Microporous Polypropylene Film Research Articles

Microporous Film, Made from β-Crystalline Phase Polypropylene

Abstract A new type microporous polypropylene film was prepared simply by biaxial drawing of β-crystalline phase polypropylene The effect of draw ratio on the pore size distribution, ethanol sorption, and porosity, as well as β-α transformation during drawing were studied For the purpose of improving its hydrophilicity ion and solute permeability, the plasma graft-polymerization technique was utilized The resulting film showed much higher permeability toward Na+, Mg++ and urea, being 3.2 × 10−6, 5.8 × 10−8 and 1.75 × 10−6 cm2/min, respectively, than the original one and had better dimensional stability.

Optimization of experiment in scanning force microscopy of polymers

A scanning force microscopy (SFM) study of an oriented polyethylene (PE) tape and a microporous isotactic polypropylene (iPP) film was conducted in the contact and tapping mode. In sub-water measurements on polymer surfaces with minimal tip-sample interactions, the images obtained in both modes correctly reproduce surface morphology and nanostructure. An advantage of the tapping mode in non-destructive imaging was shown in the observation of a weakly bound skin layer on the PE tape. This layer is destroyed during scanning with higher forces; however, its removal allows one to examine the core nanostructure of this material. Ambient-condition SFM measurements in both modes are accompanied by stronger tip-sample interactions. This leads to an overestimation of the dimensions of surface features and to a larger contribution of surface hardness to the image contrast.

Extraction and stripping study of strontium ions across D2EHPA-TBP-kerosene oil based supported liquid membranes

A Sr ion transport study across D2EHPA-TBP kerosene oil based liquid membranes supported on microporous polypropylene film has been performed. The parameters studied were the effect of di(2-ethylhexyl)phosphoric acid (D2EHPA) and TBP concentration variation in the membrane liquid, HNO3 concentration variation in the stripping phase and citric acid concentration variation in the feed solution. The optimum conditions of transport are 0.3 mol/dm3 D2EHPA, 0.1 mol/dm3 TBP, 0.01 mol/dm3 citric acid in feed and 2 mol/dm3 HNO3 in the stripping phase. The mechanism of transport observed is counter-ion coupled transport. The coupling ions are protons. The maximum flux for Sr ion transport observed is 5.33·10−5 mol·m−2·s−1 and maximum permeability under optimum conditions observed is 8.08·10−11 m−2·s−1.

Extraction of chiral ammonium cations and transport through supported liquid membranes mediated by 1,2,4-triazole-containing podands and macrocycles

Extraction of chiral primary alkylammonium salts was achieved in the presence of 1,2,4-triazole-containing macrocycles and podands with moderate enantioselectivities. Although preferential transport of ( R)-1-naphthylethylammonium salts was always observed, significant differences in both rates and selectivities were found when bulk (CHCl 3CCl 4) or supported (microporous polypropylene film) membranes were employed. The preparation of new protonionizable chiral bistriazolo-18-crown-6 macrocycles 3c, d is described.

Selective uphill transport of cyanide ion mediated by tetraphenylporphinatomanganese(III) complex through bulk and polymer-supported liquid membranes

The present paper describes the results obtained in a new system for hydroxide ion coupled transport of cyanide ion (uphill transport). The uphill transport was observed in two liquid membranes containing a tetraphenylporphinatomanganese(III) complex carrier (Mn(III)TPP). One is a bulk liquid membrane (BLM) that consists of a dichloromethane solution. The other is a polymer-supported liquid membrane (SLM) that was prepared by submerging a thin microporous polypropylene film in an o-nitrophenyl n-octyl ether solution. The OH ligand of the complex Mn(III)TPP (OH) is easily substituted with cyanide ion. The equilibrium constant of the reaction with cyanide ion is much larger than those with halide ions, CH 3COO −, and NO − 3. Only cyanide ion was transported selectively in the presence of various anions (CN −, Cl −, F −, NO − 3, CH 3COO −, etc.). We applied simple models to the uphill transport. In the BLM system, the flux of cyanide ion is governed by the diffusion processes of cyanide ion and the carrier molecule in the stagnant layers. The thicknesses of the layers and the ligand substitution reaction rate constants were estimated. In the SLM system, the flux of cyanide ion is controlled by the diffusion process of the carrier molecule obeying the Stokes—Einstein model in the membrane phase.

