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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal DOI :
The Polymer Society of Korea
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Volume & Issues
Volume 32, Issue 6 - Nov 2008
Volume 32, Issue 5 - Sep 2008
Volume 32, Issue 4 - Jul 2008
Volume 32, Issue 3 - May 2008
Volume 32, Issue 2 - Mar 2008
Volume 32, Issue 1 - Jan 2008
Selecting the target year
Investigation of the Filling Unbalance and Dimensional Variations in Multi-Cavity Injection Molded Parts
Kang, Min-A ; Lyu, Min-Young ;
Polymer Korea, volume 32, issue 6, 2008, Pages 501~508
Small injection molded articles such as lens and mobile product parts are usually molded in multi-cavity mold. The problem occurring in multi-cavity molding is flow unbalance among the cavities. The flow unbalance affects the dimensions and physical properties of molded articles. First of all, the origin of flow unbalance is geometrical unbalance of the delivery system. However, even the geometry of the delivery system is well balanced, cavity unbalance occurs. This comes from the temperature distributions in the cross-section of runner. Temperature distribution depends upon injection speed because heat generation near runner wall is high at high injection speed. Among the operational conditions, injection speed is the most significant process variable affecting the filling unbalances in multi-cavity injection molding. In this study, experimental study of flow unbalance has been conducted for various injection speeds and materials. Also, the filling unbalances were compared with CAE results. The dimensions and weights of multi-cavity molded parts were examined. The results showed that the filling unbalances vary according to the injection speeds and resins. Subsequently, the unbalanced filling and pressure distribution in the multi-cavity affect the dimensions and physical states of molded parts.
Synthesis of High Affinity Anion Exchanger Using Ultrafine Fibrous PPmb Nonwoven Fabric by Co60 Irradiation Method
Choi, Kuk-Jong ; Lee, Choul-Ho ; Hwang, Taek-Sung ;
Polymer Korea, volume 32, issue 6, 2008, Pages 509~515
The aminated polypropylene melt blown ion exchange fibers were synthesized with acrylic acid monomer onto polypropylene melt blown fibers by radiation-induced polymerization and subsequent amination. Degree of grafting was increased with increasing the acrylic acid monomer concentration and total dose. The highest degree of grafting was obtained 140% at a monomer concentration of 20 v/v% acrylic acid and total dose of 4 kGy. Optimum condition of Mohr's salt was 5.0
M. Degree of amination was increased with increasing degree of grafting. Water content was about 1.5 times higher than that of trunk polymer. The maximum ion-exchange capacity was 7.3 meq/g which was 2
3 times higher than a commercial ion exchange fiber. The average pore size was decreased and BET surface area was increased in order of PPmb, PPmb- g- AAc and APPmb- g- AAc. The average pore size and BET surface area of synthesised fibers were
The Effect of Pore Sizes on Poly(L-lactide-co-glycolide) Scaffolds for Annulus Fibrosus Tissue Regeneration
So, Jeong-Won ; Jang, Ji-Wook ; Kim, Soon-Hee ; Choi, Jin-Hee ; Rhee, John-M. ; Min, Byung-Hyun ; Khang, Gil-Son ;
Polymer Korea, volume 32, issue 6, 2008, Pages 516~522
Biodegradable polymers have been used extensively as scaffolding materials to regenerate new tissues and the ingrowth of tissue have been reported to be dependent directly of the porosity, pore diameter, pore shape, and porous structure of the scaffold. In this study, porous poly (L-lactide-co-glycolide) (PLGA) scaffolds with five different pore sizes were fabricated to investigate the effect of pore sizes for AF tissue regeneration. Cellular viability and proliferation were assayed by MTT test. Hydroxyproline/DNA content of AF cells on each scaffold was measured. sGAG analyses were performed at each time point of 2 and 6 weeks. Scaffold seeded AF cells were implanted into the back of athymic nude mouse to observe the difference of formation of disc-like tissue depending on pore size in vivo. We confirmed that scaffold with
pores displayed high cell viability in vitro and produced higher ECM than scaffold with other pore sizes in vivo.
Thermal Behavior of Nylon 6 and Bisphenol-A Polycarbonate Blends Compatibilized with an Epoxy Resin
Abdrhman, Mabrouk J.M. ; Zhang, Liye ; Zhou, Bing ; Li, Hangquan ;
Polymer Korea, volume 32, issue 6, 2008, Pages 523~528
Diglycidyl ether of bisphenol-A (DGEBA) was selected as a compatibilizer in Nylon 6 and bisphenol-A polycarbonate (PC) blends. SEM revealed a much finer morphology in the presence of DGEBA. The thermal properties, such as glass transition, melting point, crystallization temperature and rate, of the blends were examined using DSC. Overall, the introduction of DGEBA caused a strong dependence of these thermal properties on the composition due to compatibilization.
