomerism. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1657–1663, 1999     

Water flux,DSC, and cytotoxicity characterization of membranes of cellulose acetate produced from sugar cane bagasse,using PEG 600

Summary In this article, cellulose acetate produced through the homogeneous acetylation of sugar cane bagasse cellulose was used to produce membranes, using poly(ethyleneglycol) 600 (PEG 600) as an admixture. The membranes were characterized using water flux measurements (Payne’s cup), differential scanning calorimetry (DSC) and neutral red uptake (cytotoxicity). The results showed that PEG 600 acts as a crystallinity inductor and/or pore former in the cellulose acetate matrix. The induction of crystallinity is important for this system since it had not been reported on the literature yet. The results also demonstrated that the studied membranes present a nontoxic behavior.