Amperometric and colorimetric enzyme immunoassay for urinary human serum albumin using a plasma-treated membrane

By water vapour plasma glow discharge treatment, microporous hydrophobic polypropylene film was modified to make it partially hydrophilic. The plasma-treated part was a spot 6 mm in diameter and permeable to water. After treatment with octamethylenediamine and glutaraldehyde, the plasma spot membrane served as a substrate to immobilize proteins such as antibodies or enzymes. Using this membrane, an amperometric enzyme immunoassay system was established to determine human serum albumin (HSA) in urine. The measurable range with this system was from 0.5 to 100 mg l −1 HSA in urine, which is suitable for the prognosis of diabetic nephritis. The HSA values in urine samples determined by the present system showed a linear correlation with those obtained by radioimmunoassay ( r = 0.974). After keeping the antibody-immobilized plasma spot membranes at 4°C for 6 months, the same calibration graph for HSA determination was obtained. In addition, a colour-producing reaction was also performed on the immunoreacted plasma spot membrane. Reflectance spectrometric analysis demonstrated that the colour on the plasma spot membrane itself corresponded to the HSA concentration. The difference in colour between 10 and 100 mg l −1 HSA could be visually discerned.

Microporous membrane formation via thermally-induced phase separation. VII. Effect of dilution, cooling rate, and nucleating agent addition on morphology

Microporous polypropylene films were produced from nucleated and non-nucleated melt-blends of isotactic polypropylene (iPP) and dotriacontane (C 32H 66) using non-isothermal thermally-induced phase separation. Adipic acid was used as the nucleating agent. The morphology of these microporous iPP films as determined by thermal optical microscopy and scanning electron microscopy is reported. The effect on film structure of diluent crystallization is also shown.

Amperometric enzyme immunoassay for urinary human serum albumin using plasma-treated membrane

A partial modification was made to a microporous hydrophobic polypropylene film by water vapour plasma glow discharge treatment. The modified part, a spot 6 mm in diameter, became hydrophilic so that water could penetrate easily. By treating this “plasma spot membrane” with octamethylenediamine and glutaraldehyde, a membrane for immobilization of proteins was obtained. As immobilization of the antibody and the immunoreaction could be performed in the limited spot area, only small amounts (10 μl) of reagents and sample were required. Using this plasma spot membrane and a Pt-AgCl electrode, an amperometric enzyme immunoassay system was established for the measurement of urinary human serum albumin. In this system, non-specific adsorption of enzyme-labelled antigen to the membrane was only 4.4% of specific binding. The range of measurement was 0.5–200 mg l −1 of human serum albumin, which is satisfactory for the diagnosis of human kidney function.

Separation of CO 2 from gas mixtures with liquid membranes

Conventional ethanolamine based CO 2 removal processes are not energy efficient. Separation by membranes may provide considerable energy savings over conventional processes. Ideally, to be economically competitive, a membrane should not only be highly permeable, it should also have higher selectivity for the component to be separated. However, permeability and selectivity of common polymeric membranes are, in general, inversely related. Mass flux as well as selectivity of permeation can be improved by employing reactive liquid films immobilized on a sheet of microporous filter as a substitute to solid polymeric membranes. Mixtures of various amines such as monoethanolamine (MEA), diethanolamine (DEA), and amino-methyl-propanol (AMP) and polyethylene glycol (PEG) were immobilized in a microporous polypropylene film and placed in a permeator. The permeabilities of CO 2 and other hydrocarbon gases through the immobilized liquid membrane were measured under low pressure differential and isothermal conditions. The permeation characteristics and trans-membrane flux show favourable separation as compared to the conventional polymeric membrane. Separation factors as high as 145 were obtained. Environmental implications of the results for gas processing industry are discussed.

