• Macromolecular Research
• /
• 제13권1호
• /
• pp.73-79
• /
• 2005

Poly(L-lactic acid-co-succinic acid-co-l,4-butane diol) (PLASB) was synthesized by direct condensation copolymerization of L-lactic acid (LA), succinic acid (SA), and 1,4-butanediol (BD) in the bulk using titanium(IV) butoxide as a catalyst. The weight-average molecular weight ofPLASB was $2.1{\times}10^{5}$ when the contents of SA and BD were each 0.5 mol/100 mol of LA. Electrospinning was used to fabricate porous membranes from this newly synthesized bioabsorbable PLASB dissolved in mixed solvents of methylene chloride and dimethylformamide. Scanning electron microscopy (SEM) images indicated that the fiber diameters and nanostructured morphologies of the electrospun membranes depended on the processing parameters, such as the solvent ratioand the polymer concentration. By adjusting both the solvent mixture ratio and the polymer concentration, we could fabricate uniform nanofiber non-woven membranes. Cell proliferation on the electrospun porous PLASB membranes was evaluated using mouse fibroblast cells; we compare these results with those of the cell responses on bulk PLASB films.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2002년도 춘계학술대회 논문집
• /
• pp.22-27
• /
• 2002

The existing compressor steel seal used in automotive air-conditioner has the problem of oil leakage and the deterioration in shielding performance, due to the abrasion and the corrosion of the material. A new type of polymer resin seal is studied in the research. The polymer resin seal has the characteristics of high anti-abrasiveness and anti-corrosiveness, which can overcome the deflects of the steel seal. In addition, the seal needs lower manufacturing cost and is appropriate to mass production, because it is made by the injection molding method requiring no mechanical processing. The profile generation program for seal mold has been developed using the gradient method, and the molding characteristics of the seal have analyzed through the flow analysis and the warpage analysis. The program has been verified by comparing the analysis results with the measured data of the test product. The research might be said to provide the basic method to produce the polymer resin seals with various types and dimensions.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
• /
• pp.18-18
• /
• 2003

Natural clays are composed of oxide layers whose thickness is about 1nm and cations existing between the layers. A number of these layers makes primary particles with a height of about 8∼10nm and these primary particles make aggregates with a size of about 0.1∼10$\mu\textrm{m}$. When layered silicate was made to be organophilic, by exchanging the interlayer cations with organic cationic molecules, the matrix polymer can penetrate between the layers to give a nanocomposite, where 1nm-scal clay layers exist separately in a continuous polymer matrix. These nanostructured hybrid organic-inorganic composites have attracted the great interest of researchers over the last 10 years. They exhibit improved performance properties compared with conventional composites, because their unique phase morphology by layer intercalation or exfoliation maximizes interfacial contact between the organic and inorganic phases and enhances interfacial properties. Since the advent of nylon-6/montmorillonite nanocomposite developed by Toyota Motor Co., the studies on layered silicate-polymer nanocomposites have been successfully extended to other polymer systems. They greatly improved the thermal, mechanical, barrier, and even the flame-retardant properties of the polymers.

• Journal of Microbiology and Biotechnology
• /
• 제12권6호
• /
• pp.957-961
• /
• 2002

The hypolipidemic effect of exe-polymer produced in submerged mycelial culture of Hericium erinaceus (HE), Auricularia auricula-judue (AA), Flammulina veluripes (FV), Phellinus pini (PP), and Grifola frondosa (GF) was investigated in dietary-induced hyperlipidemic rats. The animals were administered with exe-polymers at the level of 100 mg/kg body weight daily for four weeks. Hypolipidemic effect was achieved in all the experimental groups, however, HE exo-polymer proved to be the most potent one, which significantly reduced the plasma triglyceride ($28.9\%$), total cholesterol ($29.7\%$), low-density lipoprotein (LDL) cholesterol ($39.6\%$), phospholipid ($16.0\%$), and liver total cholesterol ($28.9\%$) level, when compared to the saline administered (control) group. The results of the present investigation strongly demonstrate the potential of HE exe-polymer in combating hyperlipidemia in the experimental animals.