Preparation and BDNF Release Profile of BDNF-loaded PLGA Scaffolds for Tissue Engineered Nerve Regeneration
Kim, Cho-Min ; Kim, Soon-Hee ; Oh, A-Young ; Kim, Geun-Ah ; Lee, Il-Woo ; Rhee, John-M. ; Khang, Gil-Son ;
Polymer Korea, volume 32, issue 6, 2008, Pages 529~536
We manufactured poly (L-lactide-co-glycolide) (PLGA) scaffolds impregnated demineralized bone particle (DBP) and hyaluronic acid (HA) by ice-particle leaching method and tested their ability of sustained release of brain derived neurotrophic factor (BDNF). BDNF (50 and 200 ng) mixed with PLGA, DBP/PLGA, HA/PLGA and DBP/HA/PLGA scaffold. The release profiles of BDNF from BDNF loaded scaffolds were assayed using ELISA. Morphological changes of scaffolds by BDNF release were also observed by SEM. BDNF stably and sustainedly released from DBP/HNPLGA than from PLGA and DBP/PLGA scaffolds. DBP/HA/PLGA scaffolds showed the great structural changes, which demonstrated BDNF release amount from DBP/HA/PLGA scaffolds were highest in all groups. We suggest that BDNF loaded DBP/HNPLGA scaffold would be very useful for nerve regeneration.
Optimization of the Water Absorption by Crosslinked Agar-g-Poly(acrylic acid)
Wuttisela, Karntarat ; Panijpan, Bhinyo ; Triampo, Wannapong ; Triampo, Darapond ;
Polymer Korea, volume 32, issue 6, 2008, Pages 537~543
Crosslinked agar-g-poly(acrylic acid) (x-agar-g-PAA) super absorbent with a water absorbency (
) of approximately 660 g/g was synthesized by the copolymerization of agar with an acrylic acid monomer. KPS and MBA were used as the initiator and crosslinker, respectively. Grafting was performed in air. Infrared spectroscopy was used to identify the product of copolymerization. The optimum conditions to synthesize the x-agar-g-PAA superabsorbent were 0.1 g of agar, 0.1 g of the KPS initiator, for 15 min; 50% AA monomer, 0.005 g of the MBA crosslinker, for a propagation time of 5 min; and 1 M NaOH for 15 min to allow for saponification. The reaction temperature was
Preparation and Characterization of Self-aggregated Nanoparticles of Chitosan-Lipoic Acid Conjugate
Park, Eun-Ju ; Kim, Young-Jin ;
Polymer Korea, volume 32, issue 6, 2008, Pages 544~548
The objective of this study is to obtain the anti-oxidant nanoparticles based on biocompatible polymers. It was chosen to conjugate with chitosan as the biodegradable polymer and lipoic acid as the hydrophobic anti-oxidant. Lipoic acid helps the regeneration of exogenous and endogenous anti-oxidants vitamin as well as glutathione and hence acts as antioxidant indirectly. Chitosan was prepared from chitin which was deacetylated under alkali solution for the various reaction time. Lipoic acid-chitosan complex was confirmed by
-NMR. The critical aggregation concentration was measured using pyrene and the values were about
g/L. The particle shapes and sizes of the chitosan-lipoic acid nano-particles were about 135 nm that measured by DLS and TEM.
A Study on Dispersion Copolymerization of Styrene/n-Butylmethacrylate and Alumina
Bang, Hyun-Su ; Cho, Ur-Ryong ;
Polymer Korea, volume 32, issue 6, 2008, Pages 549~554
In order to synthesize polymer particle containing inorganic material, styrene and n-butylmethacrylate were copolymerized with alumina by dispersion polymerization. The weight ratio of styrene to n-butylmethacrylate was 3 : 1. A poly(N-vinyl pyrrolidon) was added as stabilizer. 2,2'-AzobisCisobutyronitrile) and 3-methacryloxypropyl trimethoxysilane were used as initiator and coupling agent, respectively. The weight ratio of 70 : 30 of isopropanol to distilled water was used as dispersion medium. According to the TEM measurement, we could confirm that alumina was dispersed into the polymer particle. The increase 'of concentration of alumina resulted in enhancement of particle size, but decreased its distribution. By the XRD method, it was found that the increase of alumina concentration showed the increase of intensity in peak and the increased 2
value. From the TGA measurement, the increase of alumina concentration caused high heat resistance of the polymer. With respect to the type of initiator, the longer half life of initiator, the smaller particle size. We also found that the increase of particle stabilizer concentration made the decreased of particle size due to the accelerated generation of polymer particle in the early stage of reaction.
