Computer simulation and comparative study on the pervaporation separation characteristics of sodium alginate and its blend membranes with poly(vinyl alcohol) to separate aqueous mixtures of 1,4‐dioxane or tetrahydrofuran

A comparative study on the pervaporation separation has been attempted for water + 1,4‐dioxane and water + tetrahydrofuran mixtures using sodium alginate and blend membranes of sodium alginate with 5, 10, and 20 mass % of poly(vinyl alcohol). Pure sodium alginate membrane has a selectivity of 111 to water at 0.35‐mol fraction of water in the feed mixture containing 1,4‐dioxane while for water + tetrahydrofuran mixture, the membrane selectivity to water was 291 at 0.31‐mol fraction of water in the feed mixture. Pervaporation results have been discussed using the solution–diffusion principles. Arrhenius activation parameters for diffusion and permeation have been computed from the temperature‐dependent pervaporation results. Furthermore, experimental results have been analyzed using the complete mixing and plug flow models to compute membrane area as well as design parameters that are useful in scale‐up operations. The plug flow model is more appropriate than the complete mixing model to analyze the pervaporation results. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1827–1840, 2004     

Moisture absorption of filled silicone rubber under electrolyte

Moisture absorptions of filled silicone rubber (SiR) under strong electrolyte have been investigated in the temperature range of 25–60°C by weight‐gain experiments. Tests were performed with the materials exposed to NaCl, HNO₃ solution, and deionized water. The diffusion results have been analyzed in terms of the Fickian diffusion law. The apparent maximum moisture content and the apparent diffusion of filled SiR in different solutions were deduced. The influences of the solution concentration and temperature on the diffusion process of filled SiR were discussed, and the microphotos of the surface of the immersed specimens were taken and analyzed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Synthesis and characterization of polyacrylamide‐grafted sodium alginate copolymeric membranes and their use in pervaporation separation of water and tetrahydrofuran mixtures

Polyacrylamide‐grafted sodium alginate (PAAm‐g‐Na‐Alg) copolymeric membranes have been prepared, characterized, and used in the pervaporation separation of 10–80 mass % water‐containing tetrahydrofuran mixtures. Totally three membranes were prepared: (1) neat Na‐Alg with 10 mass % of polyethylene glycol (PEG) and 5 mass % of polyvinyl alcohol (PVA), (2) 46 % grafted PAAm‐g‐Na‐Alg membrane containing 10 mass % of PEG and 5 mass % of PVA, and (3) 93 % grafted PAAm‐g‐Na‐Alg membrane containing 10 mass % of PEG and 5 mass % of PVA. Using the transport data, important parameters like permeation flux, selectivity, pervaporation separation index, swelling index, and diffusion coefficient have been calculated at 30°C. Diffusion coefficients were also calculated from sorption gravimetric data of water–tetrahydrofuran mixtures using Fick's equation. Arrhenius activation parameters for the transport processes were calculated for 10 mass % of water in the feed mixture using flux and diffusion data obtained at 30, 35, and 40°C. The separation selectivity of the membranes ranged between 216 and 591. The highest permeation flux of 0.677 kg/m² h was observed for 93% grafted membrane at 80 mass % of water in the feed mixture. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 272–281, 2002     

Diffusion and sorption of organic liquids through polymer membranes. VIII. Elastomers versus monocyclic aromatic liquids

Sorption and diffusion of five monocyclic aromatic liquids—three halogenated benzenes, nitrobenzene, and aniline—with five engineering polymers—ethylene propylene diene ter-polymer, nitrile butadiene rubber, styrene butadiene rubber, natural rubber, and neoprene—have been investigated in the temperature interval of 25–60°C. Solvent diffusivity into polymer membranes was determined from the immersion/weight gain experiments. Permeability coefficients were also calculated from the diffusion and sorption data. A temperature dependence of sorption and transport was also investigated to estimate the activation parameters. The experimental results and computed quantities were used to study the type of transport mechanism and the nature of polymer-solvent interactions.     

