• Korean Journal of Metals and Materials
• /
• v.49 no.5
• /
• pp.362-366
• /
• 2011

Aluminosilicate inorganic polymer binder has been studied as an alternative to ordinary Portland cement due to its higher physical properties, chemical resistance and thermal resistance. This study has been carried out in an attempt to understand the hardening characteristics of aluminosilicate binder by varying the content of calcium. Samples with four different ratios of Al, Si, and Ca were synthesized in this study with the Al:Si:Ca mol ratio being 1.00:1.85~1.98:0.29~2.12. Furthermore, an alkali silicate solution was prepared with the sodium hydroxide (NaOH) and sodium silicate (NaSi). The hardening characteristics of the specimens were analyzed using XRD, SEM, and TG/DTA. In addition, compressive strength and sintering time of specimens were measured as a function of calcium content. The results showed that the specimen containing 2.12 mol% calcium offered the highest compressive strength. However, the compressive strength of the specimen containing 0.26 mol% calcium was lower relative to the other specimens. The results displayed a distinct tendency that as more calcium was added to the inorganic polymer, setting time became shorter. When calcium was added to the inorganic polymer structure, a second phase was not formed, indicating that the addition of calcium does not affect the crystalline structure.

• Macromolecular Research
• /
• v.8 no.1
• /
• pp.44-52
• /
• 2000

Styrenic macromonomers with/without a silyloxy-functional group were synthesizedvia chain-end functionalization using 4-vinylbenzyl chloride as a terminating agent insec-butyllithium-initiated polymerization of styrene. The yields were 92 mol% for the silyloxy group and 88 mol% for the styrenic unit. Crystalline polystyrene-g-amorphous polystyrenes were synthesized by (η$^{5}$ -indenyl)-trichlorotitanium ((Ind)TiCl$_3$)-catalyzed copolymerizations of the macromonomers with styrene in the presence of methyl-aluminoxane (MAO) in toluene at 4$0^{\circ}C$. The macromonomer having $\alpha$, $\alpha$'-bis (4-[tert-butyldimethylsilyl-oxy]phenyl) group was also utilized for the preparation of a precursor of hydroxyl-functionalized syndio-tactic polystyrene. The obtained polymers were characterized by a combination of$^1$H, $^{13}$ C NMR spectroscopic, size exclusion chromatographic, and differential scanning calorimetric analysis. The (Ind)TiCl$_3$-catalyzed copolymerization of styrene with the macromonomer carrying the silyloxy functional group was found to be an efficient method to modify syndiotactic polystyrene without a great loss of physica] property by controlling the feud ratio of the macromonomer.

• Journal of Pharmaceutical Investigation
• /
• v.38 no.4
• /
• pp.249-254
• /
• 2008

Solid dispersions of poorly water-soluble drug, atorvastatin, were prepared with Eudragit L100 to improve the solubility by spray dryer. To investigate the correlation between physicochemical properties and dissolution rate of solid dispersions, the samples were characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and fourier transform infrared spectroscopy (FT-IR). SEM and DSC were found that atorvastatin is amorphous in the Eudragit L100 solid dispersion. FT-IR was used to analyze the salt formation by interaction between atorvastatin and Eudragit L100. The dissolution rate of solid dispersed atorvastatin was markedly increased compared to drug powder in stimulated intestinal juice (pH 6.8). Thus, the solid dispersed atorvastatin using the spray drying method with Eudragit L100 may be effective for the bioavailability.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.1367-1370
• /
• 2005

Microcellular foam processing of polymers requires a nucleated cell density greater than $10^9\;cells/cm^3$ so that the fully grown cells are smaller than 10 mm. A microcellular foam can be developed by first saturating a polymer sample with a volatile blowing agent, followed by rapidly decreasing its solubility in the polymer. In general, the cellular structure of crystalline polymer foams is difficult to control, compared to that of amorphous polymer foams. Since the gas does not dissolved in the crystallites, the polymer/gas solution formed during the microcellular processing is nonuniform. Moreover, the bubble nucleation is nonhomogeneous because of the heterogeneous nature of the crystalline polymer. In this paper, the effects of the crystallinity and morphology of crystalline polymers on the microcellular foam processing and on reflectivity of products are investigated. First, polymer specimens with various morphology and amount of solved blowing agent were prepared by varying the saturation pressure, saturation time and foaming condition. Then, cell morphologies according to several conditions were studied. The specimens with differing gas amount of solved and morphologies were foamed and their cellular structures were compared. The experimental results of reflectivity are compared to raw specimen and another specimen of different experimental conditions. After the experiments, recognize whether how reflectivity changes according to solved gas amount. And the effect of cell density and cell size on reflectivity is studied