Properties of Polymer-Modified Mortar with Styrene-Butyl Acrylate and Styrene Butadiene Rubber
Mun, Kyung-Ju ; Song, Hae-Ryong ; Hyung, Won-Gil ;
Polymer Korea, volume 32, issue 6, 2008, Pages 555~560
Polymer-modified mortars have been largely used as paving materials, flooring, waterproofing material, adhesives, anticorrosive linings, deck coverings, and other various materials. The various types and properties of the mixed polymer largely affect the characteristics of polymer-modified mortar that has been mixed with polymer latexes. Consequently, its application purposes are varied according to these properties. This paper investigates the typical properties of polymer-modified mortars that contain styrene and butyl acrylate latexes and styrene butadiene rubber. They are then tested to obtain air contents, water-cement ratios, flexural and compressive strengths, water absorption, and chloride-ion penetration. From the test results, the superior flexural strength of polymer-modified mortars is obtained at a S/BA-2 and a polymer-cement ratio of 20%. And, the water absorption and chloride ion penetration depth are greatly affected by the polymer-cement ratio rather than the types of polymer. In the polymer-modified mortar and concrete structures, aggregates are bound by such a co-matrix phase, resulting in the superior properties of polymer-modified mortar and concrete compared to conventional mortar and concrete.
Self-Aggregated Nanoparticles of Lipoic Acid Conjugated Hyaluronic Acid
Hong, In-Rim ; Kim, Young-Jin ;
Polymer Korea, volume 32, issue 6, 2008, Pages 561~565
Hyaluronic acid (HA) is a natural glycosaminoglycan and is used widely in the pharmaceutical field. Lipoic acid (LA) helps the regeneration of exogenous and endogenous antioxidants such as Vitamin C and Vitamin E as well as glutathione. It also acts as antioxidant indirectly. Hydrophilic HA as a biodegradable and biocompatible polymer was conjugated with hydrophobic LA as an antioxidant to form the graft copolymer. The carboxyl group of HA was modified by adipic acid dihydrazide (ADH). The synthesis of HA-g-LA graft copolymers was characterized by FT-IR,
-NMR spectroscopy. The conjugates could form the self-assembled nanoparticles in aqueous solution. The particle size and critical aggregation concentration were verified to use the nanoparticle as a carrier fur the hydrophobic material.
Production of Polyethylene Wax via Metallocene Catalysts [(TMDS)
in the Presence of Hydrogen Gas as a Chain Transfer Reagent
Kim, Ji-Yoon ; Yoon, Seok-Young ; Yang, Young-Do ; Noh, Seok-Kyun ;
Polymer Korea, volume 32, issue 6, 2008, Pages 566~572
Polyethylene has been prepared via metallocene catalysts [(TMDS)
, 1, and [
, 2, in the presence of hydrogen as a chain transfer reagent. Increase of hydrogen flow to the polymerization reactor resulted in the drop of catalytic activity, reduction of molecular weight of polyethylene, getting narrow of molecular weight distribution of polyethylene, and melting point of the polyethylene wax. It should be noticed that it was possible to control molecular weight down to 1500 and melting temperature to 60
C of polyethylene wax using the catalyst 1 that has been developed by authors as well as the catalyst 2 from Exxon.
Blending of Silica Nanoparticles with PBA/PS Core-Shell Baroplastic Polymers
Kim, Min-Jeong ; Choi, Yong-Doo ; Ryu, Sang-Woog ;
Polymer Korea, volume 32, issue 6, 2008, Pages 573~579
PBA/PS core-shell polymer nanoparticles were synthesized by two stage emulsion polymerization and hybridized with silica nanoparticle by simple mixing in emulsion state and following precipitation into water/methanol mixture dissolving
. The stress-strain curve revealed that the elastic modulus was increased with increasing molecular weight of polymer and silica weight fraction but decreased with increasing size of core-shell nanoparticle. Especially, there was a rapid increase of elastic modulus with silica blending. As a result, 6 times higher elastic modulus was observed in PBA/PS core-shell baroplastic sample processed at 25
C under 13.8 MPa for 5 min by blending with 13.0 wt% of silica nanoparticle.
Synthesis and Characterization of Transparent Copolyimide Films (I)
Park, Jong-Su ; Chang, Jin-Hae ;
Polymer Korea, volume 32, issue 6, 2008, Pages 580~586
Copolyimides were synthesized from 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 1,3-bis(3-aminophenoxy)benzene (BAPB) with different mole ratios of 2,2-bis[4-(4-aminophenoxy)pheny1]hexafluoropropane (BAPP). The solution cast film of poly(amic acid) (PAA) was heat treated at different temperatures to create copolyimide films. The PI copolymer films were found to exhibit good optical transparencies. The thermomechanical properties, morphology, and optical transparency of PI films were examined using fourier transform infrared spectroscopy (FT-IR), wide-angle X-ray diffraction (XRD), scanning electron microscopes (SEM), differential scanning calorimeter(DSC), thermo-gravimetric analyzer (TGA), universal tensile machine (UTM), and IN - Vis. spectrometer. The glass transition temperature (
), ultimate strength, and initial modulus linearly increased with increasing BAPP mole fraction. However, thermal stability(
) of the copolyimide remains constant regardless of BAPP loadings. It was found, however, that the optical transparency decreases slightly upon increasing the BAPP content because of the formation of the charge transfer complexes.