Diffusion and Sorption of Organic Liquids Through Polymer Membranes. IX. Bromobutyl Rubber,Chlorosulfonated Polyethylene,and Epichlorohydrin Versus Substituted Monocyclic Aromatic Liquids

Sorption and diffusion of four monocyclic aromatic liquids—namely, chlorobenzene, o-dichlorobenzene, bromobenzene, and nitrobenzene into bromobutyl rubber, chlorosulfonated polyethylene, and epichlorohydrin—have been investigated in the temperature interval of 25–60°C by using a gravimetric technique. The transport results have been analyzed by using the Fickian model of diffusion. The dependence of transport coefficients on the size and shape of the penetrant molecules has been discussed. Transport coefficients have not shown any systematic variation with the penetrant size, but the results are greatly influenced by the polymer-solvent interactions. The Arrhenius activation parameters have been estimated from a temperature dependence of sorption, diffusion, and permeation coefficients. The first-order kinetic rate constants have been obtained from the time-dependent sorption data. Enthalpy and entropy of sorption for the polymer-solvent systems have been studied. The molar mass between network crosslinks was calculated from the Flory-Rehner theory. Computed parameters and experimental results are used to discuss the transport mechanism in terms of the type and nature of the polymer membranes and solvent molecules. None of the polymer membranes studied have shown any degradative reactions and significant swelling in the presence of the chosen solvents. The present results would have applications in areas such as those including the studies on barrier properties, separation science, and chemical pond lining, etc.     

Sorption,diffusion, and swelling characteristics of sodium alginate and its blend membranes with poly(vinyl alcohol) in water–acetic acid mixtures

Sorption, diffusion, and swelling characteristics of sodium alginate and its blend membranes with poly(vinyl alcohol) were investigated for water–acetic acid mixtures by using a gravimetric method at 30, 40, and 50°C. The membranes were characterized by X‐ray diffraction and Fourier transform infrared techniques. Concentration‐independent diffusion coefficients were obtained by applying Fick's relationship before completion of equilibrium sorption. Permeation coefficients were calculated from sorption and diffusion coefficients. Concentration profiles of liquids were computed considering the sheet geometry for the membrane by solving Fick's equation under suitable boundary conditions. Arrhenius activation parameters were computed for the transport processes. Experimental results and calculated quantities were discussed to understand membrane–solvent interactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1139–1150, 2004     

Investigation of the molecular transport of aliphatic and aromatic esters into engineering polymer membranes

Molecular transport as manifested by sorption and diffusion of organic esters into engineering polymer membranes, viz. nitrile butadiene rubber, styrene butadiene rubber, ethylene propylene diene terpolymer, neoprene and natural rubber, has been investigated in the temperature range 25–60°C by the sorption gravimetric technique. The sorption equilibrium for ethylene propylene diene terpolymer was lower than those of the other polymers with all the liquids. Diffusion and permeation coefficients were obtained for the polymer-solvent systems and these follow Arrhenius type behaviour in the temperature range investigated.     

Pervaporation separation of water‐isopropanol mixtures using polymeric membranes: Modeling and simulation aspects

Pervaporation technique was used to separate water + isopropanol azeotropic mixtures at 30°C using pure sodium alginate, pure poly(vinyl alcohol), and blend membranes of sodium alginate containing 10 and 20 mass % of poly(vinyl alcohol). The membrane performance was studied by calculating flux, selectivity, pervaporation separation index, and enrichment factor. Pure sodium alginate membrane gave the highest pervaporation separation index for all compositions of water. Pervaporation experiments were carried out for 10 mass % containing water + isopropanol mixture at 30, 40, and 50°C. The Arrhenius activation parameters were computed. The PV results have been analyzed by considering complete mixing and plug flow models. Design parameters, like membrane area, permeate concentrations, flux, stage cut, separation selectivity, etc., have been calculated for different feed compositions of water in the mixture. Results are explained in terms of sorption‐diffusion principles. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1143–1153, 2005     

Syntheses and characterization of blend membranes of sodium alginate and poly(vinyl alcohol) for the pervaporation separation of water + isopropanol mixtures

The blend membranes of sodium alginate and poly(vinyl alcohol) have been prepared by physical mixing in different ratios (75, 50, and 25%) of sodium alginate with poly(vinyl alcohol). The membranes were crosslinked with glutaraldehyde and used in the pervaporation separation of water + isopropanol mixtures at 30°C. The crosslinking reaction was confirmed by Fourier transform infrared spectra. Permeation flux increased with an increase in mass % of water in the feed mixture as well as with an increase in the amount of poly(vinyl alcohol) in the blend, but separation selectivity decreased. Diffusion coefficients of water + isopropanol mixtures have been calculated using the Fick's equation from the sorption data. Arrhenius activation parameters were calculated for 10 mass % of water in the feed mixture using the values of flux and diffusion coefficients obtained at 30, 40, and 50°C. The diffusion and pervaporation results have been explained on the basis of solution‐diffusion principles. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3642–3651, 2002     

