• Elastomers and Composites
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• 제34권5호
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• pp.414-422
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• 1999

방수재로 사용하는 EVA 에멀젼 수지에 라텍스 형태의 에폭시 수지, 우레탄 수지 SBR 수지를 전체 혼합물 중에 $0{\sim}50%$ 혼합하여 점성 및 경도 특성을 실험하였다. 시멘트 혼합물의 작업 가능한 한계점도는 20,000 cps이며 가사시간은 30분 이상으로 나타났다. 유색안료를 많이 혼합할수록 높은 점도를 나타내었고 시간경과에 따른 점도 상승폭도 컸다. SBR을 혼합하였을 때에는 경도가 크게 증가하였으나 에폭시 라텍스나 우레탄 라텍스를 혼합하였을 때에는 경도가 크게 증가하지 않았다. 시멘트 함량 30% 이상에서 경도가 크게 증가하였고 $50{\sim}60%$에서는 H이상의 높은 경도를 나타내었다. 고 충전시에는 라텍스의 융착보다는 시멘트 입자의 응집 및 응결에 의하여 경도가 높아졌다.

• Korea-Australia Rheology Journal
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• 제16권4호
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• pp.175-182
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• 2004

Colloidal coating solution was prepared to enhance the hydrophilic property of the film surface. Water and ethanol were used as the dispersion media and (glycidoxypropyl) trimethoxysilane (GPS) as a binder in the colloidal silica coatings. Ethylene diamine was added to the colloidal silica solution as the curing agent. The colloidal silica solution was regarded as a hard-sphere suspension model with low volume fraction of the silica particles. Rheological properties of the silica suspensions modified with GPS have been investigated as a function of pH and concentration. The acidic solution showed high viscosity change by fast hydrolysis reaction and adsorption of the organic binders on the surface of silica particles. However, the hydrolysis was slow at the basic condition and the binders combined with themselves by condensation. The viscosity change was smallest at pH 7. The viscosity increased with the curing time after adding ethylenediamine, and the increase of viscosity at low pH was higher than that at high pH. The hydrophilic properties of the coating film were investigated by the contact angle of water and film surface. The smallest contact angle was shown under the strong acidic condition of pH 2.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.152-157
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• 2003

This study represents the newly advanced formulation of hydraulic fluids for extended drain interval and introduces the performance results of used oil samples from various excavators. The used oil samples, in this paper show that there is a sharp change in viscosity drop and moderate additive depletion when viscosity index of hydraulic oil is very high. For the extension of hydraulic fluid life, it is necessary to improve the stability of viscosity and oxidation. New target properties from the used oil analysis were proposed for extended life. Performance of newly developed hydraulic oil based on used oil analysis is compared with previously used one. The properties of new formulation are the viscosity index of 140 and improved thermal stability consists of VHVI base oil. Field test results showed the possibility of extension of fluid life. Additionally, for development of high performance product, new required properties and performances were discussed.

• 전기화학회지
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• 제13권3호
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• pp.198-202
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• 2010

Lithium co-polyelectrolyte-ionic liquid systems, using poly (lithium 2-acrylamido-2-methyl propanesulfonate; PAMPSLi) and polyvinyl formamid (PVF) were prepared and their electrochemical and physical properties were measured. The conductivity of co-polymer systems, PAMPSLi/PVF/N, N-dimethyl-N-propyl-N-butylammonium tricyanomethanide (PAMPSLi/PVF/$N_{1134}$TCM) and PAMPSLi/PVF/N, N-dimethyl-N-propyl-N-butylammonium dicyanamide (PAMPSLi/PVF/$N_{1134}$DCA) exhibited low viscosity ($N_{1134}$TCM:$N_{1134}$DCA 28.6cP, 28.7cP) and higher conductivity ($2.48{\times}10^{-3}Scm^{-1}$, $2.2{\times}10^{-3}Scm^{-1}$) than homopolymer system. The ionic conductivity PAMPSLi/PVF/1-ethyl-3-methyl imidazolium dicyanamide (PAMPSLi/PVF/emImDCA) exhibited $1.54{\times}10^{-3}Scm^{-1}$ and low viscosity (emImDCA: 28.09cP). High flexibility of imidazolium cation and dissociation of lithium cation from the co-polymer chains were affected by high conductivity and low viscosity.

