• Membrane Journal
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• v.16 no.4
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• pp.294-302
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• 2006

Silver polymer electrolytes are very promising membrane materials for the separation of olefin/paraffn mixtures. Olefin molecules are known to be transported through reversible complex formation with silver ions entrapped iii polymer matrix. However, they have poor long-term stability, which is very important fur the industrial application; the selectivity through the membrane decreases gradually with time mostly due to the reduction of silver ions ($Ag^+$) into silver nanoparticles ($Ag^0$). In this study, the stability of silver polymer electrolyte was investigated for poly(vinyl pyrrolidone) (PVP) and $AgBF_4$ system containing a surfactant, i.e. $C_{18}H_{35}(OCH_2CH_2)_{20}OH$ (Brij98) as a stabilizer. The reduction behavior of silver ions to silver nanoparticles in PVP was also investigated by atomic force microscopy (AFM) and UV-visible spectroscopy. It was found that the growth of silver nanoparticles was slower and selectivity of polymer electrolyte for propylene in propylene/propane was maintained longer time when Brij98 was added as a stabilizer.

• Applied Chemistry for Engineering
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• v.29 no.6
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• pp.682-689
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• 2018

In this paper, the stability criteria of cosmeceuticals emulsion containing Broussonetia kazinoki extracts was established using the central composite design model. As optimization conditions of the emulsification using the central composite design model, concentrations of the emulsifier and emulsion stabilizer were used as a quantitative factor while emulsion stability index (ESI) and polydispersity index (PDI) were used as a reaction value. The targeted values of ESI and PDI were estimated as over 60% and the minimum number, respectively. Optimized concentrations of the emulsifier and emulsion stabilizer were 3.73 and 3.07 wt%, respectively, from the emulsification optimization based on ESI and PDI values. The estimated reaction values of ESI and PDI were 60% and 0.585, respectively. As concentrations of the emulsifier and emulsion stabilizer increased, the stability of the emulsion prepared tended to increase. The emulsifier was one of the most influential factors for ESI than the emulsion stabilizer. On the other hand, the PDI value was similarly affected by both the emulsion and emulsion stabilizer. The ESI of the cosmeceuticals emulsion prepared under experimental conditions deduced from the central synthesis planning model showed at least about 45% of the stability. However, all of the emulsions were separated after 4 weeks from the initial preparation. When the concentration of the emulsifier was more than 3.72 wt%, the ESI value was over 60%. Also the layer separation rate decreased with increasing the emulsion stabilizer concentration.

• Polymer(Korea)
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• v.39 no.1
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• pp.1-5
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• 2015

The effects of zeolite on the thermal stability of poly(vinyl chloride) (PVC) were investigated by the static thermal stability test, pyrolysis experiment and ultraviolet spectrum. The results showed that the porous zeolite could absorb hydrogen chloride (HCl), which suppressed the catalysis of HCl on thermal degradation of PVC, thus improved the thermal stability of PVC. The oxidizing acid which was loaded on zeolite had oxidated on the double bond that formed during the dehydrochlorination of PVC. This process could prohibit the growth of the conjugated polyene and improved the color of PVC. Hence, zeolite might be possible to come up with a high performance thermal stabilizer.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.95-98
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• 2001

The effect of stabilizing polymer on hGM-CSF production was investigated in suspension cell cultures of transgenic tobacco. Secreted human GM -CSF from cell suspension cultures was detected in the medium at a maximum concentration of 180 ${\mu}g/L$ by ELISA. However, the secreted hGM -CSF was unstable in the medium, and rapidly degraded after day 5. In order to stabilize the secreted hGM-CSF, three stabilizing polymers were tested, polyethylene glycol, polyvinylpyrrolidone and gelatin. Gelatin was the most effective in stabilizing the secreted GM-CSF. Following the addition of 5% (w/v) gelatin, the maximum GM -CSF concentration reached 783 ${\mu}g/L$, a 4.6-fold increase over control.

• Fibers and Polymers
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• v.4 no.4
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• pp.195-198
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• 2003

Epoxidized polybutadiene (EPB) was prepared by polybutadiene (PB) with m-chloroperbenzoic acid (MCPBA) in homogeneous solution. EPB was blended with poly(3-hydroxybutyrate) (PHB) up to 30 wt% by solution-precipitation procedure. The thermal decomposition of PHB/EPB blends was studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and differential thermal analysis (DTA). The thermograms of PHB/EPB blends contained a two-step degradation process, while that of pure PHB sample exhibited only one-step degradation process. This degradation behavior of PHB/EPB blends, which have a higher thermal stability as measured by maximum decomposition temperature and residual weight, is probably due to crosslinking reactions of the epoxide groups in the EPB component with the carboxyl chain ends of PHB fragments during the degradation process, and the occurrence of such reactions can be assigned to the exothermic peaks in their DTA thermograms.