Supported liquid membrane extraction of W(VI) ions using tri-n-octylamine as carrier

Study of the extraction of W(VI) ions using supported liquid membrane has been carried out. The carrier used for this metal ion transport, is tri-n-octylamine (TOA) dissolved in xylene. The liquid was supported in microporous polypropylene film. The parameters studied are effect of carrier concentration in the membrane, acid concentrations in the feed solution, concentration of stripping agent on transport of W(VI) ions and of temperature on the transport properties of these supported liquid membranes. The optimum conditions of transport for these metal ions determined are, TOA concentration, 0.66 mol·dm−3 (TOA); HF concentration in the feed solution, 0.01 mol·dm−3 and concentration of NaOH used as stripping agent 2.5 mol·dm−3. The maximum flux and permeability determined under optimum conditions are 3.06·10−5 mol·m−2·s−1 and 8.44·10−11 mol· ·m2·s−1 at 25±2°C and 4.21·10−5 mol·m−2·s−1 and 11.55·10−11 mol·m2·s−1 at 65°C, respectively. The diffusion coefficients for the metal ion carrier complex in the membrane have also been determined. Under the optimum conditions the value for the metal ion carrier complex is 0.14·10−11 mol·m2·s−1. Mechanism of transport and the complex formed in the presence of HF have also been discussed. The transport process involves two carrier amine molecules and two protons.

Photoautotrophic and photomixotrophic growth of strawberry plantlets in vitro and changes in nutrient composition of the medium

Explants excised from strawberry (Fragaria x ananassa Duch.) plantlets were cultured in vitro for 21 days on half-strength MS (Murashige & Skoog 1962) basal liquid medium with 20gl 1 sucrose and without sugar in the vessels capped with gas permeable microporous polypropylene film. The experiments were conducted under CO 2 nonenriched (350-450/zmol mol 1 in the culture room) and CO 2 enriched (2,000/xmolmol -I during the photoperiod in the culture room) conditions with a PPF (photosynthetic photon flux) of 200/xmol m-: s -1. The CO 2 concentration in the vessels decreased to approximately 200/xmol mol -~ during the photoperiod on day 21 under CO 2 nonenriched conditions. The fresh and dry weight, net photosynthetic rate (NPR) per plantlet, NPR per g leaf fresh weight, NPR per g leaf dry weight, the number of unfolded leaves, and ion uptake of PO]-, NO3, Ca2+, Mg2+ and K + on day 21 were the greatest under photoautotrophic (no sugar in the medium) and CO 2 enriched conditions. The residual percent of PO]- was 3% on day 21 under photoautotrophic and CO 2 enriched conditions.

An in vitro drug release rate method for lipoidal materials

A multiparticulate preparation of an osmotically mediated, controlled release system for lipoidal materials is described. Spherical beads containing a lipid carrier, an osmotic agent and a lipid soluble model drug were made and a microporous, polymeric coating applied. When placed in an aqueous medium, the coated beads controllably released first the lipid carrier (containing the model drug), then the osmotic agent. A technique is described for measuring the in vitro release rate profile of the lipoidal components of the beads using microporous polypropylene films. Sorption of the lipoidal components by the film occurred following release from the beads in an aqueous medium. Films were removed at specific times for analysis. The lipoidal components were extracted from the film with ethanol and the model drug content determined by spectrophotometry. This technique may be useful for other systems requiring release rate/dissolution testing of lipoidal agents in an aqueous medium.

Microemulsion liquid membranes. I. Cobalt transport in a surfactant-dodecane system

Cobalt transport across supported microemulsion liquid membranes containing reversed micelles of dinonylnaphthalenesulfonic acid (HDNNS) was measured as a function of organic phase composition, aqueous phase composition, stirring rate and temperature. A microporous polypropylene film served as the membrane support. The membrane phase was characterized by interfacial tension and viscosity measurements. Stirring speed and temperature effects suggest that diffusion processes play a major role in the transfer of cobalt across the membrane. The experimental results at relatively low carrier concentration are explained by a membrane transport model involving counter-diffusion of HDNNS reversed micelles and metal-reversed micelle complexes.

