Chemical initiated-grafted nylon 4 membranes

To improve the performance of nylon 4 membranes, this study attempts to utilize chemical initiation which induces different hydrophilicities vinyl monomers grafted onto nylon 4 membranes. Sodium styrene sulfonate, chloromethyl styrene, styrene, and glycidyl methacrylate were used as grafting monomers. The factors that affect the degree of grafting considered were chemical initiators, pH values, kinds and concentrations of monomers, reaction time, and temperatures. The mechanical strength and the transport properties of these chemical-initiated grafted nylon 4 membranes were also investigated. Both the water flux and the salt rejection of sodium styrene sulfonated-grafted membrane were increased significantly, compared to our previous paper,¹ and the casein rejections of all of the four grafted nylon 4 membranes studied exceeded 90%. The quaternized nylon 4-g-poly(chloromethyl styrene) membranes were prepared and possessed high water uptake behavior and high transfer number (0.99) for electrodialysis. The sulfonating process was also applied to improve the hydrophilicity of nylon 4-g-poly(glycidyl methacrylate) membrane so that the water flux and the salt rejection were both increased.     

Acrylic acid γ-ray irradiation-grafted nylon 4 membranes

This study was to improve the performances of nylon 4 membranes for washing waste-water treatment of nuclear power plants, e.g., removal of detergent and salt by membranes. The effects of the degree of grafting and ionization on the reverse osmosis performances of acrylic acid (AA)-grafted nylon 4 membranes by γ-ray irradiation modification were investigated. The relationships of operating conditions, such as feed concentrations of salt and detergent, operating temperature, and pressure, and the performances of water flux and solute rejection of the prepared membranes were obtained. Water flux of the prepared membranes was highly sensitive with the operating temperature. It was found that an increase in the operating pressure could increase the water flux and the impaction effect directly. Water flux and salt rejection were significantly improved by both ionized and nonionized AA-grafted nylon 4 membranes compared to ungrafted nylon 4 membranes. Water flux increased rapidly and solute rejection dropped off slightly as the grafted membranes were ionized. The 100% detergent rejection could be obtained by the nonionized AA-grafted nylon 4 membranes with 38.6 and 69.6% degrees of grafting under various operating conditions. Results obtained showed that these modified nylon 4 membranes were usable for washing waste-water treatment of nuclear power plants. © 1993 John Wiley & Sons, Inc.     

Investigations on nylon 4 membranes. Synthesis and transport properties. I. Synthesis of nylon 4 polymer

The synthesis of nylon 4 (polypyrrolidone) by the anionic polymerization of 2-pyrrolidone through the use of the CO₂/potassium pyrrolidonate catalyst system for use in preparing polymer membranes for separation purposes was investigated in detail. The effects of the quantity of CO₂, the potassium pyrrolidonate catalyst, and the reaction temperature on the yield and molecular weights of the nylon 4 were studied. At reaction temperatures of 50°C and a reaction time of 120 hr, a yield of 50.9% with intrinsic viscosity of 4.42 (corresponding to M_n of 108,200 and M_w of 135,850) was obtained. The molecular weight distributions of the nylon 4 were determined by gel permeation chromatography (GPC) using m-cresol as the eluting solvent and were found to have a relatively narrow distribution.     

Polyether-segmented nylon hemodialysis membranes. II. Morphologies and permeability characteristics of polyether-segmented nylon 610 membrane prepared by the phase inversion method

The relationships between the morphologies and the permeability characteristics as dialysis membrane of polyether-segmented nylon 610 (PE-Ny610) have been investigated. PE-Ny610 used are poly(propylene oxide) (PPO)-segmented nylon 610 containing 25 wt % PPO (PPO-Ny610) and poly(ethylene oxide) (PEO)-segmented nylon 610 containing 15 wt % PEO (PEO-Ny610). The morphologies in the cross section of the membranes exhibit the cellular porous structures due to liquid-liquid phase separation. On the other hand, the structures of the surfaces are mainly composed of the crystalline spherulite due to liquid-solid phase separation. These morphologies are little affected by the composition ratio of the coagulant, calcium chloride/methanol/water mixture. PEO-Ny610 membranes have shown superior membrane performances to the PPO-Ny610 membrane. The effect of PEO content in PEO-Ny610 on the adhesion of platelet onto the PEO-Ny610 film surface was investigated and it is concluded that PEO-Ny610 having > 10 wt % PEO shows a good nonthrombogenicity equal to PPO-Ny610. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1713–1721, 1997     

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.     