• Polymer(Korea)
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• v.39 no.1
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• pp.78-87
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• 2015

With aiming to prepare microcapsules having a particle size of $30-50{\mu}m$, thermally expandable capsules with relatively uniform particle sizes consisting of a n-octane/poly(acrylonitrile-co-methyl methacrylate) core/shell structure were synthesized using SPG membrane emulsification and suspension polymerization. Four steric stabilizers and five crosslinking agents were employed. When poly(vinyl alcohol) as a stabilizer was used, the prepared capsules showed a smooth and regular morphology and the liquid hydrocarbon (n-octane) was well encapsulated in the core. When 1,4-butnaediol methacrylate (BDDMA) was used as a crosslinker, the uniform capsules with the average diameter of $36.8{\mu}m$ were synthesized. The capsules prepared with 0.05 mol% BDDMA showed the best encapsulation efficiency.

• Elastomers and Composites
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• v.42 no.2
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• pp.93-101
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• 2007

In this study, for enhancing the durability of permeable pavement material polyurethane(PU) adhesives were developed, and the physical properties upon polymerization and additives were studied. PU polymerization followed the bulk polymerization of free solvent type considering ecological aspect. Additives used in this study were carbon black, calcium carbonate and ultra violet stabilizer. The property changes upon different environment were evaluated with the compressive strength which is the principal measurement of the property of pavement materials. Among polymerized PU, one formulated with esterpolyol and crosslinkable chain extender gave the highest compressive strength of $74.9kgf/cm^2$, better than commercial $60kgf/cm^2$. The strength was the highest when the material specimen contained carbon black and calcium carbonate 20 wt%, respectively. However, UV stabilizer did not show good weathering properties.

• Polymer(Korea)
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• v.24 no.5
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• pp.629-637
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• 2000

Dispersion polymerization of acrylamide in the media of t-butyl alcoho1/$H_2O$ mixtures at 30~5$0^{\circ}C$ in the presence of hydroxypropyl cellulose and ammonium persulfate as steric stabilizer and initiator, respectively, was carried out. It was studied the effects of concentrations of initiator and steric stabilizer, amount of monomer, polymerization temperature, t-butyl alcohol/$H_2O$ ratio, concentration of crosslinker, purification of monomer and nitrogen purge on the particle size of the resulting acrylamide latices and molecular weight of the latex-poly(acrylamide). In this study, poly(acrylamide) latices of 0.1~0.5 ${\mu}{\textrm}{m}$ with 470000~2080000 in (equation omitted) were prepared and the resulting PAM latices were all dissolved in water in stantly.

• Journal of Pharmaceutical Investigation
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• v.37 no.6
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• pp.349-354
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• 2007

For decades, the various virtues of ${\alpha}-lipoic$ acid (ALA), a natural material synthesized in most cells, have been intensively studied and proved. Recently it was reported that ALA caused significant bodyweight reduction via appetite suppression. Unfortunately, the efficacy requires an administration over 50 mg/kg. The low bioavailability and the short plasma half life of ALA lead us to explore novel pharmaceutical dosage forms using nanoparticles. In this study, the effect of polymeric stabilizers on the bioavailability improvement of ALA nanoparticles was investigated. The reduction of particle size via nano-comminution technology was successful resulting in volume average particle sizes of 320 - 340 nm. The in vitro release rate of ALA did not reflect the decrease of particle size, possibly because of the self polymerization of ALA during nano-comminution. The type of polymeric stabilizers could not affect the release rate either. However, the in vivo food intake results of ALA showed that nano-suspensions were more effective than microparticles or a salt form. The nano-suspension containing polyvinyl pyrrolidone as the primary stabilizer and polyacrylic acid as the secondary stabilizer showed more improved efficacy for 2 hours.

• Analytical Science and Technology
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• v.17 no.2
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• pp.98-107
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• 2004

In this study, $^1H$ NMR spectroscopy and HPLC were used to identify the type and quantity of each component in an acrylic coating materials applied for an automotive part. By the $^1H$ NMR analysis, it was found that this acrylic coating contained about 88.40 wt% of poly methyl methacrylate (PMMA), 7.05 wt% of methyl methacrylate (MMA), and 2.36 wt% of allyl methacrylate. Polymer additives such as a benzotriazole light stabilizer (Hisorb 328), an oxanilide light stabilizer, butylated hydroxy toluene (BHT), and dimethyl phthalate (DMP) were also identified and measured quantitatively from the $^1H$ NMR spectra. However, only two light stabilizers were identified by reverse phase (RP) HPLC analysis using Bondapak C18 column, methanol mobile phase, and a PDA (Photodiode array) detector. The contents of two light stabilizers in the acrylic coating were measured by a quantitative analysis through UV-Vis spectroscopy and compared with the NMR data. The analytical informations from $^1H$ NMR spetra were better than those from HPLC-PDA plot.