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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
Preparation of Monodispersed Crosslinked Polymer Beads
Polymer Korea, volume 24, issue 3, 2000, Pages 287~298
In preparing micron-sized monodisperse polystyrene beads by dispersion polymerization, the conversion, and the particle size and its distribution were affected by the reaction temperature, concentration of the monomer, solvent and initiator, molecular weight and concentration of the steric stabilizer, amount of oxygen existing in the reactor, and an appropriate combination of these starting materials. Ethanol as a dispersing agent, styrene as a monomer, PVP as a steric stabilizer, AIBN as an initiator, DVB as a cross-linking agent and toluene as a co-solvent were the basic materials for the synthesis. The reaction rate and the conversion were increased with the reaction temperature and the amount of DVB from 1 to 4%, and the conversion was saturated after 10 hours of the reaction time. The optimum reaction recipe for the preparation of the monodisperse PS beads was 25% styrene monomer, 0.5% DVB, 25% toluene, 10-15% PVP, and 2 and 4% AIBN, thereby, 3.9~4
of polystyrene beads, respectively, were successfully synthesized.
A Study on the Synthesis ann Pyrolytic Properties of SiC/Ti Hybrid Ceramic Precursor by Hydrolysis
Polymer Korea, volume 24, issue 3, 2000, Pages 299~305
In order to increase the thermal stability at high temperatures, new hybrid ceramic percursors were synthesized by chemical modification of polycarbosilane (PCS). The structure of hybrid ceramic percursors were investigated by using FT-IR and
H-NMR spectrometers. The syntheses of hybrid ceramic precursors were confirmed by monitoring the change of the adsorption peaks appearing at 0893, 1092, 609
/ on the FT-IR spectra, and also by the presence of peaks at 3.8, 2.0, 0.6 ppm on the
H-NMR spectra. The conversion of hybrid ceramic percursor was around 74 and 10 wt% higher than that of the pure PCS. After the heat-treatment at 150
, the crystalline peaks for
-SiC were observed at 2
=35.7, 42.2, 61.0
on the X-ray powder diffractogram. It showed the conversion of hybrid ceramic percursor to crystalline
Synthesis and Thermal Property of Poly(styrene-g-caprolactone) with Well-defined Structure
Polymer Korea, volume 24, issue 3, 2000, Pages 306~313
Polycaprolactone (PCL) macromer containing terminal methacrylate group was synthesized by ring-opening polymerization. The number average molecular weight of PCL macromer was 11600 g/mole and polydispersity index was 1.09. The synthesized PCL macromer was copolymerized with styrene by stable free radical polymerization using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), benzoyl peroxide, and well-defined poly(styrene-g-caprolactone)s were synthesized. The synthesized copolymers was characterized by
H-NMR and gel permeation chromatography equipped with multiangle laser light scattering detector. Thermal properties of graft copolymers were investigated by DSC.
Thermal Degradation of Thermoplastic Polyurethane Modified with Polycarbonate
Polymer Korea, volume 24, issue 3, 2000, Pages 314~325
Thermal degradation of thermoplasitc polyurethane modified polycarbonate has been investigated by means of DSC, GPC and FT-IR techniques. The polyurethanes used in this study are TPU-35 and TPU-53 containing 35.5 and 53.4 wt% of hard segments, respectively. The more content of hard segment, the higher the glass transition temperature (T
) of TPU was observed. On the other hand, the T
of the TPU modified PC decreased with the content of TPU and the annealing temperature regardless of the hard segment contents. The latter behavior nay arise from the thermal degradation of TPU upon annealing process: the observed thermal degradation temperatures were at 240 and 25
for the PC/TPU-35 and PC/TPU-53, respectively. The molecular weight, molecular weight distribution and viscosity agree well with the DSC measurement, which implicates a thermal degradation of TPU. In addition, thermal stability of the TPU modified PC linearly decreased with an incorporation of TPU. Transesterification or any interaction was not observed using FT-IR: the evidence was no frequency shift or any variance betwere the carbonyl stretching and NH group. For the specimens prepared below the degradation temperature, the enhancement of the thickness dependent impact strength of the PC/TPU blend was observed, and the morphology of the two blends was compared.d.