Characterization of a supported liquid membrane for macrocycle-mediated selective cation transport

Macrocycle-mediated cation transport has been studied using aqueous phases separated by a liquid membrane supported on a microporous polypropylene film. A macrocycle-containing organic phase was incorporated into the pores of the film. In this system, phenylhexane was found to be superior to chloroform, toluene and 1,2-dichlorobenzene as a membrane solvent in maintaining membrane integrity due to its lower water solubility and higher boiling point. Transport experiments using a bis (1-hydroxyheptyl) derivative of dicyclohexano-18-crown-6 (DC18C6) as carrier gave the selectivity sequecnes K + > Rb + > Cs + >Na + > Li + and Sr 2+ > Ba 2+ > Ca 2+. Furthermore, the addition of t-butyl or hydroxyheptyl side-chains to DC18C6 improved cation transport over that observed with DC18C6 due to the decreased distribution of the ligand from the membrane to the adjacent water phases. Cation flux was found to be independent of the rate of stirring of the water phases and to be a direct function of carrier concentration in the membrane.

A comparison between chemically and photochemically driven electron transport reactions in immobilized liquid membranes

Electron transport in immobilized liquid membranes using a microporous polypropylene film as the support was studied in the reagent concentration independent regime and was kinetically controlled under the conditions employed in this study. The velocities depended on the concentration of the carrier (Vitamin K 3) in the membrane and varied exponentially with the reciprocal of the absolute temperature. Neither the membrane thickness, concentration of the oxidant (Fe( ophen) 3 3+) nor the concentration of reductant (S 2O 4 2- or MV + generated photochemically) affect the electron transport rate. Maximum velocities at 25°C (7.8 μmol-cm -2-hr -1 and 2.5 μmol-cm -2-hr - for the S 2O 4 2- and MV + driven reactions, respectively) were obtained in the pH range of 6-7 for the reductant compartment and in the 0 to - 1 pH range in the oxidant compartment. The respective turnover rates were 2.1 hr -1 and 0.65 hr -1 based on 2e -/Vitamin K 3 for the S 2O 4 2- and MV + driven reactions, respectively. The mechanism of electron transport is best interpreted to involve formation of the hydroquinone in the membrane which then reacts with Fe( o-phen) 3 3+ in the rate-limiting electron transfer step.

A redox supported liquid membrane containing 2,5-di(tert-pentyl)hydroquinone as electron carrier

A new redox supported liquid membrane (RSLM), consisting of a microporous polypropylene film containing absorbed into its pores an organic solution of a waterinsoluble hydroquinone (electron carrier), has been studied. The hydroquinone used as electron carrier was 2,5-di(tert-pentyl)hydroquinone dissolved in a solvent mixture of diisopropylbenzene, decaline and tributyl phosphate. The ability of the RSLM to transport electrons through it and to perform membrane-controlled oxidation—reduction processes was demonstrated. Some practical applications of the RSLM in controlling the oxidation states of actinides are briefly discussed.

Origin and significance of the deviations from a pseudo first order rate law in the coupled transport of metal species through supported liquid membran

A new equation describing the permeation rate of metal species in the coupled transport through supported liquid membranes (SLM) was derived. The equation assumes that the concentration profile within the membrane never goes to zero and contains the independently measurable distribution ratios of the permeating metal species between the organic liquid membrane and the aqueous feed and strip solutions. The equation was experimentally verified by measuring the distribution ratios and the permeation rates of Eu 3+ through SLMs consisting of a 0.1 F solution of bis(2-ethylhexyl)phosphoric acid (carrier) in n-dodecane absorbed on a thin microporous polypropylene film. The conclusion was reached that the deviations from a pseudo first order rate law, often observed when measuring the coupled transport of metal species at low concentration through SLMs, originate in the non-negligible value of the distribution ratio at the SLM—strip solution interface. Nevertheless, these deviations can easily be taken into account in a quantitative way and, by an appropriate linearization of the permeation data, information can be obtained on two, newly defined, permeability coefficients of the SLM.

