• Journal of the Korean Wood Science and Technology
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• 제22권1호
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• pp.85-90
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• 1994

The flow properties of binder latices for paper coating were investigated, together with dynamic viscoelastic properties of latex films and electron micrographs of latices, under various conditions. The amphoteric latex, binder pigment latex and anionic latex were used in this work. The amphoteric latex has both anionic and cationic functional group on its surface. The binder-pigment with a core-shell structure has dual functions : plastic pigment and binder. The low shear viscosity of binder latices and clay slurry were measured with Brookfield vis cometer. At low-shear rates. the viscosity decreased with increasing particle size of latex. On the amphoteric latex surface, the carboxyl groups are assumed to be fully dissociated over the region of pH 9~12, but the density of negative groups seems to be increased because of the gradual decrease in the degree of dissociation of amino groups. Since the apparent particle size of latex increases with surface charge, the electroviscous effect can be observed. On the anionic latex surface, the charge density is assumed to be nearly constant above pH 8. However, below pH 8 the coagulation of particles could be observed probably because of the decrease in the charge density.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.49-52
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• 2006

Extrusion concrete panel is made by extrusion of high viscosity paste. The high viscosity paste is made by mix of cement, silica, reinforced fiber and thickening agent in the dry mixer and wet mixer subsequently, extrusion in the extruder, and curing in the normal steam curer and high pressure steam curer subsequently. To increase a flexural strength of the panel, it is used inorganic fiber as like asbestos. But it was known that the asbestos was harmful to human being lately, in the domestic area it is restricted usage in the construction materials. So, it is demanded the alternative material for asbestos in the extrusion concrete panel. This study is to investigate that the sepiolite is possible to be the alternative of asbestos. The 3 types of sepiolite is applied to the extrusion concrete panel. To investigate the properties of the panel with sepiolite, it is compared the control with asbestos in the flexural strength, the specific density and the spot compressive strength. From the test results, it was found that the panel with sepiolite B is higher than the control with asbestos in the flexural strength and in the density.

• 한국염색가공학회지
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• 제31권3호
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• pp.177-186
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• 2019

In this study, we investigated for synthetic hydrotalcite in chloroprene rubber foam. Experiments were carried out to find the optimum content ratio by controlling the contents of MgO and Hydrotalcite. Swelling test in toluene immersion was made to measure the crosslinking density of CR foams, and the cure properties were investigated with flat die rheometer and Mooney viscosity. The difference of hardness, tensile strength and elongation at break were observed after immersing in 7% NaCl or 21% NaCl solutions for a day and four days. In addition, the volume change and water content remaining in CR foam were measured after immersing NaCl solution. As content of MgO increased, the value of the cure torque tended to increase, but it was almost constant above 2phr of MgO. However, the Mooney viscosity decreased with increasing MgO content. The crosslinking density, determined by the swelling ratio, showed that the CR compound without MgO showed a higher degree of swelling. When the content of hydrotalcite/MgO was 3:2, it was the lowest volume change of CR form. Also, As the content of hydrotalcite decreased, the difference of mechanical properties before and after immersion NaCl solution increased.

• 대한기계학회논문집
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• 제18권3호
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• pp.670-680
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• 1994

The thermophysical properties of Non-Newtonian fluid as the function of the temperature and the concentration are needed in many rheological heat transfer and fluid mechanics problems. The present work investigated the effects of the concentration and the temperature on the thermophysical properties of purely-viscous Non-Newtonian fluids such as the isobaric thermal expansion coefficient, density, zero-shear-rate viscosity, and zero-shear-rate dynamic viscosity within the experimental temperature range from $25^{\circ}C$ to $55^{\circ}C$. The densities of the test fluids were determined as the function of the temperature by utilizing a reference density and the least square equation for the measured isobaric thermal expansion coefficient. As the concentration of purely-viscous Non-Newtonian fluid was increased up to 10,000 wppm, the densities were proportionally increased up to 0.4%. The zero-shear-rate viscosities of test fluids were measured before and after the measurements of the first thermal expansion coefficients and the densities of Non-Newtonian fluid. Even though they were changed up to approximately 22% due to thermal aging and cycling, they had no effects on the thermal expansion coefficients and the densities of Non-Newtonian fluid. The zero-shear-rate dynamic viscosities for purely-viscous Non-Newtonian fluids were compared with the values for distilled water. They showed the similar trend with the zero-shear-rate viscosities due to small differences in the densities for both distilled water and purely-viscous Non-Newtonian fluid.

