• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2005년도 춘계학술대회 논문집
• /
• pp.113-116
• /
• 2005

In this paper, a computational and experimental analysis about the flow behavior of thin polymer film in the spin coating process for stable cover layer coating of a blu-ray disc is described. The blu-ray disc, a next-generation optical disc format over 25GB, consists of a 1.1mm thick substrate and a 0.1mm tick cover layer. Generally, cover layer on the blu-ray disc is made by the polymer spin coating process. However, it is hard to secure sufficient coating uniformity around the rim on the cover layer. In order to get the uniform thickness deviation and to minimize the bead around the rim, the edge of the disc substrate can be modified into various shapes around the rim on the disc and analyzed with various parameters, such as surface tension, viscosity, and rotation speed, etc. The optimal shape of the rim was tried to get by 3 dimensional computer simulation of the polymer expulsion process.

• Korean Chemical Engineering Research
• /
• 제52권6호
• /
• pp.701-705
• /
• 2014

본 연구에서는 꾸지뽕나무의 뿌리, 줄기, 열매 및 잎으로부터 유효성분을 열수 추출하고 다양한 화장품 소재 시험을 실시하여 화장품 소재로서의 개발 가능성을 검토하였다. 세포독성시험에서 꾸지뽕나무의 뿌리, 줄기 그리고 열매 추출물은 독성을 나타내지 않았지만 잎 추출물은 $200{\mu}g/ml$ 이상의 농도에서 다소의 독성을 나타내었다. 꾸지뽕나무 뿌리추출물은 $500{\mu}g/ml$의 농도에서 81%의 tyrosinase 억제효과(미백효과)와 58%의 elastase 억제효과(주름개선효과)를 나타내었고, UVB 자외선 흡수능도 다소 보여주었다. 21일간의 온도 안정성 시험 결과, 꾸지뽕 뿌리 추출물을 포함한 액제와 로션제형은 $25^{\circ}C$에서는 안정하였으나 $47^{\circ}C$에서 점도와 입자크기가 불안정하였다. 본 연구 결과 꾸지뽕 뿌리추출물은 높은 폴리페놀 및 플라보노이드의 함량, 우수한 미백 및 주름개선 효과를 나타내어 천연 기능성 화장품 소재로서 높은 가능성을 보여주었다.

• Macromolecular Research
• /
• 제12권2호
• /
• pp.246-250
• /
• 2004

We have classified a number of aqueous ternary systems containing two different polymers into three types by focusing on the deviation of the Huggins constant k'from the additivity line. Systems of type I have negative deviations of k'; the repulsive interaction between the two different polymers dominates. In systems of type II, k' almost follows the additivity relation; the repulsive and attractive interactions between the two different polymers are balancing. Type III systems have positive deviations of k'; the attractive interactions are relatively dominant. This classification of systems is supported by the fact that the positive and negative deviations of k' from the additivity line also correspond to the sign of interaction parameter between polymer 2 and 3, Δb$\_$23/. Furthermore, we have verified the relatively high compatibility between dextran and poly(vinyl alcohol) by determining the binodal concentration of a liquid-liquid phase separation for a water/dextran/poly(vinyl alcohol) system, which is classified as type III. Thus, we found that the compositional dependence of k' closely relates to the compatibility of binary polymer mixtures in aqueous ternary systems.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집B
• /
• pp.83-89
• /
• 2000

This paper presents a pressure drop correlation for evaporation and condensation of alternative refrigerant with oil in micro-fin tubes. The correlation was developed from a data base consisting of oil-free pure and mixed refrigerants in micro-fin tube; Rl25 R134a. R32 R410a(R32/R125 50/50% mass), R22, R407c(R32/R125/R134a, 23/25/52% mass) and R32/R134a(25/75% mass). The micro-fin tube used in this paper had 60 0.2mm high fins with a 18 helix angle. The cross sectional flow area $(A_c)$ was $60.8 mm^2$ giving an equivalent smooth diameter$(D_e)$ of 8.8mm. The hydraulic diameter $(D_h)$ was estimated to the 5.45mm. The new correlation was obtained by replacing the friction factor and the tube-diameter in Bo Pierre correlation by a friction factor derived from pressure drop data for a micro-fin tube and the hydraulic diameter, respectively. This correlation was also used to predict some pressure data with a lubricant after using a mixing viscosity rule of lubricants and refrigerants. As a result, the new correlation was also well predicted to the measured data within a mean deviation of 19.0%.