• 세라미스트
• /
• 제23권1호
• /
• pp.4-15
• /
• 2020

The recent advances and popularity of 3D printing technology have centered around building polymerbased 'plastic' materials, due to their low cost, simple and efficient processing, and mechanical toughness. For this reason, printable polymers are actively recruited to create 'ceramic resins' that allow more facile fabrication of ceramic materials that are difficult to print directly. Herein, a brief history and the current state of ceramic 3D printing technology aided by polymer is summarized. In addition, a new ceramic 3D printing technology using polymer-derived ceramics (PDC) is also introduced.

• 대한기계학회논문집A
• /
• 제32권5호
• /
• pp.419-423
• /
• 2008

A new polymer replication technology using ultrasonic vibration is proposed and demonstrated. A commercial ultrasonic welder has been used in this experiment. Two different types of nickel molds have been fabricated: pillar type and pore type microstructures. Polymethyl methacrlylate (PMMA) has been used as the replication material and the optimal molding time was 2 sec and 2.5 sec for pillar-type and pore-type micromolds, respectively. Compared with the conventional polymer micromolding techniques, the proposed ultrasonic micromolding technique has the shortest processing time. In addition, only contact area between micromold and polymer substrate is melted so that the thermal shrinkage can be minimized. The fabricated PMMA microstructures have been very accurately replicated without vacuum. The proposed ultrasonic molding technique is a good alternative for high volume production.

• 반도체디스플레이기술학회지
• /
• 제11권4호
• /
• pp.7-12
• /
• 2012

Extrusion is one of the most important operations in the polymer-processing industry. Development of models for extrusion and computer tools offer a route to developing reliable and optimized process designs. The models are based on the analysis of physical phenomena encountered during the process. Balance equations for mass, momentum and energy are fundamental to the problem. A predictive computer model has been developed for the single screw extruders with conventional screws of different geometry. The model takes into account melting zones of the extruder and describes an operation of the extruder system, making it possible to predict mass flow rate of the polymer, pressure and velocity profiles along the extruder screw channel. The simulation parameters are the material and rheological properties of the polymer; the screw pitch, and screw speed.

• 폴리머
• /
• 제37권2호
• /
• pp.156-161
• /
• 2013

페놀계 산화방지제는 가공 및 사용 시 열분해를 방지함으로써 뛰어난 열 안정성을 제공하는 대표적인 1차 산화방지제이다. 그러나 NOx 가스를 포함한 특정 환경에 의해 황변이 일어나기 쉽기 때문에 2차 산화방지제를 추가로 도입하여 시너지효과를 기대하는 경우가 많다. 열에 취약한 비결정성 폴리알파올레핀 수지(APAO)에 여러 가지 페놀계 1차 및 2차 산화방지제를 도입하여 황변 여부를 조사한 결과 2차 산화방지제의 함량이 증가할수록 황변이 줄어들었으며 BHT와 같은 단순 구조의 폐놀계 산화방지제보다 긴 알킬 사슬을 도입시켜 입체장애효과를 증대시킨 산화방지제가 2차 산화방지제와의 시너지 효과가 더 큰 것으로 확인되었다.

• Elastomers and Composites
• /
• 제44권4호
• /
• pp.401-407
• /
• 2009

용액중합 스티렌-부타디엔 고무 컴파운드 가교체의 균열저항성 및 마모특성에 미치는 공정오일의 영향을 조사하기 위해 방향족 고리화합물(PCA) 성분을 다량 함유하고 있는 방향족 오일과 저 PCA 오일을 선택하였다. 인장강도 및 인열강도 결과에 의하면 방향족 오일함유 컴파운드가 저 PCA 오일함유 컴파운드에 비해 우수한 물성을 나타내었다. 또한 방향족 오일함유 컴파운드가 균열저항성이 월등히 우수하였고, 특히 인열에너지가 낮은 범위에서 더 우수한 결과를 나타내었다. 마모저항특성은 마찰에너지가 낮은 범위에서는 방향족 오일함유 컴파운드가 우수한 결과를 나타낸 반면, 높은 마찰에너지 범위에서는 저 PCA 오일 함유 컴파운드가 오히려 높은 저항성을 나타내었다.

• Design & Manufacturing
• /
• 제8권1호
• /
• 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.