Polyether-segmented nylon hemodialysis membranes. I. Preparation and permeability characteristics of polyether-segmented nylon 610 hemodialysis membrane

The effect of the coagulation condition in the phase inversion method on the permeability characteristics of poly(propylene oxide) or poly(tetramethylene oxide)-segmented nylon 610 (PPO-Ny610 or PTMO-Ny610) hemodialysis membranes, the stability of the membrane performance, and the mechanical strength were investigated. The polymers were dissolved in a solvent such as formic acid and methanol saturated with calcium chloride, and thus PPO-Ny610 and PTMO-Ny610 membranes were prepared using formic acid and a calcium chloride/methanol/water mixture as a polymer solvent and a coagulant, respectively. It is concluded that PPO-Ny610 membrane has better permeability characteristics than PTMO-Ny610 membrane, and possesses additional properties for hemodialysis membranes such as mechanical properties and permeability stability in the drying and sterilizing processes. Furthermore, the blood compatibilities of PPO-Ny610 and PTMO-Ny610 membranes were superior to regenerated cellulose membranes on the basis of the result of platelet adhesion test. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1703–1711, 1997     

Studies on syntheses and permeabilities of special polymer membranes. XIV. Permeation characteristics of modified nylon 12 membranes

The permeation characteristics and the burst strength of nylon 12 membranes treated with heat in various solutions such as aqueous solutions of formic acid, formic acid/formalin, and sodium hydroxide/ formalin were investigated under various conditions. They were significantly influenced by the treatment solution, temperature and time, and the concentration of acid and alkali in the treatment solution. In particular, nylon 12 membranes treated with formic acid/formalin remarkably improved the permeation characteristics and the burst strength. These phenomena were discussed from the standpoint of the effective pore size and pore number in the membrane, and the form and aggregation of polymer molecules forming the membrane.     

Separation of water–alcohol mixtures by pervaporation through asymmetric nylon 4 membrane

The dehydration of aqueous alcohol solutions through asymmetric nylon 4 membranes were investigated using pervaporation processes. The formation of asymmetric pervaporation membranes are discussed in terms of the content of the nonsolvent in the casting solution, polymer concentration, and compositions of the coagulation medium. The effects of the feed composition, feed temperature, and molar volume of the alcohols on the pervaporation performances of the asymmetric membranes are discussed. A separation factor of 4.72 and a permeation rate of 0.78 kg/m² h for the asymmetric membrane were obtained. Compared to the conventional homogeneous nylon 4 membrane, the asymmetric membrane can effectively overcome the pervaporation performances of the nylon 4 membrane for separation of water–alcohol mixtures. © 1994 John Wiley & Sons, Inc.     

Studies on syntheses and permeabilities of special polymer membranes. XVI. Permeation and separation characteristics of aqueous polymer solutions for acrylonitrile-styrene copolymer membranes

The permeation and separation characteristics of aqueous polymer solutions using acrylonitrile-styrene copolymer membranes were investigated under various conditions. The membranes obtained from dimethyl sulfoxide solution of acrylonitrile-styrene copolymer have not a sufficient reproducibility and stability of permeation. These lacks were improved by adding ethylene glycol or glycerol to the casting solution and treating the membranes with pressure. The permeation and separation characteristics were influenced significantly by the additional amount of above additives, the heat treatment temperature, and the operating pressure. It was found that the concentration polarization of poly(vinyl alcohol) molecules onto the surface of the acrylonitrile-styrene copolymer membranes is smaller than that onto hydrophilic polymer membranes such as membranes of cellulose acetate, cellulose nitrate, and nylon 12, etc. Moreover, the acrylonitrile-styrene copolymer membranes show better performance for separation and concentrating of aqueous polymer solutions than hydrophilic membranes.     