Permeation of metal ions through a series of two complementary supported liquid membranes

The permeation of Am 3+ and Eu 3+. through two composite supported liquid membranes, SLM, consisting of a series of two complementary SLMs, separated by an aqueous solution, has been studied. The first liquid membrane was a neutral membrane, i.e., a solution of a bifunctional neutral organophosphorous extractant in decalin. The second liquid membrane was an acidic membrane, i.e., a solution of bis(2-ethylhexyl)phosphoric acid in n-dodecane or of dinonylnaphthalene sulphonie acid in decalin. The solid support was a microporous polypropylene film. The composite SLM system had the sequence “Solution A — SLM(A) -Solution B — SLM(B) — Solution A”, where aqueous solution A promotes extraction of th the metal cations into SLM(A) and their stripping from SLM(B), and aqueous solution B promotes stripping of metal cations from SLM(A) and their extraction into SLM(B). SLM(A) and SLM(B) are a neutral or an acidic S/aVis or vice versa. The study has demonstrated that the single-stage character of SLM separations of metal ions in solution can be in principle overcome by repeating the composite SLM arrangement a number of times. The equations describing the concentration variations in the aqueous solutions which are adjacent to the acidic and neutral SLMs are also reported. They allow one to predict quantitatively the degree of enrichment of each aqueous solution as function of time and the degree of separation among different cations achievable with the composite SLM system. The overall permeability of the composite SLM system to a given cation is shown to be a function of the single-membrane permeability coefficients as well as of the volumes of the aqueous solutions and the SLM area.

Solvent extraction with immobilized interfaces in a microporous hydrophobic membrane

A new technique for solvent extraction with immobilized interfaces in a hydrophobic microporous membrane is described. No dispersion or coalescence is necessary. Extraction of acetic acid from aqueous solutions of different concentrations into either methyl isobutyl ketone or xylene through a fiat thin Celgard® 2400 microporous polypropylene film has been studied in a flow-type test cell primarily at an aqueous phase pressure 40 psi (2.75 x 10 5 Pa) greater than an essentially atmospheric organic phase pressure. Studies over a range of 20 to 60 psi (1.378 x 10 5 to 4.134 x 10 5 Pa) did not indicate any significant pressure effect for extraction with methyl isobutyl ketone. Extraction rates reported as an overall organic phase based mass transfer coefficient are influenced by the boundary layer resistances on the organic and aqueous sides. Boundary layer resistance free overall transfer coefficients have been used to obtain the intrinsic membrane transfer coefficient. A description of this intrinsic membrane transfer coefficient for acetic acid extraction using the notion of a simple unhindered diffusion of a solute through a solvent-filled tortuous porous medium of uniform pore size yields realistic estimates of the tortuosity factor of the membrane used. The potential of this new technique has been described and compared with conventional extraction techniques if hollow microporous hydrophobic fibers are utilized.

Coupled transport of picrate anion through liquid membranes supported by a microporous polymer film

Supported liquid membranes capable of separating and concentrating picrate anions in the presence of noncyclic polyoxyethylene (POE) derivatives are described. The transport of picrate across the membranes was coupled to a flow of alkali metal ions. The membranes consisted of a microporous polypropylene film whose pores were filled with an o-nitrophenyl phenyl ether solution of the POE derivatives. The POE derivatives acted as carriers of the alkali metal ions. The order of their effect on the picrate flux across the membrane was Rb > Cs > K > Na > Li. The picrate flux depended on the type and number of oxyethylene units of the POE derivative. The highest flux was observed at a number of the units near 10. The picrate flux also increased with an increase in concentration of POE derivative. However, it was not proportional to the concentration. When the electromotive force across the membrane was maintained at 0 mV with a voltage clamp, the picrate flux decreased, and it increased with increasing membrane potential.