Influence of Sizing Agent on Interfacial Adhesion and Mechanical Properties of Glass Fiber/Unsaturated Polyester Composites
Polymer Korea, volume 24, issue 3, 2000, Pages 326~332
The effects of sizing agent on the final mechanical properties of the glass fiber/unsaturated polyester composites were investigated by contact angle measurements at room temperature. In this work, glass fibers were coated by poly(vinyl alcohol), polyester, and epoxy type sizing agent and each property was compared. Contact angles of the sized glass fiber were measured by the wicking method based on Washburn equation using deionized water and diiodomethane as testing liquids. As an experimental result, the surface free energy calculated from contact angle showed the highest value in case of the glass fiber coated by epoxy sizing agent. From measurements of interlaminar shear strength (ILSS) and fracture toughness (
) of the composites, it was found that the sizing treatment on fibers could improve the fiber/matrix interfacial adhesion, resulting in growing the final mechanical properties. This was due to the enhanced surface free energy of glass fibers in a composite system.
Thermal Properties of Linear Shape Polylactic Acid/Star Shape Polylactic Acid Blends
Polymer Korea, volume 24, issue 3, 2000, Pages 333~341
Blends consisting of linear shape polylactic acid and star shape polylactic acid (L-PLLA/S-PLLA) have been prepared by melt and solution blending. The effect of blending method on the thermal properties and crystallization behavior of L-PLLA/S-PLLA blends has been investigated. The molecular weight decrease was revealed both in melt and solution blending. S-PLLA was found to be more stable than L-PLLA in the reduction of molecular weight during the course of blending due to its star shape structure. As a result, broad molecular weight distribution was obtained in solution blending. It was found that melting temperature and glass transition temperature decrease with increasing S-PLLA content. Blending method had large influence on the glass transition temperature of PLLA blends, while less effect on melting temperature. From DSC results, it can be noticed that solution blending is more effective blending method to obtain higher crystallinity than melt blending for S-PLLA and blend with higher S-PLLA content.
Preparation of Chemical and Fouling Resistant Semicrystalline Membranes
Polymer Korea, volume 24, issue 3, 2000, Pages 342~349
Hollow fiber membranes were prepared via thermally-induced phase separation process followed by stretching process from isotactic polypropylene and soybean oil system. Various operating parameters were examined in terms of their effects on the structure variation and performances of the membrane, and were optimized. Melt viscosity of the melt sample had influence on the formation of the microfibrils, and addition of nucleating agent increased the nucleation density to enhance the interspherulitic pore formation by stretching. Annealing the membrane at its stretched state relaxed the stress induced by stretching and helped the membrane maintain the stretched structure without shrinking. Solid-liquid Phase separation is more prevalent when the nucleating agent was added, and coagulation bath temperature determined the nucleation density, which affected the pore formation by stretching. In the absence of nucleating agent, nucleation was not effective and liquid-liquid phase separation governed the structure formation, which showed the opposite trend to that of the case with nucleating agent.
A Study on the Curing Behaviors of Glass/Epoxy Prepreg by Dielectrometer and the Thermal Properties of Cured Glass/Epoxy Composites
Polymer Korea, volume 24, issue 3, 2000, Pages 350~357
Curing behaviors of glass/epoxy prepreg for printed circuit boards (PCB) were studied by using dielectrometer and differential scanning calorimeter. This prepreg was showed the lowest ionic viscosity at about 115
, and then the ionic viscosity was gradully increased up to 15
. This indicated that the curing reaction of this prepreg started at 115
and the molecular weight was increased by the accelerated thermal cross-linking reaction. The loss factor and tan
values were also measured and discussed. The dielectric behaviors of this prepreg system were also measured according to the cure cycle for PCB. This material was found to be thermally stable up to about 30
and then was showed an abrupt decomposition beyond this temperature.
Miscibility and Thermal Behavior of Biodegradable Synthetic Aliphatic Polyester (Bionolle) and Poly(epichlorohydrin) Blends
Polymer Korea, volume 24, issue 3, 2000, Pages 358~365
Miscibility itnd thermal behavior of blends of synthetic biodegradable aliphatic polyester (Bionolle) with poly(epichlorohydrin) (PECH) were investigated by a differential scanning calorimetry (DSC), a dynamic mechanical thermal analyzer (DMTA) and a rotational rheometer. Observed both single glass transition temperatures from the DSC in agreement with the Fox equation and single T
changes as a function of composition from the DMTA indicate that these blend mixtures are miscible. In addition, the miscibility of this blend system was also observed from the single curve of the Cole-Cole Plot of log G′(
) vs. log C"(
) from the dynamic test using a rotational rheometer. This was further verified from the cryogenically fractured surface of BDP/PECH blends by scanning electron microscopy.