• Korean Chemical Engineering Research
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• 제47권2호
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• pp.157-162
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• 2009

본 논문은 소량 다품종 생산체계로 생산되는 정밀화학제품인 고품질 염료제조를 위한 고효율 염료결정화 분리기술에 대한 연구로써 염료 염석결정화계에서 염료의 물성과 최적조업조건에 대해 연구하였다. 먼저 염료의 물리적 특성을 알아보기 위해 밀도, 점도 등을 다양한 조건하에 측정하였다. 염료의 밀도는 물과 비슷한 특성을 보였으며, 염료 용액의 농도가 변화할 때, 밀도 변화는 거의 없었으며, 점도는 농도가 증가 할수록 증가했다. 염료 용액의 온도가 높아짐에 따라 밀도는 증가하였으나, 점도는 감소하였다. 또 염료의 용해도 실험 결과 20 wt% 염료 용액에 15 wt% KCl을 첨가하였을 때 염료결정의 생성량이 최대로 나타났다. 또한, 최적의 조업조건을 찾기 위해 다양한 변수(온도, RPM, 염첨가 방법 등)를 제어하여 시간에 따라 실험하였다. 15 wt% KCl과 20 wt% 염료용액으로 실험한 결과 최적의 조업조건은 $25^{\circ}C$, 100 RPM, 염을 한 번에 넣는 방법으로 나타났다. 또 최적 조업조건으로 실험을 수행한 결과 기존의 공정($35^{\circ}C$, 150 RPM)보다 생성량이 증가하였다. 따라서 최적화 공정을 찾음으로써 생성량 증가와 에너지 저감 효과가 기대된다.

• 한국산학기술학회논문지
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• 제15권3호
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• pp.1305-1310
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• 2014

MR 댐퍼는 자기장의 영향으로 인한 MR 유체의 응집현상으로 자기전단력을 발생한다. MR 유체는 기존유체와 자기입자로 구성되어 있다. 본 연구에서 밀도 1.3, 1.5, $1.7g/cm^3$ 그리고 점도 1,000, 10,000cP를 가지는 MR 유체 6종과 오리피스 형상 6종에 대한 MR 댐퍼의 댐핑력을 조사하였다. MR 유체의 밀도와 점도 변화에 따라서 MR 댐퍼의 댐핑력이 변하였다. 오리피스 형상변화에 대한 댐핑력은 오리피스 갭이 적고 길이가 짧을수록 크게 나타났다. 이들 연구결과로부터 MR 댐퍼의 최적설계를 위해서는 MR 유체의 선정과 오리피스 형상이 중요한 설계변수임을 확인하였다.

• 분석과학
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• 제21권3호
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• pp.159-166
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• 2008

본 연구에서는 water/oil 유화연료를 제조하여 제조된 연료의 점도, 밀도, 최적의 조사시간, 유화 안정성 등의 유화연료 특성 및 배기배출물 특성인 NOx, THC, CO의 농도와 smoke density를 측정하였다. 유화연료는 경유, 물, 유화제를 첨가한 후 homogenizer와 초음파 발생장치를 일정시간 조사하여 제조하였고, 배출가스 시험은 2476 cc diesel engine을 사용하여 engine dinamo meter로 실험하였다. 유화연료에서 함수율이 증가할수록 밀도가 증가하였으며, 점도는 함수율 60%까지는 W/O type이 형성되어 증가하다가 70%에서는 O/W type이 형성되어 감소하였다. 배출가스 시험결과 함수율이 증가할수록 NOx 농도와 smoke density는 감소하고, THC와 CO 농도는 증가하였다. 출력감소 시험 결과 함수율이 증가할수록 배출온도와 출력이 감소하였다. 위의 결과로부터 압축착화 디젤기관에 유화연료를 사용하는 것은 NOx와 smoke를 제거하는 효과적인 방법이라고 사료되어진다.