Transfer of gas to dissolved oxygen in water via porous and nonporous polymer membranes

The transfer rates of oxygen via polymer membranes in gas–membrane–gas and gas–membrane–water (dissolved oxygen) were investigated with various porous membranes and compared with results of silicone rubber sheet (nonporous, homogeneous polymer membrane). With a nonporous membrane, the permeability constant obtained by gas–membrane–gas represents the true membrane permeability in gas–membrane–water system, and consequently the transport resistance due to boundary layer can be quantitatively estimated. With a porous membrane, the data in gas–membrane–gas system (under applied pressure) merely represent the gas effusion rate of the membrane and are not directly related to the dissolved oxygen transfer rate in gas–membrane–water system. The penetration of liquid water into the pores of porous membrane is the most important controlling factor for the dissolved oxygen transfer rate of a porous membrane. With a porous membrane in which liquid water does not penetrate into the pore, the overall transfer rate of dissolved oxygen reaches the level which corresponds to that of the boundary layer found with silicone rubber membrane.     

Improvement of the mechanical properties of chitosan‐alginate wound dressings containing silver through the addition of a biocompatible silicone rubber

The benefits of associating chitosan with alginate for the production of wound dressings are well documented. However, the mechanical resistance of these devices is limited. This work aimed to improve the mechanical properties of chitosan‐alginate membranes both with and without the microbicide agent AlphaSan^® RC2000 (silver sodium hydrogen zirconium phosphate) by incorporating the liquid silicone rubber Silpuran^® 2130 A/B. Membranes containing AlphaSan^® RC2000 but without Silpuran^® 2130 A/B have increased opacity, thickness, and water absorption, but low stability in water and tensile strength. The silicone gel remained in the structure of the formulations even after successive washing steps and its inclusion in the membranes reduced their thickness and swelling in aqueous media, improving their homogeneity, adhesiveness, stability, tensile strength, and flexibility. Thus, the addition of Silpuran^® 2130 A/B proved to contribute positively to many relevant, particularly mechanical, properties of chitosan‐alginate wound dressings whether or not they contained AlphaSan^® RC2000. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41686.     

Molecular transport of aromatic hydrocarbons through lignin‐filled natural rubber composites

The diffusion and transport of organic solvents through lignin‐filled natural rubber composites have been studied in the temperature range 25–45°C. The diffusion of aromatic solvents through these samples were studied with special reference to the effect of filler concentration, penetrant size, and temperature. Transport coefficients such as diffusion, permeation, and sorption coefficients were estimated. The van't Hoff relationship was used to determine the thermodynamic parameters. The first order kinetic rate constant has been evaluated. A correlation between theoretical and experimental sorption results was evaluated. POLYM. COMPOS., 28:15–22, 2007. © 2007 Society of Plastics Engineers     

Gas permeation through water‐swollen polysaccharide/poly(vinyl alcohol) membranes

The effect of Na‐alginate content on the gas permeation properties of water‐swollen membranes prepared by varying Na‐alginate and poly(vinyl alcohol) (PVA) content in membranes was investigated. The influences of water content and crystallinity of the membranes on the gas permeation performance of the water‐swollen membranes were studied. The gas permeation rate and selectivity of Na‐alginate/PVA water‐swollen membranes were compared with those of the dry membranes. The permeation rates of nitrogen and carbon dioxide through water‐swollen membranes were in the range of 0.4–7.6 × 10^?7 to 3.7–8.5 × 10^?6 cm³ (STP)/cm² s^?1 cmHg^?1, which were 10,000 times higher than those of dry‐state membranes. The permeation rates of mixture gases through water‐swollen Na‐alginate/PVA membranes were found to increase exponentially with the increase of Na‐alginate content, whereas carbon dioxide concentration in permeates was decreased linearly. It was found that the gas permeance of the water‐swollen membranes increased with increasing the Na‐alginate content in the membrane. Gas permeation rates of the water‐swollen Na‐alginate/PVA membranes increased with increasing the water content in the membrane and decreasing the crystallinity of the membrane. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3225–3232, 2004     