Morphology and Thermal Properties of PPS/ABS Blends
Polymer Korea, volume 24, issue 3, 2000, Pages 366~373
In this study, the PPS/ABS blend system was investigated in order to collectively identify the relationship among blend morphology, chemical compatibilization and thermal property. ABS resin was chemically modified by the incorporation of maleic anhydride through reactive extrusion for enhanced compatibilization, and PPS, ABS and the modified ABS were blend by a sing twin screw extruder. The effect of chemical modification of ABS on the morphological, mechanical, and thermal properities of the resulting blend was examined. A strong interaction was observed between PPS and MABS by optical microsopy as well as scanning electron microscopy, exhibiting a well-dispersed morphological feature. The PPS/MABS blend showing a single glass transition temperature was observed in dynamic mechanical analysis, demonstrating a pseudo-homogeneous phase morphology induced by chemical compatibilization. PPS/MABS blend also exhibited an enhanced thermal stability and heat distortion temperature compared with modified PPS/ABS blend.
A Study on the Dispersion Characteristics of PP/MMT Composites
Polymer Korea, volume 24, issue 3, 2000, Pages 374~381
Composites of polypropylene (PP) and organically modified montmorillonite (org-MMT) were prepared by melt mixing in an intensive mixer. Three grades of PP's having different melt viscosities were employed to investigate the dispersion characteristics of the composites with various org-MMT's. Depending on the matrix viscosity and nature of the interlayer in org-MMT significant variations of the phase structure were found. Under the constant mixing condition and matrix viscosity, intercalation of PP chains into the interlayer of org-MMT was possible when initial interlayer distance and packing density were maintained in the optimum range; by which the loss in entropy associated with the confinement of polymer chains was compensated. The state of org-MMT particle dispersion was improved by increasing the matrix viscosity only in the case that dispersed phase is suitable for intercalation process thermodynamically, otherwise little variation was occurred regardless of the matrix viscosity. Due to the lack of specific interaction between PP and erg-MMT considered here, although the intercalation was possible for an appropriate org-MMT, the composites revealed unstable phase structure upon increasing the mixing time, which was characterized by agglomeration of the org-MMT domains.
Thermal and Electrical Properties of Poly(vinylidenefluoride-hexafluoropropylene)-based Gel-Electrolytes
Polymer Korea, volume 24, issue 3, 2000, Pages 382~388
Polymer electrolyte films consisting of poly(vinylidenefluoride-hexafluoropropylene) (PVdF-HFP), LiClO
and a mixture of ethylene carbonate (EC) and
-butyrolactone (GBL) were examined in order to obtain the best compromise between high ionic conductivity, homogeniety, dimensional and electrochemical stability. Measurements of ionic conductivity, differential scanning calorimetry and linear sweep voltammetry have been carried out for various compositions. The highest conductivity of 3.8
/ at 3
were obtained for a film of 30(PVdF-HFP)+7.8LiClO
+62.2EC/GBL. From the DSC study, it has been found that the PVdF-HFP gels are stable up to 10
, and the salt lowers the melting temperature of crystalline part of PVdF by interacting sensitively with polymer segments. When Lithium metal is in contact with the gel films, it tends to undergo corrosion and the reaction products accumulate resulting in the formation of a passive film on Li electrode. As the aging time progresses, the interfacial resistance increases continuously. Anodic stability is measured to extend up to about 4.5 V vs. Li.
