• Polymer(Korea)
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• v.24 no.6
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• pp.787-793
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• 2000

The acrylonitrile copolymer/dimethylformamide (DMF) solutions were prepared to investigate the gelation behavior and critical gel concentration (c＊). Gelation is rapidly progressed with the increase of molecular weight of copolymer, but significantly delayed with supercooling temperature and comonomer contents. The c＊ behavior showed contrary trend against gelation behavior. In dynamic viscoelastic test, two glass-transition region were observed in film obtained from gelled solution whereas one glass-transition in film obtained from true solution. This result supports the idea that an ordered junction zone is formed by the dipole-dipole interaction of intermolecularly neighboring stereo-regular parts of atactic acrylonitrile copolymer chains due to a nucleation process in the solution.

• Laser Solutions
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• v.15 no.3
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• pp.1-6
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• 2012

The friction force of patterned needle in elastomer have been investigated to verify the application for bio and plastic industry. The micro pattern on the needle surface were prepared by 266 nm, 20 ns laser and 800 nm, 220 fs laser, which were able to generate the different surface roughness. The friction force was measured by the load cell of 10 N capacity. As the results, the friction force of no patterned needle is almost constant during the needle penetrates the silicone rubber sample. However, the needle having asperities shows the variation of the friction force. The higher the surface roughness is, the smaller the friction force is until the surface roughness is very high. In our experiment conditions, the reduction of the friction force by 20 % compared to no pattern needle was achieved with straight and $50{\mu}m$ discrete line generated by 266 nm, 20 ns laser.

• Journal of the Korean Chemical Society
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• v.39 no.1
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• pp.76-80
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• 1995

Polydimethylsiloxane(PDMS)-co-poly(2-hydroxyethyl methacrylate)(PHEMA) was prepared and the degree of swelling of solvents into the polymers was examined. It was confirmed that the solubility parameter of PHEMA homopolymer is 26 (J/cm3)1/2. Ethanol was significantly absorbed into copolymers containing large amount of PHEMA, while tetrahydrofuran was effectively absorbed into copolymers containing large amount of PDMS. Absorption of polar solvents into the copolymers were increased with the increase of PDMS content. The model drug, crystal violet (CV), was more absorbable into PDMS-HPEMA copolymers than PHEMA homopolymer. Absorption of CV was decreased with the increase of PDMS content of the copolymers.

• Elastomers and Composites
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• v.44 no.3
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• pp.308-314
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• 2009

The acrylic rubber was synthesized by emulsion polymerization using n-butyl acrylate, n-butyl methacrylate, acrylonitrile, glycidylmethacrylate, and allyl methacrylate. When the contents of acrylonitrile were increased at fixed amount of crosslinking monomers, the Tg of polymers was increased with the contents of acrylonitrile, Mooney viscosity, hardness, and tensile strength also were increased. But the elongation was decreased due to the reduction of chain flexibility. The addition of the monomer for crosslinking, glycidylmethacrylate whose Tg is $56^{\circ}C$ resulted in the increased Tg of the polymer, and increased Mooney viscosity, hardness, and tensile strength, but the elongation at break was decreased with the glycidylmethacrylate contents. It was shown that this phenominon was attributed to the increment of crosslinking density by glycidylmethacrylate through the measurement of rheometer.

• Resources Recycling
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• v.27 no.4
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• pp.23-28
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• 2018

Distribution data of boric acid in water is necessary to develop a hydrometallurgical process for the recovery of boron from primary and secondary resources containing boron. Boric acid exists as $B(OH)_3$ and $B(OH)_4{^-}$ when solution pH is less than 6 and higher than 12, respectively. In the solution pH range of 6-11, condensation reaction between $B(OH)_3$ and $B(OH)_4{^-}$ results in the formation of some polymers. The mole fraction of the boron polymers such as $B_3O_3(OH)_4{^-}$ and $B_4O_5(OH){_4}^{2-}$ is proportional to the concentration of boric acid.

• Journal of radiological science and technology
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• v.46 no.2
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• pp.107-114
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• 2023

The purpose of this study was to compare the basic radiological characteristics of in-house polymer gel and commercially-available gel (BANG^TM) gel dosimeters with a spectro-photometer to use a optical computed tomography (CT) scanner. We investigated the radiological characteristics including dose linearity, absorbance spectrum, dose rate dependency and inter-and intra-reproducibility at wavelengths of 590, 600 and 630 nm. The optimal dose linearities of two gel dosimeters showed R² value of 0.939 and 0.948 at wavelengths of 590 nm and 600 nm, respectively. For two polymer gel dosimeters, there is no peak sensitivity within the range of all wavelengths in absorbance spectrum. For in-house gel dosimeter, the dose rate dependency were within 5% for all wavelengths except for the dose rate of 100 MU/min. For BANG^TM gel dosimeter, the dose rate dependency showed an error range of ±5% for all wavelengths. The inter-and intra-reproducibility of two gel dosimeters were within the range of 2.5%. We have confirmed that the two gel dosimeters was appropriate for use with a optical CT scanner.