• Elastomers and Composites
• /
• v.47 no.4
• /
• pp.282-291
• /
• 2012

Control of shape/volume, mechanical, optical, electrical, and chemical switching of materials by external stimuli such as light, temperature, pH, electric field, and pressure has attracted great attention. Among these materials, photo-responsive materials containing photochromic compounds such as azobenzene, spiropyran, and cinnamic acid groups have been the subject of intense interest in recent years. In this review, we describe the recent progress in the area of azobenzene containing polymer materials that can convert light energy into mechanical energy directly. Especially we focus our attention on light-driven actuators such as artificial muscle, motor, and valve. We summarize the photomechanical effects in liquid crystal elastomer, amorphous polymer, monolayer, and supramolecules containing azobenzene, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.8
• /
• pp.5074-5081
• /
• 2015

A method for improving the warpage of the plastic part is a method of removing residual stress of the plastic product. that a non-uniform cooling are appeared in the injection molding process make uniform cooling. this study was developed the Rapid heating and cooling device used peltier module for uniform cooling. Make the Rapid heating and cooling device(RCHD), for Traditional water cooling device(TWCD) method and the Rapid heating and cooling method warpage were compared and were analyzed and the materials used amorphous ABS polymer. various warpage were compared for the process parameters such as packing pressure, packing time, resin temperature, mold temperature, In the amorphous ABS polymer, TWCD method has higher warpage than RCHD method and show the result to be a bit more uniform cooling. The distribution state of the ABS polymer was confirmed Through the Scanning electron microscope. In the TWCD method the distribution state of the polymer be densely distributed, and RCHS method be distributed wider than TWCD method. this is that injection molded parts be seen that cooling was made uniformly, As the temperature of the mold is gradually progress, Particles of the polymer is increased this is that internal stress was reduced.

• Composites Research
• /
• v.36 no.4
• /
• pp.270-274
• /
• 2023

The stacking configuration of fiber-reinforced polymer (FRP) composites, achieved via the filament winding process, exhibits distinct variations compared to conventional FRP composite stacking arrangements. Consequently, it becomes challenging to ascertain the influence of mechanical properties based on the typical stacking structures. Thus, it becomes imperative to enhance the mechanical behavior and optimize the interleaved structures to improve overall performance. Therefore, this study aims to investigate the impact of incorporating amorphous halloysite nanotubes (A-HNTs) within different layers of five unique layer arrangements on the low-velocity impact properties of interleaved carbon fiber-reinforced polymer (CFRP) structures. The low-velocity impact characteristics of the laminate were validated using a drop weight impact test, wherein the resulting impact damage modes and extent of damage were compared and evaluated under microscopic analysis. Each interleaved structure laminate according to whether nanoparticles are added was compared at impact energies of 10 J and 15 J. In the case of 10 J, the absorption energy showed a similar tendency in each structure. However, at 15 J, the absorption energy varies from structure to structure. Among them, a structure in which nanoparticles are not added exhibits the highest absorption energy. Additionally, various impact fracture modes were observed in each structure through optical microscopy.

• Applied Chemistry for Engineering
• /
• v.29 no.6
• /
• pp.740-745
• /
• 2018

The synthesis and characterization of amorphous calcium phosphate (ACP) nanoparticles were reported in this work. We show that relatively monodisperse ACP nanoparticles with a size of sub-100 nm can be prepared by a hydrothermal reaction of calcium chloride ($CaCl_2$) and disodium adenosine triphosphate ($Na_2ATP$) in the presence of sodium phytate as an additive. Their compositions and structures were confirmed using a series of material characterization techniques. Our results exhibit that ACP nanoparticles synthesized using sodium phytate enhanced the stability of maintaining their amorphous nature and prevented from a conversion to crystalline hydroxyapatite (HAP). ACP nanoparticles with the improved stability have potential uses in biomaterial applications in regenerative medicine.

• 전기의세계
• /
• v.34 no.11
• /
• pp.696-701
• /
• 1985

glow나 arc방전에 의해서 생기는 플라즈마는 고융점을 갖는 refractory금속이나 superalloy의 용해, 제조에 이용되며, 플라즈마를 이용한 repid solidification방법은 amorphous metal이나 suepralloy제조에 이용되는 최신의 방법이다. 또한 기상반응을 이용해서 신소재로써 관심이 증대되고 있는 fine ceramics나 polymer를 만들수 있고, 높은 강도와 내마모성이 요구되는 금형, 절삭공구, 베어링, 치차부품의 표면에 질화막이나 TiC, TiN의 박막을 입히는데 이용될 수 있다. 플라즈마를 이용한 방법의 피처리물이 저온으로 유지될 수 있고, 에너지소비가 적은 점등의 여러가지 장점이 있어서 앞으로 이용이 활발해지리라고 생각되며 플라즈마의 기본성질의 이해가 성공적인 이용의 첫걸임을 부언하고 싶다.

• Design & Manufacturing
• /
• v.8 no.1
• /
• pp.23-26
• /
• 2014

The injection molding is used in more than 70% of total production of plastic products. Weld line in injection molded part is one of the defects in injection molding process. Weld line deteriorates not only appearance quality but also mechanical property. In this study weld quality has been examined according to the injection processing temperature, materials and mold designs. We selected four different materials such as PA, PP, ABS and PS as experimental materials. Weld quality increased as injection processing temperature increases. It was more dependent on materials flow ability. As a result, weld quality incase of rectangular core is better than circular core.