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고분자 나노복합소재 내의 그래핀 나노입자 분산성에 대한 유변학적 평가
하진수,송예은,주양율,황정민,윤지선,이두진 한국섬유공학회 2021 한국섬유공학회지 Vol.58 No.1
The dispersibility of nanoparticles in polymer nanocomposites significantlyaffects the mechanical, thermal, and electrical properties of the final products. The objectiveof this study is to quantify the dispersibility of nanoparticles in polymer nanocomposites. Various amounts of graphene nanoparticles were introduced in polypropylene-basedand polylactic acid-based resins through melt compounding. They were then injectionmoldedto fabricate disc-type specimens for characterizing the rheological properties ofthe nanocomposites. To evaluate the dispersibility of the nanoparticles in the composites,the associated storage (G’) and loss (G’‘) moduli were analyzed for plotting the G’-G’‘ slopes. Furthermore, the Van Gurp-Palmen plot was employed for analyzing the increase in materialelasticity with respect to the base resins and nanoparticle compositions.
하진수,김현우,이두진 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.2
For ceramic 3D printing, stereolithography (SLA) enables more precise fabrication of ceramic suspensions than other 3D printing methods. For densely-packed ceramic based 3D materials, the dispersion stability of ceramic particles in suspensions is important. As a simple method to improve dispersion stability in polymer matrix, surface modification of inorganic nanoparticles is widely used. The silane coupling agent which is a useful surface modifier has two functional groups, an inorganic group generates hydrolysis and forms a silane-functionalized surface in inorganic materials, and an organic group improves dispersion stability by forming the interpenetrating networks (IPNs). In this work, we modified several types of ceramic nanoparticles (NPs) with a vinyltriethoxysilane (VTES) and prepare ceramic nanoparticle reinforced nanocomposites. The enhanced dispersity was quantitatively evaluated using rheological methods, dynamic light scattering, and morphology observation.
유한요소법을 이용한 자동차용 조향 샤프트의 냉간 압출 공정 해석
하진수(J. S. Ha),예상돈(S. D. Ye),허관도(K. D. Hur) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.10
The steering shaft is located in the steering system. The shaft transmits the direction of rotation of handle to the gearbox. The cold forged product should be avoided the forging defect such as chevron crack. Therefore, analysis of the design variables is needed in the extrusion process. In this paper, finite element method was used in extrusion process of the shaft of steering system. Design variables such as angle of die, corner radius and length of die, corner radius and length of die land are used for analysis, and variables are analyzed by Taguchi method. The optimization of design variables had been performed to minimize the damage factor occurred during extrusion process.