• 한국분무공학회지
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• 제16권3호
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• pp.140-145
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• 2011

Gelled propellants are non-Newtonian fluids in which the viscosity is a function of the shear rate, and they have a high dynamic shear viscosity which depends on the amount of gelling agent contents. The present study has focused on the breakup process, wave development of ligament and liquid sheets formed by impinging jets with various gelling agent contents. The breakup process of like-on-like doublet impinging jets are experimentally characterized using non-Newtonian liquids. The spray shape with elliptical pattern is distributed in a perpendicular direction to the momentum vectors of the jets. Gelled propellant simulants with high viscosity jets are more stable and produce less pronounced surface waves than low viscosity jets. Gelled propellant simulants from like-on-like doublet impinging jets have the spray shape of closed rim patterns at low pressure. As the injection pressure increased, rimless patterns which were composed of ligament sheets and small droplets emerged due to the effect of the aerodynamic action.

• Advances in concrete construction
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• 제13권5호
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• pp.395-410
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• 2022

This study collected the results of material tests and full-scale pumping tests using 127 types of concrete mixtures with compressive strength ranging from 24 to 200 MPa. The results of 242 material tests showed high correlations between the viscosity of the lubricating layer and concrete, between the slump and the yield stress of concrete, between the water-binder ratio and the viscosity of lubricating layer, and between the time required to reach 500 mm of slump flow and concrete viscosity. Based on these correlations, pumpability was predicted using 101 pumping test conditions, and their accuracy was compared to the actual test results. When the rheological properties of concrete and the lubricating layer were directly measured, the prediction result showed the highest accuracy. A high accuracy can be achieved when the measured viscosity of the lubricating layer, a key determinant of concrete pumpability, is reflected in the prediction of pumpability. When measuring rheological properties is difficult, the slump test can be used to quantitatively predict the pumpability despite the lower accuracy than those of other prediction methods.

• 소성∙가공
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• 제24권6호
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• pp.381-386
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• 2015

Recently, high-strength-steel sheets have been used extensively for increasing fuel-efficiency and stability in automobiles. A study on the characteristics regarding friction factors is required because high-strength-steel sheets have higher contact pressure at the tool interface as compared to low-strength steel sheets. For the current study, a sheet friction test was used to examine the influence of several factors on friction. The friction tests were performed on two types of sheet steels (SPFC590 and SPFC980) to obtain friction coefficients as a function of contact pressure, surface roughness, lubricant viscosity, and speed. Based on the experimental results for SPFC590 and SPFC980, the friction coefficient decreased with increasing contact pressure, but the friction coefficient increased with increasing surface roughness. Also, the friction coefficient decreased with increasing lubricant viscosity and decreasing speed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.261-264
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• 2004

In this study, the experiment was carried out to investigate and analyze the strenth properties and flowability of ultra-high strength concrete accroding to types of mineral admixtures and cements. The main experimental variables were water/binder ratio $25.0\%$, water content $160kg/m^3$ and mineral admixtures such as fly ash, silica fume and meta kaolin. According to the test results, the principle conclusions are summarized as follows 1) In case of using admixtures, superplasticizer amount need more than plain concrete. 2) According to kinds of admixtures and cements, the viscosity of concrete show much difference. 3) The autogeneous shrinkage of ultra-high strength concrete is profitable that use admixture, and heat of hydration is desirable that apply considering countermeasure enough in the advance. 4) Meta kaolin is excellent in side but has viscosity enlargement efficiency a little. But, problem estimates that is not to make design strength to and $70N/mm^2$ if use mixing condition with water-binder ratio properly.

• 한국산학기술학회논문지
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• 제16권2호
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• pp.1364-1369
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• 2015

반도체 칩의 고집적화로 과거 와이어 본딩 공정에서 BUMP 공정으로 전환되면서 반도체칩과 외부 기기로 이어지는 통신선도 더욱 미세해짐으로 인해 보다 정밀한 작업이 필요한 실정이지만 PSPI의 고점도 특성상 정량제어가 어렵고 버블유입에 따른 수율의 저하가 계속되고 있는 실정이다. 따라서 본 논문에서는 반도체 BUMP 공정에서 고점도 감광성 폴리이미드(PSPI : Photosensitive Polyimide)의 도포(coating)시 발생하는 기포(gas)를 제거하여 공급하는 D&P(Degassing and Pumping) 시스템을 개발하였다.

• 한국응용과학기술학회지
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• 제18권1호
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• pp.20-28
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• 2001

Acrylic quarternary polymers were synthesized to prepare high-solid coatings. Acrylic resins were synthesized by the radical polymerization of n-butyl acrylate, methyl methacrylate, 2-hydroxyethyl methacrylate and acetoacetoxyethyl methacrylate. From the results of experiment on reaction condition to get high-solid acrylic resins with 70% solid content and viscosity of 1200cps, it was found that di-tert-amyl peroxide among the four types of initiators have lower viscosity and higher degree of conversion. The optinum initiator amount, chain transfer agent, reaction temperature and the dropping time were 5wt%, 4wt%, $150^{\circ}C$ and 5hrs, respectively.