Preparation of High Molecular Weight Atactic Poly(vinyl alcohol) Hydrogel by Electron Beam Irradiation Technique
Kim, Kyung-Sik ; Lee, Young-Jae ; Lyoo, Won-Seok ; Noh, Seok-Kyun ;
Polymer Korea, volume 32, issue 6, 2008, Pages 587~592
High molecular weight poly(vinyl alcohol) (PVA) hydrogel to be expected as a candidate material for the wound-dressing was successfully prepared by electron beam (EB) irradiation. To produce PVA hydrogels with various gel fractions, degrees of swelling in water, gel strengths, and elongations, two different number-average degrees of polymerization [(
)s] of PVA were adapted such as 1700 and 4000, and the PVA solution concentration and irradiation dose of EB were controlled to range of 5
20% and 30
100 kGy, respectively. The gel fraction and strength of PV A hydrogel were increased with increasing molecular weight of PVA, solution concentration, and irradiation dose of EB. On the contrary, the degree of swelling and elongation of PVA hydrogel were decreased. The thermal property and crystallinity related to degree of crosslinking of PVA hydrogel were examined by the analyses of differential scanning calorimetry and X-ray diffraction.
Gas Separation Membranes Prepared from Polystyrene-block-Polybutadiene/Poly(phenylene oxide) Blends for Carbon Dioxide Separation from a Flue Gas
Jung, You-Sun ; Kim, Chang-Keun ;
Polymer Korea, volume 32, issue 6, 2008, Pages 593~597
To separate carbon dioxide from a flue gas, membranes for gas separation was fabricated from polystyrene-b-polybutadiene (SB) diblock copolymer blends with poly(phenylene oxide), PPO. SB diblock copolymer formed miscible blends with PPO in the experimental range (lower than or equal to 70 wt% PPO). When the blend contained PPO whose composition is in the range of 40-50 wt%, the discontinuous phase of polybutadiene block in SB diblock copolymer, was changed to discrete phase, while polystyrene blocks containing PPO was changed to the continuous phase. A sudden decrease of the gas permeability and a sudden increase of the gas selectivity was observed at these blend compositions. A gas separation membranes having excellent mechanical properties and exhibiting advantages in gas permeability and selectivity could be fabricated from blends containing more than 50 wt% PPO.
A Study on the Improvement of the Thermal Stability of a Commercial Polyethylene Separator for Lithium Secondary Battery by an Electron Beam Irradiation
Sohn, Joon-Yong ; Lim, Jong-Soo ; Gwon, Sung-Jin ; Shin, Jun-Hwa ; Choi, Jae-Hak ; Nho, Young-Chang ;
Polymer Korea, volume 32, issue 6, 2008, Pages 598~602
In this study we prepared crosslinked separators with the improved thermal stability by irradiating a commercial polyethylene (PE) separator for lithium secondary battery with an electron beam, and the thermal and mechanical properties of the prepared separators were evaluated as a function of the absorption dose. The thermal shrinkage of electron beam irradiated separator was decreased with increasing absorption dose. As a result of the shutdown behavior using an AC impedance, it was observed that the irradiated separator had the better shutdown function than the unirradiated separator. The modulus of the irradiated separator was enhanced as the absorption dose was increased, while the tensile strength and the break elongation of the irradiated separator were decreased.
Strength and Durability of Polymer Modified Mortar according to Monomer Ratio of Methyl Methacrylate and Butyl Acrylate
Mun, Kyung-Ju ; Hyung, Won-Gil ;
Polymer Korea, volume 32, issue 6, 2008, Pages 603~609
The purpose of this study is to clarify the effect of the monomer ratio on properties of the polymer-modified mortars using methyl methacrylate-butyl acrylate (MMA/BA) latexes, and to obtain basic data necessary to develop appropriate latexes for cement modifiers. From the test results, the total pore volume of polymer-modified mortars using MMA/BA latexes is linearly reduced with an increase in the bound MMA content and increased in the polymer-cement ratio. In general, the superior flexural and compressive strength of polymer-modified mortars using MMA/BA latexes is obtained at a bound MMA content of 70 or 80 percent and a polymer-cement ratio of 15%. And, the water absorption and chloride ion penetration depth are greatly affected by the polymer-cement ratio rather than the bound MMA content.