• 한국가금학회지
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• 제43권1호
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• pp.31-38
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• 2016

Consumers demand fresh and high-quality eggs. Egg quality may be represented by shell color, shell weight, egg weight, shell thickness, shell density, albumen height, yolk color, albumen pH and viscosity. Various factors such as strain, age of hen, storage temperature, humidity, the presence of $CO_2$ and storage time affect egg quality. Therefore, we investigated the effects of storage time and temperature on egg quality to define the freshness of Korean market eggs. A total of 1,800 eggs were used for this experiment and were separated into 45 treatments with 40 eggs in each. The treatments were consisted of 15 storage periods (2 d to 30 d) and 3 storage temperatures ($2^{\circ}C$, $12^{\circ}C$, $25^{\circ}C$). Each egg was weighed and broken, and the height of the thick albumen, Haugh units (HU), egg shell color and yolk color were measured by a QCM+system. We also observed the physiochemical properties of eggs such as yolk pH, albumen pH and albumen viscosity. The egg weight, shell weight, albumen height, HU and albumen viscosity significantly decreased with increasing storage time and temperature. However, the albumen and yolk pH significantly increased with increasing storage period and temperature. The interaction effects between the storage period and temperature were significant for shell weight, shell density, egg weight, albumen height, HU, yolk color, yolk pH, albumen pH and albumen viscosity. In the analysis of the correlation with egg quality, the storage temperature exhibited a higher correlation coefficient than the storage period. In conclusion, storage time and temperature are the major factors affecting egg quality, but the storage temperature is a more sensitive determinant of egg quality deterioration compared with the storage period.

• 한국세라믹학회지
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• 제56권4호
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• pp.360-364
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• 2019

PZT suspensions for photo-curable 3D printing were fabricated and their characteristics were evaluated. After mixing the PZT, photopolymer, photo-initiator, and dispersant for 10 min by using a high-shear mixer, the viscosity characteristics were investigated based on the powder content. To determine an appropriate dispersant content, the dispersant was mixed at 1, 3, and 5 wt% of the powder and a precipitation test was conducted for two hours. Consequently, it was confirmed that the dispersibility was excellent at 3 wt%. Through thermogravimetric analysis, it was confirmed that weight reduction occurred in the photopolymer between 120? and 500?, thereby providing a debinding heat treatment profile. The fabricated suspensions were cured using UV light, and the polymer was removed through debinding. Subsequently, the density and surface characteristics were analyzed by using the Archimedes method and field-emission scanning electron microscopy. Consequently, compared with the theoretical density, an excellent characteristic of 97% was shown at a powder content of 87 wt%. Through X-ray diffraction analysis, it was confirmed that the crystallizability improved as the solid content increased. At the mixing ratio of 87 wt% powder and 13 wt% photo-curable resin, the viscosity was 3,100 cps, confirming an appropriate viscosity characteristic as a stereolithography suspension for 3D printing.

• 폴리머
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• 제24권3호
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• pp.374-381
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• 2000

Polypropylene (PP)과 중간층이 유기성분으로 치환된 montmorillonite (org-MMT)의 복합체를 회분식 혼련기에서 용융혼련하여 org-MMT의 구조, 연속상의 점도, 그리고 혼련시간이 복합체의 상구조 형성에 미치는 영향에 대하여 고찰하였다. 혼련조건과 연속상의 점도가 일정할 때 PP사슬이 여러 가지 org-MMT의 중간층으로 삽입되는 정도는 org-MMT자체의 구조 인자에 의하여 결정되었다. 즉, 특정한 상호인력이 존재하지 않는 경우에는 삽입과정에 발생하는 고분자 사슬의 엔트로피 감소를 보충할 수 있는 환경의 조성이 필수적이며 이러한 조건은 최적의 중간층높이와 packing density가 유지될 때 만족되었다. 열역학적으로 삽입이 가능한 org-MMT의 분산 상태는 연속상의 점도가 증가할수록 호전되었으나 그렇지 못한 경우는 연속상의 점도상승이 분산상태의 향상을 유도하지 못하였다. 본 연구에서 고려된 PP/org-MMT 복합체들은 흔련 시간이 증가됨에 따라 뭉침 현상에 의하여 상구조가 변하는 불안정성을 나타내었다.