• Economic and Environmental Geology
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• v.43 no.3
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• pp.223-233
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• 2010

The effects of extracellular polymeric substances (EPS) of Pseudomonas aeruginosa on adsorption and redox state alteration of dissolved As, Cr and U were investigated through batch experiments. Surfaces of bacterial cells were either vigorously washed or unwashed. Solutions of As(V), Cr(VI) and U(VI) were inoculated with the bacterial cells under no nutrient condition, and total aqueous concentrations and redox state alteration were monitored over time. No As adsorption occurred onto bacteria or EPS; however, unwashed bacteria reduced about 60% As(V) to As(III). Unwashed bacteria also led to removal of 45% total dissolved Cr and reduction of 64% Cr(VI). About 80% U(VI) was removed from solution with unwashed bacteria as well. Such electrochemical reduction of the elements was likely due to reducing capacity of EPS itself or detoxifying reduction of the bacteria which kept their viability under protection of EPS. The results indicated that bacterial biofilm may significantly control the redox state and subsequent mobility of As, Cr and U in natural geologic settings.

• Applied Chemistry for Engineering
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• v.9 no.3
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• pp.440-444
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• 1998

Poly(phenylene sulfide-co-phenylene sulfide sulfone), PPS/PPSS copolymers were synthesized from p-dichlobenzene(DCB), p-dibromobenzene(DBB), p-diiodobenzene(DIB), 4-chlorophenyl sulfone(CPS) and sodium sulfide as comonomers under high temperature and pressure utilizing N-methyl-2-pyrrolidinone(NMP) as solvent. The yield of PPS/PPSS copolymer shoed maximum at $190^{\circ}C$ with [DBB]/[CPS] and [DIB]/[CPS] comonomer pair, while [DCB]/[CPS] pair exhibited maximum yield at $230^{\circ}C$. The change of yield is in the order of I>Br>Cl as leaving groups were in accordance with nucleophilic aromatic substitution reaction mechanism suggested for the synthesis of PPS type polymers. The molecular weight of PPS/PPSS copolymer was the highest($M_w=8,330g/mol$) with [DBB]/[CPS] comonomers in which [CPS] was 10 mole%. The PPS/PPSS copolymer made with 10 mole% of [CPS] showed about $15^{\circ}C$ higher $T_g$ and $15^{\circ}C$ lower $T_m$ than those of PPS homopolymer, which may be useful from the processing and thermal property point of view. The PPS/PPSS copolymer with 30 mole% of CPS or above did not exhibit Tm. The PPS/PPSS copolymer obtained with comonomer feed ratio of [DBB]/[CPS] = 95/5 mole% under $240^{\circ}C$ showed even higher molecular weight($M_w=10,300g/mole$) than PPS homopolymer made under similar reaction condition, retaining high crystallinity and thermal stability.

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.1028-1034
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• 1999

Poly(lactic acid) is expected to be one of the most promising biodegradable polymers. However, the high molecular weight polymer could be obtained by ring-opening polymerization process conventionally, which raises the production cost and decreases the final yield. In this study, linear and star-shaped poly(L-lactic acid)s were prepared by direct solution polycondensation method and their physical and thermal properties were examined. Tin compounds were found to be effective catalyst for the preparation of high molecular weight polymers. When 0.2g (0.5 wt % of monomer) of $SnCl_2$ and 100 mL of p-xylene were used, the polymer yield and molecular weight were relatively high. As a means to obtain higher molecular weight polymer easily in the direct polycondensation system, dipentaerythritol(dipet) or pentaerythritol(pet) was introduced as a multifunctional branching monomer to provide a star-shaped poly(lactic acid). Moderately high molecular weight polymers with the inherent viscosity values up to 1.14 dL/g(weight-average molecular weight of about 140000 by GPC) were obtained and could be cast strong and transparent films.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.226-231
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• 1998

Hot melt adhesive which is solventless type has been widely used due to the possibility of automated adhesion process. The main purpose of this study is the development of polyamide based hot melt adhesive to improve the property of conventional ethylene-vinyl acetate hot melt adhesive, which has an inherent problem against heat resistance. In this study, it was found that the terpolymers of nylon 6, nylon 66, and nylon 12(CM831, 843P types) instead of nylon homopolymer were suitable base resins for hot melt adhesive, since the disruption of regularity in the polymer chains reduced the crystallinity, resulting in lower melting point and melt viscosity. According to the results, the optimum adhesion property could be obtained by the using 75/25~50/50 weight radio of CM831/843P resin as a base resin. Terpene resin was used as tackifier to improve adhesion and wetting properties. The best result can be obtained with the 10 wt.% addition of terpene resin. The terpene resin acted as proper tackifier in this system which decreased the melt temperature and viscosity, but increased the mechanical strength of adhesive itself. Also, the rheological property of the adhesive changed from typical non-Newtonian behavior to Newtonian behavior as terpene resin was added.