• Magazine of the Korean Society of Agricultural Engineers
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• v.35 no.4
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• pp.38-46
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• 1993

This study is to analyze effect of exposure environment and mode of ASR on the engineering properties of synthetic lightweight aggregate concrete, such as dynamic modulus of elasticity and ultrasonic pulse velocity. The results of this study are summarized as foflows ; 1. The expansion rate of each exposure environment in 380$^{\circ}$C and NaCI 4% solution was shown higher than in 20$^{\circ}$C and normal water. The expansion rate of each exposure mode was largely shown in order of fjill immersion, wetting/drying, half immersion. 2. The dynamic modulus of elasticty and ultrasonic pulse velocity of each exposure environment in 38$^{\circ}$C and NaCl 4% solution was shown less than in 20$^{\circ}$C and normal water. The dynamic modulus of elasticity and ultrasonic pulse velocity of each exposure mode was shown smaller in order of full immersion, wetting/drying, half imersion.3. The relation between dynamic modulus of elasticity and ultrasonic pulse velocity was highly significant. The dynamic modulus of elasticity was increased with increase of ultrasonic pulse velocity. The decreasing rate of the dynamic modulus of elasticity was shown 2.1~3.4 times higher than the ultrasonic pulse velocity at each age, exposure environment and mode, respectively. 4. The expansion of each exposure environment and mode was increased with increase of curing age. The dynamic modulus of elasticity and ultrasonic pulse velocity of those concrete was increased with increase of curing age. At the curing age 28 days, the highest properties was showed at each type concrete, it was gradually decreased with increase of curing age. Specially, at the curing age 98 days of full immersion, the rate of expansion of type D was shown 3.95 times higher than the type A. But the dynamic modulus of elasticity and ultrasonic pulse velocity was decreased 17% and 8.3%.

• The Korean Journal of Rheology
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• v.11 no.1
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• pp.34-43
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• 1999

Flow-induced voids during resin impregnation and poor fiber wetting have known to be highly detrimental to the performance of composite parts manufactured by resin transfer molding(RTM) process. In this study, in order to overcome these serious problems encountered in RTM, the effects of surface modification by using silane coupling agent as a surface modifier on the flow characteristics, the wetting between resin and fiber, and void content were investigated. For the experiments of microscopic flow visualization and curing in a beam mold, glass fiber mats having plain weaving structure and epoxy resin were used. Modifying the fiber surface was found to result in a significant decrease of dynamic contact angle between resin and fiber and increase of wicking rate. Therefore, it was confirmed that the surface modification employed in this study could improve the wettability of reinforcing fibers as well as micro flow behavior. In addition, It was revealed that high temperature and low penetration rate of the resin are more favorable processing conditions to reduce the dynamic contact angle. However, surface modified fiber mat was found to have lower permeability than the unmodified one, which may be explained in terms of the decrease of contact time between resin and fiber owing to improvement of wetting. It was also exhibited that surface modification had a significant influence on void formation in RTM process, resulting in a decrease of overall void content due to the improvement of wetting in cured composite parts.

• Membrane and Water Treatment
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• v.6 no.3
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• pp.237-249
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• 2015

In this study we investigate a laboratory scale vacuum membrane distillation system to produce pure water from model oil in water emulsion. Experimental determination of liquid entry pressure (LEP) of a commercial Durapore$^{TM}$ GVPH flat sheet membrane using model emulsions in various oil concentrations has been carried out. Two different methods of liquid entry pressure determination - a frequently used, so-called static and a novel dynamic method - have been investigated. In case of static method, LEP value was found to be 2.3 bar. No significant effect of oil content on LEP was detected up to 3200 ppm. In contrast, LEP values determined with dynamic method showed strong dependence on the oil concentration of the feed and decreased from 2.0 bar to a spontaneous wetting at 0.2 bar in the range 0-250 ppm, respectively. Vacuum membrane distillation tests were also performed. The separation performance is evaluated in terms of flux behavior, total organic carbon removal and droplet size distribution of the feed and final retentate. No significant effect of oil content on the flux was found ($5.05{\pm}0.31kgm^{-2}h^{-1}$) up to 250 ppm, where a spontaneous wetting occurred. High separation performance was achieved along with the increasing oil concentration between 93.4-97.0%.

• ETRI Journal
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• v.38 no.6
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• pp.1179-1189
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• 2016

A chemorheological analysis of a no-flow underfill was conducted using curing kinetics through isothermal and dynamic differential scanning calorimetry, viscosity measurement, and solder (Sn/27In/54Bi, melting temperature of $86^{\circ}C$) wetting observations. The analysis used an epoxy system with an anhydride curing agent and carboxyl fluxing capability to remove oxide on the surface of a metal filler. A curing kinetic of the no-flow underfill with a processing temperature of $130^{\circ}C$ was successfully completed using phenomenological models such as autocatalytic and nth-order models. Temperature-dependent kinetic parameters were identified within a temperature range of $125^{\circ}C$ to $135^{\circ}C$. The phenomenon of solder wetting was visually observed using an optical microscope, and the conversion and viscosity at the moment of solder wetting were quantitatively investigated. It is expected that the curing kinetics and rheological property of a no-flow underfill can be adopted in arbitrary processing applications.

