Elasticity of ion‐exchange resin beads in solvent mixtures

The effect of the solvent composition on the elasticity of strong and weak cation‐ and anion‐exchange resin beads was studied. Poly(styrene‐co‐divinylbenzene) resins containing sulfonic acid or quaternary ammonium groups and an acrylic acid resin crosslinked with divinylbenzene were immersed in water, NaCl solutions, or aqueous alcohol solutions and the shear modulus was measured with a uniaxial compression method. The elastic data were compared with the swelling properties. In pure water the shear moduli increased when the crosslink density, counterion valence, counterion size, and functional group size increased. Two additional phenomena in the elastic behavior were observed when the swelling degree of the resins was changed by the addition of alcohol or salt. A decrease of the modulus was observed when moving from the fully swollen state to a less swollen state, and a steep upturn of the modulus took place at a characteristic swelling region. The depth of the minimum and the location of the transition from the rubbery to the glassy state depended on the characteristics of the resins. The finite expansibility of the polymer chains and the glass transition explained these findings. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1256–1264, 2001     

Porosity variation and swelling of styrene-divinylbenzene copolymers

Summary The porosity measured for two series of diluent-modified styrene (S) — divinylbenzene (DVB) copolymers (10 and 20 wt.-% of DVB) was found to depend on sample pre-treatment. A correlation between the volume fraction of the polymer in the swollen gel and the volume fraction of octane used as diluent has been established assuming the isotropic swelling of the sample pretreated with water before porosity determination.     

Removal of inorganic mercury from mine waste water by ion exchange

The present study has been undertaken to investigate a process that might remove inorganic mercury from mine waste water streams by use an ion exchange resin system. A number of commercial resins have been evaluated as ion exchangers and the mercury content of the waste water, ranging from 70 to 90 ppm, is reduced to a permitted level of 34 ppb. Dowex XZS‐1, a strong cationic ion exchanger in a gel Form, has the most pronounced selectivity for mercury. The loaded resin was regenerated efficiently using HCl solutions, due to increased competition between Hg and hydronium ions and formation of an HgCl ₄ ²⁻ ionic complex. © 2000 Society of Chemical Industry     

Mechanical characterization and chemical resistances of cured unsaturated polyester resins modified with vinyl ester resins based on recycled poly(ethylene terephthalate)

Unsaturated polyester resin (UP) was prepared from glycolyzed oligomer of poly(ethylene terephthalate) (PET) waste based on diethylene glycol (DEG). New diacrylate and dimethacrylate vinyl ester resins prepared from glycolysis of PET with tetraethylene glycol were blended with UP to study the mechanical characteristics of the cured UP. The vinyl ester resins were used as crosslinking agents for unsaturated polyester resin diluted with styrene, using free‐radical initiator and accelerator. The mechanical properties of the cured UP resins were evaluated. The compressive properties of the cured UP/styrene resins in the presence of different vinyl ester concentrations were evaluated. Increasing the vinyl ester content led to a pronounced improvement in the compression strength. The chemical resistances of the cured resins were evaluated through hot water, solvents, acid, and alkali resistance measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3175–3182, 2007     

The study of water behaviour in regenerated cellulosic fibres by low-resolution proton NMR

Regenerated cellulosic fibres and comparative materials were studied in the hydrated state by low-resolution proton NMR. Experiments at variable pH and temperatures have shown that the shortened T₂ relaxation times of water within fully swollen cellulosic fibres are dominated by proton exchange with accessible cellulose hydroxyl groups. Proton exchange is accelerated by both acid and base catalysis, with relaxation data used to estimate rate constants for acid, base and neutral mechanisms. Complementary deuterium exchange measurements suggest that accessible cellulose regions below the immediate water interface may not contribute effectively to the proton exchange relaxation mechanism, with two-site relaxation models sensitive only to the direct pore surface area. Differences between surface-relaxing water and deuterium-exchanging water can therefore be used to determine an apparent depth of the accessible cellulose, which is greater for viscose and modal compared to lyocell. However, from relaxation data lyocell has a higher pore surface area. This work also confirmed that water interacting with accessible cellulose experiences motional restriction, allowing an intra-molecular dipolar contribution to relaxation. However, in the fully swollen state water molecules are diffusing rapidly between all internal fibre environments and there is no evidence of specific binding.     

