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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal DOI :
The Polymer Society of Korea
Editor in Chief :
Volume & Issues
Volume 24, Issue 6 - Nov 2000
Volume 24, Issue 5 - Sep 2000
Volume 24, Issue 4 - Jul 2000
Volume 24, Issue 3 - May 2000
Volume 24, Issue 2 - Mar 2000
Volume 24, Issue 1 - Jan 2000
Selecting the target year
Synthesis and Characterization of HEMA-PCL Macromer Grafted onto Starch
Polymer Korea, volume 24, issue 2, 2000, Pages 141~148
Polycaprolactone (PCL) was blended with corn starch to produce biodegradable compost films and the biodegradability and mechanical properties were investigated. As the compatibilizer for the immiscible PCL/starch blend, 2-hydroxyethylmethacrylate (HEMA)-PCL macromer was grafted onto starch by initially grafting HEMA to starch and then grafting of PCL onto HEMA via ring opening polymerization of
-caprolactone. When biodegradability of the PCL grafted starch-g-DEMA copolymers was compared with that of starch by the modified Sturm test, graft copolymers degraded at much slower rates due to the presence of the non-degradable HEMA. With the addition of the graft copolymer up to 5 wt% to the blend, the elongation-at-break of the starch/PCL blend increased substantially, while the tensile strength and modulus did not change much. SEM observation of the blend containing 2 wt% copolymer clearly indicated that the interfacial adhesion between the starch and PCL was strengthened by the copolymer.
Synthesis and Characteristics of Highly Oil-absorptive Expanded Polyurethane
Polymer Korea, volume 24, issue 2, 2000, Pages 149~158
Oil-absorptive expanded polyurethane (EPU) was prepared with a lypophilic polyol, polypropyleneglycol (PPG) as the soft segment, and toluenediisocyanate (TDI) and
as the hard segment. PPGs haying various average molecular weights ((equation omitted) : 1000, 2000, 3000) were employed to investigate that the soft segment content was consequent on the oil-absorptivity and the mechanical properties of the EPUs. As (equation omitted) of PPG was decreased from 3000 to 1000, the oil-absorptivity and the tensile strength of the EPUs increased from 1460 to 3010% and from 0.26 to 0.55
respectively. As the hard segment content ratio,
([NCO]/[OH]) was increased from 1.0 to 1.2, the tensile strength of the EPUs increased from 0.56 to 0.95
, due to the formation of allophanate and/or biuret bondings. However, as the surfactant (S-A) content was increased from 1.0 to 2.5 pbw, the oil-absorptivity was decreased from 3634 to 3312%, due to the formation of closed cell structures.
Preparation of Polymethylene-bridged Half-Titanocenes and Investigation of Their Styrene Polymerization Properties
Polymer Korea, volume 24, issue 2, 2000, Pages 159~167
The polymethylene-bridged dinuclear half-titanocenes [(CH
(n=5(10), 7(11), 9(12)) have been synthesized by treating the distannylated derivatives of the ligands with two equivalents of TiCl
in toluene. All complexes are characterized by IR,
C NMR and mass spectrometry. In order to examine the catalytic properties of the dinuclear complexes styrene polymerization has been conducted in the presence of MMAO. From the polymerization experiments it was found that ( i ) all the prepared complexes 10-12 produced syndiotactic polystyrenes, ( ii ) the complex 12 holding the longest bridging ligand exhibited the highest activity but produced a polymer having the smallest molecular weight among the polymethylene-bridged dinuclear half-titanocenes. This behavior was attributed to the influence of electron-donating caused by the polymethylene bridge between two active centers as well as the effect of steric congestion around metal center caused by the proximal distance between two active sites.s.
Synthesis and Monomer Reactivity Ratio of PNIPAAM-PMMA Random Copolymer
Polymer Korea, volume 24, issue 2, 2000, Pages 168~173
Radical copolymerization of N-isopropylacrylamide (NIPAAM) with methyl methacrylate (MMA) was carried out in 1,4-dioxane using 2,2'-azobisisobutyronitrile (AIBN). To investigate the reactivity ratios of NIPAAM and MMA at different reaction temperatures, the copolymerization was allowed to proceed to low conversion (less than 10 wt%), and the reaction temperatures were 50, 60, and 7
. The monomer reactivity ratios of NIPAAM and MMA were estimated by the graphical methods according to the Finemann-Ross equation. The
values for NIPAAM-MMA were 0.259 and 2.782 at 5
, 0.271 and 2.819 at 6
, and 0.286 and 2.915 at 7
, respectively. As the reaction temperature increased, the
values increased. The activation energy difference was estimated by comparing the reactivity ratios at different reaction temperatures.