• Journal of ILASS-Korea
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• v.20 no.3
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• pp.181-186
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• 2015

This study presents the dynamic wetting characteristics of an impact droplet on hole-patterned textured surfaces. The flat surfaces were manufactured by a drilling machine to generate the micro-order holes, leading to make the surface hydrophobic. Other flat surfaces were fabricated by the anodizing technique to make hydrophilic texture surfaces with a nanometer order. For hydrophilic and hydrophobic textured surfaces with similar texture area fractions, the impinging droplet experiments were conducted and compared with flat surface cases. As results, an anodized textured surface decreases apparent equilibrium contact angle and increases contact diameters, because of increase in contact area and surface energy. This is attributed to more penetration inside holes from larger capillary pressure on nanometer-order holes. On the other hand, temporal evolution of the contact diameter is smaller for the hydrophobic textured surface from less penetration on the micro-order holes.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1047-1050
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• 2013

Molecular dynamic simulations were performed to examine the wetting behavior of a graphite surface textured with nanoscale pillars. The contact angle of a water droplet on parallelepiped or dome-shaped pillars was investigated by systematically varying the height and width of the pillar and the spacing between pillars. An optimal inter-pillar spacing that gives the highest contact angle was found. The droplet on the dome-covered surface was determined to be more mobile than that on the surface covered with parallelepiped pillars.

• Corrosion Science and Technology
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• v.9 no.2
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• pp.87-91
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• 2010

It is pointed out that non-wetting behavior of liquid Zn alloy occurs on high-tensile strength steels, which usually contain Si and Mn. There have been a lot of investigations to improve the above wettability of liquid Zn alloy with steels containing Si and Mn. Although those studies evaluated the wettability qualitatively by observation of the surface of steels galvanized by Zn or exfoliation test of Zn with substrate steels and so on, it is required to evaluate the wettability of liquid Zn with steels by measuring contact angle, work of adhesion, spreading velocity etc. which are usually used to assessment of general wetting behavior. In the present work, we evaluated the wettability of liquid Zn with steels containing Si and Mn by applying a sessile drop method to measure the change in contact angle and diameter of liquid Zn droplet wetted on steels.

• Korean Journal of Optics and Photonics
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• v.17 no.4
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• pp.347-353
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• 2006

The electro-wetting effect can be implemented as a fast means to move liquid interfaces. A continuous and numerical method would be required in measurement of electro-wetting liquid interfaces. We propose an /in-situ/ measurement method to characterize the dynamic change in curvature of liquid interfaces. In the proposed method, variation of light intensity transmitted through the liquid interfaces is measured, leading to numerical determination of the liquid curvatures. Experimental results obtained from our efficient method are confirmed by the direct images of a streak camera.

• Polymer(Korea)
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• v.34 no.1
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• pp.52-57
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• 2010

The low viscous epoxy resin(bisphenol F) with carboxylic acid as the reductants was introduced for high performance and reliability in the ACA with a low melting point alloy filler system. The curing characteristics of the epoxy resin and temperature dependant viscosity characteristic of epoxy resin at the melting temperature of LMPA were investigated by dynamic mode of differential scanning calorimetry (DSC) and rheometer, respectively. Based on these thermo-rheological characteristics of epoxy resin and LMPA, the optimum process system was designed. In order to remove the oxide layer on the surface of LMPA particle, three different types of carboxyl acid-based reductant were added to the epoxy resin. The wetting angles were about $18^{\circ}$ for carboxypropyldisilioxane, and $20.3^{\circ}$ for the carboxy-2-methylethylsiloxane, respectively.

• Polymer(Korea)
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• v.38 no.3
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• pp.397-405
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• 2014

To manufacture of high-performance semi-structural double-sided adhesive tape, 2-ethylhexyl acrylate (2-EHA) and acrylic acid (AAC) were used, and the syrup was prepared by UV irradiation in this study. The effects of the thickness, various inorganic filler contents, and filler types on the semi-structural properties of acrylic double-sided adhesive tape were investigated. The peel strength increased with increasing thickness and wetting time. In case of the thin thickness (under $250{\mu}m$) with decreasing true density of inorganic filler, the peel strength increased with increasing wetting time. The initial peel strength showed a higher value at a big size of inorganic filler, and the filler's size in adhesive tapes was confirmed by SEM images. The peel strength and dynamic shear strength increased as a proportional relationship with various inorganic fillers and contents, and these inorganic fillers in $0.1{\mu}m$ thickness indicated more effect on the dynamic shear strength of double-sided adhesive tape. From these results the thin acrylic double-sided adhesive tape determined to be use for applications as a high-performance semi-structural.