Antimicrobial performance and the cure and mechanical properties of peroxide‐cured silicone rubber compounds

Nanosilver colloid, Ag‐based zeolite compound, and 2‐hydroxypropyl‐3‐piperazinylquinolinecarboxylic acid methacrylate (HPQCAM) were used as antimicrobial agents and/or mechanical property improvers in peroxide‐cured silicone rubber vulcanizates. The vulcanizates were prepared by using a two‐roll mill followed by a hydraulic press in order to vulcanize the rubber compounds, and their cure characteristics, mechanical properties, and antibacterial performance were assessed. The antimicrobial performance of the silicone rubber compounds was examined through plate‐count‐agar and drop‐plate‐agar methods, as well as the halo test. The results suggested that the addition of all of the antimicrobial agents slightly increased the cure time, except for the Ag‐based zeolite. The addition of all of the antimicrobial agents also affected the mechanical properties of the rubber vulcanizates. The Ag‐based zeolite gave the silicone rubber compound with the most improved mechanical properties, whereas HPQCAM was the most effective antimicrobial agent, as determined by the occurrence of the inhibition zone and 99% reductions of Staphylococcus aureus and Escherichia coli. The changes in silicone rubber surface with the addition of antibacterial agent were shown by progressive decreases in water contact angle. This result was observed only for the HPQCAM agent and was associated with diffusion and the releasing mechanism of the HPQCAM to kill the bacteria. The optical lightness of the silicone vulcanizates decreased with increasing nanosilver content but increased with increasing amounts of Ag‐based zeolite or HPQCAM. J. VINYL ADDIT. TECHNOL., 19:113–122, 2013. © 2013 Society of Plastics Engineers     

Kinetics of the thermal degradation and thermal stability of conductive silicone rubber filled with conductive carbon black

The kinetics of the thermal degradation and thermal stability of conductive silicone rubber filled with conductive carbon black was investigated by thermogravimetric analysis in a flowing nitrogen atmosphere at a heating rate of 5°C/min. The rate parameters were evaluated by the method of Freeman–Carroll. The results show that the thermal degradation of conductive silicone rubber begins at about 350°C and ends at about 600°C. The thermal degradation is multistage, in which zero‐order reactions are principal. The kinetics of the thermal degradation of conductive silicone rubber has relevance to its loading of conductive carbon black. The activation energies are temperature‐sensitive and their sensitivity to temperature becomes weak as temperature increases. In addition, the conductive silicone rubber filled with conductive carbon black has better thermal stability than that of silicone rubber without any fillers. Also, conductive silicone rubber filled with conductive carbon black has better thermal stability than that of silicone rubber filled with the same amount of silica. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1548–1554, 2003     

Function and performance of silicone copolymers(II): Syntheses and interfacial behavior of siliconized acrylic copolymers

Polysiloxane‐containing copolymers were synthesized and characterized by nuclear magnetic resonance and elemental analysis. These copolymers were neutralized by triethylamine. The copolymers could be self‐emulsified to form emulsions in water with and without cosolvent PCS and exhibited excellent defoaming abilities. These copolymers were also used as emulsifiers to emulsify silicone oil in water to form stable oil‐in‐water emulsions. This emulsion again exhibited defoaming properties, more efficiently than that of the self‐emulsified emulsion of siliconized acrylic copolymer (SAA). © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 805–811, 1999     

Behavior of sulfonated poly(ether ether ketone) in ethanol–water systems

The behavior of sulfonated poly(ether ether ketone) (sPEEK) membranes in ethanol–water systems was studied for possible application in direct ethanol fuel cells (DEFCs). Polymer membranes with different degrees of sulfonation were tested by means of uptake, swelling, and ethanol transport with dynamic measurements (liquid–liquid and liquid–gas systems). Ethanol permeability was determined in an liquid–liquid diffusion cell. For membranes with an ion‐exchange capacity (IEC) between 1.15 and 1.75 mmol/g, the ethanol permeability varied between 5 × 10^?8 and 1 × 10^?6 cm²/s, being dependent on the measuring temperature. Ethanol and water transport in liquid–gas systems was tested with pervaporation as a function of IEC and temperature. Higher IEC accounted for higher fluxes and lower water/ethanol selectivity. The temperature had a large effect on the fluxes, but the selectivity remained constant. Furthermore, the membranes were characterized with proton conductivity measurements. The proton diffusion coefficient was calculated, and a transition in the proton transfer mechanism was found at a water number of 12. Membranes with high IEC (>1.6 mmol/g) exhibited larger proton diffusion coefficients in ethanol–water systems than in water systems. The membrane with the lowest IEC exhibited the best proton transport to ethanol permeability selectivity. The use of sPEEK membranes in DEFC systems depends on possible modifications to stabilize the membranes in the higher conductive region rather than on modifications to increase the proton conductivity in the stable region. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polyacrylonitrile‐g‐poly(vinyl alcohol) membranes for the pervaporation separation of dimethyl formamide and water mixtures