Pore structure control of mesoporous carbon monoliths derived from mixtures of phenolic resin and ethylene glycol

Mesoporous carbon monoliths derived from phenolic resin mixtures have been prepared in the process based on polymerization-induced phase separation. The effect of the composition of resin mixtures and the resin curing temperature on the pore structure of carbon monoliths has been systematically investigated, with emphasis on controlling the apparent porosity and pore size distribution. Fractal dimensions have been introduced to evaluate the morphologies of the carbon monoliths. The results showed that mesoporous carbon monoliths with narrow pore size distribution were obtained. The pore structure of carbon monoliths could be controlled by changing the resin curing temperature and the content of ethylene glycol, curing catalyst and water in the resin mixtures. The apparent porosity of carbon monoliths varied from 54.27% to 26.83%. Carbon monoliths had narrower pore size distribution when more ethylene glycol and higher resin curing temperature were employed. The pore structure of carbon monoliths would be changed radically when the initial resin samples were prepared with excess water (9.8 wt%), i.e. porous carbon foams with sponge structure were obtained. Carbon monoliths inherit their porosity from precursing cured resins where it was formed as a result of phase separation of resin-rich and glycol-rich phases. Volume contraction had certain effect on the pore structure of carbon monoliths.     

Investigation of pore structure of ion exchange membranes

The pore structure of heterogeneous ion exchange membranes was studied by the mercury penetration method using a commercially available apparatus. Results obtained from the porosymmetrical measurements show that the membranes possess two layers, the upper one being less porous than the lower backing layer. The distribution of the pores in width and length is non-homogeneous. Anion exchange membrane MA-41 has a relatively more homogeneous pore structure.Application of the mercury penetration method makes it possible to quantitatively assess the degree of mechanical destruction of anion exchange membranes during the working period. It was found that membranes operated at the cathode and anode compartments of the electrodialysis unit are destroyed more quickly.     

Preparation and characterization of high loading porous crosslinked poly(vinyl alcohol) resins

Porous crosslinked poly(vinyl alcohol) resin beads have been prepared by a two-step pathway involving a pre-crosslinking reaction followed by a reverse suspension crosslinking reaction with epichlorohydrin as crosslinker. The reaction conditions have been optimized for the two steps in order to obtain resins with various pores sizes. The crosslinking density of these resins was calculated from their swelling properties by a modified Flory equation. High loading of hydroxyl groups is one of the important characteristics of these resins (attaining ca. 17 mmol/g). The porosity, pore volume, pore structure and the swelling behavior in water of these resins have been studied.     

Preparation of poly (ethylene glycol) acrylate grafted polystyrene resin for solid-phase peptide synthesis

The solid-phase synthesis resin with high loading capacity was prepared through grafting poly (ethylene glycol) acrylate monomer from Merrifield resins via activators generated by electron transfer atom transfer radical polymerization. The grafted resins demonstrate well-swellability in both polar and nonpolar solvent such as dichloromethane, dimethylformamide, ethanol, tetrahydrofuran, acetonitrile, methanol and water. Particularly, the swelling ability of the grafted resin has reached two-fold of Merrifield resin in the polar solvent such as acetonitrile, methanol and water, and it enable high functional loadings up to 0.5–1.2 mmol g⁻¹ compared with the conventional polystyrene-grafting-poly (ethylene glycol) (0.15–0.25 mmol g⁻¹). This resin was derived to be used for synthesis of a difficult sequence-acyl carrier protein fragment 65-74 (ACP 65-74). The quantity and purity of peptide obtained from the grafted resin were higher than when the commercial Wang resin was used. The synthesis efficiency enhanced with the increase of grafting chains’ length within the range of hydroxyl capacity at 0.5–1.0 mmol g⁻¹. It was relative that the longer grafting chains were favor to suppress the hydrophobicity of the Merrifield resin.     

USANS study of porosity and water content in sponge-like hydrogels

Ultra small-angle neutron scattering (USANS) methods and equilibrium swelling measurements are combined to characterize correlation length, pore volume fraction, and gel-phase water content in sponge-like hydrogels. USANS invariant analysis is applied to poly(hydroxyethylmethacrylate) gels prepared with 40-80 vol. % of an extractable porogen. These gels are strongly opaque in the swollen state, but become transparent upon drying due to shrinkage or disappearance of the pores. The correlation length associated with porosity is measured by fitting USANS data to an appropriate scattering model. By combining swelling measurements with USANS invariant analysis, it is possible to determine the equilibrium volume fraction of pores and the concentration of water in the gel phase without performing contrast variation measurements.     