A Study on the Synthesis of ACE/PP-g-AN Hybrid Fibers by Irradiation and Separation of Uranium
Polymer Korea, volume 24, issue 2, 2000, Pages 174~181
The ACF/PP-g-AN copolymers were synthesized by the irradiational grafting of acrylonitrile onto ACF/PP hybrid fabric. The synthesis of the ACF/PP-g-AN copolymer was evidenced by the band of -C=N absorption peak at 2250
/ and amidoximation was evidenced by the band of -OH and -NH
peak at 3450
/ on FT-IR spectrum. The optimal time for the uranium ion adsorption equilibrium on ACF/PP-g-AN copolymers was 8 days and the optimal pH was 8. The adsorption capacities of ACF/PP-g-AN copolymers increased according to the content of amidoxime and were not varied even after more than 10 times of regeneration.
A Study on the Equilibrium Cyclic Oligomer of Poly(alkylene terephthalate) by Using RIS Model
Polymer Korea, volume 24, issue 2, 2000, Pages 182~193
Molar cyclization equilibrium constant (K
) of poly(alkylene terephthalate) (PAT) cyclics was calculated by the Monte Carlo simulation on the basis of rotational isomeric state (RIS) model. The experimental
of PAT cyclics, which was not clearly explained by the Jacobson-Stockmayer theory and the method of Flory, Suter, and Mutter however, was explained well by the direct computational method with the reaction radius
. The effect of PAT conformation on
of PAT cyclics was investigated by changing its statistical weight parameters,
of PAT cyclics obtained by the direct computation method with various radii and the radius
was slightly changed with
. Consequently, it was concluded that
of PAT cyclics is strongly dependent on the configuration of each PAT and affected by the change of its conformation to some extent.
Diffusion Coefficients of Polyimide/N-Methyl-2-Pyrrolidone Systems below Glass Transition Temperature
Polymer Korea, volume 24, issue 2, 2000, Pages 194~200
The diffusion coefficients in polyimide/N-methyl-2-pyrrolidone (NMP) systems were proposed using tile Vrentas-Duda's hole free volume theory. Several free volume parameters included in the diffusion coefficients were obtained from the fundamental physical properties of polyimide and NMP and group contribution theory, and the pre-exponential diffusion coefficient, D
was also determined from the dynamic swelling behavior of polyimide in NMP solution. The experimental swelling behavior of polyimide films in NMP was well described by the theoretical one using the proposed diffusion coefficient.t.
Chemo-mechanical Analsis of Bifunctional Linear DGEBA/Linear Amine Resin Casting Systems
Polymer Korea, volume 24, issue 2, 2000, Pages 201~210
To determine the effect of chain length of linear amine curing agents on the thermal and mechanical properties, standard epoxy resin, diglycidyl ether of bisphenol A (DGEBA) was cured with diethylenetriamine (DETA), triethylenetetraamine (TETA) and tetraethylenepentaamine (TEPA) in a stoichiometrically equivalent ratio. From this work, the effect of linear amine curing agents on the thermal and mechanical properties was significantly influenced by chain length of curing agents. In contrast, the results showed that the DGEBA/DETA system had higher values than the DGEBA/TETA and DGEBA/TEPA system in the density, shrinkage (%), thermal expansion coefficient, tensile modulus, and flexural strength. Whereas the DGEBA/DETA cure system had lower values than the DGEBA/TETA and DGEBA/TEPA cure system in the maximum exothermic temperature, conversion (%), and T
. These findings imply that the differences in the maximum conversion about the chain length of curing agents affect the thermal and mechanical properties.s.
Polarized Light Emission of Liquid Crystalline Polymer Blends
Polymer Korea, volume 24, issue 2, 2000, Pages 211~219
Fluorene-based light emitting polymer blends with liquid crystalline characteristics were studied on effective energy transfer and dichroic characteristics. Incorporating 0.5 wt% of the non-liquid crystalline into the liquid crystalline polymer suppressed the PL emission at 420 nm on photoexcitation at 360 nm, but generated a new PL emission of the non-liquid crystalline polymer at 480 nm. The highest PL intensity at 480 nm, which was 13 times stronger than those of the two polymers before blending, was observed for a blend with 2.0 wt% of the non-liquid crystalline polymer. When the molecules of the blends were aligned on a rubbed polyimide surface by a heating-cooling process, the dichroic ratio and the order parameter were 2.0 and 0.25, respectively. Time-correlated single photon counting (TCSPC) study revealed that the time required for energy transfer between the two chromophores was shortened by 93 ps when the blends were aligned on the rubbed polyimide surface by the heating-cooling process. The thermal treatment also enhanced the energy transfer efficiency by 9%.