Poly(vinyl alcohol) as well as its grafted copolymer membranes with polyacrylonitrile (PAN‐g‐PVA) were prepared and used to separate water and dimethyl formamide mixtures by the pervaporation technique. The three following membranes were prepared: (1) pure PVA; (2) 46% grafted PAN‐g‐PVA; and (3) 93% grafted PAN‐g‐PVA. Pervaporation separation experiments were carried out at 25°C for the feed mixture containing 10 to 90% water. By use of the transport data, permeation flux, separation selectivity, swelling index, and diffusion coefficients have been calculated. By increasing the grafting of the membrane, flux decreased, whereas separation selectivity increased slightly over that of pure PVA membrane. Arrhenius activation parameters for transport processes were calculated for 10 mass % water containing feed mixture by using flux and diffusion data obtained at 25, 35, and 45°C. Transport parameters were discussed in terms of sorption‐diffusion principles. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 4091–4097, 2004     

New gasoline and gas barrier from plasticized carbon black reinforced butyl rubber/high‐density polyethylene blends

The effects of the high‐density polyethylene volume fraction on the curing characteristics and network structure of rubber blends have been studied in terms of the torque, scorch time, optimum curing time, Mooney viscosity, number of elastically effective chains, viscosity, interfacial tension, glass‐transition temperature, scanning electron microscopy, internal friction, sound velocity, acoustic attenuation, polymer–solvent interaction parameter, swelling index, and gel fraction. The applicability of the blends for gasoline barriers has been examined through the changes in the electrical resistance and volumetric swelling in gasoline versus time at room temperature. The transport mechanism of the solvent through the crosslinked butyl rubber/high‐density polyethylene blends is governed by Fickian diffusion law. The transport coefficients, namely, the diffusion coefficient, intrinsic diffusion, and permeation coefficient, have been computed. The experimental data for the permeation coefficient are in good agreement with the values calculated by Maxwell's model and far from those of Robeson's model. In addition, some thermodynamics parameters, namely, the standard entropy, standard enthalpy, and standard Gibbs free energy, have been estimated as functions of the high‐density polyethylene concentration of the butyl rubber blends. Furthermore, the applicability of butyl rubber/high‐density polyethylene composites for Freon gas barriers and antistatic charge dissipation has been examined. Finally, the mechanical properties, such as the tensile strength, hardness, stiffness, and elongation at break, of butyl rubber composites with different high‐density polyethylene concentrations have been evaluated. The increase in the mechanical properties is due to the increase in the crosslinking density and the interfacial adhesion of the blend. This proves that these new blends have important technological applications as gasoline and Freon barriers and for antistatic charge dissipation with good mechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1237–1247, 2006     

Surface resistance and diffusion characteristics of toluene into calcium carbonate‐ and polymer‐coated calcium carbonate‐filled natural rubber composites

Solvent absorption has been followed in compression‐molded rubber vulcanizates for toluene in natural rubber (gum), calcium carbonate (CC)‐filled natural rubber composites, and polymer‐encapsulated calcium carbonate (PCC)‐filled natural rubber composites. The surface resistance is found to affect the absorption process of the composites. Diffusion from the sample sides is considered for thickness and the diffusion coefficients corrected accordingly. Aspects of the effect of PMMA on the equilibrium toluene take up, Fickian mode of transport; transport coefficients; activation parameters; and crosslink density are studied. The sorption results have been interpreted in terms of first‐order kinetic model. The crosslink densities calculated from equilibrium sorption successfully to explain the transport coefficient values of the composites. POLYM. ENG. SCI., 53:2487–2497, 2013. © 2013 Society of Plastics Engineers