Poly(vinylidene fluoride-co-hexafluoro propylene) membranes prepared via thermally induced phase separation and application in direct contact membrane distillation

A non-toxic and environmentally safe diluent, acetyl tributyl citrate, was employed to prepare poly(vinylidene fluoride)-co-hexafluoropropylene membranes via thermally induced phase separation. Effects of the polymer concentration on the phase diagram, membrane morphology, hydrophobicity, pore size, porosity and mechanical properties (tensile stress and elongation at break) were investigated. The results showed that the pore size and porosity tended to decrease with increasing polymer concentration, whereas the contact angle, liquid entry pressure and mechanical properties showed the opposite trend. In direct contact membrane distillation operation with 3.5 wt-% sodium chloride solution as the feed solution, the prepared membranes performed high salt rejection (>99.9%). Furthermore, the prepared membranes retained excellent performance in long-term stability tests regarding the permeate flux and salt rejection.     

Molecular‐imprinted nylon membranes for the permselective binding of phenylalanine as optical‐resolution membrane adsorbents

Nylon 6, nylon 6,6, and terephthalic phenylene polyamide (TPPP) were functionalized by phase‐inversion molecular imprinting to add L ‐phenylalanine recognition ability. Formic acid containing 20 wt % nylon and 8 wt % L ‐phenylalanine was used as the solvent for the cast solution of the imprinting process. The resultant porous membranes behaved as membrane adsorbents that separated the L /D mixture of the substrate. The imprinted nylon 6 and nylon 6,6 presented high selectivity to the L ‐form substrate with respect to the TPPP membranes, but the imprinted TPPP membranes showed higher binding capacity with 0.57 μmol/g for L ‐phenylalanine. The apparent partition coefficients of L ‐ and D ‐forms by the imprinted membranes were 6.8, 4.2, and 1.7 for nylon 6, nylon 6,6, and TPPP, respectively. The separation manner of the L ‐ and D ‐forms from the mixture was also confirmed by membrane filtration under 1.5 kgf/cm² of applied pressure. The imprinted nylon 6, nylon 6,6, and TPPP membranes had separation factors of L ‐ and D ‐phenylalanines of 1.1, 1.1, and 1.2, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 620–626, 2005     

Suppression of gold nanoparticle agglomeration and its separation via nylon membranes

Use of ultraporous nylon membrane is one of the most widely employed techniques for removal of hard and soft nanoparticles in the semiconductor industry,and the accurate determination of membrane pore size is necessary in order to avoid manufacturing defects caused by contamination.The gold nanoparticle has several benefits for the evaluation of polymeric membranes;however,the nanoparticles agglomerate easily on the nylon membrane and make it difficult to evaluate the membrane precisely.The properties of 2-amino-2-hydroxymethyl-1,3-propanediol (ADP) ligand in gold nanoparticle solution were systematically investigated,and ADP was utilized for improved evaluation of the nylon membranes.Nylon membrane used in this study was prepared by phase inversion techniques.Ultrathin dense layer on top of the membrane surface and Darcy structures in the microporous membrane support were observed.The gold particle rejection was carried out at various pH values from 4 to 14 and higher rejection was observed at pH 4 and 8.The suppression of gold colloid agglomeration using ADP and monodispersity of gold colloids was also analyzed by confocal laser scanning microscopy (CLSM),transmission electron microscopy (TEM),and scanning electron microscopy (SEM).van der Waals interaction energy of the particles was reduced in the addition of ADP.The presence ofADP ligand in the gold solutions prevented the agglomeration of gold nanoparticles and reduced the adsorption of the particles on the nylon membrane surface,leading to precise evaluation of membrane pore sizes.     