Macroporous poly(EGDMA-co-HEMA) networks: Morphological characterization from their behaviour in the swelling process

Polymer beads of ethylene glycol dimethacrylate and 2-hydroxyethyl methacrylate [poly(EGDMA-co-HEMA)] were synthesized by suspension polymerization using different EGDMA contents and stirring speeds. The matrix pore system and the degree of crosslinking are evaluated mainly from the degree of swelling in water, and a mathematical model to describe the network morphology is proposed. The distribution of water into the network was determined from evaporation kinetics of swollen samples, then parameters such as porosity and increase of pore and network volumes were calculated. Networks with a highly stable system of pores were formed when the EGDMA content is higher than 10 mol% for stirring speeds higher than 300 rpm.     

强酸型阳离子交换树脂合成乙基叔丁基醚的研究

利用大孔聚苯乙烯-二乙烯苯型共聚物,经卤化、磺化处理改性制备得到强酸型阳离子交换树脂LH-1。采用树脂A、B、C、D和LH-1阳离子交换树脂作催化剂,以乙醇和异丁烯为原料,对合成乙基叔丁基醚的反应进行研究。结果表明,树脂的酸交换容量越大,催化活性越好。乙基叔丁基醚合成还与其孔结构密切相关,且孔结构的影响比酸交换容量更大。LH-1树脂在实验条件下表现出最好的活性。     

SWELLING OF A CHELATING MACROPOROUS RESIN DURING METAL ION EXCHANGE

ABSTRACT

The kinetics of heavy metal ion exchange onto a commercial chelating resin was investigated from the standpoint of the swelling-shrinking experienced by the resin bead during the overall ion exchange process. Temporal measurements of the volume variations were carried out for every step of an operational cycle, metal load, elution and regeneration of the ion exchanger, using a microreactor mainly composed by a reaction cell, an optical microscope and an image treatment system. Experimental results were properly fitted to an empirical equation, whose parameters were used to characterize and compare different systems. A pseudosteady state kinetic model, which takes into account the volume variations of the resin bead during the ion exchange reaction, fits fairly well to experimental results, and was used to obtain the effective diffusion coefficients of the metals through the macroporous matrix. Finally, the study of the batch ion exchange kinetics of transition metal cations was completed with a potentiometric titration and other equilibrium determinations. These results were compared with those derived from swelling measurements.     

Evaluation of a Bidisperse Pore Model for Ion Exchange Kinetics in Porous Media

A previously published bidisperse pore model that considers in turn ion interdiffusion in macro- and micro-pores as competitive and step-by-step processes was evaluated. The ion exchange rate of H⁺/Ni²⁺ on gel and macroporous strong acid resins was measured under conditions favoring a particle diffusion controlled mechanism. The interdiffusion coefficients were obtained using a bidisperse pore and quasi-homogenous resin phase kinetic models, respectively. The overall rate of H⁺/Ni²⁺ exchange on the macroporous resin is lower than in the gel resin. It was shown that ion interdiffusion in the micropores of the porous resin could also be important.     

Effect of porosigen on the swelling behavior and drug release of porous N‐isopropylacrylamide/poly(ethylene glycol) monomethylether acrylate copolymeric hydrogels

A series of porous thermoreversible hydrogels were prepared from N‐isopropylacrylamide (90 mol %) and poly(ethylene glycol) methylether acrylate (10 mol %), which was derived from poly(ethylene glycol) monomethylether, N,N′‐methylenebisacrylamide, and porosigen, or poly (ethylene glycol) (PEG) with different molecular weights (MWs). The influence of pore volume in the gel on the physical properties, swelling kinetics, and solute permeation from these porous gels was investigated. The results show that the surface areas, pore volumes, and equilibrium swelling ratios for the porous gels increased with increasing MW of PEG, but the shear moduli and effective crosslinking densities decreased with increasing MW of PEG. The results from the dynamic swelling kinetics show that the transport mechanism was non‐Fickian. The diffusion coefficients of water penetrating into the gels increased with increasing pore volume of the gels. In addition, we also studied solute permeation through the porous gel controlled by temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5490–5499, 2006     