Effects of Mixing Mode on the Fracture Properties of Silica and Carbon Black Filled NR Vulcanizates
Polymer Korea, volume 24, issue 2, 2000, Pages 220~227
Silica and carbon black filled natural rubber (NR) vulcanizates were prepared with different mixing modes and amounts of fillers. Curing characteristics, morphology. and tear properties of the NR vulcanizates were investigated. The NR vulcanizates filled with silica and carbon black sequentially showed longer induction time (
), cure index (
), and lower maximum torque (
) than the NR vulcanizates filled with them simultaneously, during curing process. The former showed superior dispersion of fillers and tear properties to the latter. The NR vulcanizates containing 30 phr of silica showed excellent properties in the experimental range.
A Study on the Preparation of Polyimide/Clay Nanocomposites
Polymer Korea, volume 24, issue 2, 2000, Pages 228~236
The preparation of organophilic clay from Na
-MMT was achieved by intercalation of alkylammonium bromide. The dispersed organophilic clay in NMP was then added to the solution of polyamic acids (BPDA-PPD, BTDA-ODA/ MPD) in NMP. After curing at 30
, thin films of the polyimide/clay nanocomposite were prepared. The results of X-ray diffraction (XRD) shelved that the d-spacings of dried polyamic acid (PAA)-clay complexes increased in proportion to the chain length of the onium ion and patterns of two kinds of PAA-clay complexes were similar. The d-spacings of approximately 13.2
for the polyimide/clay nanocomposites were independent of the initial onium ion chain length and the species of PAA. From the study of XRD and transmission electron microscopy (TEM), we found layered silicates were dispersed in polyimide matrix and the resultants were intercalated nanocomposites. TGA result showed thermal stability of polyimide nanocomposite improved a little more than the pure polyimide. From the result of dynamic mechanical property, we found that the storage modulus of the nanocomposites had increased by 1.2-1.8 times of the pure polyimides.s.
Influence of Oxidation Inhibitor on Carbon-Carbon Composites: 5. Studies on Anti-oxidation Properties of the Composites
Polymer Korea, volume 24, issue 2, 2000, Pages 237~244
Phenolic resin used as a precursor of carbonized matrix for carbon-carbon composites was modified by addition of molybdenum disilicide (MoSi
) in various concentrations of 0, 4, 12 and 20% by weight to improve the anti-oxidation properties of the composites. The green body was manufactured by a prepreg method and was submitted to carbonization up to 110
. In this work, the oxidation behavior of carbon-carbon composites with MoSi
as an oxidation inhibitor was investigated at the temperature range of 600-100
in an air environment. The carbon-carbon composites with MoSi
showed a significantly improved oxidation resistance due to both the reduction of the porosity formation and the formation of mobile diffusion barrier for oxygen when compared to those without MoSi
. Carbon active sites should be blocked, decreasing the oxidation rate of carbon. This is probably due to the effect of the inherent MoSi
properties, resulted from a formation of the protective layer against oxygen attack in the composites studied.
Effect of Surface Free Energies on Mechanical Properties of Epoxy/Polyurethane Blend System
Polymer Korea, volume 24, issue 2, 2000, Pages 245~251
A blend system prepared from epoxy(EP) and polyurethane (PU) was investigated in terms of the contact angle and mechanical properties. The contents of EP/PU were varied within 100/0~100/60 phr in the presence of 20 phr DDM (4,4'-diamino diphenyl methane) as a curing agent for epoxy resin. Contact angle measurements were performed employing a Rame-Hart contact angle goniometer. Deionized water and diiodomethane were chosen as the testing liquids. In this work, Owens-Wendt and Wu's models using a geometric mean were studied to analyze the surface free energy of blend system. For the mechanical and toughening properties of the casting specimens, the critical stress Intensity factor (
) and impact test were performed. Especially, the impact test was carried out at room and cryogenic temperatures. As a result, specific or polar component of the surface free energy of the blend system was largely influenced on the addition of the PU resulting in increasing the impact strength for the excellent low- temperature performance.