• 한국진공학회지
• /
• 제14권3호
• /
• pp.143-146
• /
• 2005

본 연구에서는 결맞는 x-선을 이용하여 표면의 거동 현상을 관찰할 수 있는 새로운 실험 방법인 x-선 상관 분광법(x-ray photon correlation spectroscopy)을 소개하고 이를 이용하여 측정한 고분자 박막에서의 거동 현상에 대한 결과를 보고하고자 한다. 이 방법은 파장이 짧은 x-선 영역에 동역학 광산란(dynamic light scattering) 원리를 적용하여 나노 스케일의 동역학 현상을 관찰할 수 있다. 또한 x-선 산란을 이용하므로 동역학 현상과 동시에 구조 특성을 측정할 수 있다. 본 논문에서는 글래스 전이보다 높은 온도에서, 기판에 코팅된 고분자 박막의 표면 거동현상을 온도와 파수의 함수로 측정하였다. 박막의 두께가 두꺼울 때에는 점성이 높은 액체에서와 계산된 이론에서와 같은 표면 거동 현상이 관찰되었고, 얇은 박막에서는 갇힘 현상에 의한 효과를 관찰하였다.

• 폴리머
• /
• 제28권6호
• /
• pp.460-467
• /
• 2004

폐폴리(염화 비닐) 수지 [waste poly(vinyl chloride), RPVC]와 폐폴리에틸렌 수지 (waste polyethylene, RPE)를 용융 블렌드하여 이들의 형태학적 특성과 유변학적 성질을 관찰하였다. 대수 가감 법칙 (Log additivity rule)으로 계산된 값과 측정된 토크 변화를 비교해보면, 고분자 블렌드는 서로 비상용성을 나타내는 음의 편차 거동을 보였다. 평형판 레오미터와 모세관 레오미터를 사용하여 측정한 블렌드의 유변학적 성질은 용융 상태에서 전단 속도가 증가함에 따라 전단 점도가 감소하는 경향을 보였다. RPVC/RPE 블렌드에 상용화제를 첨가하면 단순 블렌드보다 전단 점도가 증가하였으며 이는 상용성이 증가하여 분산상 크기가 감소하는 것을 확인하였다. 전단 점도 측정 후 얻은 시료를 전자 현미경으로 관찰해 보면 전단속도가 증가함에 따라 분산상의 크기가 약간씩 커지는 것이 관찰되었고 또한, 시료의 표면층보다 내부의 분산상이 커지는 것이 관찰되었다.

• 설비공학논문집
• /
• 제7권3호
• /
• pp.435-449
• /
• 1995

In this paper, pressure drop through a capillary tube is modeled to determine the length of a capillary tube for a given set of conditions. HCFC-22 and its alternatives, HFC-134a, R407B, and R410A are used as working fluids. The conditions on which the model is tested are as follows : condensing temperature; 40.0, 45.0, 50.0, $55.0^{\circ}C$, degree of subcooling;0.0, 2.5, $5.0^{\circ}C$, capillary tube exit condition;choked flow, capillary tube diameter;1.2~2.4mm, mass flow rate;5.0~50.0g/sec. The results justify the use of Stoecker's model which yields the results very close to the values in ASHRAE handbook. While McAdams' method yields much better results than Duckler's in calculating the viscosity of the fluid in 2-phase, the friction factor suggested by Stoecker seems to be the best for capillary tubes of large diameter used in residential air conditioners. For each refrigerant, 372 data with various variables are calculated by the model. The results show that capillary tube length varies very uniformly with changes in condensing temperature and degree of subcooling. Based on this fact, regression analysis is performed to determine the dependence of mass flow rate on the length and diameter of a capillary tube, condensing temperature, and degree of subcooling. Thus determined correlation yields a mean deviation of 2.36% for 1,488 data, showing an excellent agreement.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 제38회 하계학술대회
• /
• pp.1542-1543
• /
• 2007