Water‐vapor‐permeable polyurethane resin

The reaction of methylene diphenylene diisocyanate with ethylene glycol, dimethyl dimethoxysilane, dimethyl diethyloxysilene, and other additives in the presence of N,N‐dimethylformamide and toluene to form the structure of water‐vapor‐permeable polyurethane (PU) resin was proven with Fourier transform infrared spectra. Experimental results clearly showed that the amount of oxygen that permeated the film made with the PU resin increased with an increase in the concentration of ethylene glycol, diethylene glycol, or triethylene glycol. This was due to an increased number of hydrophilic groups attached to the backbone of the PU resin molecules. These hydrophilic groups, because of the intermolecular interactions between PU resin molecules, made PU resin molecules form an expanded conformation with large porosities. Interestingly, the water vapor permeability of the PU resin appeared to increase with an increasing concentration of ethylene glycol, dimethyl dimethoxysilane, or dimethyl diethoxysilane but not to increase with an increasing concentration of diethylene glycol, triethylene glycol, or poly(ethylene glycol) with dimethyl dimethoxysilane. The former was due to intermolecular interactions resulting in an expanded conformation with large porosities, but the latter was due to intramolecular interactions resulting in a compact conformation or a micellelike structure with small porosities. Therefore, the water vapor permeability of the former increased, but the latter remained unchanged or decreased. Our experimental results suggest that the use of poly(ethylene glycol) 400, ethylene glycol, dimethyl dimethoxysilane, and other strong hydrophilic compound in the preparation of modified PU resins substantially raises the amount of water vapor diffusing into films made with these resins. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2002–2010, 2002     

反应诱导相分离热解法制备交联互通状多孔炭单体

以酚醛树脂和乙二醇混合物经过反应诱导相分离热解后形成的多孔炭单体制备复杂形状SiC陶瓷。通过用场发射扫描电子显微镜和压汞仪对多孔炭进行表征,分别研究了乙二醇含量、催化剂含量以及预固化温度对多孔炭的孔形貌、尺寸及分布的影响。结果表明：乙二醇含量可以影响多孔炭单体的形成,以及孔的形貌、大小和分布;催化剂含量和预固化温度对多孔炭的影响不显著。     

Novel Bifunctional Resins in Metal Ion Separations: Ion Exchange/Coordination Resins and Ion Exchange/Precipitation Resins

Abstract

Dual mechanism bifunctional polymers (DMBP's) as metal ion extractants are described within the context of two new examples. The carboxylic acid/pseudocrown resin is a new example of the DMBP class of resins described as ion exchange/ coordination resins. The polyethylene glycol ligand within the resin functions as a coordinating site for metal ions which are brought into the resin via ion exchange with the acid ligand. Initial studies with alkali metal ions are presented. The third general class of DMBP's is also presented. In this case, precipitation is the reaction occurring along with ion exchange thus yielding the ion exchange/precipitation resins. Barium recovery from aqueous solution via barium sulfate precipitation is described.     

A novel method to prepare magnetic polymer‐based anion exchangers and their application

Magnetic microspheres with ion‐exchange features were prepared by applying a swelling and penetration process using polystyrene–divinylbenzene‐based anion‐exchange resins as starting materials. The polymeric anion‐exchange particles were swollen with an aqueous solution of N‐methyl‐2‐pyrrolidone, followed by incubation with superparamagnetic iron oxide nanoparticles to allow them to penetrate into the swollen particles. The pH value in the solution of magnetic nanoparticles could significantly influence the uptake of magnetic nanoparticles by the swollen anion‐exchange particles. Higher amounts of magnetic nanoparticles entrapped within anion exchangers could be achieved at pH 10–12. An increase in the concentration of magnetic nanoparticles led to a higher density of magnetic nanoparticles entrapped within the interior of anion exchangers and, thus, higher magnetization of the magnetic anion exchangers. Loading of the magnetic nanoparticles onto the exchanger had no effect on anion‐exchange functionality. The utility of the resulting magnetic anion‐exchange resins was demonstrated for the isolation of plasmid pEGFP‐C1 from Escherichia coli cell lysates. The magnetic anion‐exchange microspheres could be easily collected within a few seconds in a magnetic field. Thus, automation of the protocol for DNA isolation using these magnetic anion‐exchange resins has a high potential. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40725.     

Curable resins based on recycled poly(ethylene terephthalate) for coating applications

Poly(ethylene terephthalate) waste was depolymerised in the presence of diethylene- or tetraethylene glycol and manganese acetate as a catalyst. An epoxy resin was then prepared by the reaction of these oligomers with epichlorohydrin in presence of NaOH as a catalyst. The produced oligomers were condensed with maleic anhydride and ethylene glycol to produce unsaturated polyester. The chemical structures of the resulting epoxy and unsaturated polyester resins were confirmed by ¹HNMR. The vinyl ester resins were used as cross-linking agents for unsaturated polyester resin diluted with styrene, using free radical initiator and accelerator. The 2-amino ethyl piprazine was used as hardener for epoxy resins. The curing behaviour of the unsaturated polyester resin, vinyl ester resins and styrene was evaluated at different temperatures ranged from 25 to 55 °C to calculate the curing activation energy of the system. The cured epoxy and unsaturated polyester resins were evaluated in coating application of steel.