Polyether-segmented nylon hemodialysis membranes. III. Preparation and properties of new polyether-segmented nylon

In order to apply a blood-compatible polymer to hemodialysis membrane, a new polyether-segmented nylon which dissolved in common organic solvents was designed. The basic polyether-segmented nylon was synthesized by melt polycondensation from sebacic acid, m-xylenediamine, and α,ω-bisaminopropyl-poly(ethylene oxide). To improve the solubility, azelaic acid and hexamethylenediamine were copolycondensed with the basic copolymer. The solubility was correlated with the heat of fusion (ΔH_m) of the copolymer. When ΔH_m is < 30 mJ/mg, the polymer is soluble in dimethylsulfoxide and makes a stable solution. The nonthrombogenicity was investigated in the viewpoint of adhesion of platelet onto the copolymer surface. It is made clear that the surface of the block copolymer, having > 10 wt % of poly(ethylene oxide), suppresses the adhesion of platelet, and the composition of the nylon block has no effect on the adhesion of platelet. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1723–1729, 1997     

高相对粘度尼龙6溶液性能研究

以二甲基亚砜、甲酰胺、间甲酚、硫酸、甲酸、甲酸／二氯甲烷为溶剂,考察高相对粘度尼龙6的溶解性能;研究尼龙6溶液的流变性能及溶剂对尼龙6晶体结构的影响。结果表明:二甲基亚砜和甲酰胺不宜作高相对粘度尼龙6的冻胶纺丝溶剂,硫酸、甲酸和间甲酚比较适宜;提高温度有利于降低剪切速率,质量分数为12％的间甲酚溶液和质量分数为9％的甲酸溶液作溶剂,其尼龙6溶液分别在50～60℃和45℃以上有较好的可纺性;溶剂对尼龙6晶体结构的形成有着重要的影响。     

Ionically crosslinked poly(acrylic acid) membranes. III. Reverse osmosis results for dry cast membranes

The reverse osmosis properties of ionically crosslinked polyacrylic acid membranes were investigated in terms of the salt separation of a 0.1% NaCl solution and water flux. The membranes were synthesized and crosslinked with the metal ion Al³⁺ via the dry casting technique described in a previous paper. The effect of such variables as the polymer concentration in the casting solution, the ratios of solvents used (DMF/H₂O), the ratio of monomer to the crosslinking agent (AA/Al), the evaporation time and temperature, and the nonsolvent nature and treatment times were studied in some detail. The most important variable was found to be the length and nature of the treatment in the nonsolvents acetone and methanol. In the best series of the membranes that were synthesized, fluxes of more than 3.0 gfd, with salt separations at the 80%–85% level, were obtained.     

Studies on syntheses and permeabilities of special polymer membranes. 27. Concentration of poly(styrene sulphonic acid) in various aqueous solutions using poly(vinylidene fluoride) membranes

The permeation characteristics of poly(vinylidene fluoride) membranes in the separation and concentration of poly(styrene sulphonic acid), from various aqueous solutions were investigated under various conditions. The rejection of the polymer from its aqueous solution was high, because electrostatic repulsions between the charges along polymer chains cause chain extension. When a salt, such as sodium chloride, and sulphuric acid were added to the aqueous solution and the pH was changed, the configuration of the poly(styrene sulphonic acid) molecules changed significantly with the added amounts of salt. The permeation characteristics were influenced markedly by the conformational changes of polymer molecules and the viscosities of permeating liquids. The rejections were dependent on the conformational changes: the permeation rates were mainly governed by the viscosities. Poly(vinylidene fluoride) membranes had much superior resistance to acid, i.e. even when immersed in concentrated sulphuric acid for 7 days, the permeation characteristics did not change at all. The membranes were also effective for the concentration of poly(styrene sulphonic acid) and the removal of sulphuric acid from aqueous mixtures since the concentration of these solutes were optimum.     