Study on the Improved Abrasion Resistance of Polycarbonate Substrate by UV-curable Organic/Inorganic Hybrid Coatings
Polymer Korea, volume 24, issue 3, 2000, Pages 389~398
Transparent, abrasion resistant coatings with 4~13
thickness were prepared by spin-coating on polycarbonates with organic/inorganic hybrid solutions, followed by UV curing and heat treatment at 12
for 12 hours. The coating solutions were composed of inorganic phase and organic phase in 0:100, 20:80, 30:70, 50:50, 80:20 wt% ratios, respectively, mixed with photoinitiator, senaitizer and surfactant. The inorganic phase was formed by sol-gel reaction of TEOS and silane coupling agent MPTMS in 1 : 2 or 2 : 1 molar ratios, the organic phase consisted of difunctional urethane acrylate oligomeric resin, multifunctional acrylate TMPTA and HDDA in 4 : 3 : 3 wt% ratio. The coating systems were investigated by FT-IR,
Si-NMR spectra. In addition, TGA/DSC for thermal analysis and SEM, AFM observation for coated surface were examined. Gererally, the homogeneity of phases, the surface smoothness of coating and abrasion resistance were improved with the higher content of inorganic component. Namely, coating system with below 10
surface roughness and T
showed only 10% decrease in light transmittance after abrasion test, whereas uncoated polycarbonate substrate exhibited 46% decrease..
Nanocomposites Based on Montmorillonite and Thermotropic Liquid Crystalline Polyester
Polymer Korea, volume 24, issue 3, 2000, Pages 399~406
A thermotropic liquid crystalline polymer (TLCP) containing a flexible spacer was synthesized from hydroquinone, p-hydrofybenzoic acid, and 1,6-dibromohexane. Intercalation of TLCP in layered clays is accomplished by heating the polymer with dodecyl ammonium-montmorillonite (C
-MMT) above melt transition temperature (T
). Liquid crystallinity of the TLCP/C
-MMT hybrid was not observed when
-MMT content was above 1 wt%. Some of the
-MMTs in TLCP were highly dispersed in a nanometer scale, but some of them were agglomerated. Thermal and morphological properties of the nanocomposites were examined by differential scanning calorimetry (DSC), thermogravimetric analyzer (TGA), polarized optical microscope, and electron microscopes (SEM and TEM). TEM).
Photosensitive Polyimides Having Aromatic Sulfonyloxyimide Groups in the Main Chain
Polymer Korea, volume 24, issue 3, 2000, Pages 407~417
Photosensitive polyimides having cyclobutane or phenyl and aromatic sulfonyloxyimide units in the main chain have been synthesized and the photodegradation behavior was investigated in relation with the polymer structure. The polyimides were prepared by condensation polymerization of N-hydroxyl and sulfonyl chloride. The prepared polyimides were stable up to 25
without thermal degradation. It has been found that the photodegradation of polyimides upon irradiation of 254 nm UV light results from scission of N-O bonds or ring opening of imides moiety by spectroscopic measurements. The polyimides were useful as positive working photodegradable polymers. Especially, the positive tone image of polyimide containing a pyromellitic diimide moiety exhibited high sensitivity and resolution.
Preparation and Swelling Behavior of Cross-Linked Films of Hydroxypropyl Chitosan Possessing Cholesteric Liquid-Crystalline Order
Polymer Korea, volume 24, issue 3, 2000, Pages 418~430
A new hydroxylpropyl chitosan (HPCTO) capable of forming both thermotropic and lyotropic liquid crystalline phases was synthesized by reaction of alkali chitosan with propylene oxide and its solid films cross-linked with glyoxal were prepared by casting the liquid crystalline solution in methanol. The thermal and swelling properties of the cross-linked films were investigated. The films displayed fingerprint patterns characteristic of cholesteric liquid-crystalline phase, and their pitches increased with increasing temperature and cross-linker concentration. The cross-linked samples exhibited an anisotropic swelling in both water and methanol, suggesting that the two-dimensional cross-linking preferentially performs between HPCTO molecules. The degree of anisotropy highly depended on the solvent, but hardly on the cross-linker concentration investigated.
Synthesis and Characterization of Poly(lactic-co-mandelic acid)s by Direct Solution Polycondensation
Polymer Korea, volume 24, issue 3, 2000, Pages 431~436
To improve the thermal and mechanical properties of homo poly(L-lactic acid), DL-mandelic acid, one of the natural
-hydroxy acid with aromatic ring as the side-chain residue was used as the comonomer. Copolymers with different contents of mandelic acid were prepared and characterized. The resulting copolymers were mostly amorphous. As the amount of mandelic acid in the monomer feed increased, the molecular weight of the resulting polymers tended to decrease linearly. T
of the copolymer, however, were found to shift toward higher temperature, suggesting the improved thermal stability by increasing content of mandelic acid moiety. Tensile measurements of cast films showed somewhat improved values in the copolymers with mandelic acid content of 5 and 10 wt%.%.%.