Oxidation of Ascorbic Acid by Crosslinked Poly(4-vinyl pyridine)-Cu(II) Complexes 2. Effect of Crosslinker
Polymer Korea, volume 24, issue 2, 2000, Pages 252~258
Various crosslinked poly(4-vinylpyridines) (CHP4VP) having different degrees of crosslinking were synthesized by radical copolymerization of 4-vinylpyridine with if N,N' -1, 6-hexamethylenebisacrylamide, and CHP4VP- Cu(II) complexes were prepared by the method of adsorption equilibrium. The catalytic activity of the complexes for the oxidation of ascorbic acid (AA) was investigated. The oxidation of AA by these complexes showed a kinetic behavior of the Michaelis-Menten type. The catalytic activity of CHP4VP-Cu(I ) catalytic system was increased with increasing the degree of crosslinking of CHP4VP, and its activity was scarcely decreased even after repeated use. However, the tendency of the catalytic activity of CHP4VP-Cu(II) complexes was decreased for the oxidation of AA when compared with that of the previously reported catalytic system containing crosslinked poly(4-vinylpyridine) prepared using N,N'-methylenebisacrylamide as a crosslinker. These results indicate that the degree of crosslinking of CHP4VP and the hydrophobicity of the crosslinker play an important role in the catalytic system of the oxidation of AA.
Mechanical Properties and Ionic Conductivities of Plasticized Gel Polymer Electrolyte Based on P(VdF-co-HFP)
Polymer Korea, volume 24, issue 2, 2000, Pages 259~267
Gel polymer electrolytes were prepared from poly(vinylidene fluoride-co-hexafluoro propylene)[P(VdF-co-HFP)] that had higher mechanical properties as well as higher dielectric constant (
=8~13) than other polymeric matrix. Mechanical properties and ionic conductivities have been investigated as a function of blend ratio of electrolyte solution and polymer matrix. Ethylene carbonate (EC)/
-BL) and lithium triflate (LiCF
) were used as solvent and salt, respectively. The mechanical properties such as tensile strength, tensile modulus, compression modulus, and dynamic shear modulus were evaluated. The highest ionic conductivity was 1.09
S/cm for PVH40 containing 28.6 wt% of P(VdF-co-HFP) at
. Tensile strength, tensile modulus and compression modulus were increased with P(VdF-co-HFP) content and abruptly changed between PVH70 and PVH80. Dynamic shear moduli showed a typical gel behavior and changed with shear strain.
Fabrication and Properties of Conductive Carbon Fiber/Polyethylene Composite Films Fabricated under High Intensity Electric Fields : Effect of Polymer Sublayer
Polymer Korea, volume 24, issue 2, 2000, Pages 268~275
We investigated the effect of polymer sublayer on volumetric resistivity and tensile strength of carbon fiber (CF)/polyethylene composite films fabricated under high intensity electric fields. The dependence of volumetric resistivity and tensile strength of the films on the polymer sublayer thickness or mass part exhibited complex behavior according to CF content and CF layer density in the films. As the thickness of polymer sublayer increases, two groups of processes at thermo-mechanical forming stage would take effects in the properties of the films. The first group comprises the increase of polymer layer thickness having reduced CF content compared with central or upper part of the film and insufficient wetting of CF resulting in the loosened structure near upper film side. The second group, on the other hand, is the improvement of mobility of molten sublayer leading to better distribution of CF throughout the film thickness and the formation of more compact structure. The different degree of contribution of these two competing processes at varied CF content and CF layer density could explain complex dependence of the film properties on the polymer sublayer. These results are important to optimize the electrical and mechanical properties of highly conductive polymer films, which can be used as electromagnetic interference shielding materials.
Preparation and Physical Properties of Conductive Poly(acrylonitrile) Fabrics Containing Polypyrrole
Polymer Korea, volume 24, issue 2, 2000, Pages 276~280
A conductive poly(acrylonitrile)/polypyrrole composite fabric was prepared. A conductive composite was prepared by the impregnation of PAN fabric into a mixed solution of pyrrole and oxidant in order to induce the in-situ polymerization of a conducting polymer into the matrix fabric. In the composite formation, the reaction condition was optimized to achieve the best properties, and the effect of the externally-added arylsulfonate dopants on the physical properties was examined. As a result, the best properties of electrical conductivity, thermal stability, and fastness to washing, was observed in the composite containing an antraquinonesulfonate (AQSA) dopant.
Synthesis of Ion Conducting Polymer Having Low Temperature Characteristics: II. Synthesis and Characterization of Amorphous Polyester
Polymer Korea, volume 24, issue 2, 2000, Pages 281~286
A series of amorphous polyesters were synthesized from amorphous polyether and sebacoyl chloride. The structure and competition of the obtained aliphatic polyester were confirmed by
H-NMR and FT-IR. The number average molecular weights (M
) of the obtained polymer were ranging from 8000 ~ 15000. These polyesters showed no crystallinity and their glass transition temperatures (T
) were around -77
. For comparison, aliphatic polyesters were also synthesized from poly(ethylene glycol) (PEG) with M
of 200, 400, and 1000. As the M
of PEG increased, the melting point of the obtained polyester increased, and the crystallinity of the obtained polyester increased showing 8.8%, 16.2%, and 46.7%, respectively.ively.y.