This paper presents the effect of driving waveform for piezoelectric bend mode inkjet printhead with optimized mechanical design. Experimental and theoretical studies on the applied driving waveform versus jetting characteristics were performed. The inkjet head has been designed to maximize the droplet velocity, minimize voltage response of the actuator and optimize the firing frequency to eject ink droplet. The head design was carried out by using mechanical simulation. The printhead has been fabricated with Si(100) and SOI wafers by MEMS process and silicon direct bonding method. To investigate how performance of the piezoelectric ceramic actuator influences on droplet diameter and droplet velocity, the method of stroboscopy was used. Using the water based ink of viscosity of 11.8 cps and surface tension of 0.025N/m, it is possible to eject stable droplets through 64 nozzles average velocity of 4.05 m/s with standard deviation of 0.06 m/s and average diameter of $29.2\;{\mu}m$ with standard variation of $0.5\;{\mu}m$.

• 폴리머
• /
• 제26권5호
• /
• pp.559-567
• /
• 2002

Poly (vinyl chloride) (PVC)와 vinyl chloride(VC)/acrylonitrile(AN) 함량비에 따른 poly-(VC-co-AN)와의 블렌드 필름을 제조하여 morphology, 점도, 동적 점탄성 및 기계적 물성을 고찰하였다. 블렌드의 morphology는 전반적으로 matrix-domain 형태의 비상용계로 공중합체에서 VC 함량이 증가할수록 morphology는 다소 균일하였다. 특히 VC 함량이 77.21%인 MO-01 블렌드의 경우 PVC가 많은 영역에서 상용성은 우수하였다. 블렌드 용액의 점도는 전반적으로 비상용성으로 인하여 negative deviation을 보이나, MO-01 블렌드에서 PVC 함량이 90%일 때 급격한 점도의 증가를 보였으며, 저장탄성율 및 T$_{g}$ 거동에서 MO-01 블렌드의 경우 상용성 블렌드의 T$_{g}$ 변화와 경향이 유사하였으나 MO-02 및 MO-03의 경우 비상용성 블렌드의 경향을 나타내었다. PVC와 poly(VC-co-AN)의 블렌드에서 VC의 함량이 가장 높은 MO-01와 90:10인 조건에서의 상용성이 가장 뛰어났으며, 블렌드 필름의 기계적 물성의 향상은 발견할수 없었다.

• 한국재료학회지
• /
• 제31권9호
• /
• pp.532-538
• /
• 2021

In this study, a spray dryer is used to make granules of Y₂O₃ and YF₃, and then Y₅O₄F₇ is synthesized following heat treatment of them under Ar gas atmosphere at 600 ℃. Single and binary monomer mixtures are compared and analyzed to optimize photocurable monomer system for DLP 3D printing. The mixture of HEA and TMPTA at 8:2 ratio exhibits the highest photocuring properties and low viscosity with shear thinning behavior. The optimized photocurable monomer and synthesized Y₅O₄F₇ are therefore mixed and applied to printing process at variable solid contents (60, 70, 80, & 85 wt.%) and light exposure times. Under optimal light exposure conditions (initial exposure time: 1.2 s, basic exposure time: 5 s), YOF composites at 60, 70 & 80 wt.% solid contents are successfully printed. As a result of measuring the size of the printed samples compared to the dimensions of the designed bar type specimen, the deviation is found to increase as the YOF solid content increases. This shows that it is necessary to maximize the photocuring activity of the monomer system and to optimize the exposure time when printing using a high-solids ceramic slurry.