Polyether-segmented nylon hemodialysis membranes. IV. Membrane morphologies and permeability characteristics of dialysis membrane composed of poly(ethylene oxide)-segmented Ny69/M10

Dialysis membrane was prepared by a phase inversion method using a new polyether-segmented nylon which dissolves in common organic solvents such as dimethylsulfoxide. The polyether-segmented nylon contained poly(ethylene oxide) block and nylon block (random copolyamide: Ny69/M10) prepared by sebacic acid, azelaic acid, m-xylenediamine, and hexamethylenediamine. The morphologies and permeability characteristics of the membranes were investigated. It was shown by scanning electron microscope observation that the membrane had a fingerlike structure when dimethylsulfoxide was used as a polymer solvent, and a spongelike structure when an additive such as calcium chloride was added to the polymer solution. The high permeability for the solutes such as urea and vitamin B₁₂ were observed in comparison with the polyether-segmented Ny610 membranes prepared by a phase inversion method. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1731–1737, 1997     

Selective permeability of PVA membranes. I. Radiation-crosslinked membranes

The water and salt transport properties of ionizing radiation crosslinked poly(vinyl alcohol) (PVA) membranes were investigated. The studied membranes showed high permeabilities and low selectivities for both water and salt. The results were found to be in accord with a modified solution–diffusion model for transport across the membranes, in which pressure-dependent permeability coefficients are employed.     

Separation of liquid mixtures by using polymer membranes. III. Grafted poly(vinyl alcohol) membranes in vacuum permeation and dialysis

A series of poly(vinyl alcohol) membranes were modifed by radiation-induced graft copolymerization with acrylic acid and methacrylic acid monomers. These grafted poly(vinyl alcohol) membranes were then tested for their separation and permeability characteristics in vacuum permeation and dialysis experiments. The permselectivity of the membranes toward methanol and water was studied on a vacuum permeation apparatus at 30, 40, and 50°C. The permeation process was found to be a temperature-activated process. The logarithm of the permeation rate varied linearly with the reciprocal of the absolute temperature. The permeability of the grafted membranes was found to increase with the degree of grafting, with no appreciable selectivity toward water in binary mixtures. The acrylic acid-grafted membranes generally showed greater improvement in permeability than the methacylic-grafted membranes. The permeability of the grafted membranes toward methanol, sodium chloride, urea, creatinine, and uric acid was studied in a dialyzer. In all cases, the grafted membranes showed an improved permeability toward these solutes over the commercial poly(vinyl alcohol) membranes. The dialysis results were then compared with those obtained for dialysis-grade cellophane membranes. For the case of sodium chloride, urea, and methanol, the permeability of the grafted membranes was comparable to that of cellophane. A comparison of commercial and grafted poly(vinyl alcohol) membranes in their permeability toward ionic solutes exhibited somewhat anomalous behavior in that the permeability of the commercial membranes was higher than that of the grafted membranes. This related to the ionic nature of the modified membrane. The permeability coefficients determined in the dialysis experiments were found to be directly related to the degree of hydration of the grafted membrane. This behavior was attributed to changes in the size and shape of voids within the membrane structure.     

Novel ion-containing reverse osmosis membranes. I. Preparation and selected properties

Grafting and subsequent quaternization of 2-and 4-vinylpyridine to poly(vinyl chloride) (PVC) and to poly[3,3-bis(chloromethyl)oxetane], Penton, films have been exploited to prepare novel ion-containing membranes. 2-Vinylpyridine-grafted “Penton” films are the most attractive system for further study since the PVC grafts were unstable under the requisite extraction conditions. Although the sterically less hindered 4-vinylpyridine-grafted films were easier to quaternize, weight gain calculations indicated that complete quaternizations were only achieved with the 2-vinylpyridine-grafted films. High ionic concentrations were obtained in the grafted membranes. The mechanical properties of the wet films were measured. Salt absorption studies demonstrated that significant salt exclusion was achieved at relatively high salt concentrations although the grafted films sorbed up to 30 vol % water.